The mid-high latitude whistler mode chorus waves observed around substorm onsets |
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Authors: | JunYing Yang JinBin Cao ChunXiao Yan LiuYuan Li and YuDuan Ma |
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Affiliation: | (1) Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, 100080, China;(2) Graduate University of Chinese Academy of Sciences, Beijing, 100039, China |
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Abstract: | Using the data of LFEW/TC-2, we studied the dawn side chorus around substorm onsets during a strong geomagnetic storm in November
2004. During this storm, LFEW/TC-2 observed 14 dawnside chorus events. Nine of them were associated with substorms and occurred
within 40 min around the substorm onsets. The frequencies of waves have a very good correlation with the half equatorial electron
cyclotron frequencies. Chorus can be excited in the region near magnetic equatorial plane and then propagate to the mid and
high latitudes. When the wave frequencies reach the local lower hybrid frequencies, chorus can be reflected due to the lower
hybrid resonance. The time delay between the chorus and its echo is about 28 min. Previous observations show that the chorus
can propagate at most to the magnetic latitudes of 40°. LFEW/ TC-2 found for the first time that the chorus in space could
propagate to the magnetic latitude of 70°. Since most of the previous chorus observations are made close to the magnetic equatorial
plane, our results are important for the studies of excitation and propagation of whistler mode wave, and relevant relativistic
electron acceleration in the magnetosphere.
Supported by the National Natural Science Foundation of China (Grant Nos. 40621003, 40523006, 40704028, 40604018), 973 Program
of China (Grant No. 2006CB806305), and the Specialized Research Fund for State Key Laboratories of China. |
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Keywords: | chorus substorm onset electron acceleration |
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