Session 2: Solar, Planetary and Space Physics

Title:  Solar wind-magnetosphere interaction: energy transfer pathways and their predictability
Author(s):  D. Vassiliadis  Invited Speaker
Contact: Dr  Dimitrios  Vassiliadis, USRA at NASA/GSFC, 

  The coupling of the solar wind to planets has been studied for several decades now. Much of the recent progress in understanding the complexity of the interaction is due to the variability of the magnetospheres in the solar system. The interaction with the terrestrial system is evidently the best known, although by far not the simplest one. The geospace and the surrounding solar wind constitute an input-output system where the various parts of the energy budget are measured simultaneously by a fleet of spacecraft. We integrate these measurements by combining plasma physics and simulation models with system analysis methods.  
  The large-scale energy transfer is dominated by magnetic reconnection and its effects which supply electromagnetic and kinetic energy at the rate of ~10^15 W to the magnetosphere with part of it eventually dissipating at the ionospheric boundary. The storage-release of magnetic energy and its transformation to kinetic energy takes place continually through convection and more explosively during magnetospheric substorms. Long known from its effects, ranging from auroral displays to the more recent disruptions of electric power grid operation, this interaction involves many spatial and temporal pathways: The overall disturbance levels are represented by regional and global magnetic indices. Index time series were the first to be reproduced accurately by nonlinear dynamical systems driven by solar wind parameter data. The models have subsequently been used in prediction of the indices based on real-time interplanetary field and plasma parameters from the ACE and WIND spacecraft ( The model time scales represent the physical responses, namely the directly driven convection and the less predictable substorm. 
  Currently the approach has been extended to modeling the spatial distribution as well as temporal variations. Data from ground magnetometer arrays have replaced the scalar indices to provide magnetic field maps in the polar cap and auroral zone regions. The magnetic field models are coupled to ionospheric conductances from incoherent scatter radar measurements to result in a nonlinear electrodynamic model of the high-latitude ionosphere. This is a 2D projection of the energy storage-release in the overlying magnetosphere. Verification of the model against measurements in representative convection and substorm types will be discussed. At the same time, new missions have revealed the higher-order complexities of this electrodynamic "circuit." Magnetic field measurements from the commercial satellite constellation Iridium have diplayed the large-scale distribution of field-aligned currents coupling the outer magnetosphere to the ionosphere while the detailed structure of the currents and the role of parallel particle acceleration has been further elucidated by NASA's FAST and Polar. Future programs are targeted to continuous monitoring and spatial mapping of the solar wind-magnetosphere coupling effects. The crucial difference with modern campaigns such as "Living with a Star" is that at this point significant attention is paid to the transition from modeling to regular forecasting and operations.