Publication Date:
2014-02-13
Description:
Data from the MESSENGER Neutron Spectrometer (NS) have been used to identify energetic neutrons (0.5–8 MeV energy) associated with solar events that occurred on 4 June 2011. Multiple lines of evidence, including measurements from the NS and the MESSENGER Gamma-Ray Spectrometer, indicate that the detected neutrons have a solar origin. This evidence includes a lack of time-coincident charged particles that could otherwise create local neutrons from nearby spacecraft material as well as enhanced count rates from multiple neutron inelastic scatter gamma-ray lines that are consistent with a large fluence of external neutrons interacting with local spacecraft material. The shape of the energy spectrum of the detected neutrons shows a relative enhancement of neutrons in the energy range 0.8–3 MeV compared with cosmic-ray-generated neutrons from the spacecraft or Mercury. The spectral shape of the measured neutron fluence spectrum is consistent with a previously modeled fluence spectrum of neutrons that originate at the Sun and are propagated through the MESSENGER spacecraft to the NS. These measurements provide a compelling detection of solar neutrons in the energy range 0.5–8 MeV and suggest that a large number of low-energy threshold ion evaporation reactions were taking place on the Sun during the neutron event.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
