Structured Slow Solar Wind Variability: Streamer-blob Flux Ropes and Torsional Alfv\'en Waves

TL;DR

This paper investigates the structured variability of the slow solar wind, focusing on flux ropes near the heliospheric current sheet and torsional Alfvén waves, using numerical simulations to understand their origins and signatures.

Contribution

It provides a detailed analysis of flux ropes and torsional Alfvén waves in the slow solar wind, linking reconnection processes to observable structures and signatures.

Findings

Reconnection at the heliospheric current sheet forms flux ropes resembling streamer blobs.

Simulated torsional Alfvén waves propagate along S-Web arcs, showing distinct signatures.

Results suggest complex interactions influencing particle acceleration in the solar wind.

Abstract

The slow solar wind exhibits strong variability on timescales from minutes to days, likely related to magnetic reconnection processes in the extended solar corona. Higginson2017b presented a numerical magnetohydrodynamic simulation which showed interchange magnetic reconnection is ubiquitous and most likely responsible for releasing much of the slow solar wind, in particular along topological features known as the Separatrix-Web (S-Web). Here, we continue our analysis, focusing on two specific aspects of structured slow solar wind variability. The first type is present in the slow solar wind found near the heliospheric current sheet, and the second we predict should be present everywhere S-Web slow solar wind is observed. For the first type, we examine the evolution of three-dimensional magnetic flux ropes formed at the top of the helmet streamer belt by reconnection in the heliospheric current sheet (HCS). For the second, we examine the simulated remote and in situ signatures of the large-scale torsional Alfv\'en wave (TAW) which propagates along an S-Web arc to high latitudes. We describe the similarities and differences between the reconnection-generated flux ropes in the HCS, which resemble the well-known "streamer blob'' observations, and the similarly structured TAW. We discuss the implications of our results for the complexity of the HCS and surrounding plasma sheet, and the potential for particle acceleration, as well as the interchange reconnection scenarios which may generate TAWs in the solar corona. We discuss predictions from our simulation results for the dynamic slow solar wind in the extended corona and inner heliosphere.