Constraining Differential Emission Measure and Energy Estimates for Microflares and Active Regions by Combining SDO/AIA and RHESSI
Abstract
Direct diagnostics of the fundamental parameters of solar coronal phenomena remains an active and challenging goal. Constrained, spatially resolved values of many parameters, such as the magnetic field strength, temperature, emission measure, and energy, are often difficult to achieve. However, the advent of the Atmospheric Imaging Assembly (AIA) on board SDO provides us with greater opportunity to pursue these measurements.
Here, we present differential emission measure (DEM) analysis of a selection of recent microflares and hot active regions, utilising a combination of high temperature RHESSI data, and forward-fitting temperature mapping, a procedure developed by Achwanden et al. (2011) for SDO/AIA. This procedure models the plasma temperature as a Gaussian distribution, and uses the instrument response functions to find the distribution which best reproduces the observed fluxes in each AIA wavelength. The accuracy of the method is examined, including an investigation of uncertainties and the temperature range over which the DEM is reasonably constrained. We also study the ability of the method to accurately represent the flux in all of the AIA wavelengths simultaneously. This technique is combined with RHESSI spectral data to produce complementary time-dependent DEM measurements for four microflares from June - August 2011, and one set of post-flare loops from 2010 October 16. In general, the high temperature emission measure fitted by RHESSI has a steeper spectral index than that observed with AIA. However, we illustrate how the high temperature RHESSI data can be used to further inform the AIA fitting procedure, improving the results. We also expand on the AIA forward fitting to produce spatial energy maps of microflares and active regions, also allowing estimates of the total energy of these regions to be made.- Publication:
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American Astronomical Society Meeting Abstracts #220
- Pub Date:
- May 2012
- Bibcode:
- 2012AAS...22050905I