Modeling magnetohydrodynamics and non equilibrium SoHO/UVCS line emission of CME shocks

Abstract

We provide a guideline to interpret the UVCS emission lines (in particular O VI and Si XII) during shock wave propagation in the outer solar corona. We use a numerical MHD model performing a set of simulations of shock waves generated in the corona and from the result we compute the plasma emission for the O VI and Si XII including the effects of NEI. We analyze the radiative and spectral properties of our model with the support of a detailed radiation model including Doppler dimming and an analytical model for shocks, and, finally, we synthesize the expected O VI 1032A line profile. We explain several spectral features of the observations like the absence of discontinuities in the O VI emission during the shock passage, the brightening of Si XII emission and the width of the lines. We use our model also to give very simple and general predictions for the strength of the line wings due to the ions shock heating and on the line shape for Limb CMEs or Halo CMEs. The emission coming from post-shock region in the solar corona roughly agrees with the emission from a simple planar and adiabatic shock, but the effect of thermal conduction and the magnetic field may be important depending on the event parameters. Doppler dimming significantly influences the O VI emission while Si XII line brightens mainly because of the shock compression. Significant shock heating is responsible for the wide and faint component of the O VI line usually observed which may be taken as a shock signature in the solar corona.

11 pages, 12 figures, 2 appendixes

References in corpus (5)

• Direct Detection of a CME-Associated Shock in LASCO White Light Images
• Collisional Ionization Equilibrium for Optically Thin Plasmas. I. Updated Recombination Rate Coefficients for Bare though Sodium-like Ions
• Far UV Spectra of Fast Coronal Mass Ejections Associated with X-class Flares
• Far Ultraviolet Spectra of a Non-Radiative Shock Wave in the Cygnus Loop
• Heating of Heavy Ions by Interplanetary Coronal Mass Ejection (ICME) Driven Collisionless Shocks

Cited by in corpus (5)

• Three-Dimensional MHD Simulation of the 2003 October 28 Coronal Mass Ejection: Comparison with LASCO Coronagraph Observations
• Origin and Ion Charge State Evolution of Solar Wind Transients during 4 -- 7 August 2011
• Simulating AIA observations of a flux rope ejection
• Reconnection in weakly stochastic B-fields in 2D
• Hydrogen Non-Equilibrium Ionisation Effects in Coronal Mass Ejections