Probing chromospheric fine structures with a Hα proxy using MURaM-ChE

Abstract

H$\alpha$ observations of the solar chromosphere reveal dynamic small-scale structures known as spicules at the limb and rapid blue and red shifted excursions (RBEs/RREs) on-disk. We want to understand what drives these dynamic features, their magnetohydrodynamic (MHD) properties and their role in energy and heat transport to the upper solar atmosphere. To do this, we aim to develop a proxy for synthetic H$\alpha$ observations in radiative-MHD simulations to help identify these features. We use the chromospheric extension to the MURaM code (MURaM-ChE) to simulate an enhanced network region. We develop a proxy for H$\alpha$ based on a photon escape probability. This is a Doppler-shifted proxy that we use to identify fine structures in the line wings. We study on-disk features in 3D, obtaining their 3D structure from the absorption coefficient. We validate the H$\alpha$ proxy by comparing it against features detected in the wings of H$\alpha$ synthesized using MULTI3D. We detect numerous small-scale structures rooted at the network patches, similar to observations in H$\alpha$. The dynamics of an example feature (RBE) at a Doppler shift of 37 km/s show that flux emergence and consequent reconnection drive the formation of this feature. Pressure gradient forces build up to drive a flow along the field line carrying the feature, making it a jet. There is strong viscous and resistive heating at the first appearance of the feature associated with the flux emergence. At the same time and location, a heating front appears and propagates along the field lines at speeds comparable to the Alfven velocity. We show that a synthetic observable based on an escape probability is able to reliably identify features observed with the H$\alpha$ spectral line. We demonstrate its applicability by studying the formation, dynamics and properties of an RBE.

16 pages, 15 figures. Accepted for publication in A&A

References in corpus (11)

• Chromospheric Anemone Jets as Evidence of Ubiquitous Reconnection
• Extension of the MURaM radiative MHD code for coronal simulations
• On the generation of solar spicules and Alfvénic waves
• Generation of Solar Spicules and Subsequent Atmospheric Heating
• Search for high velocities in the disk counterpart of type II spicules
• On fibrils and field lines: The nature of H$\alpha$ fibrils in the solar chromosphere
• The Dynamics of Rapid Redshifted and Blueshifted Excursions in the Solar Halpha line
• Spicules and downflows in the solar chromosphere
• H-alpha features with hot onsets III. Fibrils in Lyman-alpha and with ALMA
• Formation of H$\epsilon$ in the solar atmosphere
• On the Response of the Transition Region and the Corona to Rapid Excursions in the Chromosphere

Cited by in corpus (1)

• Statistical properties of spicules in MURaM-ChE