Preliminary analysis of the Changvan neutron monitor operation in latitude surveys during 2019-2020

Abstract

Within our solar system, space weather is influenced by the solar wind and the interplanetary magnetic field carried by the solar wind plasma. Severe solar storms can expose people to increased radiation levels, shut down electrical systems, and interfere with radio signals. Space weather probably affects the weather and climate on our planet, but we do not yet have a precise understanding of the influence. Some aspects of space weather can be monitored at ground level with a detector, such as a “neutron monitor,” that measures cosmic rays from outer space. We have developed a portable “Changvan” neutron monitor to investigate the energy spectrum of cosmic rays and its solar modulation, i.e., variations over the typically 11-year sunspot cycle. The Changvan monitor located inside the insulated shipping container comprises three proportional counters in the standard-design neutron monitors, but the central counter is deficient in the lead producer. This monitor records counting rates during passage through a range of geomagnetic latitudes, which this technique is called “latitude survey.” The ultimate goal of the latitude surveys is to help accurately interpret data from every neutron monitor in a space environment that is always changing. In this work, we show a preliminary analysis of Changvan monitor data collected from two latitude surveys during 2019-2020 on the Chinese icebreaker MV Xue Long from Shanghai, China to Zhongshan station, Antarctica and back. A strong anti-correlation can be observed between the Changvan monitor count rate and barometric pressure.

Analysis of neutron monitor count rates and timing distributions from latitude surveys

“…The Changvan neutron monitor provided count rate data at a one-second resolution, as well as hourly time-delay histograms. We examined the count rate data from Changvan and cleaned it using the onesecond distribution and count rate ratios, following the steps described in section 3 of [8]. Our initial approach involved attempting to correct the count rate data for pressure using a survey in 2019.…”

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

“…Finally, we calculated the hourly average tube ratios (T1/T2, T2/T3, and T3/T1) for both surveys and plotted them on a single long plot as a function of time. Figure 4 in Khamphakdee et al (2021) shows these ratios after correcting for the instrumental issues mentioned earlier. However, the ratios still had some outliers.…”

“…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).…”

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

“…We then made histograms of the 1-second distribution for each tube for each hour. We removed three types of bad seconds from an hour, as reported in [8]. The first type of bad data is obvious outliers that accumulate ≥ 30 counts in one second.…”

“…We used a higher level of deviation for the ratios regarding T2 for greater statistical accuracy. We removed points outside a range of three standard deviations (±3 ) for T3/T1 count rate ratio, four standard deviations (±4 ) the T1/T2 and T2/T3 count rate ratios, all relative to the mean value of the Gaussian distribution [8].…”