Modeling of ground albedo neutrons to investigate seasonal cosmic ray‐induced neutron variations measured at high‐altitude stations

Abstract

This paper investigates seasonal cosmic ray‐induced neutron variations measured over a long‐term period (from 2011 to 2016) in both the high‐altitude stations located in medium geomagnetic latitude and Antarctica (Pic‐du‐Midi and Concordia, respectively). To reinforce analysis, modeling based on ground albedo neutrons simulations of extensive air showers and the solar modulation potential was performed. Because the local environment is well known and stable over time in Antarctica, data were used to validate the modeling approach. A modeled scene representative to the Pic‐du‐Midi was simulated with GEANT4 for various hydrogen properties (composition, density, and wet level) and snow thickness. The orders of magnitudes of calculated thermal fluence rates are consistent with measurements obtained during summers and winters. These variations are dominant in the thermal domain (i.e., En < 0.5 eV) and lesser degree in epithermal and evaporation domains (i.e., 0.5 eV < En < 0.1 MeV and 0.1 MeV < En < 20 MeV, respectively). Cascade neutron (En > 20 MeV) is weakly impacted. The role of hydrogen content on ground albedo neutron generation was investigated with GEANT4 simulations. These investigations focused to mountain environment; nevertheless, they demonstrate the complexity of the local influences on neutron fluence rates.

Analysis of the Forbush Decreases and Ground‐Level Enhancement on September 2017 Using Neutron Spectrometers Operated in Antarctic and Midlatitude Stations

“…Thanks to the CHINSTRAP project, neutron spectra were recorded since December 2015, including periods during solar events. Neutron spectra dynamics can be investigated in the framework of long‐term (Hubert, Pazianotto, et al, ; i.e., CR seasonal variations) and short‐term (solar events) analyses.…”

“…Significant FD events occurring in August 2011 and March 2012 were recorded by the neutron spectrometer operated in the Pic du Midi observatory (Cheminet, Hubert, Lacoste, Boscher, et al, ; Hubert, Pazianotto, et al, ). Figure presents the amplitude A FD measured during these previous events as well as data obtained during the September 2017 event at the Pic du Midi and Concordia station.…”

“…Analyses of previous events provide similar trends, for example, a certain homogeneity of amplitude for epithermal, evaporation, and cascade domains, while thermal energies are more impacted. It is not simple to physically explain this phenomenon, but it could be explained due to the thermalization process of the scene of albedo neutrons which favor the reinforcement of the thermal energies (Rühm et al, ; Hubert, ; Hubert, Pazianotto, et al, ).…”

Status and Perspectives on the Cosmic‐Ray Neutron Method for Soil Moisture Estimation and Other Environmental Science Applications

“…Repeating the field experiment using different neutron detector systems at different environmental settings may clarify the application. Additionally, more well‐defined energy ranges may be inferred from measurements using a neutron spectrometer composed of detectors of various moderator thicknesses (e.g., Bonners Spheres) (Hubert et al, 2016). An alternative approach is to model the response of neutron detectors using information on the composition and the dimension of the neutron detectors.…”

Experimental Evidence of Ground Albedo Neutron Impact on Soft Error Rate for Nanoscale Devices

“…Previous works [7] [8] investigated the impact of ground albedo neutrons in spectrum, particularly in the thermal, epithermal and evaporation domains. The objective was to interpret the neutron fluxes dynamics recorded in high altitude stations (in the Pic-du-Midi in French Pyrenees and the Concordia polar station) and to correlate these variations according to the hydrogen content mainly induced by precipitations and snowfalls.…”