The acceleration and radiation of solar energetic particles (electrons and ions) interacting with multiple small-scale dissipation regions resulting from the magnetic energy release process, mimicked by a cellular automaton model, is presented. Each burst of magnetic energy release is associated with a reconnecting current sheet (RCS) in which the particles are accelerated by a direct electric field. We calculate the distribution functions of the kinetic energy of the particles and the X-ray spectra and gamma-ray fluxes produced by them. Finally we compare our results with the existing observations.

Magnetic clouds, as subsets of Interplanetary Coronal Mass Ejections, are modulating the interplanetary space. We present six observed magnetic clouds and simulate them according to the circular and the new elliptic cylindrical models. Both models apply to magnetic clouds attached to the sun and the simulations estimate the characteristics of the clouds, such as probable shapes, orientation of their axis, duration, etc. In general, magnetic clouds can be described by closed (attached) cylindrical models, but in cases of constant solar wind speed the elliptic cloud fits better observations than the circular one. (This presentation is supported by the Greek-Czech Bilateral Cooperation).

Magnetic storms are a central element of space weather: they have severe impacts on both space-borne and ground-based technological systems and therefore their prediction is a major goal of the space community. The most widely used statistical describer of magnetic storm activity is the Dst index. Balasis et al. (2006) applied a wavelet analysis technique to the Dst time series and showed that distinctive alterations in the scaling parameters of the index occur as an intense magnetic storm approaches. A similar spectral signature, i.e., transition from anti-persistent to persistent behavior prior to the storm, was not found for the main driver of the Dst index, the VBSouth electric field component. Therefore it was indicated that while the magnetosphere is mostly driven by the solar wind the critical feature of persistency in the magnetosphere is the result of a combination of solar wind and internal magnetospheric activity rather than interplanetary variations alone. Physical mechanisms originating in the magnetosphere and possibly related to the revealed behavior will be discussed.

Gaia, the forthcoming astrometric mission of ESA, will provide unprecedented positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and throughout the Local Group. Gaia data of Extended Objects (galaxies, AGN host galaxies, planetary nebulae etc) require special treatment. The Gaia Division Unit Extended Objects (EO) of CU4 (Object Processing) develops the algorithms for the proper reduction of the corresponding observations. We present the status of progress of its Work Packages, achievements and remaining problems.

Bow shock has been studied so far mostly as a boundary that influences the particles incident from the upstream region (of solar origin). In this study we provide for the first time observational evidence from the EPE and CPME experiments onboard the IMP-8 and the DOK-2 experiment onboard Interball Tail spacecraft that ions leaking from the magnetosphere during storms or substorms are affected by the quasi perpendicular bow shock and are either transmitted into the upstream region or are (temporally) trapped in the magnetosheath, downstream from the shock, in a magnetic configuration opposite to the magnetic mirror. The observations examined in this study suggest that magnetospheric energetic (> 50 keV) ions show general flows along the field lines, in the direction from the magnetosheath toward the interplanetary space, in both sides of the shock (upstream and downstream) and characteristic cross-field anisotropic distributions just downstream from the shock consistent with a ’trapped population’. The IMP-8 and Interball Tail spacecraft observed intensity gradients towards the magnetosheath in a series of successive bow shock crossings (within several hours), which strongly suggest a spatial modulation of magnetospheric ions at the quasi-perpendicular bow shock. Highest peaks of ion intensities and veryt strong spectrum at energies of  100 − 400 keV were observed just at the shock front and suggest additional acceleration of magnetospheric particles at the bow shock. The observations at / near the Earth’s bow shock examined in this study are well explained in terms of the Shock Drift Acceleration (SDA). The phenomenon discussed here appears to be an important mechanism that influences the particle distributions near the Earth’s bow shock and may have important implications in other shocks in our solar system (planetary, heliospheric, interplanetary and corotating shock waves), and the interstellar medium (supernova shocks). An example near the Jovian bow shock is also presented and discussed.

We present energetic ion, magnetic field and plasma observations from the Polar spacecraft in the magnetosheath and the region upstream from the bow shock during the major storm on May 4, 1998. In particular, we concentrate on the examination of the flux-time profiles, pitch angle distributions and energy spectra of the energetic (~<1 MeV) ion bursts observed on May 4, 1998 near the bow shock during four bow shock compressions (~0655, ~0707, ~0920 and 0947). Our analysis revealed: (a) Highest flux peaks in association with bow shock crossings, (b) Field aligned anisotropies suggesting beams from the direction of the bow shock in the upstream region (c) Energy dependent reflection coefficient, (d) Strong cross-field anisotropies downstream from the shock (adjacent magnetosheath), (d) Extremely large values of the downstream magnetic field BD (~ 80 nT), solar wind speed (Vsw ~800 km/sec), magnetic field jump ratio N = BD/BU (~ 4.5), and induced electric field E =|VswxB|, and (e) Quasi-perpendicular bow shock structure with quiet magnetic field. All the above observations are consistent with the major predictions of SDA. We infer, therefore, that energetic ions of a preexisting population of solar origin were accelerated at the quasi-perpendicular bow shock front by drifting on it in the presence of the strong induced electric field and increased their energies. Ions reflected at the bow shock were observed in the upstream region as field aligned beams. Ions transmitted in the downstream region appeared characteristic cross-field anisotropies (Anagnostopoulos and Kaliabetsos, 1994).

