Physics
Scientific paper
May 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agusmsm22a..04w&link_type=abstract
American Geophysical Union, Spring Meeting 2009, abstract #SM22A-04
Physics
2407 Auroral Ionosphere (2704), 2716 Energetic Particles: Precipitating, 2753 Numerical Modeling, 2772 Plasma Waves And Instabilities (2471), 2790 Substorms
Scientific paper
Shear Alfven waves are a natural plasma mode which propagates along the magnetic field, transmitting energy and information. In the Earth's magnetosphere, shear Alfven waves have been shown to be related to substorm onset, perhaps being the medium by which information regarding the initiation region may propagate to the ionosphere. There may also be a direct relationship between shear Alfven waves and the auroral signatures which signify substorm onset. Numerical simulations and laboratory experiments have demonstrated that shear Alfven waves of short perpendicular extent can support parallel electric fields which accelerate electrons in collisionless plasma typical of magnetospheric conditions. Recent observations using data from the Canadian Geospace Monitoring (CGSM) array and THEMIS ground-based observatories have shown that the onset of ULF wave activity and structuring of the breakup arc can occur to within ˜ 10s of ULF wave activity at geosynchronous orbits, posing the question as to how this rapid magnetosphere- ionosphere coupling can occur. Shear Alfven waves may provide the key: either through direct propagation, or by accelerating electrons in the magnetosphere which communicate the initiation process to the ionosphere. In this talk, we will present simulation results from a self-consistent drift-kinetic numerical model in a night- side magnetic field topology. The simulation code (DK-1D) has been successfully modified to included inhomogeneities in the magnetic field and ambient plasma. The simulation follows the interaction between shear Alfven waves and electrons as they travel through the warm plasma of the central plasma sheet/plasma sheet boundary layer towards the ionosphere. We will also present case studies using a combination of CGSM and THEMIS observations which, together with the simulation results, will address this fundamental question.
Jonathan Rae I.
Rankin Robert
Watt C. E.
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