16th Conference of Hel.A.S

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Session: Heliophysics and the Solar System

Name: Ms. Antonopoulou Alexandra (NOA, NKUA)
Coauthors: Balasis Georgios (NOA)
Papadimitriou Constantinos (SPARC, NKUA, NOA)
Boutsi Adamantia Zoe (NOA, NKUA)
Rontogiannis Athanasios (ECE NTUA)
Koutroumbas Konstantinos (NOA)
Daglis Ioannis A. (NKUA, HSC)
Type: Poster
Title: Convolutional Neural Networks for Automated ULF Wave Classification in Swarm Time Series
Abstract:
Ultra-low frequency (ULF) magnetospheric plasma waves play a key role in the dynamics of the Earth’s magnetosphere and, therefore, their importance in Space Weather phenomena is indisputable. Magnetic field measurements from recent multi-satellite missions (e.g., Cluster, THEMIS, Van Allen Probes and Swarm) are currently advancing our knowledge on the physics of ULF waves. In particular, Swarm satellites, one of the most successful missions for the study of the near-Earth electromagnetic environment, have contributed to the expansion of data availability in the topside ionosphere, stimulating much recent progress in this area. Coupled with the new successful developments in artificial intelligence (AI), we are now able to use more robust approaches devoted to automated ULF wave event identification and classification. The goal of this effort is to use a popular machine learning method, widely used in Earth Observation domain for classification of satellite images, to solve a Space Physics classification problem, namely to identify ULF wave events using magnetic field data from Swarm. We construct a Convolutional Neural Network (ConvNet) that takes as input the wavelet spectrum of the Earth’s magnetic field variations per track, as measured by Swarm, and whose building blocks consist of two alternating convolution and pooling layers, and one fully connected layer, aiming to classify ULF wave events within four different possible signal categories: (1) Pc3 wave events (i.e., frequency range 20–100 MHz), (2) background noise, (3) false positives, and (4) plasma instabilities. Our preliminary experiments show promising results, yielding successful identification of more than 97% accuracy. The same methodology can be easily applied to magnetometer data from other satellite missions and ground-based arrays.
Name: Dr. Sigiava Aminalragia-Giamini (SPARC; NKUA)
Coauthors: Jiggens Piers (ESA ESTEC)
Evans Hugh (ESA ESTEC)
Aran Angels (University of Barcelona)
Matthiä Daniel (DLR)
Sandberg Ingmar (SPARC; NKUA)
Anastasiadis Anastasios (NOA)
Daglis Ioannis A. (NKUA; HSC)
Papadimitriou Constantinos (SPARC; NKUA)
Balasis Georgios (NOA)
Type: Oral
Title: Characterization of the Sun-Earth L2 radiation environment using ESA Standard Radiation Environment Monitor (SREM) measurements: Solar Energetic Particle events and Galactic Cosmic Rays
Abstract:
In this work we present results on the analysis of SREM measurements from the HERSCHEL and PLANCK missions in the Sun-Earth Lagrange 2 point (L2). The datasets from these two missions are unique as over their duration they measured the L2 radiation environment which is poorly characterised so far, but of prime interest for important current and future missions, such as the James Webb Space Telescope and the ATHENA X-ray Telescope. The two main sources of particle radiation in L2 are Solar Energetic Particle (SEP) events and Galactic Cosmic Rays (GCRs). We have applied an advanced artificial intelligence method on the HERSCHEL and PLANCK SREM measurements for the derivation of high quality particle fluxes during identified SEP events. We present SREM-derived SEP proton fluxes up to energies of 1 MeV and discuss the SEP characteristics in L2. Comparisons of our results to concurrent data from Earth-orbiting missions are shown. Moreover, we also resolve Galactic Cosmic Rays (GCR) spectra from SREM measurements, something which has not been done so far. GCR fluxes for protons as well as alpha (helium) particle are successfully derived, and we show comparisons of our results to established GCR models and data.
Name: Dr. Anastasios Anastasiadis (National Observatory of Athens/IAASARS)
Coauthors: Papaioannou Athanasios (National Observatory of Athens/IAASARS)
Vainio Rami (University of Turku, Turku, Finland)
Aran Angels (Universitat de Barcelona, Barcelona, Spain)
Vourlidas Angelos (Applied Physics Laboratory, The Johns Hopkins University,USA)
Kouloumvakos Athanasios (Applied Physics Laboratory, The Johns Hopkins University,USA)
Paouris Evangelos (Applied Physics Laboratory, The Johns Hopkins University,USA)
Balasis George (National Observatory of Athens/IAASARS)
Vasalos George (National Observatory of Athens/IAASARS)
Gianakis Omiros (National Observatory of Athens/IAASARS)
Type: Oral
Title: Are we ready for the next giant leap?
Abstract:
Space Weather effects on Earth and the inner heliosphere is of increasing importance as human spaceflight is preparing for lunar and Mars missions. As concerns Solar Energetic Particle (SEP) events, decades of measurements and theoretical considerations have vastly increased our knowledge and understanding while fostered the development of Space Weather prediction models. Currently, two extraordinary missions, NASA’s Parker Solar Probe (launched in 2018) and ESA’s Solar Orbiter (launched in 2020) survey un-explored vantage points within the heliosphere. State-of-the-art Space Weather tools such as ASPECS (Advanced Solar Particle Event Casting System) [http://phobos-srv.space.noa.gr/], need to be expanded and provide forecasts across the heliosphere. This work frames such a transition, physically and technically offering insight in the challenges that are faced today. Acknowledgements: The ASPECS system was developed, receiving funding through the ESA activity Solar Energetic Particle (SEP) Advanced Warning System (SAWS) ESA Contract No. 4000120480/NL/LF/hh.
Name: Dr. Georgios Balasis (National Observatory of Athens)
Coauthors: Boutsi Adamantia Zoe (NOA; NKUA)
Papadimitriou Constantinos (NOA; NKUA)
Potirakis Stelios (UNIWA)
Pitsis Vasilis (NKUA)
Daglis Ioannis A. (NKUA)
Anastasiadis Anastasios (National Observatory of Athens)
Giannakis Omiros (National Observatory of Athens)
Type: Poster
Title: Investigation of Dynamical Complexity in Swarm-Derived Geomagnetic Activity Indices Using Information Theory
Abstract:
In 2023, ESA Swarm constellation mission celebrates 10 years in orbit, offering one of the best-ever surveys of the topside ionosphere. Among its achievements, it has been recently demonstrated that Swarm data can be used to derive space-based geomagnetic activity indices, similar to the standard ground-based geomagnetic indices monitoring magnetic storm and magnetospheric substorm activity. Recently, many novel concepts originated in time series analysis based on information theory have been developed, partly motivated by specific research questions linked to various domains of geosciences, including space physics. Here, we apply information theory approaches (i.e., Hurst exponent and a variety of entropy measures) to analyze the Swarm-derived magnetic indices from 2015, a year that includes 3 out of 4 most intense magnetic storm events of the previous solar cycle, including the strongest storm of solar cycle 24. We show the applicability of information theory to study the dynamical complexity of the upper atmosphere, through highlighting the temporal transition from the quiet-time to the storm-time magnetosphere, which may prove significant for space weather studies.
Name: Dr. Anna Belehaki (National Observatory of Athens)
Coauthors: No coauthors were included.
