Thermal Imaging of Multi-Temperature Flare Plasma with RHESSI Visibilities A.Caspi S. Krucker, G. Hurford, J. McTiernan Space Sciences Laboratory University of California, Berkeley, CA 94720

2 Motivation – Super-hot plasma Super-hot (T > 30 MK) thermal component discovered in 1981 –Much hotter than measurements from SXR instruments –Later BCS measurements showed super-hot temps were common No direct imaging observations –EUV imagers limited by temp. response –SXR/HXR imagers limited by ∆E/E  Location and origins of super-hot plasma were unknown… (… until now!) (Lin et al. 1981) December 17, 2010AGU Fall 2010

3 Motivation – RHESSI RHESSI: –Observes ~3 keV to ~17 MeV –~1 keV FWHM in SXRs/HXRs –Imaging over arbitrary time/energy bands w/ angular resolution down to ~2 arcsec –Fourier imaging using rotation modulation Routinely observes super-hot component in X-class flares  Can study thermal emission comprehensively to determine the evolution and origins of super-hot plasma December 17, 2010AGU Fall 2010

December 17, 2010AGU Fall Motivation – Multiple temperatures

December 17, 2010AGU Fall Imaging – Multiple sources

December 17, 2010AGU Fall Imaging – Visibilities X-ray visibilities are an exact analog to visibilities in radio astronomy Complex numbers – measurements of the Fourier components of the source Linear – at a given energy and (u,v) point: V tot = V sh + V c … not directly invertible due to energy dependence  Need a normalized representation

December 17, 2010AGU Fall Imaging – Relative visibilities Energy dependence Spatial dependence Measured

December 17, 2010AGU Fall Imaging – Results

Mathematically simple Computationally inexpensive Fully automatable Super-hot and GOES sources are spatially distinct Super-hot is higher, elongated  Likely heated directly in the corona (Caspi & Lin 2010) 9 Imaging – Results December 17, 2010AGU Fall 2010

December 17, 2010AGU Fall Summary Traditional imaging can cause source confusion New technique combines spectroscopy and imaging (using visibilities) to allow visualization of thermal components of spectral model –Completely generalizable for multiple thermal components (e.g. binned DEM model) Super-hot source spatially distinct from cooler GOES plasma Morphology and time evolution suggest formation directly in corona

EXTRA SLIDES

December 17, 2010AGU Fall Relative Visibilities

December 17, 2010AGU Fall Relative Visibilities (generalized)