Van Allen Probes Bibliography is from August 2012 through September 2021 Notice:
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A positive correlation between energetic electron butterfly distributions and magnetosonic waves in the radiation belt slot region
Author | Yang, Chang; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Wang, Shui; Spence, H.; Reeves, G.; Baker, D.; Blake, J.; Funsten, H.; |
Keywords | butterfly distributions; Electron acceleration; Landau resonance; magnetosonic wave; Radiation belt; Van Allen Probes; Wave-particle interaction |
Abstract | Energetic (hundreds of keV) electrons in the radiation belt slot region have been found to exhibit the butterfly pitch angle distributions. Resonant interactions with magnetosonic and whistler-mode waves are two potential mechanisms for the formation of these peculiar distributions. Here we perform a statistical study of energetic electron pitch angle distribution characteristics measured by Van Allen Probes in the slot region during a three-year period from May 2013 to May 2016. Our results show that electron butterfly distributions are closely related to magnetosonic waves rather than to whistler-mode waves. Both electron butterfly distributions and magnetosonic waves occur more frequently at the geomagnetically active times than at the quiet times. In a statistical sense, more distinct butterfly distributions usually correspond to magnetosonic waves with larger amplitudes and vice versa. The averaged magnetosonic wave amplitude is less than 5 pT in the case of normal and flat-top distributions with a butterfly index BI = 1 but reaches \~ 35\textendash95 pT in the case of distinct butterfly distributions with BI > 1.3. For magnetosonic waves with amplitudes >50 pT, the occurrence rate of butterfly distribution is above 80\%. Our study suggests that energetic electron butterfly distributions in the slot region are primarily caused by magnetosonic waves. |
Year of Publication | 2017 |
Journal | Geophysical Research Letters |
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Number of Pages | |
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Date Published | 03/2017 |
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URL | http://doi.wiley.com/10.1002/2017GL073116 |
DOI | 10.1002/2017GL073116 |