First Experimental Detection of Radiation Belt "Zebra Stripe" Pattern Generation
Abstract
The "zebra stripes" are persistent patterns of the Earth's inner radiation belt. They are noticeable structured peaks and valleys in the spectrograms of trapped energetic particles. Previous works showed that the energy separation between two consecutive peaks (or valleys) in these spectrograms decreases linearly with time. Thus, the width of the "zebra stripes" is similar to a visual timer in that it indicates the time spent since some initial triggering time t=0.
Although several theories have been proposed to describe the structure and evolution of the "zebra stripe" patterns in the Earth's inner belt, they have never been tested experimentally. The objective of this observationally-driven study is to expose the processes triggering the "zebra stripes" of the Earth's inner radiation belt—in other words, to highlight some of the processes driving the dynamics of the inner radiation belt. Years of measurements by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instruments onboard the Van Allen Probes are algorithmically analyzed to determine hundreds of "zebra stripe" triggering events. We report on magnetic activity indices and solar wind parameters observed during these triggering times, together with ground-based and space-based field observations. Preliminary analysis of a sample of events seems to indicate that "zebra stripe" triggering is predominantly associated with times of fast solar wind variations, particularly times when the interplanetary magnetic field (IMF) turns southward. This first result suggests that prompt penetration electric fields are one of the drivers of inner radiation belt dynamics. It is the first time that "zebra stripe" triggering events are detected and analyzed. This study also illustrates how inner belt particle measurements can be used as remote sensing tools to reconstruct electric field time history.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSM54A..03L
- Keywords:
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- 2720 Energetic particles: trapped;
- MAGNETOSPHERIC PHYSICS;
- 2730 Magnetosphere: inner;
- MAGNETOSPHERIC PHYSICS;
- 2772 Plasma waves and instabilities;
- MAGNETOSPHERIC PHYSICS;
- 2774 Radiation belts;
- MAGNETOSPHERIC PHYSICS