Modeling the 2017 September 10 Long Duration Gamma Ray Flare

Ryan, J.; Nolfo, G. A. de; Gary, D.

doi:10.22323/1.358.1144

Cited by 1 publication

(2 citation statements)

References 6 publications

(8 reference statements)

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“…A natural alternative to the CME-shock scenario is represented by the flare-loop model (Ryan & Lee 1991;Mandzhavidze & Ramaty 1992;Chupp & Ryan 2009;Grechnev et al 2018;Ryan & de Nolfo 2018;de Nolfo et al 2019;Ryan et al 2019;de Nolfo et al 2021). If particles are produced and injected on closed field lines, all of them will tend to precipitate on the solar atmosphere after a relatively long residence time associated with particle trapping and second-order Fermi acceleration.…”

Section: Discussionmentioning

confidence: 99%

“…Despite the significant progress in recent years as a result of the observations of the Fermi Large Area Telescope (LAT; see Ajello et al 2021 and references therein), the involved processes are still controversial. Two main competing scenarios have been proposed to explain the acceleration of the interacting particles responsible for the origin of LDGRFs and their subsequent precipitation into the solar atmosphere: (1) particle trapping with/without continuous acceleration within large (1 R e ) coronal loops, characterized by a delayed onset representing the time required by the ions to exceed the pion production threshold energy (Ryan & Lee 1991;Mandzhavidze & Ramaty 1992;Chupp & Ryan 2009;Grechnev et al 2018;Ryan & de Nolfo 2018;de Nolfo et al 2019;Ryan et al 2019;de Nolfo et al 2021), and (2) coronal mass ejection (CME)-driven shock acceleration, i.e., the dominant mechanism for gradual solar energetic particle (SEP) events measured in situ (Wild et al 1963;Ramaty et al 1987;Cliver et al 1993;Kocharov et al 2015;Pesce-Rollins et al 2015;Plotnikov et al 2017;Gopalswamy et al 2018a;Jin et al 2018;Kahler et al 2018;Kouloumvakos et al 2020). In the latter case, the high-energy photon emission is also referred to as late-phase γ-ray emission (Share et al 2018) or sustained γ-ray emission (Kahler et al 2018).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Statistical Relationship between Long-duration High-energy Gamma-Ray Emission and Solar Energetic Particles

Bruno,

de Nolfo,

Ryan

et al. 2023

ApJ

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Large solar eruptions are often associated with long-duration γ-ray emission extending well above 100 MeV. While this phenomenon is known to be caused by high-energy ions interacting with the solar atmosphere, the underlying dominant acceleration process remains under debate. Potential mechanisms include continuous acceleration of particles trapped within large coronal loops or acceleration at coronal mass ejection (CME)-driven shocks, with subsequent back-propagation toward the Sun. As a test of the latter scenario, previous studies have explored the relationship between the inferred particle population producing the high-energy γ-rays and the population of solar energetic particles (SEPs) measured in situ. However, given the significant limitations on available observations, these estimates unavoidably rely on a number of assumptions. In an effort to better constrain theories of the γ-ray emission origin, we reexamine the calculation uncertainties and how they influence the comparison of these two proton populations. We show that, even accounting for conservative assumptions related to the γ-ray flare, SEP event, and interplanetary scattering modeling, their statistical relationship is only poorly/moderately significant. However, though the level of correlation is of interest, it does not provide conclusive evidence for or against a causal connection. The main result of this investigation is that the fraction of the shock-accelerated protons required to account for the γ-ray observations is >20%–40% for six of the 14 eruptions analyzed. Such high values argue against current CME-shock origin models, predicting a <2% back-precipitation; hence, the computed number of high-energy SEPs appears to be greatly insufficient to sustain the measured γ-ray emission.

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