Why is the flare corona so bright for so long?

Advisor: Jiong Qiu

Solar flares are the most energetic events in the solar system. A solar flare releases a large amount of magnetic energy into structures called post-reconnection flare loops (PRFLs) formed by magnetic reconnection. Plasmas in flare loops are heated to more than 10 million kelvin and radiate X-ray and extreme-ultraviolet photons. Observations in the past decades have revealed that flare plasmas cool much more slowly than expected, and it has not been understood what physics governs the slow cooling. Qiu and Longcope (2016) have conducted thought experiments suggesting that *each* of the thousands of PRFLs may have to be heated in two phases, an impulsive intense pulse followed by a more gradual low-magnitude tail heating, to explain the prolonged flare emission. Other scenarios have been proposed considering suppressed thermal conduction by turbulence or PRFL expansion effect. These different mechansims will lead to different assessment of flare heating energy.

In this project, we will test several hypotheses on the underlying mechanisms for slow cooling. We will use an observation-constrained modeling approach, the Ultraviolet Foot-point Calorimeter (UFC) method developed in our group, to model heating and cooling of PRFLs in a solar flare, and examine whether the prolonged emission is caused by suppressed thermal conduction, which redistributes flare energy in time, or by prolonged heating, which requires excess energy into flare heating.

In this project, student will run numerical experiments with different physical parameters characterizing various physical regimes, and compare model results with observed flare emission by the NASA spcecraft, the Solar Dynamics Observatory, to verify or falsify proposed hypotheses. Experience with coding in Python is preferred.