Fermi-LAT observations of the gamma-ray emission from the quiescent sun - first 6 years in orbit

The quiescent sun is a steady source of high energy gamma-ray emission due to the interactions of cosmic ray (CR) protons and electrons with matter and photons in the solar environment. Such interactions lead to two components of the emission with distinctly different spatial distributions and spectra: a point-like emission from the solar disk due to the CR cascades in the solar atmosphere, and the extended emission from the inverse Compton (IC) scattering of CR electrons off solar photons that is coming from the whole heliosphere. The Fermi-LAT Collaboration has reported the detection of the gamma-ray emission from the quiescent sun in a previous publication, based on the first 18 months of observations. In this paper we present the results of the first 6 years of observations. The new Pass 8 event-level analysis was applied to the data set. Significantly larger photon statistics and better instrument performance allow us to explore both components of the emission in greater details and let us better comparisons of data with current models of the IC component. Moreover, the longer period of observations allows us to study the variations of the emission over the solar cycle.