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A Statistical Study to Determine the Origin of Long-duration Gamma-Ray Flares

Journal Article · · The Astrophysical Journal (Online)
 [1];  [2];  [3];  [4]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Colorado, Boulder, CO (United States). Ann and H.J. Smead Aerospace Engineering Sciences
  3. SLAC National Accelerator Lab. and Stanford Univ., Menlo Park, CA (United States). W.W. Hansen Experimental Physics Lab., Kavli Inst. for Particle Astrophysics and Cosmology and Dept. of Physics
  4. National Inst. of Nuclear Physics (INFN), Pisa (Italy)
+ Show Author Affiliations
Two scenarios have been proposed to account for sustained ≥30 MeV gamma-ray emission in solar flares: (1) prolonged particle acceleration/trapping involving large-scale magnetic loops at the flare site, and (2) precipitation of high-energy (>300 MeV) protons accelerated at coronal/interplanetary shock waves. To determine which of these scenarios is more likely, we examine the associated soft X-ray flares, coronal mass ejections (CMEs), and solar energetic proton events for (a) the long-duration gamma-ray flares (LDGRFs) observed by the Large Area Telescope on Fermi, and (b) delayed and/or spatially extended high-energy gamma-ray flares observed by the Gamma-ray Spectrometer on the Solar Maximum Mission, the Gamma-1 telescope on the Gamma satellite, and the Energetic Gamma-Ray Experiment Telescope on the Compton Gamma-Ray Observatory. For the Fermi data set of 11 LDGRFs with >100 MeV emission lasting for ≥~2 hr, we search for associations and reverse associations between LDGRFs, X-ray flares, CMEs, and SEPs, i.e., beginning with the gamma-ray flares and also, in turn, with X-class soft X-ray flares, fast (≥1500 km s-1) and wide CMEs, and intense (peak flux ≥2.67 × 10-3 protons cm-2 s-1 sr-1, with peak to background ratio >1.38) >300 MeV SEPs at 1 au. While LDGRFs tend to be associated with bright X-class flares, we find that only one-third of the X-class flares during the time of Fermi monitoring coincide with an LDGRF. However, nearly all fast, wide CMEs are associated with an LDGRF. These preliminary association analyses favor the proton precipitation scenario, however there is a prominent counter-example of a potentially magnetically well-connected solar eruption with >100 MeV emission for ~10 hr for which the near-Earth >300 MeV proton intensity did not rise above background.
Research Organization:
Los Alamos National Laboratory (LANL)
Sponsoring Organization:
USDOE; National Science Foundation (NSF); Atmospheric and Environmental Research (AER), Lexington, MA (United States)
Grant/Contract Number:
AC52-06NA25396
OSTI ID:
1473799
Report Number(s):
LA-UR-17-27146
Journal Information:
The Astrophysical Journal (Online), Journal Name: The Astrophysical Journal (Online) Journal Issue: 1 Vol. 864; ISSN 1538-4357
Publisher:
Institute of Physics (IOP)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (8)

Source of Energetic Protons in the 2014 September 1 Sustained Gamma-ray Emission Event journal February 2020
On the Shock Source of Sustained Gamma-Ray Emission from the Sun journal November 2019
Magnetic Flux Reconnection in Flaring Active Regions with Sustained Gamma-Ray Emission journal November 2018
The Disappearing Solar Filament of 2013 September 29 and Its Large Associated Proton Event: Implications for Particle Acceleration at the Sun journal May 2019
Comparing Long-duration Gamma-Ray Flares and High-energy Solar Energetic Particles journal July 2019
Fermi -LAT Observations of the 2017 September 10 Solar Flare journal September 2018
Comparing Long-Duration Gamma-Ray Flares and High-Energy Solar Energetic Particles text January 2019
On the Shock Source of Sustained Gamma-Ray Emission from the Sun text January 2019

Figures / Tables (9)

FIG. 1(p. 6)figure FIG. 1
FIG. 2(p. 7)figure FIG. 2
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FIG. 5(p. 11)figure FIG. 5
TABLE 1(p. 14)table TABLE 1
TABLE 2(p. 15)table TABLE 2
TABLE 3(p. 15)table TABLE 3
TABLE 4(p. 16)table TABLE 4

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Related Subjects

58 GEOSCIENCES
79 ASTRONOMY AND ASTROPHYSICS
Heliospheric and Magnetospheric Physics
solar flares