We have developed a regularized inversion method to recover the Differential Emission Measure from solar data (both broad-band imaging and high resolution spectroscopy) using a GSVD approach, detailed in Hannah & Kontar A&A 539, A146 2012 (arXiv version). This is a computationally fast code, produces both vertical and horizontal error estimates, requires no initial guess solution from the user and can force a positive DEM solution.

Download

Download the regularization code and examples [30 KB, zipped archive]
Test with IDL 6.3 to 8.1. SolarSoftWare is recommended but no specific packages are required for the regularization to run. However the SDO/AIA and CHIANTI SolarSoft code is required to run the examples: need "aia chianti" in your SSW instrument list.

A poster demonstrating the regularization method applied to solar data from the Hinode 5 meeting (Oct-2011) is available here [pdf, 1.9MB].

This code is an updated and optimized version of the regularization method used on RHESSI data to obtain electron spectra (Kontar et al. 2004 Sol Phys) available in SSW x-ray package $SSW/packages/xray/idl/inversion/.

The code is distributed under a Creative Commons through the Attribution-Noncommercial-Share Alike 3.0 license (can copy, distribute and adapt the work but full attribution must be given and cannot be used for commercial purposes)

Regularization Code

data2dem_reg.pro
Main driver program

dem_inv_make_constraint.pro
Calculates the chosen constraint matrix

dem_inv_gsvdcsq.pro
Performs GSVD

dem_inv_reg_parameter.pro
Calculates the regularization parameter

dem_inv_reg_parameter_pos.pro
Additional version that calculates reg param and solution for positive case

dem_inv_reg_solution.pro
Calculates the regularized solution

dem_inv_reg_resolution.pro
Calculates the DEM horizontal error (temperature resolution)

dem_inv_confidence_interval.pro
Calculates the DEM vertical error

Example Code

These are batch scripts so are executed as:
IDL> @aia_example
and will calculate the regularized DEM for the simulated data given and plot the regularized DEM, the residuals and the RK matrix (diagonal where regularization robustly worked).

aia_example.pro
SDO/AIA with a Gaussian DEM Model

aia_example_ar.pro
SDO/AIA with the CHINATI Active Region DEM Model

line_example.pro
Hinode/EIS with the CHINATI Quiet Sun DEM Model

Revision History

[08-Mar-2012] Minor changes to include proper reference to paper.

[25-Jan-2012] Minor changes to data2dem_reg.pro so that it no longer returns unnecessary diagnostic information.

[18-Nov-2011] Software available online. Check individual files for revision history prior to release.

Last Updated: 08/03/2012