Ground Pc3–Pc5 wave power distribution and response to solar wind velocity variations

• Published in: Planetary and space science Vol. 55; no. 6; pp. 743 - 754
• Main Authors: Vassiliadis, D., Mann, I.R., Fung, S.F., Shao, X.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2007
• Subjects: High-speed stream; Magnetic storms; Solar wind–magnetosphere coupling; ULF magnetospheric waves; Viscous interaction; ULF magnetospheric waves; Viscous interaction; Solar wind–magnetosphere coupling; Magnetic storms; High-speed stream
• ISSN: 0032-0633; 1873-5088
• DOI: 10.1016/j.pss.2006.03.012

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, V SW. We use linear and nonlinear (rank-order) correlation and filtering methods to quantify the effective coupling of the wave power to V SW 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 V SW is characterized by an increase starting 3 days before the V SW 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 V SW 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 d V SW/d t effect. The correlation results are confirmed by calculating the finite-impulse response, which shows clearly the decay of the ULF waves after the V SW 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.