Late Phase Gamma-Ray Emission in Two Flares Observed by RHESSI

In our detailed catalog paper, Share et al. (2018), we define Late Phase Gamma Ray Emission as >100 MeV radiation that is distinctly different from impulsive phase flare emission. This definition includes events known as Long Duration Gamma Ray Flares. But it also allows for short duration events (minutes to tens of minutes) that overlap the impulsive flare emission, such as those observed by Fermi/LAT on 2011/08/09, 2011/09/06, 2011/09/24, 2012/03/07 (first peak), 2012/06/03, 2012/11/27. 2013/04/11, 2013/10/11, and 2014/09/01 that we detail in the appendix of our paper. Another example, is the intense >100 MeV peak detected at 11 UT on 2017/09/10 that has been interpreted as impulsive flare emission, but was shown by Kouloumvakos et al. (2020) to have a time history that is distinct from the flare nuclear-line emission and is naturally explained by CME-shock accelerated protons returning to the Sun. In this presentation we detail our study of the 2003/10/28 and 2005/01/20 events observed by RHESSI where we reveal Late Phase Gamma Ray Emission in the distinct time profiles of >10 MeV emission relative to flare-produced nuclear line emission. Late phase emission was detected up to five hours after the flare in January.