Probing chromospheric fine structures with an Hα proxy using MURaM
The solar chromosphere consists of poorly understood, dynamic fine structures. In this work we use the MURaM code, which has recently been updated to include the NLTE physics required to treat the chromosphere. Our simulations of an enhanced network element show finely structured chromospheric features, akin to the rapid red and blue shifted excursions (RREs and RBEs) observed in the wings of the Hα line and dynamic fibrils detected in the line core. Using a proxy for Hα, we identify features in the line wings. We find numerous fine structures detected by the proxy to be rooted at the network patches, similar to observations in Hα. These ubiquitous features could play a crucial role in mass and energy supply to the corona. The dynamics of one such feature (RBE) at a Doppler shift of 37km/s shows that flux emergence and consequent reconnection events drive the formation of this feature. Lorentz forces further expand the field and compress the plasma locally. This drives a flow along the field line carrying the feature, making it behave like a jet. It forms in the mid chromosphere (2-4 Mm above the solar surface) and has a lifetime of 246s. It has a maximum length of 3.4 Mm and also shows lateral displacement during its lifetime. There is strong viscous and resistive heating at the birth of the feature which propagates a heating front at Alfv ́enic speeds.
Sanghita Chandra is a PhD student at the Max Planck Institute for Solar System Research in Germany, working with Dr. Robert Cameron and Prof. Sami Solanki. She is using radiative MHD simulations with MURaM-ChE (Chromospheric Extension to the MURaM code) to study fine-structures in the solar chromosphere. She has developed a proxy for Hα using MURaM-ChE. This proxy can be used to identify features in the wings of the Hα line and is being incorporated into MURaM-ChE. She completed her integrated Bachelors and Masters in Physics from the Indian Institute of Science Education and Research, Kolkata in 2022. Her Master’s thesis was ‘Using Kinematic Dynamo Modeling to Probe the Solar Magnetic Cycle’ with Prof. Dibyendu Nandi. She studied the behavior of the solar dynamo with a special focus on solar grand minima episodes. She was a Department of Science and Technology(DST), Government of India – INSPIRE scholar during this time. She was also an Indian Academy of Sciences fellow (2019) and Jagadis Bose National Science Talent Search (JBNSTS) scholar (2015; 2017). Besides running numerical simulations to understand the Sun, she enjoys hiking, Indian classical singing and dance, reading and sports.