Type: Oral
Title: European Research Infrastructures to support ionospheric monitoring and modeling capabilities
Abstract:
The talk presents latest developments funded by the European Commission, aiming at improved ionospheric predictions based on empirical, data assimilation and machine learning models and at open access to relevant data collections and codes. Three European research projects are implemented to provide methodologies and models for the specification of large-scale ionospheric storm effects and the identification of travelling ionospheric disturbances (TechTIDE/Horizon 2020), to provide novel forecasting models for ionospheric irregularities (T-FORS/Horizon Europe) and to integrate all required data collections and scientific models in a unified research environment that supports standardized registration and discovery with open access (PITHIA-NRF/Horizon 2020). The talk highlights the main results and summarizes collaboration opportunities.
Name: Ms. Olga Belli (National & Kapodistrian Univ. of Athens)
Coauthors: Daglis Ioannis A. (Department of Physics, University of Athens)
Type: Poster
Title: Study of the Ring Current Response to ICMEs and CIRs
Abstract:
We have conducted an investigation of the storm-time ring current to different solar wind drivers. To this end we have analysed measurements of protons and oxygen ions by the RBSPICE instrument on-board the NASA Van Allen Probes mission during a number of selected CME-driven and CIR-driven storms. To identify patterns of characteristic behaviour of the two ion species, we have studied the evolution of the ion pressure for all selected storms, using the method of superposed epoch analysis. This work is part of the Bachelor thesis of the leading author.
Name: Ms. Zoe Boutsi (National Observatory of Athens)
Coauthors: Balasis George (National Observatory of Athens)
Dimitrakoudis Stavros (National and Kapodistrian University of Athens)
Daglis Ioannis (National and Kapodistrian University of Athens)
Tsinganos Kanaris (National and Kapodistrian University of Athens)
Papadimitriou Constantinos (National Observatory of Athens)
Giannakis Omiros (National Observatory of Athens)
Type: Oral
Title: Investigation of the Geomagnetically Induced Current Index Levels in the Mediterranean Region During the Strongest Magnetic Storms of Solar Cycle 24
Abstract:
Geomagnetically Induced Currents (GICs) constitute an integral part of space weather research and are a subject of ever-growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. Here, we exploit data from the HellENIc GeoMagnetic Array, which is deployed in Greece, complemented by magnetic observatories in the Mediterranean region (Italy, France, Spain, Algeria, and Turkey), to calculate values of the GIC index, that is, a proxy of the geoelectric field calculated entirely from geomagnetic field variations. We perform our analysis for the most intense magnetic storms (Dst < −150 nT) of solar cycle 24. Our results show that GIC index increases are well correlated with storm sudden commencements. However, the GIC indices do not exceed “low” activity levels despite the increases in their values, at all magnetic stations/observatories under study during the selected storm events.
Name: Mr. Georgios Chouliaras (University of St. Andrews)
Coauthors: No coauthors were included.
Type: Oral
Title: Magnetic flux emergence: Effects of partial ionisation
Abstract:
We have performed 3-D numerical simulations to investigate the effect of partial ionization to the process of magnetic flux emergence. In our study, we have modified the single fluid MHD equations to include the presence of neutrals and we have performed two basic experiments: one that assumes a fully ionized plasma (FI case) and one that assumes a partially ionized plasma (PI case). We find that the PI case brings less dense plasma at and above the solar surface. Furthermore, we find that partial ionization alters the emerging magnetic field structure leading to a different shape of the polarities in the emerged bipolar regions compare to the FI case. The amount of emerging flux into the solar atmosphere is larger in the PI case, which has the same initial plasma beta with the FI case, but larger initial magnetic field strength. The expansion of the field above the photosphere occurs relatively earlier in the PI case and we confirm that the inclusion of partial ionization reduces the cooling due to the adiabatic expansion. However, it does not appear to work as a heating mechanism of the atmospheric plasma. The performance of these experiments in three dimensions shows that PI does not prevent the formation of unstable magnetic structures, which erupt into the outer solar atmosphere. Georgios Chouliaras , Dr Vasilis Archontis
Name: Prof. Ioannis Daglis (University of Athens)
Coauthors: No coauthors were included.
Type: Oral
Title: Predicting the dynamics of outer Van Allen belt relativistic electrons
Abstract:
The EU H2020 SafeSpace project has focused on the improvement of our capabilities to predict the dynamics of relativistic electrons in the outer Van Allen belt in geospace. To this end, we have implemented a synergistical approach to improve the space weather forecasting capabilities from the current lead times of a few hours to 2-4 days. We have combined the solar wind acceleration model MULTI-VP with the heliospheric propagation models Helio1D and EUHFORIA to compute the evolution of the solar wind from the surface of the Sun to the Earth orbit. The forecasted solar wind conditions are then fed into the ONERA Geoffectiveness Neural Network, to forecast the level of geomagnetic activity with the Kp index as the chosen proxy. The Kp index is used as the input parameter for the IASB plasmasphere model and for the Salammbô radiation belts code. The plasma density is used to estimate VLF wave amplitude and then VLF diffusion coefficients, while the predicted solar wind parameters are used to estimate the ULF diffusion coefficients through the NKUA EMERALD model. Plasmaspheric density and VLF/ULF diffusion coefficients are used by the Salammbô radiation belts code to deliver a detailed flux map of energetic electrons. Finally, particle radiation indicators are also provided as a prototype space weather service of use to spacecraft operators and space industry, accessible at http://www.safespace-service.eu. The performance of the prototype service has been evaluated in collaboration with space industry stakeholders. The work leading to this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace (Radiation Belt Environmental Indicators for the Safety of Space Assets) project.
Name: Mr. Ioannis Dakanalis (UOA, NOA/IAASARS)
Coauthors: No coauthors were included.
Type: Oral
Title: Detection and line profile analysis of swirling structures on the solar atmosphere from multiwavelength observations
Abstract:
Ubiquitous vortical motions in the solar atmosphere have been recently revealed by high resolution observations from both space-borne and ground-based observatories in quiet, as well as, in active regions. In chromospheric observations obtained in spectral lines, such as the Halpha and Ca II IR, they manifest themselves as swirling dark spiral- and circular-shaped patches known as “chromospheric swirls”. Their suggested contribution to the channelling of energy, mass and momentum from the sub-photospheric to the higher layers of the solar atmosphere places them amongst potential candidates for atmospheric heating. In this context, their detection and statistical information concerning their population and several significant physical parameters and properties are of vital importance. To complement visual inspection and automated detection methods based on the, often ill-derived, horizontal velocity field we have developed a novel automated detection method, which is purely based on their morphological characteristics. The algorithm was applied on high resolution observations obtained with the Crisp Imaging SpectroPolarimeter (CRISP) of the Swedish 1-m Solar Telescope (SST) in three chromospheric spectral lines, namely, the Halpha, Ca II IR and Ca II K lines, in order to derive statistical information and explore the response of swirls in different heights of the chromosphere. In this presentation we focus on the morphological characteristics of swirling structures with co-spatial detections in all three chromospheric lines and the profile analysis performed to derive significant physical parameters, such as line-of-sight velocities, FWHM and equivalent widths. We also discuss the response of these swirling chromospheric structures in co-aligned observations obtained by the Interface Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO) space observatories that map the Transition Region and Solar Corona.
Name: Dr. Stavros Dimitrakoudis (National & Kapodistrian Univ. of Athens)
Coauthors: No coauthors were included.
