The Common Origin of High-energy Protons in Solar Energetic Particle Events and Sustained Gamma-Ray Emission from the Sun

<p>It has recently been shown that the sustained gamma-ray emission (SGRE) from the Sun that lasts for hours beyond the impulsive phase of the associated flare is closely related to radio emission from interplanetary shocks (Gopalswamy et al. 2019, JPhCS, 1332, 012004, 2019). This relationship supports the idea that >300 MeV protons accelerated by CME-driven shocks propagate toward the Sun, collide with chromospheric protons and produce neutral pions that promptly decay into >80 MeV gamma-rays. There have been two challenges to this idea. (i) Since the location of the shock can be halfway between the Sun and Earth at the SGRE end time, it has been suggested that magnetic mirroring will not allow the high energy protons to precipitate. (ii) Lack of correlation between the number protons involved in the production of >100 MeV gamma-rays (Ng) and the number of protons (Nsep) in the associated solar energetic particle (SEP) event has been reported. In this paper, we show that the mirror ratio problem is no different from that in flare loops where electrons and protons precipitate to produce impulsive phase emissions. We also suggest that the lack of Ng &#8211; Nsep correlation is due to two reasons: (1) Nsep is underestimated in the case of eruptions happening at large ecliptic latitudes because the high-energy protons accelerated near the nose do not reach the observer. (2) In the case of limb events, the Ng is underestimated because gamma-rays from some part of the extended gamma-ray source do not reach the observer.</p>

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Forecasting Solar Energetic Particle Events and Associated False Alarms

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317011036 ◽

2017 ◽

Vol 13 (S335) ◽

pp. 324-327

Author(s):

Bill Swalwell ◽

Silvia Dalla ◽

Robert Walsh

Keyword(s):

Energetic Particle ◽

Solar Energetic Particle ◽

High Energy ◽

False Alarms ◽

Solar Event ◽

Solar Energetic Particle Events ◽

Two Factors ◽

Very High Energy ◽

Solar Events ◽

Very High

AbstractBecause of the significant dangers they pose, accurate forecasting of Solar Energetic Particle (SEP) events is vital. Whilst it has long been known that SEP-production is associated with high-energy solar events, forecasting algorithms based upon the observation of these types of solar event suffer from high false alarm rates. Here we analyse the parameters of 4 very high energy solar events which were false alarms, with a view to reaching an understanding as to why SEPs were not detected at Earth. We find that in each case at least two factors were present which have been shown to be detrimental to SEP production.

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Particle Acceleration in Solar Flares and Coronal Mass Ejections

Symposium - International Astronomical Union ◽

10.1017/s0074180900162746 ◽

2000 ◽

Vol 195 ◽

pp. 15-25

Author(s):

R. P. Lin

Keyword(s):

Particle Acceleration ◽

Energy Release ◽

Coronal Mass Ejections ◽

Solar Flares ◽

Gamma Ray ◽

Solar Energetic Particle ◽

High Energy ◽

Total Rate ◽

Solar Energetic Particle Events ◽

High Energy Particles

The Sun accelerates ions up to tens of GeV and electrons up to 100s of MeV in solar flares and coronal mass ejections. The energy in the accelerated tens-of-keV electrons and possibly ~1 MeV ions constitutes a significant fraction of the total energy released in a flare, implying that the particle acceleration and flare energy release mechanisms are intimately related. The total rate of energy release in transients from flares down to microflares/nanoflares may be significant for heating the active solar corona.Shock waves driven by fast CMEs appear to accelerate the high-energy particles in large solar energetic particle events detected at 1 AU. Smaller SEP events are dominated by ~1 to tens-of-keV electrons, with low fluxes of up to a few MeV/nucleon ions, typically enriched in 3He. The acceleration in gamma-ray flares appears to resemble that in these small electron-3He SEP events.

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High-Energy Solar Gamma-Ray Observations

Highlights of Astronomy ◽

10.1017/s1539299600018700 ◽

1998 ◽

Vol 11 (2) ◽

pp. 755-758

Author(s):

M. Yoshimori ◽

N. Saita ◽

A. Shiozawa

Keyword(s):

Particle Acceleration ◽

Gamma Rays ◽

Solar Flares ◽

Gamma Ray ◽

Solar Maximum ◽

High Energy ◽

The Sun ◽

Long Duration ◽

New Findings ◽

Gamma Ray Emission

In the last solar maximum, gamma-rays associated with solar flares were observed with GRANAT, GAMMA-1, CGRO and YOHKOH. The gamma-ray energies ranged from 100 keV to a few GeV. We obtained several new findings of gamma-ray emission on the Sun: (1) Gamma-ray production in the corona, (2) GeV gamma-ray production in very long duration flares, (3) Electron-rich flares, (4) Gamma-ray lines and solar atmospheric abundances and (5) Possible location of gamma-ray emission. We present the observations of these new findings and discuss high energy phenomena relating to particle acceleration and gamma-ray production during solar flares.

