Characteristic scales of magnetic switchback patches near the Sun and their possible association with solar supergranulation and granulation

TL;DR

This study analyzes magnetic switchback patches near the Sun using Parker Solar Probe data, revealing their characteristic scales and suggesting they originate from the low solar corona influenced by surface convection patterns.

Contribution

It identifies the spatial scales of magnetic switchbacks and links their formation to solar surface convection, providing new insights into their origin and behavior.

Findings

Periodic spatial modulations match solar granulation and supergranulation scales.

Switchback occurrence depends on the source region, not radial distance.

Switchbacks likely form in the low corona and are modulated by surface convection.

Abstract

Parker Solar Probe (PSP) data recorded within a heliocentric radial distance of 0.3 AU have revealed a magnetic field dominated by Alfv\'enic structures that undergo large local variations or even reversals of the radial magnetic field. They are called magnetic switchbacks, they are consistent with folds in magnetic field lines within a same magnetic sector, and are associated with velocity spikes during an otherwise calmer background. They are thought to originate either in the low solar atmosphere through magnetic reconnection processes, or result from the evolution of turbulence or velocity shears in the expanding solar wind. In this work, we investigate the temporal and spatial characteristic scales of magnetic switchback patches. We define switchbacks as a deviation from the nominal Parker spiral direction and detect them automatically for PSP encounters 1, 2, 4 and 5. We focus in particular on a 5.1-day interval dominated by switchbacks during E5. We perform a wavelet transform of the solid angle between the magnetic field and the Parker spiral and find periodic spatial modulations with two distinct wavelengths, respectively consistent with solar granulation and supergranulation scales. In addition we find that switchback occurrence and spectral properties seem to depend on the source region of the solar wind rather than on the radial distance of PSP. These results suggest that switchbacks are formed in the low corona and modulated by the solar surface convection pattern.