Coronal gamma-ray bremsstrahlung from solar flare-accelerated electrons

Krucker, S., Hurford, G.J., MacKinnon, A.L. , Shih, A.Y. and Lin, R.P. (2008) Coronal gamma-ray bremsstrahlung from solar flare-accelerated electrons. Astrophysical Journal Letters, 678(1), L63-L66. (doi: 10.1086/588381)

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The Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) provides for the first time imaging spectroscopy of solar flares up to the γ-ray range. The three RHESSI flares with best counting statistics are analyzed in the 200-800 keV range revealing γ-ray emission produced by electron bremsstrahlung from footpoints of flare loops, but also from the corona. Footpoint emission dominates during the γ-ray peak, but as the γ-ray emission decreases the coronal source becomes more and more prominent. Furthermore, the coronal source shows a much harder spectrum (with power-law indices γ between 1.5 and 2) than the footpoints (with γ between 3 and 4). These observations suggest that flare-accelerated high-energy (~MeV) electrons stay long enough in the corona to lose their energy by collisions producing γ-ray emission, while lower energetic electrons precipitate more rapidly to the footpoints.

Item Type:Articles
Glasgow Author(s) Enlighten ID:MacKinnon, Dr Alexander
Authors: Krucker, S., Hurford, G.J., MacKinnon, A.L., Shih, A.Y., and Lin, R.P.
College/School:College of Social Sciences > School of Education
Journal Name:Astrophysical Journal Letters
ISSN (Online):2041-8213

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
465931Solar, stellar and cosmological plasmas: a synthesis of data, modelling and theory.Declan DiverScience & Technologies Facilities Council (STFC)ST/F002149/1Physics and Astronomy