Solar Flares and Alan Gabriel by G A

Solar Flares and Alan Gabriel by G. A. Doschek Space Science Division Naval Research Laboratory Presented at Atomic physics, plasma spectroscopy, and solar physics from space: Celebrating the achievements of Alan Gabriel Institut d’Astrophysique Spatiale CNRS-Université Paris-Sud Orsay, France 20 June 2013 presented by video link from Washington, DC, USA Work supported by 6. 1 NRL/ONR funds

The X-ray Spectrum of Solar Flares • Alan made seminal contributions towards understanding the X-ray spectrum of solar flares, particularly the so-called “satellite lines” produced by dielectronic recombination and electron impact excitation. • A. H. Gabriel – “Dielectronic Satellite Spectra for Highly-Charged Helium-like Ion Lines, Mon. Not. R. astr. Soc. , 160, 99 (1972) 529 citations as of 17 June 2013

The Standard Flare Model: What are the Non-thermal and Bulk Motions?

The NASA OSOs and Solar Maximum Mission, the Japanese Hinotori Mission and the US Do. D P 78 -1 Mission

From Gabriel 1972, Mon. Not. R. astr. Soc. , 160, 99

Solar Flare Iron Line Spectra

Chromospheric Evaporation and Non-thermal Motions in Flares

Non-thermal motions in flares

But alas, it is rather tragic that the high spectral resolution X-ray investigation of flares ceased after Yohkoh! However, highly ionized iron lines appear in the EUV, where spectral-imaging with multi-layer optics can be used (SOHO/CDS, Hinode/EIS)

Fe XXIII Flare Profiles (EIS) 150 km/s

Flare Image and Mass Motions

Flare Observed by Hinode/Extreme-ultraviolet Imaging Spectrometer (EIS)

What Next with Highly Ionized Iron Lines? • We need sensitive imaging X-ray spectrometers that can observe the Fe XXV + satellite lines near 1. 9 Å and the Fe XXVI + satellite lines near 1. 8 Å in the reconnection region. – More sensitive Bragg spectrometers with imaging capabilities? – Microcalorimeters? • We need more sensitive and higher spatial resolution EIS-type instruments (Solar-C? ) with hard X-ray imaging observations (advanced RHESSI? ) • Summary: Alan Gabriel was a key individual in the ground floor investigation of the high temperature components of solar flares