* Astronomy

Title: A Flare Observed in Coronal, Transition Region and Helium I 10830 angstrom Emissions
Author: Zhicheng Zeng, Jiong Qiu, Wenda Cao, Philip G. Judge

On June 17, 2012, we observed the evolution of a C-class flare associated with the eruption of a filament near a large sunspot in the active region NOAA 11504. We obtained high spatial resolution filtergrams using the 1.6 m New Solar Telescope at the Big Bear Solar Observatory in broad-band TiO at 706 nm (bandpass:10 angstroms) and He I 10830 angstrom narrow-band (bandpass: 0.5 angstrom, centered 0.25 angstroms to the blue). We analyse the spatio-temporal behavior of the He I 10830 angstrom data, which were obtained over a 90" x 90" field of view with a cadence of 10 sec. We also analyse simultaneous data from the Atmospheric Imaging Assembly and Extreme Ultraviolet Variability Experiment instruments on board the Solar Dynamics Observatory spacecraft, and data from Reuven Ramaty High Energy Solar Spectroscopic Imager and GOES spacecrafts. Non-thermal effects are ignored in this analysis. Several quantitative aspects of the data, as well as models derived using the "0D" Enthalpy-Based Thermal Evolution of Loops model (EBTEL: Klimchuk et al. 2008) code, indicate that the triplet states of the 10830 angstrom multiplet are populated by photoionization of chromospheric plasma followed by radiative recombination. Surprisingly, the He II 304 angstrom line is reasonably well matched by standard emission measure calculations, along with the C IV emission which dominates the AIA 1600 angstrom channel during flares. This work lends support to some of our previous work combining X-ray, EUV and UV data of flares to build models of energy transport from corona to chromosphere.

Read more (4139kb, PDF)