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Journal Articles The Astrophysical Journal Year : 2022

Strong Perpendicular Velocity-space Diffusion in Proton Beams Observed by Parker Solar Probe

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1
B. Chandran
D. Larson
K. Paulson
B. Alterman
S. Badman
  • Function : Author
S. Bale
J. Bonnell
T. Bowen
J. Verniero
K. Klein
E. Lichko
R. Livi
M. Mcmanus
A. Rahmati
  • Function : Author
D. Verscharen
J. Walters
  • Function : Author
P. Whittlesey

Abstract

Abstract The SWEAP instrument suite on Parker Solar Probe (PSP) has detected numerous proton beams associated with coherent, circularly polarized, ion-scale waves observed by PSP’s FIELDS instrument suite. Measurements during PSP Encounters 4−8 revealed pronounced complex shapes in the proton velocity distribution functions (VDFs), in which the tip of the beam undergoes strong perpendicular diffusion, resulting in VDF level contours that resemble a “hammerhead.” We refer to these proton beams, with their attendant “hammerhead” features, as the ion strahl. We present an example of these observations occurring simultaneously with a 7 hr ion-scale wave storm and show results from a preliminary attempt at quantifying the occurrence of ion-strahl broadening through three-component ion VDF fitting. We also provide a possible explanation of the ion perpendicular scattering based on quasilinear theory and the resonant scattering of beam ions by parallel-propagating, right circularly polarized, fast magnetosonic/whistler waves.
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Dates and versions

insu-03578713 , version 1 (17-02-2022)

Licence

Attribution - CC BY 4.0

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B. Chandran, D. Larson, K. Paulson, B. Alterman, S. Badman, et al.. Strong Perpendicular Velocity-space Diffusion in Proton Beams Observed by Parker Solar Probe. The Astrophysical Journal, 2022, 924 (2), pp.112. ⟨10.3847/1538-4357/ac36d5⟩. ⟨insu-03578713⟩
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