Type: Oral
Title: Long-term Trends and Occurrence Distributions of Geomagnetic Fluctuations as Revealed by 37 Years of CARISMA Observations at 5s Cadence
Abstract:
The rate of change of the horizontal component of the geomagnetic field is a useful proxy for determining the severity of geomagnetically induced currents (GIC). While contemporary measurements for geomagnetic disturbances (GMD) are available from a number of arrays, short timescale datasets are not ideal for the characterisation of extreme events since their data sets are rarely indicative of the most extreme geomagnetic conditions. The CANOPUS array, subsequently expanded and operated as the CARISMA magnetometer array (www.carisma.ca), has been in continuous operation in Canada since 1986, first with a 5-second and then more recently with a 1-second cadence. Using that long timebase dataset we are able to evaluate the occurrence distributions of 5-second cadence measurements for up to 12,000 operational days for each of several stations, until the end of 2022. The CANOPUS/CARISMA GMD occurrence distributions, overall, appear to be well-approximated by log-normal rather than power law distributions. However, for extreme events, the local time at which the largest GMD typically occurs rotates away from the midnight sector, such that the largest events in the tail of the distribution most often occur instead at dawn. This has significant implications for assessing the size of expected extreme GMD events, and indeed the local time of the largest vulnerability, with clear applications for assessing extreme space weather impacts on the electric power grid.
Name: Ms. Adamantia Dimitrakoula (National & Kapodistrian Univ. of Athens)
Coauthors: Nasi Afroditi (NKUA, Greece)
Katsavrias Christos (NKUA, Greece)
Sandberg Ingmar (SPARC, Greece & Aerospace Science and Technology, NKUA, Greece)
Daglis Ioannis A. (NKUA, Greece & Hellenic Space Center, Greece)
Type: Poster
Title: Impact of Interplanetary Coronal Mass Ejections on the dynamic variations of the electron population in the outer Van Allen belt
Abstract:
The outer Van Allen radiation belt is an environment with intense variability due to complex mechanisms that are part of the solar–terrestrial coupling. A fundamentally important effect is the acceleration of seed electrons to relativistic and ultra-relativistic energies. In our work, we examine 16 events from the Van Allen Probes era (2012 – 2018), which have been chosen according to the interplanetary driver of the geomagnetic disturbance. The selected events were driven by Interplanetary Coronal Mass Ejections (ICMEs). We have calculated the electron Phase Space Density (PSD) for distinct values of the first adiabatic invariant (μ=100,1000,5000 MeV/G) corresponding to the different energies of the electrons in the outer radiation belt. Furthermore, we have studied the response of the electron population for different K values (K=0.03,0.09,0.15 G^(1⁄2) R_E), in order to compare the differences between the two main acceleration mechanisms and their dependence on the electron pitch angle. This is achieved by performing a Superposed Epoch Analysis (SEA) of the geomagnetic disturbance events, taking into consideration the parameters of solar wind and the state of the magnetosphere. We compare and discuss the variability of the electron PSD for different values of the adiabatic invariants, using time and radial profiles, the effects of the ICMEs on the outer radiation belt and how the different electron populations are affected.
Name: Dr. Nikolaos Georgakarakos (New York University Abu Dhabi)
Coauthors: No coauthors were included.
Type: Oral
Title: An explanation for the number asymmetry between the L4 and L5 Jupiter Trojans.
Abstract:
More than 10000 Jupiter Trojans have been detected so far. They are moving around the L4 and L5 triangular Lagrangian points of the Sun-Jupiter system and their distributions can provide important clues about the early evolution of the Solar System. A longstanding problem regarding those two groups of asteroids is their number asymmetry, i.e. the L4 swarm being more populous than the L5 one. In this work, we explore two scenarios that may explain that asymmetry. In the first one, Jupiter undergoes a fast outward migration caused by the giant planet instability in the early Solar System. In the second scenario, we investigate the early evolution of Jupiter and its two Trojan swarms by introducing the possible perturbations of a free floating planet (FFP) invading the Solar System. We find that both scenarios could potentially explain the unbiased number asymmetry of N4/N5 ~ 1.6 for the known Jupiter Trojans. The uncertainties of the system parameters, such as Jupiter's eccentricity and inclination as well as the inclination distribution of Jupiter Trojans are also taken into account. Regarding the FFP scenario, we propose that the FFP should have a mass of at least of a few tens of Earth masses and its orbital inclination is allowed to be as high as 40 degrees.
Name: Dr. Manolis Georgoulis (Academy of Athens, RCAAM)
Coauthors: No coauthors were included.
Type: Oral
Title: Fundamental Understanding and Forecasting of Solar Energetic Events
Abstract:
We attempt a brief but hopefully encompassing overview of the solar energetic events that impact the ever-changing space weather conditions in the heliosphere, with a further aim to present desired methodologies employed to predict these events and their repercussions. Eruptive manifestations of interest are solar flares, coronal mass ejections (CMEs) and solar energetic particle (SEP) events. A basic physical understanding of their triggering and interconnections helps guide the objectives of the forecast methods employed. In recent years, predictive methodologies have evolved to include artificial intelligence applications such as machine- and deep-learning methods. We report that no winning methodology (and no winning data set) has been designated so far for forecasting and that machine- and deep-learning methods are by no means a panacea. We also briefly touch on the pressing needs and gaps of knowledge that must be tackled in order to facilitate a transformative, decisive improvement in solar and space weather forecasting. The presentation draws from and delineates a roadmap paper written synergistically in the framework of COSPAR’s International Space Weather Action Teams (ISWAT), that also aims to project into future developments, in both the sort (i.e., within 5 years) and the long (10 years or more) term.
Name: Dr. Costis Gontikakis (Academy of Athens, RCAAM)
Coauthors: Georgoulis M.K. (RCAAM, Academy of Athens)
Kontogiannis I. (Leibniz-Institut für Astrophysik Potsdam, Germany)
Type: Poster
Title: Study of the evolution of hot plasma emission prior to flares and CMEs
Abstract:
Solar flares and coronal mass ejections (CMEs) are the most energetic solar phenomena. The mechanisms causing these events are not yet fully understood. It is likely that major flare events and CMEs are associated with magnetic flux ropes, i.e., twisted structures that are formed in the triggering active regions, and are filled with hot plasma of ~5 million Kelvin. This plasma can be detected in active regions in the pre-flare state via EUV filtergrams taken by the Atmospheric Imaging Assembly (AIA) telescope, on board the Solar Dynamics Observatory (SDO). In this study, we use a combination of AIA filtergrams to derive the emission of the hot Fe XVIII ion (formation temperature~7 million Kelvin) spectral line. We studied the emission prior to ten flares (M-class and X-class), aiming to detect flux-rope related Fe XVIII emission and examine whether this emission is typical before the onset of major flares.
