Observations of the 1991 June 11 solar flare with COMPTEL

Abstract

The COMPTEL instrument onboard the Compton Gamma-Ray Observatory (CGRO) is sensitive to ),-rays in the energy range from 0.75 to 30 MeV and to neutrons in the energy range from 10 to 100 MeV.During the period of unexpectedly high solar activity in June 1991, several flares from active region 6659 were observed by COMPTEL. For the flare on June 11, we have analyzed the COMPTEL telescope data, finding strong 2.223 MeV line emission, that declines with a time constant of 11.8 minutes during the satellite orbit in which the flare occurs. It remains visible for at least 4 hours. We obtained preliminary values for the 2.2 MeV and 4-7 MeV fluences. Neutrons with energies above 20 MeV have been detected and their arrival time at the Earth is consistent with the v-ray emission during the impulsive phase. ~TRODUCTIONCOMPTEL is a useful instrument for studying solar flares. It is able to measure V -rays in the energy range from 0.75 MeV to 30 MeV and to derive the direction of the incoming radiation. When operating in its full-telescope mode, COMPTEL uses a double scattering of a v-quantum to get spectral and directional information. In this case, Compton scattering of the ),-ray is the fundamental process.

Estimating the impact of the 1991 Pinatubo eruption on mesospheric temperature by analyzing HALOE (UARS) temperature data

“…It is nontrivial to separate a Pinatubo-related signature from other natural contributions (such as a solar signal) when analysing temperature data and this issue could potentially explain some of the disagreements in the observations. The 11-year solar cycle exhibited a maximum around 1990 with several solar flares occurring in June 1991 (Rank et al, 1994). Remsberg (2009) demonstrated that an 11-year oscillation fitted to the HALOE temperature data between 40 • S -40 • N in the middle atmosphere is approximately in phase with solar UV flux measurements for most altitudes.…”

Estimating the impact of the 1991 Pinatubo eruption on mesospheric temperature by analyzing HALOE (UARS) temperature data

“…Kerzenmacher et al, 2006) when analyzing temperature data, and this issue could potentially explain some of the disagreements in the observations. The 11-year solar cycle exhibited a maximum around 1990, with several solar flares occurring in June 1991 (Rank et al, 1994). Remsberg (2009) demonstrated that an 11-year oscillation fitted to the HALOE temperature data between 40 • S-40 • N in the middle atmosphere is approximately in phase with solar UV flux measurements for most altitudes.…”