THE RADIATED ENERGY BUDGET OF CHROMOSPHERIC PLASMA IN A MAJOR SOLAR FLARE DEDUCED FROM MULTI-WAVELENGTH OBSERVATIONS

Abstract

This paper presents measurements of the energy radiated by the lower solar\natmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare\n(SOL2011-02-15T01:56) in response to an injection of energy assumed to be in\nthe form of nonthermal electrons. Hard X-ray observations from RHESSI were used\nto track the evolution of the parameters of the nonthermal electron\ndistribution to reveal the total power contained in flare accelerated\nelectrons. By integrating over the duration of the impulsive phase, the total\nenergy contained in the nonthermal electrons was found to be $>2\\times10^{31}$\nerg. The response of the lower solar atmosphere was measured in the free-bound\nEUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II\nat 304\\AA\\ and H I (Ly$\\alpha$) at 1216\\AA\\ by SDO/EVE, the UV continua at\n1600\\AA\\ and 1700\\AA\\ by SDO/AIA, and the WL continuum at 4504\\AA, 5550\\AA, and\n6684\\AA, along with the Ca II H line at 3968\\AA\\ using Hinode/SOT. The summed\nenergy detected by these instruments amounted to $\\sim3\\times10^{30}$ erg;\nabout 15% of the total nonthermal energy. The Ly$\\alpha$ line was found to\ndominate the measured radiative losses. Parameters of both the driving electron\ndistribution and the resulting chromospheric response are presented in detail\nto encourage the numerical modelling of flare heating for this event, to\ndetermine the depth of the solar atmosphere at which these line and continuum\nprocesses originate, and the mechanism(s) responsible for their generation.\n