Multiple Sources of Solar High-energy Protons

During the 24th solar cycle, the Fermi Large Area Telescope (LAT) has observed a total of 27 solar flares possessing delayed gamma-ray emission, including the exceptionally well-observed flare and coronal mass ejection (CME) on 2017 September 10. Based on the Fermi/LAT data, we plot, for the first time, maps of possible sources of the delayed >100 MeV gamma-ray emission of the 2017 September 10 event. The long-lasting gamma-ray emission is localized under the CME core. The gamma-ray spectrum exhibits intermittent changes in time, implying that more than one source of high-energy protons was formed during the flare-CME eruption. We find a good statistical correlation between the gamma-ray fluences of the Fermi/LAT-observed delayed events and the products of corresponding CME speed and the square root of the soft X-ray flare magnitude. Data support the idea that both flares and CMEs jointly contribute to the production of subrelativistic and relativistic protons near the Sun.

Automated summary

The study found that both solar flares and coronal mass ejections (CMEs) contribute to the production of subrelativistic and relativistic protons near the Sun. There is a statistical correlation between the gamma-ray fluences of delayed events observed by Fermi/LAT and the products of corresponding CME speed and the square root of the soft X-ray flare magnitude.