부산대학교 도서관

We investigate the near-Earth observation of interplanetary protons and electrons that result from the in-flight beta decay of low-energy (1-10 MeV) solar neutrons. We use in situ measurements throughout solar cycle 23 of 1-11 MeV protons and 50--400keV electrons by the 3DP experiment on board the Wind spacecraft. We select a sample of isolated large (X-class) eastern hemisphere flares occurring during quiescent interplanetary conditions with the goal of discriminating neutron-decay particles from primary solar energetic particles. Unfortunately, all major flares of solar cycle 23 have to be excluded, with the largest flare in our sample being a X3.6 flare. For these relatively small event sizes, no in situ events due to the decay of solar flare neutrons are observed by Wind. From the one event with simultaneous γ-ray observations, we estimate the expected signal of neutron-decay protons in the Wind/3DP detectors. We use theoretical calculations of the spectrum of escaping neutrons at the Sun combined with an interplanetary propagation model to predict the neutron-decay proton spectrum expected near the Earth. We find that the expected spectrum is indeed well below the background intensities. However, using the estimates derived from the largest solar event of cycle 23 (2003 October 28) and assuming the flare would have occurred isolated in the eastern hemisphere, a clear signal above 5 MeV is expected to be seen. [ABSTRACT FROM AUTHOR]