スピーカー：Kledsai Poopakun (チェンマイ大学・タイ)

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

アブストラクト：
The Galactic cosmic ray spectrum manifests pronounced variations over the
11-year sunspot cycle and more subtle variations over the 22-year solar
magnetic cycle. An important tool to study these variations is repeated
latitude surveys with neutron monitors (NMs) onboard icebreakers in
conjunction with land-based references. We revisit 13 annual latitude
surveys from 1994 to 2007 using reference data from the Mawson NM instead
of McMurdo NM (which closed in 2017). We then consider two more latitude
surveys (2018 and 2019) with a monitor similar to the 3NM64 in the previous
surveys but without lead rings around the central tube, a so-called
``semi-leaded neutron monitor.''  The new surveys extend the linear
relationship among data taken at different cutoff rigidity ranges. They
also confirm the ``crossover'' measured near solar minima during epochs of
opposite solar magnetic polarity and the absence of a crossover for epochs
having the same solar magnetic polarity.