Enhancement of hydrogen emission during flare onset and main phase with radiative-hydrodynamic simulations and investigation of their potential for beam diagnostics
Malcolm Druett
Northumbria University
Zharkova, V.V. (Northumbria University) Dobranskis, R.R. (Northumbria University)
In this study we present a comparison of the evolution of flare emissions in IRIS observations during the onset and main phase with updated radiation-hydrodynamical simulations (Zharkova and Kobylinsky 1993). In September 2014, Heinzel and Kleint detected Balmer Continuum enhancement observed with IRIS during the X1 flare SOL2014-03-29 appearing during the flare onset and suggested that the IRIS NUV window could provide a beam precipitation diagnostics, through the inspection of continuum enhancements and possibly by change in Balmer decrements and H-alpha line polarization.

Analysis of this and other data has been conducted in order to determine the mechanisms displaying the enhancements including radiation, thermal processes and non-thermal excitation and ionization caused by electron beams. Beam characteristics for these events are derived from the RHESSI spectra. Resulting continuum enhancements and line emission features are compared to, and explained using, the predictions derived from radiation-hydrodynamical models of elementary flare structures in the presence of electron beams with the characteristics derived from observation.

The numerical method is enhanced by using updated forms of the source functions and higher precision processes, in order to produce more accurate solutions. The solutions are expanded over a time series to explain the evolution of Lyman, Balmer and Paschen continuum enhancements and line profile features throughout the duration of a flare.

Enhancements are then used to diagnose beam characteristics and this method is compared with the beam diagnostic from RHESSI HXR spectra.