The effects of driving time scales on coronal heating in a stratified atmosphere

Abstract

Aims: We investigate the atmospheric response to coronal heating driven by random flows with different characteristic time scales and amplitudes. Methods: We conducted a series of 3D MHD simulations of random driving imposed on a gravitationally stratified model of the solar atmosphere. In order to understand differences between alternating current (AC) and direct current (DC) heating, we considered the effects of changing the characteristic time scales of the imposed velocities. We also investigated the effects of the magnitude of the velocity driving. Results: Complex foot point motions lead to a proliferation of current sheets and energy dissipation throughout the corona. For a given amplitude, DC driving typically leads to a greater rate of energy injection when compared to AC driving. This leads to the formation of larger currents, increased heating rates and higher temperatures in DC simulations. There is no difference in the spatial distribution of energy dissipation across simulations, however, energy release events in AC cases tend to be more frequent and last for less time. Higher velocity driving is associated with larger currents, higher temperatures and the corona occupying a larger fraction of the simulation volume. In all cases, most of heating is associated with small energy release events, which occur much more frequently than large events. Conclusions: When combined with observational results showing a greater abundance of power in low frequency modes, these findings suggest that energy release in the corona is likely to be driven by long time scale motions. In the corona, AC and DC driving will occur concurrently and their effects remain difficult to isolate. The distribution of field line temperatures and the asymmetry of temperature profiles may reveal the frequency and longevity of energy release events and therefore the relative importance of AC and DC heating.

14 pages, 15 figures

References in corpus (12)

• Highly Efficient Modeling of Dynamic Coronal Loops
• Coronal heating by MHD waves
• Nonlinear Instability of kink oscillations due to shear motions
• Fine strand-like structure in the solar corona from MHD transverse oscillations
• Nonlinear Fast Magnetoacoustic Wave Propagation in the Neighbourhood of a 2D magnetic X-point: Oscillatory Reconnection
• First direct measurements of transverse waves in solar polar plumes using SDO/AIA
• A global view of velocity fluctuations in the corona below 1.3 $R_{\odot }$ with CoMP
• A Fast and Accurate Method to Capture the Solar Corona/Transition Region Enthalpy Exchange
• Phase mixing of nonlinear Alfven waves
• Chromospheric evaporation and phase mixing of Alfvén waves in coronal loops
• The effects of driving time scales on heating in a coronal arcade
• Forward modelling of heating within a coronal arcade

Cited by in corpus (2)

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