Ground Pc3–Pc5 wave power distribution and response to solar wind velocity variations |
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| Institution: | 1. ST at Code 673, NASA/Goddard Space Flight Center, USA;2. Department of Physics, University of Alberta, Canada;3. Code 672, NASA/Goddard Space Flight Center, USA;4. Department of Astronomy, University of Maryland, USA;1. University of California, Los Angeles, USA;2. The Johns Hopkins University, Laurel, USA;3. Dartmouth College, Hanover, USA;4. University of Minnesota, Minneapolis, USA;1. Department of Radio Science and Engineering, School of Electrical Engineering, Aalto University, Espoo 02150, Finland;2. Center of Space and Atmospheric Research (CSAR), Physical Sciences Department, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114, USA;1. Serena University, La Serena, Chile;2. Space Research Institute, Moscow, Russia;3. Geological and Geophysical Institute of Hungary, Tihany, Hungary;4. University of Santiago de Chile, Santiago, Chile;5. GFZ German Research Centre for Geosciences, Potsdam, Germany;6. Kyushu University, Fukuoka, Japan;1. Centre for Space and Atmospheric Research, Embry-Riddle Aeronautical University, 600 S. Clyde Morris Blvd., Daytona Beach 32114, FL, USA;2. Aalto University, POBox 17800, 00076 AALTO, Finland;1. Max-Planck-Institut für Sonnensystemforschung, 37077 Göttingen, Germany;2. National Institute for Space Research, Sao Jose dos Campos, SP, Brazil;3. Space Research Institute of the Austrian Academy of Sciences, Graz, Austria;1. GPHI UMBC/NASA GSFC, Code 673, Greenbelt, MD 20771, USA;2. Faculty of Problems of Physics and Power Engineering, Moscow Institute of Physics and Technology, Russia;3. NASA Goddard Space Flight Center, Code 674, Greenbelt, MD 20771, USA;1. ETH Zürich, Computer Science Department, Universitätsstrasse 6, 8092 Zürich, Switzerland;2. Paul Scherrer Institute, CH-5234 Villigen, Switzerland;3. MIT, Department of Physics, 77 Massachusetts Avenue, MA 02139, United States;4. China Institute of Atomic Energy, Beijing, 102413, China |
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| Abstract: | We examine the magnetospheric wave power in the Pc3–Pc5 range in terms of its growth and decay characteristics and its distribution in L shell in response to the interplanetary plasma bulk velocity, VSW. We use linear and nonlinear (rank-order) correlation and filtering methods to quantify the effective coupling of the wave power to VSW variations. These methods are applied to measurements from 26 ground magnetometers of the IMAGE array and NOAA's GOES-10 spacecraft at geosynchronous orbit, taken over 2 years of solar-maximum activity (2002–2003). We find that the ground ULF wave power is structured in the range 3.5<L<6.4 and distributed uniformly in the range 6.4<L<15 (uncertainties in L are estimated to be ±0.5). The response of the wave power to the VSW is characterized by an increase starting 3 days before the VSW peak, intensifying several hours before the peak, and is followed by a fast decrease in the next 2 days. The rapid decay of ULF waves has two stages: one at τ=?6±2 h before the solar wind velocity reaches its peak, and one at the VSW peak, τ=0. We suggest that the first one is brought about by wave–particle interaction with inner-magnetospheric populations while the second one is a dVSW/dt effect. The correlation results are confirmed by calculating the finite-impulse response, which shows clearly the decay of the ULF waves after the VSW peak. The response of the wave power at geosynchronous orbit is remarkably similar to that of the ground wave power at comparable L shells. The above findings characterize the inner-magnetospheric response to interplanetary high-speed streams, as opposed to the more short-lived, higher-amplitude response to CMEs. |
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