How Nonlinearity Changes Different Parameters in the Solar Corona

Abstract

We consider different velocity amplitudes of incident waves to study nonlinearity effects on the plasma parameters around a magnetic null point in the solar corona. This could query the seismological methods used to observe and interpret damping profiles of oscillations of magnetic structures, based on linear theory. To this end, initially symmetric fast magnetoacoustic waves with three different amplitudes are applied to the system to pursue the effect of nonlinearity on the resulting plasma heating and flows. The dynamic evolution is investigated by solving the resistive MHD equations in a Cartesian domain by the PLUTO code. The considered magnetic null point is surrounded by an initially constant density and temperature plasma. Pursuing the partition of different energy components can shed light on our understanding of the energy release mechanisms. It is found that nonlinear behavior could be the reason for the occurring magnetic reconnection and the related excitation of coronal jets. Furthermore, the fully nonlinear simulation run results in a high temperature and a high current density accumulation and less twisting along the wave accumulation direction, which is even higher than the heating at the magnetic null point itself. Moreover, it is found that there is no significant amplification in the velocity profile. This could be related to the fact that there are not any clear correlations between jets and flares. Furthermore, it is illustrated that the period of the oscillations depends on the amplitude of the initial perturbation, obtaining a shorter period for the fully nonlinear case.

The Effect of Resistivity on the Periodicity of Oscillatory Reconnection

“…Studies have shown, through the use of magnetic field extrapolations from magnetogram observations, that magnetic null points are ubiquitous within the solar atmosphere (e.g., Longcope 2005;Régnier et al 2008). Due to this ubiquity, multiple studies have been made on the role of null points, in particular how they interact with the motion of magnetohydrodynamic (MHD) waves through wave propagation (e.g., McLaughlin & Hood 2004, 2005, 2006aMcLaughlin et al 2011;Sabri et al 2022Sabri et al , 2023 and mode conversion (e.g., McLaughlin & Hood 2006b;Thurgood & McLaughlin 2012;Tarr & Linton 2019;Pennicott & Cally 2021;Yadav et al 2022), but also as sources of slow, fast, and Alfvén waves (e.g., Lynch et al 2014;Karpen et al 2017;Thurgood et al 2017).…”