X-ray and ultraviolet investigation into the magnetic connectivity of a solar flare

LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon Cedex, France
e-mail: hamish.reid@obspm.fr

Received: 8 May 2012
Accepted: 12 July 2012

Abstract

We investigate the X-ray and UV emission detected by RHESSI and TRACE in the context of a solar flare on the 16th November 2002 with the goal of better understanding the evolution of the flare. We analysed the characteristics of the X-ray emission in the 12–25 and 25–50 keV energy range while we looked at the UV emission at 1600  Å . The flare appears to have two distinct phases of emission separated by a 25-s time delay, with the first phase being energetically more important. We found good temporal and spatial agreement between the 25–50 keV X-rays and the most intense areas of the 1600  Å  UV emission. We also observed an extended 100-arcsec  < 25 keV source that appears coronal in nature and connects two separated UV ribbons later in the flare. Using the observational properties in X-ray and UV wavelengths, we propose two explanations for the flare evolution in relation to the spine/fan magnetic field topology and the accelerated electrons. We find that a combination of quasi separatrix layer reconnection and null-point reconnection is required to account for the observed properties of the X-ray and UV emission.