Sequential Small Coronal Mass Ejections Observed In~situ and in White-Light Images by Parker Solar Probe

TL;DR

This study reconstructs the morphology and kinematics of a series of small coronal mass ejections observed by Parker Solar Probe, revealing their sequential nature, magnetic structures, and in situ signatures, advancing understanding of solar wind acceleration.

Contribution

First detailed imaging and modeling of sequential small CMEs by PSP, linking remote sensing with in situ data to understand their structure and origin.

Findings

Six discrete transients identified and modeled.

CME2 first hits PSP, with magnetic flux ropes detected.

In situ data shows signatures consistent with modeled flux ropes.

Abstract

We reconstruct the morphology and kinematics of a series of small transients that erupt from the Sun on 2021 April 24 using observations primarily from Parker Solar Probe (PSP). These sequential small coronal mass ejections (CMEs) may be the product of continuous reconnection at a current sheet, a macroscopic example of the more microscopic reconnection activity that has been proposed to accelerate the solar wind more generally. These particular CMEs are of interest because they are the first CMEs to hit PSP and be simultaneously imaged by it, using the Wide-field Imager for Solar Probe (WISPR) instrument. Based on imaging from WISPR and STEREO-A, we identify and model six discrete transients, and determine that it is the second of them (CME2) that first hits PSP, although PSP later more obliquely encounters the third transient as well. Signatures of these encounters are seen in the PSP in situ data. Within these data, we identify six candidate magnetic flux ropes (MFRs), all but one of which are associated with the second transient. The five CME2 MFRs have orientations roughly consistent with PSP encountering the right sides of roughly E-W oriented MFRs, which are sloping back towards the Sun.