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Megavolt parallel potentials arising from double-layer streams in the Earth's outer radiation belt
F S Mozer1, S D Bale1, J W Bonnell1
1Space Sciences Laboratory, University of California, Berkeley, California 94720, USA.
Physical Review Letters
|January 31, 2014
Summary
Massive electric double layers observed by the Van Allen probes accelerate electrons in Earth's radiation belt. These double layers create significant voltage drops, potentially explaining electron acceleration mechanisms.
Area of Science:
- Space Physics
- Plasma Physics
Background:
- Double layers with electric fields parallel to magnetic field lines are observed in Earth's outer radiation belt.
- These phenomena are linked to in situ relativistic electron acceleration.
Purpose of the Study:
- Investigate the role of double layers in relativistic electron acceleration.
- Determine the characteristics and potential origin of these double layers.
Main Methods:
- Analysis of high time-resolution data from the Van Allen probes.
- Observation of numerous double layers and measurement of parallel potential drops.
Main Results:
- Thousands of double layers were observed in short intervals, generating substantial net parallel potential drops (up to 230,000 V in 1 min, over 1,000,000 V in 6 min).
- The observed double-layer speed matches electron acoustic speed, suggesting a novel electron acoustic mode.
- Instantaneous parallel potential along a magnetic field line reached tens of kilovolts.
Conclusions:
- Double layers are a significant mechanism for accelerating electrons in Earth's radiation belt.
- The findings suggest a new plasma acceleration mode (electron acoustic mode).
- Similar double-layer mechanisms may operate in other planetary magnetospheres, solar flares, and astrophysical contexts.
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