Name: Dr. Christos Katsavrias (National & Kapodistrian Univ. of Athens; NASA-GSFC)
Coauthors: Di Matteo Simone (NASA-Goddard Space Flight Center, Greenbelt, MD, USA)
Kepko Lawrence (NASA-Goddard Space Flight Center, Greenbelt, MD, USA)
Viall Nicholeen (NASA-Goddard Space Flight Center, Greenbelt, MD, USA)
Greeley Ashley (NASA-Goddard Space Flight Center, Greenbelt, MD, USA)
Type: Oral
Title: Properties of periodic density structures (PDSs) from L1 to 1 AU and related magnetospheric response
Abstract:
The solar wind contains structures at vastly different scales, from small scale 1–2 min magnetic holes to large-scale coronal mass ejections and stream interaction regions. In the past years, the “mesoscales” which here we define as radial scale sizes L ∼ 100 to several 1,000 Mm, or equivalently time scales of t ∼ a few minutes to several hours based on typical solar wind speeds, have gain scientific interest as they have been detected in a broad range of phenomena in the Sun to Earth chain. A subset of mesoscale solar wind structures are quasi‐periodic proton density enhancements, termed periodic density structures (PDSs). PDSs have been routinely detected at L1 and compared with Earth’s magnetospheric field fluctuations. Nevertheless, investigations on their propagation and evolution are challenging due to the limited amount of interplanetary multi-spacecraft observations. In this work we exploit multi-point and multi-satellite observations from L1 to 1 AU covering solar wind, foreshock, magnetosheath, magnetosphere, and radiation belts. We provide insight to some important questions such as: a) what is the azimuthal extend of PDSs at various size scales, b) does the bowshock and/or the Earth's magnetosheath affect the PDSs and consequently how the PDSs affect the magnetosphere and particularly the outer radiation belt.
Name: Dr. Ioannis Kontogiannis (Leibniz Institute for Astrophysics Potsdam)
Coauthors: No coauthors were included.
Type: Oral
Title: The evolution of net electric currents in solar active regions hosting delta-spots
Abstract:
Active regions that host delta-spots, i.e., opposite magnetic polarity sports sharing the same penumbra, often produce the strongest flares and coronal mass ejections. Their highly complex magnetic field configurations require the presence of strong volume electric currents. This work presents new results regarding the development of these electric currents during flux emergence and the subsequent magnetic interactions within active regions. It utilizes a method based on image segmentation to determine more accurately the total unsigned non-neutralized (net) electric currents, Inn, injected to the corona. It has been found that Inn is significantly higher in strongly flaring regions, particularly before eruptive flares and strongly correlated with CME kinematic characteristics. The method is then applied on a sample of emerging active regions belonging to different magnetic complexity classes. Active regions with delta-spots contained systematically higher net electric currents. The temporal evolution of Inn exhibited intricate temporal evolution, with distinct events of increase, indicative of the various types of interactions between opposite magnetic polarities. The rate of increase of Inn during these events is strongly correlated with the flaring productivity of the source regions. In particular, active regions that produced X-class flares, such as NOAA 11158 and the superflaring region NOAA 12673, exhibited considerably higher rates of increase, as a consequence of strongly interacting opposite magnetic polarity partitions. The detailed study of net electric currents during these interactions can contribute to a better understanding of the origin of net electric currents in solar active regions.
Name: Ms. Varvara Kotsiourou (National & Kapodistrian Univ. of Athens)
Coauthors: Daglis Ioannis A. (National & Kapodistrian Univ. of Athens)
Type: Oral
Title: Effect of magnetospheric substorms on the enhancement of the ring current according to observations from the Van Allen Probes mission.
Abstract:
The ring current is a dynamic current system whose structure and intensity can change dramatically on many time scales, depending on the level of disturbances induced by the solar wind. During intense geomagnetic activity, the composition of the ring current changes due to large amounts of energy released into the Earth's inner magnetosphere. There is a significant enhancement of the ring current related to geomagnetic storms, while there is poor knowledge of the contribution of non storm substorms on the ring current dynamics. In this study we have utilized data from the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) and from Helium Oxygen Proton Electron (HOPE) instrument and we have examined the ring current variation during non-storm time (SYM-H > −50 nT), super-substorms (AL >-1000 nT) and non-storm time normal-substorms (-500nT
Name: Dr. Athanasios Kouloumvakos (The Johns Hopkins University, APL)
Coauthors: Mason G. M. (The Johns Hopkins University Applied Physics Laboratory)
Ho G. C. (The Johns Hopkins University Applied Physics Laboratory)
Allen R. C. (The Johns Hopkins University Applied Physics Laboratory)
Type: Oral
Title: Energetic Particle Measurements from the Suprathermal Ion Spectrograph (SIS) during the the First 3 Years of SolO mission
Abstract:
Through the first three years of the Solar Orbiter mission, the Suprathermal Ion Spectrograph (SIS), part of the Energetic Particle Detector (EPD) suite, has observed a plethora of solar energetic particles (SEP) events close to the Sun. SIS is a high-mass resolution sensor that performs precise measurements of heavy ion composition (from He to Fe) for an energy range from ∼100 keV/nucleon up to several MeV/nucleon. SIS has observed a wide variety of SEP events, each with unique properties, including impulsive 3He-rich SEP events with properties similar to those previously observed at 1 au but in the absence of phenomena such as jets and small coronal mass ejections, interplanetary ion dropout events, suprathermal particles from corotating interaction regions, and extended 3He-rich periods spanning multiple days. In my presentation, I will highlight selected results from SIS for the first three years of the SolO mission and discuss how these shape our understanding of the sources of 3He-rich events and the production of long time periods abundant with this rare isotope of He.
Name: Dr. Alexios Liakos (IAASARS/National Observatory of Athens)
Coauthors: Liakos Alexios (IAASARS/National Observatory of Athens)
Bonanos Alceste (IAASARS/National Observatory of Athens)
Xilouris Emmanouil (IAASARS/National Observatory of Athens)
Koschny Detlef (TU Munich, Germany)
Boumis Panayotis (IAASARS/National Observatory of Athens)
Bellas-Velidis Ioannis (IAASARS/National Observatory of Athens)
Moissl Richard (NEOCC, ESA/ESRIN, Italy)
Marousis Athanasios (IAASARS/National Observatory of Athens)
Type: Oral
Title: NELIOTA: Results from the 6.5 yr monitoring campaign for lunar impact flashes
Abstract:
We present scientific results from the long-term observations of lunar impact flashes of the ESA-funded NELIOTA program. Using the 1.2 m Kryoneri telescope and the fast frame-rate cameras of the system, NELIOTA has observed over 175 validated lunar impact flashes since the beginning of its operation in early 2017, while other ~100 have been characterized as suspected. We will present results concerning the dimensions, the masses and the appearance frequency of the meteoroids in the vicinity of the Earth. Moreover, statistics for the temperatures of the collisions and the calculation of the meteoroid frequency on various distances from the Earth and the Moon provide quantitative results for the risk assessment for space and satellite missions as well as for future establishment of lunar bases.
