Chemical composition of solar energetic particle events and their association with ground level enhancement

Solar energetic particle (SEP) events originate from solar flares and coronal mass ejections. Ground level enhancement (GLE) is a sudden increase in the count rate of a ground neutron monitor. When GLE occurs, the associated SEP event shows a large peak intensity and fluence in the proton intensity of the high energy channels in the Geostationary Operational Environmental Satellite (GOES). This study examined the chemical composition ratio at the moment of SEP events to determine what is occurring at the SEP event origin site on the solar surface. This study used the data of the Solar Isotope Spectrometer (SIS) onboard the Advanced Composition Explorer (ACE) satellite for SEP events, which was confirmed by proton intensity data from the GOES satellite. The chemical compositions dur-ing the SEP events with and without GLE related to the solar flares in M5 class were compared. In addition, the solar wind composition in a normal quiet time and the solar photosphere abundance observed by spectroscopy were compared with the selected SEP events. As expected, all elements except helium showed less than a hundredfold increase in intensity at the SEP event periods than on quiet-day events. The helium intensity surged more than a thousandfold increase for SEP events with and without GLE. The abundance of the heavy elements at the periods of the SEP event accompanied by GLE was greater than that of the solar photosphere. Although it is gen-erally believed that the erupted emission of electromagnetic radiation, including gamma and x-rays, called a flare, escapes from the deep undersurface core, the relatively higher abundance of helium compared to other elements at the moment of the flare blowing out the SEP events suggests that nuclear fusion by the magnetic confinement is occurring near the solar surface. (c) 2023 COSPAR. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).