The proposed investigation addresses the problem of solar atmospheric heating via studying non-thermal dynamics during small scale magnetic reconnection in the transition region. Non-thermal energy is…

This is a $531,567 grant awarded by the National Aeronautics and Space Administration (NASA) Shared Services Center to the Bay Area Environmental Research Institute (BAERI), a non-profit research organization. The grant was awarded on June 28, 2018 and has a completion date of June 27, 2022.

The purpose of the grant is to study non-thermal dynamics during small-scale magnetic reconnection events in the solar transition region using data from NASA's Interface Region Imaging Spectrograph (IRIS) spacecraft. The research aims to investigate how these reconnection events and associated energetic electron beams may contribute to heating the lower solar atmosphere. The grant involves a combination of IRIS data analysis, magnetic hydrodynamics simulations, and radiation-hydrodynamics modeling to synthesize observations and test the proposed scenario of non-thermal heating. There was no set-aside designation associated with this contract award.

The proposed investigation addresses the problem of solar atmospheric heating via studying non-thermal dynamics during small scale magnetic reconnection in the transition region. Non-thermal energy is considered to be a substantial fraction of the total energy released by magnetic reconnection and studies of large-scale events such as solar flares have confirmed this point. With the unprecedented spatial and temporal resolution of iris, we are now able to investigate non-thermal dynamics in small-scale, reconnection-driven events. Such events are ubiquitous on the sun and considered as a possible energy source for heating the low solar atmosphere; and non-thermal energy produced during these events could contribute additionally to the local thermal and kinetic energy balance. Non-thermal dynamics often manifest themselves as impulsive brightenings. We will use the iris instrument to identify collimated brightenings originated from small-scale reconnection sites, which appear to be jet like with a plane-of-the-sky apparent velocity (more than 1000 KM/s) significantly higher than the local alfven speed (estimated to be within 200-450 KM/s in the upper chromospheretransition region). They are possibly consequences of non-thermal dynamics because IT is unlikely for local plasma to actually move at such high speeds. Observations of such super-alfvenic jets from iris data were reported in our preliminary work and we proposed that the observation could be due to energetic electron beams, which originate in reconnection sites and deposit their energy in solar atmosphere. We propose to conduct numerical experiments to test the proposed scenario of non-thermal heating. We will use high-resolution MHD simulations of a three-dimensional reconnection site, large-scale radiative MHD simulations, both along with a particle tracer code to investigate the production of energetic electron beams. The results of these simulations will then be used: (1) to synthesize slit-jaw and spectral data and compare with iris observations; and (2) as the input to the radiative-hydrodynamic radyn code to investigate the deposition of the non-thermal energy carried by electron beams into their surrounding plasma as they travel, and compare results with iris observations. We will obtain statistics of such events by collecting and analyzing observations of super-alfvenic jets. The comparison between these observations and the simulations will provide insights into the obscure non-thermal process in the transition region.