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SUMMARY:Plasma heating and particle acceleration by magnetic reconnection 
 in solar and stellar flares - Prof. Philippa Browning (Manchester)
DTSTART:20191028T140000Z
DTEND:20191028T150000Z
UID:TALK129196@talks.cam.ac.uk
CONTACT:Chris Hamilton
DESCRIPTION:Solar flares are dramatic releases of stored magnetic energy i
 n the solar corona\, with signatures across the electromagnetic spectrum d
 ue to heating of the plasma and the generation of high-energy (non-thermal
 ) electron and ion beams.  It is widely accepted that energy is released t
 hrough the process of magnetic reconnection\, but many questions remain. U
 nderstanding flares may also shed light on the long-standing question of h
 ow the solar corona itself is heated to temperatures of over a million deg
 rees K\, as it is likely this results from the combined effect of many sma
 ll “nanoflares”.\n\nRelaxation theory in which the magnetic field rela
 xes to a state of minimum energy subject to conserved helicity provides a 
 powerful framework to interpret energy dissipation in flares. I will descr
 ibe models of confined solar flares in twisted magnetic flux ropes\, showi
 ng how  free magnetic energy may be converted into heat and non-thermal pa
 rticle kinetic energy through magnetic reconnection. First\, energy releas
 e   in individual flux ropes will be discussed\, with relaxation triggered
  by the ideal kink instability. Using 3D magnetohydrodynamic simulations c
 oupled with a test-particle code\, it will be shown how multiple magnetic 
 reconnections can both heat plasma and accelerate charged particles.  Forw
 ard modelling of the observational signatures in EUV\, hard X-rays and mic
 rowaves will be described\, and the potential for observational identifica
 tion of twisted magnetic fields discussed. Then\, interacting magnetic flu
 x ropes will be considered\, showing how instability in a single unstable 
 loop may trigger reconnection with stable neighbours\,  leading to an "ava
 lanche" of heating events\, with important implications for solar coronal 
 heating.\n\nMany other stars exhibit flares\, and I will discuss recent wo
 rk on modelling  flares in T-Tauri stars. In particular\, the enhanced rad
 io luminosity of these stars relative to scaling laws for the Sun and othe
 r Main Sequence stars will be considered\, based on a model in which the f
 lare fills a magnetic flux rope with non-thermal electrons.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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