First Author: Fritz, T. A.,

Co-Authors: 

Title: The source of energetic particles in the inner magnetosphere,

Reference: Presented on April 29, 2000 at the European Geophysical Society meeting in Nice, France as part of Symposium ST14: Energetic electrons and ions in the inner magnetosphere during geomagnetic storms.

Reference Type: Contributed Talk

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Abstract: 
Energetic particle instrumentation on the Polar satellite has discovered that significant fluxes of energetic particles are continuously present in the region of the dayside magnetosphere where they cannot be stably trapped.  This region is associated with either open magnetic field lines or a magnetic topology associated with pseudo-trapping.  Two distinct features [Time-Energy Dispersion (TED) signatures and Cusp Energetic Particle (CEP) events] are observed in these energetic particle fluxes that strongly suggest a local acceleration of mostly shocked solar wind particles.  These thermalized solar wind fluxes form diamagnetic cavities in the cusp with strong turbulence that apparently energize a fraction of their number to energies of 100s and 1000s of kiloelectronvolts.  The decay of these cavities forms a layer of energetic particles on the magnetopause as well as permits such particles to enter the equatorial nightside magnetosphere to distances as close as s! ix earth radii due to drift caused by gradient and curvature effects in the local geomagnetic field.  The fluxes of these particles have all of the properties associated with the ring current and can probably supply the magnitude of the cross tail current required.   As the magnetopause position is compressed due to a variable solar wind pressure during periods of geomagnetic storms the radial position that these particles arrive in the nightside equatorial plane will be determined by the value of the subsolar compressed magnetic field.   As these particles drift through the inner magnetosphere they cause the extended asymmetric phase of the ring current as they are lost from the opposite flank of the magnetosphere from that which they entered.  Eventually sufficient fluxes are built up at pitch angles away from equatorially mirroring values to permit many particles to complete a full drift around the Earth and the ring current enters the familiar symmetric phase.