Energy and mass transport associated with impulsive spicular flows in solar coronal holes

TL;DR

This study combines MHD simulations and observations to investigate how spicules in solar coronal holes contribute to coronal heating and solar wind acceleration through shock waves, magnetic reconnection, and wave dissipation.

Contribution

It provides new insights into the mechanisms of spicule formation, their role in mass and energy transport, and their impact on coronal heating and solar wind in coronal holes.

Findings

Spicules are driven by shocks and magnetic reconnection caused by surface turbulence.

Spicule upflows sustain the solar wind with a flux above 10^{-9} kg m^{-2} s^{-1}.

Wave dissipation heats the corona to about 1 MK.

Abstract

How the solar atmosphere is heated from a temperature of about $5,000-6,000$\,K in the lower atmosphere to about $1-2$\,MK in the corona has challenged the astrophysical community for about 80 years. The same puzzle exists for the stellar coronae heating as well. In this study, we present a series of findings on solar spicules and their subsequent impact on the corona within a coronal hole environment, characterized by locally open magnetic field lines, combining insights from MHD simulations with observations. We find that the convective and turbulent motions around the solar surface cause plenty of shocks and small-scale magnetic reconnection in the lower atmosphere. The combined effects of shock compression and reconnection outflows then drive the formation of groups of spicules with a quasi-period of about $300$\,s and width of $\sim 200-500$\,km. The spicule upflows provide an averaged mass flux above $10^{-9}$\,kg\,m$^{-2}$\,s$^{-1}$ in the lower corona to sustain the solar wind in coronal holes, and they continuously trigger further new local slow-mode waves and shocks. These waves supply an energy flux of $10-100$\,W\,m$^{-2}$ in the lower corona, and they are dissipated by heat conduction and compression heating to sustain the corona temperature of about $1$\,MK. The results also indicate that the upward propagating disturbances (PDs) observed in extreme ultraviolet (EUV) passbands are caused by both spicule upflows and slow-mode waves and shocks. Our findings help to understand the long standing problem of coronal heating and the origin of solar winds in coronal hole regions.