Change search
ReferencesLink to record
Permanent link

Direct link
Impulsive and long duration high-energy gamma-ray emission from the very bright 2012 march 7 solar flares
Show others and affiliations
2014 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 789, no 1, 20- p.Article in journal (Refereed) Published
Abstract [en]

The Fermi Large Area Telescope (LAT) detected gamma-rays up to 4 GeV from two bright X-class solar flares on 2012 March 7, showing both an impulsive and temporally extended emission phases. The gamma-rays appear to originate from the same active region as the X-rays associated with these flares. The >100 MeV gamma-ray flux decreases monotonically during the first hour (impulsive phase) followed by a slower decrease for the next 20 hr. A power law with a high-energy exponential cutoff can adequately describe the photon spectrum. Assuming that the gamma rays result from the decay of pions produced by accelerated protons and ions with a power-law spectrum, we find that the index of that spectrum is similar to 3, with minor variations during the impulsive phase. During the extended phase the photon spectrum softens monotonically, requiring the proton index varying from similar to 4 to >5. The >30 MeV proton flux observed by the GOES satellites also shows a flux decrease and spectral softening, but with a harder spectrum (index similar to 2-3). Based on these observations, we explore the relative merits of prompt or continuous acceleration scenarios, hadronic or leptonic emission processes, and acceleration at the solar corona or by the fast coronal mass ejections. We conclude that the most likely scenario is continuous acceleration of protons in the solar corona that penetrate the lower solar atmosphere and produce pions that decay into gamma rays. However, acceleration in the downstream of the shock cannot be definitely ruled out.

Place, publisher, year, edition, pages
2014. Vol. 789, no 1, 20- p.
Keyword [en]
Sun: flares, Sun: X-rays, gamma rays
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-148364DOI: 10.1088/0004-637X/789/1/20ISI: 000338103400020ScopusID: 2-s2.0-84902595718OAI: diva2:736416

QC 20140806

Available from: 2014-08-06 Created: 2014-08-05 Last updated: 2014-08-06Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Jackson, Miranda S.
By organisation
Particle and Astroparticle Physics
In the same journal
Astrophysical Journal
Astronomy, Astrophysics and Cosmology

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 25 hits
ReferencesLink to record
Permanent link

Direct link