# Why switchbacks may be related to solar granulation

Naïs Fargette, Benoit Lavraud, Alexis Rouillard, Victor Réville, Tai Phan, Stuart D. Bale, Thierry Dudok de Wit, Clara Froment, Justin Kasper, Jasper S. Halekas, et al.

<figure><img src="image_1.png" /></figure>

## To cite this version:

Naïs Fargette, Benoit Lavraud, Alexis Rouillard, Victor Réville, Tai Phan, et al. Why switchbacks may be related to solar granulation. vEGU21, 2021, Online, France. 10.5194/egusphere-egu21-15707. insu-03559282

HAL Id: insu-03559282

https://insu.hal.science/insu-03559282

Submitted on 7 Feb 2022

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_3.png" /></figure>

Why switchbacks may be related to solar granulation

**Naïs Fargette**<fnref n="1" />, Benoit Lavraud<fnref n="1" />,<fnref n="2" />, Alexis Rouillard<fnref n="1" />, Victor Réville<fnref n="1" />, Tai Phan<fnref n="3" />, Stuart D. Bale<fnref n="3" />, Thierry Dudok De Wit<fnref n="4" />, Clara Froment<fnref n="4" />, Justin Kasper<fnref n="5" />, Jasper S. Halekas<fnref n="6" />, Philippe Louarn<fnref n="1" />, Anthony W. Case<fnref n="7" />, Kelly E. Korreck<fnref n="7" />, Davin E. Larson<fnref n="3" />, David Malaspina<fnref n="8" />,<fnref n="9" />, Marc Pulupa<fnref n="3" />, Michael L. Stevens<fnref n="7" />, Phyllis L. Whittlesey<fnref n="3" />, and Matthieu Berthomier<fnref n="10" />

Parker Solar Probe data below 0.3 AU have revealed a near-Sun magnetic field dominated by Alfvénic structures that display back and forth reversals of the radial magnetic field. They are called magnetic switchbacks, they display no electron strahl variation consistent with magnetic field foldings within the same magnetic sector, and are associated with velocity spikes during an otherwise calmer background. They are thought to originate either at the photosphere through magnetic reconnection processes, or higher up in the corona and solar wind through turbulent processes.

In this work, we analyze the spatial and temporal characteristic scales of these magnetic switchbacks. We define switchbacks as a deviation from the parker spiral direction and detect them automatically through perihelia encounters 1 to 6. We analyze the solid angle between the magnetic field and the parker spiral both over time and space. We perform a fast Fourier transformation to the obtained angle and find a periodical spatial variation with scales consistent with solar granulation. This suggests that switchbacks form near the photosphere and may be caused, or at least modulated, by solar convection.

<footnote n="1">¹Institut de Recherche en Astrophysique et Planétologie, CNRS, UPS, CNES, Toulouse, France (nais.fargette@irap.omp.eu)</footnote>

<footnote n="2">²Laboratoire d'Astrophysique de Bordeaux, CNRS, Bordeaux, France</footnote>

<footnote n="3">³Space Sciences Laboratory, University of California, Berkeley, Berkeley, CA, USA</footnote>

<footnote n="4">⁴ LPC2E, CNRS and University of Orléans, Orléans, France</footnote>

<footnote n="5">⁵Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, US</footnote>

<footnote n="6">⁶Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa, United States</footnote>

<footnote n="7">⁷Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, US</footnote>

<footnote n="8">⁸Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, USA</footnote>

<footnote n="9">⁹Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA</footnote>

<footnote n="10">¹⁰Laboratoire de Physique des Plasmas, CNRS, Sorbonne Université, Ecole Polytechnique, Observatoire de Paris, Université Paris-Saclay, Paris, France</footnote>