The Stability of the Electron Strahl against the Oblique Fast-magnetosonic/Whistler Instability in the Inner Heliosphere
| Autor: | Seong-Yeop Jeong, Joel B. Abraham, Daniel Verscharen, Laura Berčič, David Stansby, Georgios Nicolaou, Christopher J. Owen, Robert T. Wicks, Andrew N. Fazakerley, Jeffersson A. Agudelo Rueda, Mayur Bakrania |
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| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: |
Plasma Physics (physics.plasm-ph)
Astrophysics - Solar and Stellar Astrophysics Physics - Space Physics F300 Space and Planetary Science Physics::Space Physics FOS: Physical sciences Astrophysics::Solar and Stellar Astrophysics Astronomy and Astrophysics F500 Solar and Stellar Astrophysics (astro-ph.SR) Space Physics (physics.space-ph) Physics - Plasma Physics |
| ISSN: | 2041-8205 |
| Popis: | We analyze the micro-kinetic stability of the electron strahl in the solar wind depending on heliocentric distance. The oblique fast-magnetosonic/whistler (FM/W) instability has emerged in the literature as a key candidate mechanism for the effective scattering of the electron strahl into the electron halo population. Using data from Parker Solar Probe (PSP) and Helios, we compare the measured strahl properties with the analytical thresholds for the oblique FM/W instability in the low- and high-$\beta_{\parallel c}$ regimes, where $\beta_{\parallel c}$ is the ratio of the core parallel thermal pressure to the magnetic pressure. Our PSP and Helios data show that the electron strahl is on average stable against the oblique FM/W instability in the inner heliosphere. Our analysis suggests that the instability, if at all, can only be excited sporadically and on short timescales. We discuss the caveats of our analysis and potential alternative explanations for the observed scattering of the electron strahl in the solar wind. Furthermore, we recommend the numerical evaluation of the stability of individual distributions in the future to account for any uncertainties in the validity of the analytical expressions for the instability thresholds. Comment: Accepted in ApJL |
| Databáze: | OpenAIRE |
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