Publication Date:
2018-06-28
Description:
We present observational evidence of drift resonance between westward propagating odd mode standing ultralow frequency waves and energetic protons. Compressional ∼13 mHz (Pc4 band) waves and proton flux oscillations at 〉50 keV were detected at ∼03 hr magnetic local time by the Arase satellite on 15 April 2017. The azimuthal wave number (m number) is estimated to be ∼−50 from ground observations, while the theory of drift resonance gives m ∼− 49 for odd mode waves and ∼110-keV protons, providing evidence that the drift resonance indeed took place in this event. We also found a steep earthward gradient of proton phase space density, which can quantitatively explain the wave excitation. The observed waves show typical features of giant pulsations (Pgs), regarding local time, m number, and flux oscillations. This study, therefore, has great implications to the field line mode structure and excitation mechanism of Pgs. ©2018. American Geophysical Union. All Rights Reserved.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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