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Experimental Determination of the Conditions Associated with “Zebra Stripe” Pattern Generation in the Earth’s Inner Radiation Belt
  • Solène Lejosne,
  • Forrest Mozer
Solène Lejosne
University of California, Berkeley

Corresponding Author:solene@berkeley.edu

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Forrest Mozer
University of California, Berkeley
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The “zebra stripes” are peaks and valleys commonly present in the spectrograms of energetic particles trapped in the Earth’s inner belt. Several theories have been proposed over the years to explain their generation, structure and evolution. Yet, the plausibility of various theories has not been tested due to a historical lack of ground-truth, including in-situ electric field measurements. In this work, we leverage the new visibility offered by the database of NASA Van Allen Probes electric drift measurements to reveal the conditions associated with the generation of zebra stripe patterns. Energetic electron flux measurements by the Radiation Belt Storm Probes Ion Composition Experiment between January 1, 2013 and December 31, 2015 are systematically analyzed to determine 370 start times associated with the generation of zebra stripes. Statistical analyses of these events reveal that the zebra stripes are usually created during substorm onset, a time at which prompt penetration electric fields are present in the plasmasphere. All the pieces of experimental evidence collected are consistent with a scenario in which the prompt penetration electric field associated with substorm onset leads to a sudden perturbation of the trapped particle drift motion. Subsequent inner belt drift echoes constitute the zebra stripes. This study exemplifies how the analysis of trapped particle dynamics in the inner belt and slot region provides complimentary information on the dynamics of plasmaspheric electric fields. It is the first time that the signature of prompt penetration electric fields is detected in near‐equatorial electric field measurements below L=3.
Jul 2020Published in Journal of Geophysical Research: Space Physics volume 125 issue 7. 10.1029/2020JA027889