Location
Yosemite National Park
Start Date
2-11-2014 11:30 AM
End Date
2-11-2014 12:00 PM
Description
Plasma waves play a fundamental role in the energization and loss of charged particles in the inner magnetosphere. The free energy for these waves is supplied from the anisotropic ring current ion and electron velocity distributions that develop during geomagnetic storms. To investigate ring current dynamics on a global scale, we use our four-dimensional (4-D) ring current-atmosphere interactions model (RAM-SCB) which evolves the H+, O+, and He+ ion and electron distribution functions in dynamically varying magnetic and electric fields. A distinct feature of RAM-SCB is the use of a self-consistently calculated magnetic field in force balance with the anisotropic ring current plasma pressure. The model boundary was recently expanded from geosynchronous orbit to 9 Re, where the plasma boundary conditions are specified from the empirical plasma sheet model of Tsyganenko and Mukai [2003] based on Geotail data. We simulate the transport, acceleration, and loss of energetic particles from the magnetotail to the inner magnetosphere during several geomagnetic storms that occurred since the launch of the Van Allen Probes in August 2012. We find increased anisotropies in the ion and electron velocity distributions due to dispersed injections and energy dependent drifts and losses. These unstable distributions induce the growth of plasma waves which further affect the near-Earth radiation environment. The linear growth rate of whistler-mode waves maximizes in the dawn local time sector, while electromagnetic ion cyclotron (EMIC) waves are most intense in the afternoon sector in agreement with previous satellite observations. We compare our results with simultaneous plasma and field observations from the Energetic particle, Composition, and Thermal plasma (ECT) and the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigations on the Van Allen Probes. An improved understanding of the highly coupled inner magnetosphere system is provided.
Modeling Wave Generation Processes in the Inner Magnetosphere
Yosemite National Park
Plasma waves play a fundamental role in the energization and loss of charged particles in the inner magnetosphere. The free energy for these waves is supplied from the anisotropic ring current ion and electron velocity distributions that develop during geomagnetic storms. To investigate ring current dynamics on a global scale, we use our four-dimensional (4-D) ring current-atmosphere interactions model (RAM-SCB) which evolves the H+, O+, and He+ ion and electron distribution functions in dynamically varying magnetic and electric fields. A distinct feature of RAM-SCB is the use of a self-consistently calculated magnetic field in force balance with the anisotropic ring current plasma pressure. The model boundary was recently expanded from geosynchronous orbit to 9 Re, where the plasma boundary conditions are specified from the empirical plasma sheet model of Tsyganenko and Mukai [2003] based on Geotail data. We simulate the transport, acceleration, and loss of energetic particles from the magnetotail to the inner magnetosphere during several geomagnetic storms that occurred since the launch of the Van Allen Probes in August 2012. We find increased anisotropies in the ion and electron velocity distributions due to dispersed injections and energy dependent drifts and losses. These unstable distributions induce the growth of plasma waves which further affect the near-Earth radiation environment. The linear growth rate of whistler-mode waves maximizes in the dawn local time sector, while electromagnetic ion cyclotron (EMIC) waves are most intense in the afternoon sector in agreement with previous satellite observations. We compare our results with simultaneous plasma and field observations from the Energetic particle, Composition, and Thermal plasma (ECT) and the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigations on the Van Allen Probes. An improved understanding of the highly coupled inner magnetosphere system is provided.