Generation of proton beams at switchback boundary-like rotational discontinuities in the solar wind

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Autori principali: Lin, Rong, Bacchini, Fabio, He, Jiansen, Pezzini, Luca, Peng, Jingyu
Natura: Preprint
Pubblicazione: 2025
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author Lin, Rong
Bacchini, Fabio
He, Jiansen
Pezzini, Luca
Peng, Jingyu
author_facet Lin, Rong
Bacchini, Fabio
He, Jiansen
Pezzini, Luca
Peng, Jingyu
contents Alfvénic rotational discontinuities (RDs) are abundant in the inner heliosphere and can be used to model the boundary of switchbacks, i.e. Alfvénic magnetic kinks. To investigate the effects of RDs on proton kinetics, we model a pair of switchback-boundary-like RDs with a hybrid Particle-In-Cell (PIC) approach in a 2D system. We find that, at one of the boundary RDs, a significant population of protons remains trapped over long times, creating a secondary beam-like component with temperature anisotropy $T_\perp/T_\|\gtrsim4$ in the proton velocity distribution function that excites ion cyclotron waves within the downstream portion of the transition layer. Further analysis suggests that the static electric field in the vicinity of the RD is the key factor in trapping the protons. This work indicates that switchback boundaries could represent a viable environment for the creation of proton beams in the heliosphere; it also highlights the need to investigate RD sub-structures, especially the embedded current systems of interplanetary RDs. Finally, this paper underscores the importance of high-resolution observations of the solar wind velocity distributions around RDs.
format Preprint
id arxiv_https___arxiv_org_abs_2512_10406
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Generation of proton beams at switchback boundary-like rotational discontinuities in the solar wind
Lin, Rong
Bacchini, Fabio
He, Jiansen
Pezzini, Luca
Peng, Jingyu
Space Physics
Solar and Stellar Astrophysics
Plasma Physics
Alfvénic rotational discontinuities (RDs) are abundant in the inner heliosphere and can be used to model the boundary of switchbacks, i.e. Alfvénic magnetic kinks. To investigate the effects of RDs on proton kinetics, we model a pair of switchback-boundary-like RDs with a hybrid Particle-In-Cell (PIC) approach in a 2D system. We find that, at one of the boundary RDs, a significant population of protons remains trapped over long times, creating a secondary beam-like component with temperature anisotropy $T_\perp/T_\|\gtrsim4$ in the proton velocity distribution function that excites ion cyclotron waves within the downstream portion of the transition layer. Further analysis suggests that the static electric field in the vicinity of the RD is the key factor in trapping the protons. This work indicates that switchback boundaries could represent a viable environment for the creation of proton beams in the heliosphere; it also highlights the need to investigate RD sub-structures, especially the embedded current systems of interplanetary RDs. Finally, this paper underscores the importance of high-resolution observations of the solar wind velocity distributions around RDs.
title Generation of proton beams at switchback boundary-like rotational discontinuities in the solar wind
topic Space Physics
Solar and Stellar Astrophysics
Plasma Physics
url https://arxiv.org/abs/2512.10406