Patches of magnetic switchbacks and their origins

TL;DR

This study analyzes Parker Solar Probe data to investigate the spatial and temporal characteristics of magnetic switchback patches in the solar wind, suggesting their origin is likely linked to solar surface phenomena.

Contribution

It provides evidence that switchback patches have an intrinsic temporal modulation originating at the Sun, independent of the spacecraft's position, and compares magnetic properties between quiescent and active intervals.

Findings

Switchback patches show temporal modulation independent of PSP's position.

Quiescent intervals are less Alfvénic and have shallower power spectra.

Switchback patches may be related to solar surface flux emergence phenomena.

Abstract

Parker Solar Probe (PSP) has shown that the solar wind in the inner heliosphere is characterized by the quasi omni-presence of magnetic switchbacks ("switchback" hereinafter), local backward-bends of magnetic field lines. Switchbacks also tend to come in patches, with a large-scale modulation that appears to have a spatial scale size comparable to supergranulation on the Sun. Here we inspect data from the first ten encounters of PSP focusing on different time intervals when clear switchback patches were observed by PSP. We show that the switchbacks modulation, on a timescale of several hours, seems to be independent of whether PSP is near perihelion, when it rapidly traverses large swaths of longitude remaining at the same heliocentric distance, or near the radial-scan part of its orbit, when PSP hovers over the same longitude on the Sun while rapidly moving radially inwards or outwards. This implies that switchback patches must also have an intrinsically temporal modulation most probably originating at the Sun. Between two consecutive patches, the magnetic field is usually very quiescent with weak fluctuations. We compare various parameters between the quiescent intervals and the switchback intervals. The results show that the quiescent intervals are typically less Alfv\'enic than switchback intervals, and the magnetic power spectrum is usually shallower in quiescent intervals. We propose that the temporal modulation of switchback patches may be related to the "breathing" of emerging flux that appears in images as the formation of "bubbles" below prominences in the Hinode/SOT observations.