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Variable Ion Compositions of Solar Energetic Particle Events in the Inner Heliosphere: A Field Line Braiding Model with Compound Injections

The Astrophysical Journal ◽

10.3847/1538-4357/ac3233 ◽

2022 ◽

Vol 924 (1) ◽

pp. 22

Author(s):

Fan Guo ◽

Lulu Zhao ◽

Christina M. S. Cohen ◽

Joe Giacalone ◽

R. A. Leske ◽

...

Keyword(s):

Magnetic Field ◽

Energetic Particle ◽

Radial Distance ◽

Solar Energetic Particle ◽

The Sun ◽

Ion Composition ◽

Source Regions ◽

Solar Energetic Particle Events ◽

Composition Ratios ◽

Inner Heliosphere

Abstract We propose a model for interpreting highly variable ion composition ratios in solar energetic particle (SEP) events recently observed by the Parker Solar Probe (PSP) at 0.3–0.45 au. We use numerical simulations to calculate SEP propagation in a turbulent interplanetary magnetic field with a Kolmogorov power spectrum from large scales down to the gyration scale of energetic particles. We show that when the source regions of different species are offset by a distance comparable to the size of the source regions, the observed energetic particle composition He/H can be strongly variable over more than two orders of magnitude, even if the source ratio is at the nominal value. Assuming a 3He/4He source ratio of 10% in impulsive 3He-rich events and the same spatial offset of the source regions, the 3He/4He ratio at observation sites also vary considerably. The variability of the ion composition ratios depends on the radial distance, which can be tested by observations made at different radial locations. We discuss the implications of these results on the variability of ion composition of impulsive events and on further PSP and Solar Orbiter observations close to the Sun.

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Strength of Coronal Mass Ejection‐driven Shocks near the Sun and Their Importance in Predicting Solar Energetic Particle Events

The Astrophysical Journal ◽

10.1086/521716 ◽

2007 ◽

Vol 670 (1) ◽

pp. 849-856 ◽

Cited By ~ 23

Author(s):

Chenglong Shen ◽

Yuming Wang ◽

Pinzhong Ye ◽

X. P. Zhao ◽

Bin Gui ◽

...

Keyword(s):

Coronal Mass Ejection ◽

Energetic Particle ◽

Solar Energetic Particle ◽

The Sun ◽

Solar Energetic Particle Events ◽

Mass Ejection

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Mean High-Energy Ionic Charge States during the September 2017 Solar Energetic Particle Events Observed by ACE and STEREO

10.22323/1.358.1102 ◽

2019 ◽

Author(s):

Allan Labrador ◽

Luke Sollitt ◽

Christina Cohen ◽

Eric Christian ◽

Alan C. Cummings ◽

...

Keyword(s):

Energetic Particle ◽

Solar Energetic Particle ◽

High Energy ◽

Ionic Charge ◽

Solar Energetic Particle Events ◽

Charge States

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Fermi Large Area Telescope observation of high-energy solar flares: constraining emission scenarios

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316000259 ◽

2015 ◽

Vol 11 (S320) ◽

pp. 51-56

Author(s):

Nicola Omodei ◽

Melissa Pesce-Rollins ◽

Vahè Petrosian ◽

Wei Liu ◽

Fatima Rubio da Costa ◽

...

Keyword(s):

Solar Flares ◽

Gamma Ray ◽

Solar Energetic Particle ◽

Cosmic Ray ◽

Impulsive Phase ◽

High Energy ◽

Solar Energetic Particle Event ◽

Emission Scenarios ◽

Large Area ◽

Gamma Ray Emission

AbstractThe Fermi Large Area Telescope (LAT) is the most sensitive instrument ever deployed in space for observing gamma-ray emission >100 MeV. This has also been demonstrated by its detection of quiescent gamma-ray emission from pions produced by cosmic-ray protons interacting in the solar atmosphere, and from cosmic-ray electron interactions with solar optical photons. The Fermi-LAT has also detected high-energy gamma-ray emission associated with GOES M-class and X-class solar flares, each accompanied by a coronal mass ejection and a solar energetic particle event, increasing the number of detected solar flares by almost a factor of 10 with respect to previous space observations. During the impulsive phase, gamma rays with energies up to several hundreds of MeV have been recorded by the LAT. Emission up to GeV energies lasting several hours after the flare has also been detected by the LAT. Of particular interest are the recent detections of three solar flares whose position behind the limb was confirmed by the STEREO satellites. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources.

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