Name: Dr. Olga Malandraki (NOA/IAASARS)
Coauthors: Karavolos Michalis (National Observatory of Athens)
Kokkinis Dimitris (National Observatory of Athens/IAASARS)
Nikolaos Milas (National Observatory of Athens/IAASARS)
Crosby Norma (Royal Belgian Institute for Space Aeronomy, Brussels, Belgium)
Dierckxsens Mark (Royal Belgian Institute for Space Aeronomy, Brussels, Belgium)
Núñez Marlon (Universidad de Málaga, Málaga, Spain)
Posner Arik (Heliophysics, NASA Headquarters, Washington, DC, USA)
Heber Bernd (Christian-Albrechts-University of Kiel, Kiel, Germany)
Kuehl Patrick (Christian-Albrechts-University of Kiel, Kiel, Germany)
Type: Oral
Title: Forecasting and analysis of solar particle radiation storms: A state-of-the-art solution provided by the HESPERIA SEP Real-Time Forecasting products
Abstract:
For human spaceflight beyond low-Earth orbit, particularly outside the Earth's magnetosphere, it is essential to provide accurate predictions of Solar Energetic Particle (SEP) occurrences. SEPs with energies ranging from tens of keV to a few GeV, are a significant component in the description of the space environment. SEP events feature a wide range of energy spectrum profiles and can last for a few hours to several days or even weeks. As well as posing a threat to modern technology that heavily relies on spacecraft and posing a major radiation hazard to astronauts, they can also constitute a threat to avionics and commercial aircraft in extreme circumstances. The SEP Real-Time Forecasting HESPERIA products have been developed under the HESPERIA H2020 project (Project Coordinator: Dr. Olga Malandraki) and since 2015 provide significant results concerning the prediction of SEP events. More specifically, the HESPERIA UMASEP-500 product makes real-time predictions of the occurrence of >500 MeV proton events and Ground Level Enhancement (GLE) events based on the analysis of soft X-ray and high energy differential proton fluxes measured by the GOES satellite network. The HESPERIA REleASE product, based on the Relativistic Electron Alert System for Exploration (REleASE) forecasting scheme, generates real-time predictions of the proton flux (30-50 MeV) at L1, making use of relativistic and near-relativistic electron measurements by the SOHO/EPHIN and ACE/EPAM experiments, respectively. Lastly, the HESPERIA REleASE Alert is a notification system based on the forecasts produced by the HESPERIA REleASE product and informs about the expected radiation impact in real-time using an illustration and a distribution system for registered users. The real-time and highly accurate forecasts as well as the timely performance offered by the HESPERIA products have attracted the attention of various space organizations (e.g. NASA/CCMC, SRAG) and also led to the selection and integration of them into the ESA Space Weather (SWE) Service Network (https://swe.ssa.esa.int/noa-hesperia-federated). The integration process, based on the strict guidelines posed by ESA, has determined the current form of the HESPERIA products using state-of-the-art technologies and paradigms concerning both the graphical user interface and the mechanisms to provide the forecasting results to the end users with a high-quality experience. We will present the HESPERIA products as provided through the ESA SWE Service Network under the Space Radiation Expert Service Centre (R-ESC). Moreover, solar radiation storms successfully predicted during Solar cycle 25 will also be presented and discussed. (Work performed in the frame of ESA Space Safety Programme’s network of space weather service development and pre-operational activities and supported under ESA Contract 4000134036/21/D/MRP).
Name: Dr. Stergios Misios (National Obaservatory of Athens)
Coauthors: No coauthors were included.
Type: Oral
Title: Solar cycle influences on the atmosphere and climate
Abstract:
Understanding the influence of solar irradiance variability on the Earth’s surface could help us articulate climate variations prior to the era of the dominant anthropogenic forcing. Recent studies, including coordinated multi-model activities like the CMIP5, have further supported some earlier evidence that the solar irradiance variability influences the stratosphere/troposphere system and large scale atmospheric and ocean circulation on decadal time scales. However, many regional patterns demonstrate substantial uncertainties because of the internal variability of the climate system. Climate models help us to understand the mechanisms contributing to the surface response and using carefully designed model simulations and rigorous statistical analysis it is now possible to identify decadal signatures of the solar cycle forcing on precipitation and surface temperature. I will present efforts to simulate irradiance changes over the 11-yr sunspot cycle with the aid of global models of the Earth’s climate and discuss how total and spectral irradiances influence the stratosphere, troposphere, and the oceans.
Name: Dr. Kostas Moraitis (University of Ioannina)
Coauthors: Archontis Vasilis (University of Ioannina)
Zhuleku Juxhin (University of Ioannina)
Chouliaras George (University of St Andrews)
Type: Oral
Title: Understanding a flux emergence simulation through magnetic helicity
Abstract:
We study a resistive magneto-hydrodynamic (MHD) flux emergence simulation from the point of view of magnetic helicity. The simulation includes a twisted flux tube that emerges from below the photosphere into a model corona that has an oblique, ambient magnetic field, and where the process of partial ionization is also considered. We calculate relative magnetic helicity and its two components, often referred to as, the self and mutual helicities, in the volume above the photosphere, following the most accurate computation method. The evolution of these helicities indicate the occurrence of three events in the simulation. We study the morphological characteristics of each of them and relate them with the evolution of helicities around the events. The use of magnetic helicity helps us to identify that the three events are different in nature, and that they occur at different locations in the simulation volume.
Name: Ms. Georgia Moutsiana (University of Athens / IASA)
Coauthors: Clark George (JHU / APL)
Gkioulidou Matina (JHU / APL)
Daglis Ioannis (NKUA , HSC)
Mauk Barry (JHU / APL)
Type: Poster
Title: A statistical study of the features of ion acceleration events in the Jovian magnetotail using Juno/JEDI data
Abstract:
Planetary magnetospheres across our solar system are known to be very efficient accelerators of charged particles. Moreover, the energization processes of magnetotail plasma populations are thought to share similarities among the various magnetospheres. In the present study, we focus on the Jovian magnetosphere, which contains a variety of ion species with different charge states, resulting in a diverse set of acceleration-relevant factors that can be tested. Therefore, we investigate the features of ion acceleration processes in the Jovian magnetosphere, utilizing measurements from the Juno mission. In particular, we use magnetic field data from the MAG instrument, and energetic ion data from the JEDI instrument, in order to investigate the energization of hydrogen (~50 keV to ~1 MeV), oxygen (~170 keV to ~2 MeV) and sulfur (~170 keV to ~ 4MeV) ions during dipolarization events in the Jupiter’s magnetosphere. At this point, we present a statistical study of the characteristics of heavy ion acceleration processes in the Jovian magnetotail, such as the maximum energy of each ion species, as well as the Magnetic Local Time (MLT) position and radial distance for each event. Results of our study are a first step towards a comparative analysis of energization processes around dipolarization events in the magnetotails of Earth and Jupiter.
Name: Ms. Konstantina Moutsouroufi (National & Kapodistrian Univ. of Athens)
Coauthors: Sergis Nick (HSC)
Daglis Ioannis (UOA; HSC)
Achilleos Nicholas (University College London)
Type: Oral
Title: A Magnetospheric Stress Index: Construction and application to Saturn magnetosphere using long-term Cassini measurements.
Abstract:
A planet’s magnetosphere is being shaped by the forces applied to it, both externally and internally. Α magnetosphere strained by changes in external or internal pressures, correspondingly results in deformation of its magnetic field lines in almost all of its range. In order to study the dynamic changes in Saturn’s magnetosphere, it is useful to have a quantitative measure of its average stress, which can be compared to the measured fluctuations during a spacecraft’s individual passes. The most extensive and detailed field-and-particle measurements of the Saturn system were provided by the Cassini mission, and have expanded our understanding of the planet’s magnetosphere. In the present study we introduce and calculate a Magnetospheric Stress Index using measurements of Saturn’s magnetic field, obtained throughout the Cassini mission (2004-2017) near the equatorial plane of the magnetosphere, between 4 and 8 planet radii (RS), expanding previous works. The proposed index is similar to indices that have been developed to monitor the Earth’s and Jupiter’s magnetospheric stresses. The index indicates any unusual deviations from the average magnetospheric conditions and distinguishes them from smaller deviations expected due to usual fluctuations in the solar wind. Hence, the proposed index depicts the temporal magnetospheric deformation, despite the limitation of single-spacecraft measurements, and the lack of magnetopause monitoring.
