Development of a Method for Determining the Search Window for Solar Flare Neutrinos

Neutrinos generated during solar flares remain elusive. However, after 50 years of discussion and search, the potential knowledge unleashed by their discovery keeps the search crucial. Neutrinos associated with solar flares provide information on otherwise poorly known particle acceleration mechanisms during a solar flare. For neutrino detectors, the separation between atmospheric neutrinos and solar flare neutrinos is technically encumbered by an energy band overlap. To improve differentiation from background neutrinos, we developed a method to determine the temporal search window for neutrino production during solar flares. Our method is based on data recorded by solar satellites, such as the Geostationary Operational Environmental Satellite (GOES), the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and GEOTAIL. In this study, we selected 23 solar flares above X5.0 class that occurred between 1996 and 2018. We analyzed the light curves of soft X-rays, hard X-rays, $\gamma $ -rays, line $\gamma $ -rays from neutron capture as well as the derivative of soft X-rays. The average search windows are determined as follows: 4178 s for soft X-ray, 700 s for the derivative of soft X-ray, 944 s for hard X-ray (100 – 800 keV), $1{,}586$  s for line $\gamma $ -ray from neutron captures, and 776 s for hard X-ray (above 50 keV). This method allows neutrino detectors to improve their sensitivity to solar flare neutrinos.