Fine structure and motion of the bow shock and particle energisation mechanisms inferred from Magnetospheric Multiscale (MMS) observations
<p>This study presents new observations of fine structure and motion of the bow shock formed in the solar wind, upstream of the Earth's magnetosphere. NASA's Magnetospheric Multiscale (MMS) mission has recorded data during 11 encounters with a shock oscillating with frequency of 1 &l...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-05-01
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| Series: | Annales Geophysicae |
| Online Access: | https://angeo.copernicus.org/articles/40/315/2022/angeo-40-315-2022.pdf |
| Summary: | <p>This study presents new observations of fine structure and motion of the bow shock formed in the solar wind, upstream of the Earth's
magnetosphere. NASA's Magnetospheric Multiscale (MMS) mission has recorded data during 11 encounters with a shock oscillating with frequency of
1 <span class="inline-formula">mHz</span>. Shocks move with a speed of 4–17 <span class="inline-formula">km s<sup>−1</sup></span>; have thickness of 100 <span class="inline-formula">km</span>, i.e. an ion gyroradius; and represent
cascades of compressional magnetic field and plasma density structures of increasing frequencies or smaller spatial scales. Induced density
gradients initiate chains of cross-field current-driven instabilities that heat solar wind ions by the stochastic <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><mover accent="true"><mi>E</mi><mo mathvariant="normal" stretchy="true">̃</mo></mover><mo>×</mo><mi>B</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="c5b90f4b48e0c97ddce090346e963891"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-40-315-2022-ie00001.svg" width="29pt" height="13pt" src="angeo-40-315-2022-ie00001.png"/></svg:svg></span></span> wave
energisation mechanism. The theoretical ion energisation limits are confirmed by observations. We have identified the ion acceleration mechanism
operating at shocks and explained double-beam structures in the velocity space. The nature of this mechanism has been revealed as a stochastic
resonant acceleration (SRA). The results provide for the first time a consistent picture of a chain of plasma processes that generate collisionless
shocks and are responsible for particle energisation.</p> |
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| ISSN: | 0992-7689 1432-0576 |