Physics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsm11b1739l&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #SM11B-1739
Physics
[2730] Magnetospheric Physics / Magnetosphere: Inner, [2752] Magnetospheric Physics / Mhd Waves And Instabilities, [2784] Magnetospheric Physics / Solar Wind/Magnetosphere Interactions
Scientific paper
In this work, we investigate a strong poloidal ULF wave event in the noon sector observed by THEMIS during its coast phase on May 29th, 2007. In this event, five THEMIS probes were lined up in the same outbound path, and consecutively observed narrow-band ULF pulsations in the Pc4 and Pc5 frequency range from 0700UT to 1200UT. This configuration allows us to investigate the spatial and temporal characteristics of the ULF wave activity. The oscillation is strongest in the radial component of the magnetic field and extended in the region from 5 to 9.5 Re at discrete L shells around 1200 LT. The peak frequency of the pulsation decreases with increasing L shell from 10mHz to 4mHz. In the region outside the plasmapause, the wave power decreases and then increases, showing a temporal evolution that appears to be related to the evolution of the plasmasphere. We will also discuss the possible excitation mechanism of this poloidal ULF wave with simultaneous observations of WIND satellite in the solar wind and of Cluster satellites in the magnetosheath. The solar wind velocity is relatively steady and there is no sudden impulse of the solar wind dynamic pressure during this time period. Cluster observe narrow band fluctuations in the number density of the sheath plasma. The frequencies of these fluctuations are similar to the frequencies of some of the narrow-band poloidal pulsations as observed by THEMIS. This correlation seems to support the idea that density fluctuations in the upstream might be responsible for the generation of the poloidal ULF wave at certain location where the local field line resonance frequency matches some of the driving frequencies.
Angelopoulos Vassilis
Ergun Robert E.
Glassmeier K.-
Li Xiaoliang
Liu Wende
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