New insights into the proton precipitation sites in solar flares

Abstract

The Reuven Ramaty High Energy Solar Spectrocopy Imager (RHESSI) $\gamma$-ray observations of the extraordinary GOES X25 flare SOL2003-10-28T11:10 are revisited to investigate previously reported conclusions that flare-accelerated electrons and protons precipitate along spatially separated flare loops. In contrast to previous works which reconstructed 2.223 MeV images over extended time periods ($\sim$20 minutes), we selected shorter integration times of the order of 2 to 3 minutes. Using simulations of the 2.223 MeV profile in combination with observations of the prompt $\gamma$-ray lines from the INTEGRAL mission, we obtain two separated integration time ranges representing the peak of the flare and the start of the decay, respectively. The resulting $\gamma$-ray images are then compared to GONG white-light (WL) observations to identify where along the flaring ribbons electrons and protons precipitation occurs. We point out that previously reported results comparing RHESSI hard X-ray (HXR) and $\gamma$-ray images only hold if the relative time evolution in the two energy ranges is the same. As the decay times for the 28 October 2003 is different at the considered two energy ranges (200-300 keV and around 2.223 MeV), the previously published conclusion that electrons and protons precipitate at different locations is an overstatement. Using shorter integration times reveals that the $\gamma$-ray and HXR sources spatially coincide with the WL flare ribbons. Our key conclusion is that electron and proton precipitation sites coincide with the flare ribbons, suggesting that the electron and proton precipitation sites are the same, at least within RHESSI's imaging capabilities. This result solves the twenty-years-long mystery around the previously reported different electron and proton precipitation sites.

arXiv commentAccepted for publication in A&A. 7 pages, 5 figures. Final version, after all review processes (referee, language editor and proof)

References in corpus (13)

• An Observational Overview of Solar Flares
• Global Energetics of Thirty-Eight Large Solar Eruptive Events
• Properties of Energetic Ions in the Solar Atmosphere from γ -Ray and Neutron Observations
• Continuum Enhancements in the Ultraviolet, the Visible and the Infrared during the X1 flare on 2014 March 29
• The height of a white-light flare and its hard X-ray sources
• On the origin of 3 seismic sources in the proton-rich flare of October 28, 2003
• Properties of the energetic particle distributions during the October 28, 2003 solar flare from INTEGRAL/SPI observations
• Correlation of hard X-ray and white light emission in solar flares
• Imaging Spectroscopy of a White-Light Solar Flare
• Absence of linear polarization in Halpha emission of solar flares
• Gamma-ray emission from the impulsive phase of the 2017 September 06 X9.3 flare
• Heating of the solar photosphere during a white-light flare
• Coupling between magnetic reconnection, energy release, and particle acceleration in the X17.2 2003 October 28 solar flare

Cited by in corpus (1)

• Nonthermal electron acceleration in turbulent post-flare coronal loops