Response functions of semi-leaded neutron monitor count rates and leader rates from latitude surveys during 2019-2020

Abstract

We have developed a portable neutron monitor ("Changvan") with three sections to investigate cosmic ray spectral variations via latitude surveys. The Changvan uses the NM64 design for two sections, but the third lacks the lead producer, so we call this a "semi-leaded" neutron monitor. The Changvan was operated on two voyages on the Chinese icebreaker Xuelong between Shanghai and Antarctica during 2019 and 2020. Repeated measurements with the same detector over different phases of the solar cycle provide precise information about cosmic ray spectral variation. In addition, we tested two techniques to track spectral variations, which can be implemented at fixed stations. The count rate ratio of unleaded vs. leaded counters varies with geomagnetic cutoff rigidity, indicating sensitivity to the cosmic ray spectrum. Histograms of the time delay between successive neutron counts determine the leader fraction, also used to monitor short-term and solar-cycle spectral variations. We report measurements of the response functions of the count rates and leader rates of the unleaded and leaded counters during these two latitude surveys.

Solar Magnetic Polarity Effect on Neutron Monitor Count Rates: Comparing Latitude Surveys and Antarctic Stations

“…The We used count rate data provided in Khamphakdee et al (2021) for the complete survey data in 2018 and only the southbound data in 2019. We obtained additional data in the 2019 survey year from Yakum et al (2022). We present an overview of the data as a function of time in Figure 3 for both survey years.…”

Solar Magnetic Polarity Effect on Neutron Monitor Count Rates: Comparing Latitude Surveys and Antarctic Stations

“…Solar Modulation Effect on Neutron Monitor The tracks of the ship-borne neutron monitor latitude surveys conducted during the periods of 1994-2007 [1] and 2019-2020 [6,7] are overlaid onto a contour map of the vertical cutoff rigidity (GV) calculated for February 11, 2019 at 12:00 UT. we used count rate data provided in [6].…”

“…we used count rate data provided in [6]. For additional data in the 2019 survey year, we obtained it from [7].…”