Low energy ion flux / spectral modulation and magnetic field directional variations with the Jupiter rotation period (~10 hours) were observed by Ulysses during its Distant Jupiter Encounter, as long as Ulysses moved from north to south heliolatitudes, between days 290/2003 - 90/2004. In general this ~10 hour ion modulation was found to be more evident around times of passage of CIRs and was observed by Ulysses after the detection of Jovian bKOM and nKOM ~10 hours emissions. In addition, characteristic ~40 min periodic variations were often seen superimposed on the ~10 hour flux increases (for example days 348-352/03). However, a more surprising ion phenomenon could be seen observed in the heliosphere between days ~320-332/03. Previous studies have already shown that Ulysses observed the passage of a coronal mass ejection (CME) between d. 320-324 / 03 (Koning et al. [2005]) and that Jovian >~3 MeV electrons werw ejected within the CME (McKibben et al, 2005). On days 329-331 / 03 (25-27, November 2003), a series of ~10h separated short (~1-3 hours) duration low energy (~0.05 - ~2.00 MeV) ion bursts were observed by the spacecraft ACE, which were accompanied by ~10 hour spectral variation of low energy (~40 - ~100 keV) electrons and ~10/5 hour quasi-periodic IMF directional variations. At those times, ACE was at a distance of ~240 RE from Earth and located near IMF lines connecting Sun with Jupiter. The analysis of energetic ion pitch angle distributions suggest that a large scale particle layer was “near” ACE for a long time (~2.5 days) and approached / removed quasi-periodically (~10 hours) from the ACE spacecraft. During the main phase of ACE ion bursts, field aligned flows from the antisunward direction were observed, but a comparison of simultaneous observations at ACE, Goetail, IMP-8 and geostationary spacecrafts (LANL-01A, LANL-02A, LANL-97A, 1994-084, 1991-080, 1990-095) rather suggest that the Earth’s magnetosphere / bow shock was not the source of the ~10 / 5 quasi-periodic ion flows. We believe that the Jovian magnetosphere triggered by the impact of the CIRS (CME) was most probably the source of the ~10 quasi-periodicities in low energy ion observations in the outer (inner) heliosphere during the time period examined in this study.

Our study investigates the importance of substorm-induced electric fields in accelerating ions, which eventually lead to the build-up of the ring current during geospace magnetic storms. For this purpose we use a three-dimensional dynamic ion-tracing model to calculate the particle motion. In order to produce a representative and realistic view of the ring current, a large number of test particles is required. In addition, the investigation of transport and the mechanism of energization for a wide range of initial conditions is critical aspect of our study. This simulation approach imposes high computational needs, while execution times for different initial conditions may significantly vary. Our simulation scenario is being run on a parallel platform to drastically reduce the total execution time. We also experiment with dynamic task scheduling schemes to achieve load balancing of computations and further increase performance. In this way, we are able to produce a large number of maps depicting the temporal and spatial variations of ion energy densities in the inner magnetosphere in reasonable wall-clock times. We have traced both O+ and H+ ions originating in the plasma sheet and we examine their relative influence on the ring current development. The results of the simulation show that for both ion species the inclusion of substorm-induced electric fields renders ion acceleration much more efficient.

In this study we simulate storm-time substorms isolated and periodic ones by using a three-dimensional dynamic ion-tracing model. We follow the transport and acceleration of ions, under the influence of a background convection electric field with a superposed impulsive electric field due to magnetic field dipolarizations, as observed by spacecraft during substorm expansion. We examine the relative influence of O+ and H+ ions originating in the plasma sheet on the ring current development. Maps of the temporal and spatial variations of ion¬ energy densities in the inner magnetosphere are constructed. Initial results suggest that the difference in energization is much more prominent for O+ ions, which have been observed to be preferentially accelerated by substorm-induced electric fields. Multiple periodic substorms have a distinctly cumulative effect on the ring current development, influencing both the earthward penetration and the energization of ions.

We present results from numerical simulations that study the interaction of a pair of twisted, buoyant magnetic flux tubes, which rise from the solar interior into the outer atmosphere of the Sun. The aim of our new model is to reproduce some of the dynamic solar phenomena in a self-consistent manner. We perform non-linear simulations in 2D and 3D numerical experiments by solving the compressible and resistive MHD equations using a Lagrangian remap, shock capturing code (Lare2D). For some aspects of the problem, we consider the evolution of the system using both uniform and locally enhanced resistivity. The two flux tubes start to rise at the same time but from a different height below the photosphere. The leading (first) tube, which is originally located nearer to the surface, rises and eventually expands above the photosphere forming a magnetized atmosphere for the upcoming system (second tube). Current sheets, high-velocity reconnection jets, plasmoids, loop brightnenings and arcade flare-like structures are formed, for the first time in such numerical experiments, self-consistently by the emergence, expansion and the dynamical interaction between the two emerging flux systems.