Astrophysics Research Seminar: Professor Philippa Browning, Jodrell Bank Centre

Professor Philippa Browning, of the Jodrell Bank Centre for Astrophysics, University of Manchester, will be presenting a seminar on her research.

Plasma heating and particle acceleration by magnetic reconnection in solar and stellar flares

Abstract: Solar flares are dramatic releases of stored magnetic energy in the solar corona, with signatures across the electromagnetic spectrum due to heating of the plasma and the generation of high-energy electron and ion beams. It is widely accepted that energy is released through the process of magnetic reconnection, but many questions remain. Understanding flares may also shed light on the long-standing question of how the solar corona itself is heated to temperatures of over a million degrees K, as it is likely this results from the combined effect of many small “nanoflares”.

I will describe simulations of confined solar flares in twisted magnetic flux ropes, showing how free magnetic energy may be converted into heat and non-thermal particle kinetic energy through magnetic reconnection. First, energy release in individual flux ropes will be discussed, triggered by the ideal kink instability. Using 3D magnetohydrodynamic simulations coupled with a test-particle code, it will be shown how multiple magnetic reconnections can heat plasma and accelerate charged particles. Forward modelling of the observational signatures in EUV, hard X-rays and microwaves will be described, and the potential for observational identification of twisted magnetic fields discussed. Then, interacting magnetic flux ropes will be considered, showing how instability in a single unstable loop may trigger reconnection with stable neighbours, leading to an "avalanche" of heating events, with important implications for solar coronal heating. Many other stars exhibit flares, and I will discuss recent work on modelling radio emission in flares in T-Tauri stars. In particular, the enhanced radio luminosity of these stars relative to scaling laws for the Sun and other Main Sequence stars will be considered.

All welcome to attend.

Host: Dr Sven van Loo