Zhu, Xingyu;
He, Jiansen;
Duan, Die;
Verscharen, Daniel;
Owen, Christopher J;
Fedorov, Andrey;
Louarn, Philippe;
(2023)
Non-field-aligned Proton Beams and Their Roles in the Growth of Fast Magnetosonic/Whistler Waves: Solar Orbiter Observations.
The Astrophysical Journal
, 953
(2)
p. 161.
10.3847/1538-4357/acdc17.
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Abstract
The proton beam is an important population of the non-Maxwellian proton velocity distribution in the solar wind, but its role in wave activity remains unclear. In particular, the velocity vector of the proton beam and its influence on wave growth/damping have not been addressed before. Here we explore the origin and the associated particle dynamics of a kinetic wave event in the solar wind by analyzing measurements from Solar Orbiter and comparing them with theoretical predictions from linear Vlasov theory. We identify the waves as outward-propagating circularly polarized fast magnetosonic/whistler (FM/W) waves. The proton’s velocity distribution functions can destabilize FM/W waves. According to linear Vlasov theory, the velocity fluctuations of the core and the beam associated with FM/W waves render the original field-aligned background drift velocity non-field-aligned. This non-field-aligned drift velocity carrying the information of the velocity fluctuations of the core and the beam is responsible for the wave growth/damping. Specifically, for the FM/W waves we analyze, the non-field-aligned fluctuating velocity of the beam population is responsible for the growth of these unstable waves in the presence of a proton beam. In contrast, the core population plays the opposite role, partially suppressing the wave growth. Remarkably, the observed drift velocity vector between the core and the beam is not field aligned during an entire wave period. This result contrasts the traditional expectation that the proton beam is field aligned.
| Type: | Article |
|---|---|
| Title: | Non-field-aligned Proton Beams and Their Roles in the Growth of Fast Magnetosonic/Whistler Waves: Solar Orbiter Observations |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/acdc17 |
| Publisher version: | https://doi.org/10.3847/1538-4357/acdc17 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third-party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10175572 |
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