Name: Ms. Afroditi Nasi (National & Kapodistrian Univ. of Athens)
Coauthors: Katsavrias Christos (UOA)
Aminalragia-Giamini Sigiava (UOA; SPARC)
Papadimitriou Konstantinos (UOA; SPARC)
Sandberg Ingmar (SPARC; UOA)
Balasis Georgios (IAASARS, NOA)
Daglis Ioannis A. (UOA; HSC)
Type: Oral
Title: Investigating the acceleration efficiency of VLF/ULF waves on different populations of outer radiation belt electrons, through multi-point observations and modeling
Abstract:
During the second half of 2019, the Earth’s magnetosphere was impacted by a sequence of Corotating Interaction Regions (CIRs) during four consecutive solar rotations. Based on the solar wind properties, the CIRs can be divided in four groups, with the 3rd group, which arrived on August-September 2019, resulting in significant multi-MeV electron enhancements, up to ultra-relativistic energies of 9.9 MeV. Each CIR group has a different effect on the outer radiation belt electron populations; we investigate them by exploiting combined measurements from the Van Allen Probes, THEMIS, and Arase satellites. We produce Phase Space Density (PSD) radial profiles and inspect their dependence on the values of the first and second adiabatic invariants (μ,K), ranging from seed to ultra-relativistic electrons and from near-equatorial to off equatorial mirroring populations, respectively. Focusing on the 3rd CIR group, and in order to assess the relative contribution of radial diffusion and gyro-resonant acceleration, we perform numerical simulations of the radiation belt environment, combining several relevant models: EMERALD (NKUA), GEO model (NKUA), Salammbô (ONERA), VLF model (IAP), Plasmaspheric model (BIRA-IASB), FARWEST (ONERA). We further compare the temporal evolution of the simulated electron PSD with the above observations. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870437 for the SafeSpace project. Complete author list: A. Nasi (1), C. Katsavrias (1), S. Aminalragia-Giamini (1,2), N. Dahmen (3), A. Brunet (3), C. Papadimitriou (1,2), S. Bourdarie (3), O. Santolik (4), I. Sandberg (2,5), F. Darrouzet (6), Y. Miyoshi (7), W. Li (8), G. Balasis (9), H. Evans (10), I. A. Daglis (1,11), V. Pierrard (6), E. Botek (6), B. Grison (4), I. Kolmasova (4), D. Pisa (4), T. Mitani (12), A. Matsuoka (13), I. Shinohara (12), T. Takashima (12), T. Hori (7) (1) Department of Physics, UOA, Greece. (2) SPARC, Greece. (3) ONERA, France. (4) IAP, Czechia. (5) Department of Aerospace Science and Technology, UOA, Greece. (6) BIRA-IASB, Belgium. (7) ISEE, Nagoya University, Japan. (8) Center for Space Physics, Boston University, USA. (9) IAASARS, NOA, Greece. (10) ESTEC, ESA, The Netherlands. (11) Hellenic Space Center (HSC), Greece. (12) ISAS, JAXA, Japan. (13) Kyoto University, Japan.
Name: Prof. Alexander Nindos (University of Ioannina)
Coauthors: No coauthors were included.
Type: Oral
Title: Recent advances in our understanding of the solar chromosphere
Abstract:
The solar chromosphere is traditionally defined as a ~2000-km-thick layer lying above the photosphere. Its emission can be detected in strong optical and UV spectral lines as well as in infrared, millimeter-wavelength (mm-λ) and submillimeter-λ continua. The pertinent spectral observations indicate that the chromosphere is highly inhomogeneous and dynamic. Although several of the observational building blocks of the chromosphere have been established a long time ago, the physics dictating their properties and dynamics is not. This is because the chromosphere is intrinsically complex. It is the layer of the solar atmosphere where the transition from a plasma-dominated regime to a magnetic-field-dominated regime takes place. It is also a region where interactions between ions and neutrals can be relevant. Furthermore, the formation of the chromospheric spectral lines are associated with nonequilibrium effects. Observations of the radio continuum at mm-λ provide a unique chromospheric diagnostic. The non-flaring Sun continuum mm-λ emission is of thermal origin. The emission mechanism is free-free and electrons are almost always in LTE; hence, there is no need to consider non-LTE effects, abundances, ionization and excitation equilibria, that are common sources of uncertainty in other parts of the spectrum. However, old mm-λ observations of the Sun were underexploited due to the lack of appropriate instruments. With the advent of the Atacama Large Millimeter and submillimeter Array (ALMA), chromospheric data at mm-λ with unprecedented angular resolution (a few seconds of arc or less), temporal resolution (1-2 s) and sensitivity have been accumulating. In this talk I review recent advances in our understanding of the chromosphere using ALMA observations. Special emphasis will be given on the new results on the temperature structure of the chromosphere, the chromospheric network and spicules, small-scale dynamic phenomena and oscillations, prominences and filaments, as well as sunspots.
Name: Dr. Evangelos Paouris (GMU & JHU/APL)
Coauthors: Kouloumvakos Athanasios (Johns Hopkins University Applied Physics Laboratory)
Vourlidas Angelos (Johns Hopkins University Applied Physics Laboratory)
Papaioannou Athanasios (Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing of the National Observatory of Athens)
Type: Oral
Title: CME forecasting from L5 utilizing STEREO-A heliospheric imagers: Focus on the period June 2020 – June 2021
Abstract:
Coronal Mass Ejections (CMEs) are the drivers of the most intense geomagnetic storms. The early and accurate prediction of CMEs is crucial for Space Weather forecasting. The deployment of the STEREO mission enabled the unique opportunity to observe CMEs from multiple viewpoints in the inner heliosphere, tracking CMEs all the way from Sun to Earth. As mankind returns soon to the Moon, and ventures beyond further in the future, space weather forecasts take a new role in protecting human exploration efforts. Spacecraft dedicated to Space Weather stationed at the Lagrangian L4 and L5 points would be very beneficial for improving forecasts. In this work, we present lessons learned from the STEREO mission focusing on the period June 2020 – June 2021 while STEREO-A was around the L5 point, with a separation angle from Earth between 50 and 70 degrees. We use heliospheric imagers to estimate the Time-of-Arrival (ToA) and the Speed-on-Arrival (SoA) of Earth-directed CMEs and compare the results with the in situ signatures at L1. We also present preliminary results of CME kinematics and energetics. Finally, we will highlight our Space Weather perspective analysis of the fastest (so far) CME of solar cycle 25, encountered in the corona by PSP on September 5, 2022. This unique event was recorded simultaneously by in situ instruments and imagers dispersed throughout the inner heliosphere.
