Cosmic ray survey to Antarctica and coupling functions for neutron component near solar minimum (1996-1997) 1. Methodology and data quality assurance

摘要

During the 1996-1997 austral summer, a 3NM-64 neutron monitor was operated on board the ship Italica to record cosmic ray neutron intensities in ocean areas from Italy to Antarctica and back. Two bare BF3 counters also measured the flux of thermalized neutrons. The main purpose of this research was the determination of an accurate latitude curve of cosmic ray nucleonic intensity during solar minimum to be used for obtaining the coupling function appropriate for this phase of solar cycle. Accuracy was achieved through reliable instrumentation and proper control of the experiment and by determining and applying for the first time all corrections, for (1) changes in vertical atmospheric mass column, by taking into account wind effect; (2) oscillations of the ship produced by sea roughness; (3) atmospheric temperature changes; (4) primary cosmic ray temporal variations including north-south asymmetry; and (5) temporal variations in the cosmic ray east-west effect, caused by asymmetric shielding on the ship. In this paper we describe the experiment, present the complex procedure of data reduction which was required for the survey data, evaluate the intensity changes produced by primary cosmic ray temporal variations, correct the data for meteorological effects, and present the "fully corrected" daily values of neutron intensity as a function of threshold rigidity. Several independent tests are applied to evaluate the quality of the "fully corrected" data and to determine their residual statistical uncertainty. In two companion papers, all meteorological effects are investigated in detail, geomagnetic effects are evaluated, and coupling functions are computed. [References: 35]