Shock propagation and ALMA diagnostics

Background

The solar chromosphere is very dynamic permeated by episodic heating events and propagating acoustic waves that steepen into shocks. It is difficult to observationally determine how the thermodynamic variables, like density and temperature, vary because most diagnostic spectral features formed there are formed outside Local Thermodynamic Equilibrium (LTE) and are very non-linearly and non-locally dependent on the conditions. ALMA provides diagnostics that are more linearly and locally dependent on the physical conditions, thus offering a complementary diagnostic opportunity. Acoustic waves are naturally occuring in stellar atmospheres. They can be excited by specific events but they are also continuously excited by stochastic motions in the convection zone. Because of the density exponentially decreasing with height, waves will get increased amplitude when travelling upwards and will eventually shock. RADYN was originally written to study these waves and shocks (Carlsson & Stein 1992, 1995, 1997).

Goal

The goal of this project is to simulate acoustic waves travelling through the atmosphere and look at the signatures in lines and continua that can be observed with ALMA.

Method

 

1. Use an existing starting model similar to VAL3C.

 

 

Use RADYN with atmdyn.val3c and param.he_flare_em from the radyn/input directory but switch off the beam heating and switch on waves

 

2. Run with various wave parameters.

 

 

Vary amp and period and make sure you get shocks in the upper chromosphere. Start with amp=0.1, period=150 and increase/decrease from there.

 

3. Study diagnostics.

 

 

Especially diagnostics available with ALMA (could be extended to include IRIS diagnostics). This is done using RH and proper model atoms.