Imaging spectroscopyImaging spectroscopyin electron spacein electron space

Marco Prato

Pure and Applied Mathematics DepartmentUniversity of Modena and Reggio Emilia, Italy

CNR – INFM LAMIA, Genova, Italy

IX RHESSI WorkshopGenova, September 3rd 2009

www.dima.unige.it/~piana/mida/group.html

Previously…Previously…

Back to spectroscopy…Implementation of a software for the reconstruction of the mean electron flux spectrum in a flare given the X-ray spectrum observed by RHESSI and a cross section

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X-ray spectrum

Mean electron flux spectrum

Bremsstrahlung cross section

Massone A.M., Piana M. and Prato M. 2008, “Regularized solution of the solar bremsstrahlung inverse problem: model dependence and implementation issues”, Inverse Problems in Science and Engineering 16, 523-545

The ideaThe ideaRHESSI – NESSI IV, Paris, 3-4 April 2006

The spectroscopy software can be used here!

X-rays

Electrons

Reformulation of the methodReformulation of the methodTemporal modulation data

Count visibilities Count imagesFourier Transform

Electron imagesElectron visibilities

Regularized Inversion

Fourier Transform

x y

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Piana M., Massone A.M., Hurford G.J., Prato M., Emslie A.G., Kontar E.P. and Schwartz R.A. 2007, “Electron flux spectral imaging of solar flares through regularized analysis of hard X-ray source visibilities”, The Astrophysical Journal 665, 846-855

N.B.: The electron visibilities extend over a greater energy range than the count visibilities!

New testNew testRHESSI – NESSI V, Berkeley, 6-8 November 2006

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New test improvedNew test improved7th RHESSI Workshop, Santa Cruz, 25-29 June 2007

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Local fluxLocal flux7th RHESSI Workshop,

Santa Cruz, 25-29 June 20078th RHESSI Workshop,

Potsdam, 2-6 September 2008

Simulated dataSimulated data8th RHESSI Workshop, Potsdam, 2-6 September 2008

Prato M., Piana M., Emslie A.G., Hurford G.H., Kontar E.P. and Massone A.M., “A regularized visibility-based approach to astronomical imaging spectroscopy”, SIAM Journal on Imaging Sciences, in press

TodayToday

• New method to get electron images of a flare

• Software close to be ready

• Test on simulated data ok

• Test on (few) real data ok

• Need to understand why and how to use it

• Push people to use it

What we can do from electron mapsWhat we can do from electron maps get the variation of the electron spectrum in both space and time

at a more elementary level, "locate" (using centroids) where the electrons are (and the structure of the region in which they propagate), rather than where the X-rays are (which is of diagnostic, but not physical, interest)

locate the region of steepest spectrum, which is most likely the acceleration region itself

examine the variation of electron spectrum with position to understand the physical processes associated with electron propagation in the source (Emslie, Barrett & Brown 2001)

examine source asymmetries in order to better understand the flare geometry, and compare results with other observations (magnetograms, UV images, optical images)