Name: Mr. Constantinos Papadimitriou (National & Kapodistrian Univ. of Athens)
Coauthors: Balasis Georgios (National Observatory of Athens)
Daglis Ioannis A. (Hellenic Space Center)
Wing Simon (Johns Hopkins University)
Type: Oral
Title: Information-theoretic measures for electron acceleration in the outer radiation belt
Abstract:
Uncovering the underlying mechanisms that drive the dynamics and evolution of the energetic particles that comprise the Earth’s radiation belts is one of the greatest challenges that the science of Space Physics faces. The complicated interplay between solar drivers and the response of the terrestrial magnetosphere creates a highly dynamic area, in which energetic particles are trapped and accelerated from very low, thermal energies to ultra-relativistic ones. Since the nature of many of these interactions is far from being a simple, linear one, traditional methods such as correlation studies are not ideally equipped to detect these kinds of relations. Fortunately, the field of Information Theory has produced a wide range of entropy-based causality measures and methodologies for their application, that aim exactly at uncovering causal links between various parameters, even when these are non-linear and complex in nature. In this work, we present such an approach, which by utilizing both electron flux data from the MagEIS instrument on board the RBSP (Radiation Belt Storm Probes) satellites, as well as solar wind parameters and magnetospheric indices attempts to shed some light on the acceleration processes of equatorial electrons, located near the peak of the outer radiation belt, as it examines the causal relations between electrons at low (~50 keV), middle (~500 keV) and high energies (>2 MeV), and the effect that those external and internal parameters have on these relations. We show significant information flow from low energy electrons into high energy ones as well as from some solar wind/geomagnetic field parameters. This work will form the basis for more thorough future research on the mechanisms underlying radiation belts dynamics.
Name: Dr. Athanasios Papaioannou (National Observatory of Athens)
Coauthors: Anastasiadis A. (National Observatory of Athens)
Vasalos G. (National Observatory of Athens)
Milas N. (National Observatory of Athens)
Leila Mays M. (NASA Goddard Space Flight Center)
Jones J. (NASA Goddard Space Flight Center)
Quinn P. (NASA Johnson Space Center)
Semones E. (NASA Johnson Space Center)
Whitman K. (NASA Johnson Space Center)
Barzilla J. (KBR-Wyle Laboratory)
Type: Poster
Title: Predicting the Impact of Solar Energetic Particles - the ADVISOR Research Project
Abstract:
A system that is in place to predict the impact of Solar Energetic Particles (SEPs) on the radiation environment is of paramount importance for the upcoming critical space exploration missions. In the coming years, astronauts will be sent to the Moon and Mars, expanding the frontiers of current knowledge. Therefore, reliable prediction systems that will deliver timely warnings on the potential of a solar eruptive event to give rise to an upcoming SEP are much needed. Currently, thorough evaluation, understanding, validation, expansion and optimization of such available predicting systems are taking place. The ADVISOR (OptimizAtion, DeliVery & Installation of the ASPECS tOol for Space WeatheR research within ISEP) project [https://members.noa.gr/atpapaio/advisor/] builds upon the ASPECS (Advanced Solar Particle Event Casting System) tool [http://phobos-srv.space.noa.gr/], a 3-tier system combining the forecasting of flares, the statistical forecast of events on the basis of flare and CME characteristics and physics and analytical modeling for predicting particle flux profiles, leading to the complete time profile of SEPs at respective energies of interest. Taking into account the initial efforts that resulted to the integration of the ASPECS’s outputs to the NASA Community Coordinated Modeling Center (CCMC) SEP Scoreboard [https://ccmc.gsfc.nasa.gov/scoreboards/sep/], with the involvement of NASA SRAG (Space Radiation Analysis Group) and the Moon to Mars (M2M) Space Weather Analysis Office, ADVISOR improves and stabilizes the functionalities and outputs offered by ASPECS. In this work, all technical and scientific refinements and updates are presented.
Name: Mr. Nikolaos Sioulas (UCLA)
Coauthors: No coauthors were included.
Type: Poster
Title: Magnetic field spectral evolution in the inner heliosphere
Abstract:
Leveraging data from the Parker Solar Probe and Solar Orbiter missions, we examine the radial evolution and underlying plasma parameter dependence of power and spectral index anisotropy in the wave vector space of solar wind turbulence, spanning heliocentric distances 0.06 ≤ R ≤ 220 Rs. Our observations reveal that near the Sun, the inertial range is constrained to a narrow range of scales, displaying a power-law exponent of αΒ = -3/2, independent of plasma parameters. Turbulence spectra associated with large magnetic energy excesses and low Alfvénic contents steepen considerably with distance, unlike highly Alfvénic intervals that preserve their near-Sun scaling. As the distance increases, the inertial range extends to larger spatial scales, progressively steepening, on average, towards an αB = -5/3 scaling. Our study also uncovers distinct radial evolutions of anisotropic turbulence signatures in fast (Vsw ≥ 400 km/s) and slow (Vsw ≤ 400 km/s) wind streams. Slow wind streams at Earth's orbit exhibit a "critically balanced" cascade, with anisotropy decreasing with diminishing heliocentric distance. In contrast, fast streams retain their near-Sun anisotropic properties, more closely reflecting a "dynamically aligned" cascade.
Name: Ms. Konstantina Thanasoula (National & Kapodistrian Univ. of Athens)
Coauthors: Katsavrias Christos (Department of Physics, National and Kapodistrian University of Athens, Greece)
Nasi Afroditi (Department of Physics, National and Kapodistrian University of Athens, Greece)
Daglis Ioannis A. (1.Department of Physics, National and Kapodistrian University of Athens, Greece. 2.Hellenic Space Center, Greece)
Balasis Georgios (IAASARS, National Observatory of Athens, Greece)
Sarris Theodore (Department of Electrical Engineering, Democritus University of Thrace, Greece)
Type: Poster
Title: The dependence of radial diffusion coefficients on solar/interplanetary drivers
Abstract:
Radial diffusion driven by Ultra Low Frequency (ULF) waves has been established as one of the most important mechanisms of the radiation belt dynamics because it contributes to relativistic electron enhancements and losses in the outer Van Allen belt. Many previous studies have investigated the dependence of ULF wave power spectral density and radial diffusion coefficients (DLL) on solar wind parameters. In this study, we conduct a statistical analysis of radial diffusion coefficients, which contributes to relativistic electron radial diffusion quantification, in order to look into their dependence on different solar/interplanetary drivers (25 events of Interplanetary Coronal Mass Ejections (ICMEs) and 46 events of Stream Interaction Regions (SIRs) of which the 16 events are SIRs with shock and the 30 events are SIRs without shock). Specifically, we study how the solar wind parameters influence the behavior of radial diffusion coefficients especially when the dynamic pressure of the solar wind is maximized. The data originate from the "SafeSpace" database, which was created using magnetic and electric field measurements by the THEMIS satellites in the 2011-2019 time period and includes radial diffusion coefficients (DLL) and ULF wave power spectral density (https://synergasia.uoa.gr/modules/document/?course=PHYS120). Our results indicate notable differences between ICME and SIR driven disturbances at the ratio of DLLE to DLLB. A significant energy dependence to the ratio of DLLE to DLLB is observed, which is further depending on the radial distance and the different mu values.
Name: Ms. Alexandra Triantopoulou (National & Kapodistrian Univ. of Athens)
Coauthors: Nasi Afroditi (NKUA, Greece)
Katsavrias Christos (NKUA, Greece)
Sandberg Ingmar (SPARC & Aerospace Science and Technology, NKUA, Greece)
Daglis Ioannis A. (NKUA, Greece & Hellenic Space Center, Greece)
Type: Poster
Title: Impact of high-speed solar wind streams on the dynamic variations of the electron population in the outer Van Allen belt
Abstract:
More than half a century after the discovery of Van Allen radiation belts, their dynamics are still not fully understood. The variability of the outer radiation belt electrons is related to geospace disturbances due to the interaction of solar wind with the terrestrial magnetosphere. The relativistic and ultra-relativistic electron population can be enhanced or depleted depending on the balance of the various acceleration and loss mechanisms. This variability depends significantly on the solar wind driver type. One of the most common solar wind drivers that affect, amongst others, the electrons of the outer radiation belt is the High-Speed Streams (HSSs) following Stream Interaction Regions (SIRs). Their effect on the various energetic electron populations is a major theme of space research. In this work, we examine the electron phase space density (PSD) during 30 SIRdriven events that occurred during the RBSP era (2012-2018), in terms of superposed epoch analysis (SEA), for seed, relativistic and ultra-relativistic electrons (μ=100, 1000, 5000 MeV/G). Furthermore, we examine three distinct values of the second adiabatic invariant (K=0.03, 0.09, 0.15 G1/2RE) in order to compare the differences between local acceleration and radial diffusion. In addition, we selected the time of maximum solar wind pressure (Pswmax) as the zero epoch time for all events, with the aim of extracting a statistical study, through time and radial profiles, of the response of the outer belt electron population on this solar wind driver
Name: Prof. Kanaris Tsinganos (National & Kapodistrian Univ. of Athens)
Coauthors: No coauthors were included.
Type: Oral
Title: Title of invited talk: Latest developments in understanding our Sun via recent space probes, in conjuction with the pioneering discoveries of the founder of Solar & Space Physics Eugene Parker
Abstract:
The latest developments and current understanding of our life-giver Sun, the Lydian stone (Λυδία λίθος) of astrophysics and the shaper of Space Weather will be discussed. First, the emergence of the Solar Wind (SW) will be presented, from his cradle in the lowest parts of the superhot solar atmosphere, to its termination at the Heliopause, dramatically affecting in between the terrestrial environment and the entire planetary system. Although the importance of the discovery of the SW for Heliophysics is equivalent to Kepler laws for planetary motion (in a vacuo systema planetarium) and Newton’s laws of motion and universal gravitation which explained them, the original SW paper by Parker, when submitted to the Astrophysical Journal (ApJ), was rejected by two eminent referees. This interesting historical fact will also be noted in the talk, via Parker’s and Chandrasekhar’s (ApJ editor) personal narratives to the speaker. Extension of the universal SW idea to General Relativity and the recent observation of the shadow of the black hole at the centre of the galaxy Messier 87 (M87) together with the powerful jet expelled from the disk around the M87 supermassive black hole, in conjuction with our theoretical predictions, will be also shortly discussed. Next, we shall follow the various solar fireworks and the corresponding plasma physics and magnetohydrodynamics through the pioneering studies and discoveries handed down to us by the greatest Heliospheric and Space physicist of our century, Eugene Parker (1927 – 2022). Finally, some recent findings by the Solar Orbiter and Parker Solar probe spacecrafts orbiting the Sun will be presented, including that of more than 1500 small, flickering coronal brightenings nicknamed “campfires”. These nanoflares, which had not been observed before, seem to represent a previously unseen fine structure of the region where the coronal heating mystery is suspected to be rooted. They can be theoretically understood as the basic inescapable result of the nonequilibrium of nonsymmetric topologies of magnetic fields in the restless and superhot magnetohydrodynamic solar atmosphere.
Name: Prof. Loukas Vlahos (Aristotle University of Thessaloniki)
Coauthors: No coauthors were included.
Type: Oral
Title: Transport of particles in a fractal environment of coherent structures
Abstract:
In a fully developed strongly turbulent magnetized plasma, the coherent structures (current sheets, magnetic filaments, large-amplitude magnetic disturbances, vortices, shocks, tangential discontinuities, etc) form a fractal environment. We will show that the transport of particles in a finite volume of fully developed strong turbulence cannot be analyzed with the Fokker Planck Equation (FPE), and the estimate of the escape time of particles from a finite turbulent volume is not a trivial problem. We will explore several examples of test particle simulations in fully developed MHD strong turbulence from astrophysical and laboratory environments where particles are transported in space and energy. We will show that the proper transport equation to analyze the evolution of the distribution function of particles in a multi-scale environment is the Fractional Transport Equation (FTE), which can be constructed based on the synergy of an MHD code, capturing the large-scale evolution and the formation of the coherent structures, and a test particle code, capturing the kinetic evolution of the particles.
Name: Dr. Eugene Zhuleku (University of Ioannina)
Coauthors: Archontis Vasilis (University of Ioannina)
Type: Oral
Title: 3D MHD magnetic flux emergence simulations of toroidal flux tubes in the Sun
Abstract:
Active regions on the Sun are produced by magnetic flux tubes emerging from the solar interior to the surface. However, previous models based on cylindrical tubes led to sunspots drifting apart for large distances, contradicting observations of sunspots with fixed distance over time. To address this discrepancy, we present results from 3D MHD simulations investigating the emergence of toroidal flux tubes with feet anchored at the base of the numerical box. This approach ensures that the emerging spots will drift apart up to a certain point, depending on the major radius of the initial toroidal tube. Using the Lare3D code, we numerically solve the 3D time-dependent compressible, resistive MHD equations in cartesian coordinates. Our simulations span from the convection zone to the corona, with a plane parallel stratification of the solar interior and atmosphere. We initiate the simulations with a toroidal magnetic flux tube at the bottom of the convection zone and let it rise buoyantly to the surface. We consider cases with and without the inclusion of a pre-existing ambient magnetic field. Our preliminary results indicate that the initial twist and size of the torus significantly impact the dynamics of the flux emergence and eruption of the emerging flux ropes. Specifically, we find that altering the size of the torus or the magnetic twist can lead to a formation and eruption of flux ropes or no eruptions at all. Furthermore, the inclusion of a pre-existing magnetic field can result in the formation of a blowout jet in some cases, while in others only a standard jet is produced. We additionally test the effect of the initial magnetic filed strength on the flux rope formation and eruption. This study presents a novel parameter investigation to identify the underlying physical parameters that govern the formation and eruption of magnetic flux ropes. Our findings have important implications for understanding the processes that drive magnetic flux emergence and eruption in the Sun. They may also provide insights useful for studying large scale eruptions that can impact space weather. Further experimentation of toroidal flux tube emergence in MHD simulations can shed light on the complex interplay between magnetic fields and plasma flows in the solar atmosphere.
Name: Dr. Yannis Zouganelis (European Space Agency)
Coauthors: No coauthors were included.
Type: Oral
Title: Unlocking the Secrets of the Sun: Early Discoveries and Future Prospects of the Solar Orbiter Mission
Abstract:
The ESA/NASA Solar Orbiter mission was launched in 2020 and commenced its nominal science operations in 2022. So far, it has successfully completed three close encounters with the Sun, with the most recent one taking place in April 2023 at a distance of 0.29 au. The mission has yielded an abundance of unique data combining high-resolution imaging and spectroscopy of the Sun with detailed in-situ measurements of the surrounding heliosphere. Solar Orbiter enables us to study the Sun's corona in an unprecedented level of detail, allowing us to determine the link between observed solar wind streams and their source regions on the Sun. Over the course of the ten-year mission, the highly elliptical orbit will progressively become more inclined to the ecliptic plane. Thanks to this new perspective, Solar Orbiter will deliver images and comprehensive data of the unexplored Sun’s polar regions and its far side. This presentation will offer an overview of the mission and summarise the science results obtained during the first three years in orbit. Furthermore, it will provide insight into future science opportunities, particularly in collaboration with other space- and ground-based observatories.