Research Report
ICRR Inter-University Research Program 2021
Research Subject: A joint observation of near earth space through ~100 GeV
cosmic rays using the Akeno and the GRAPES-3 muon telescope
Principal Investigator: Dr. Pravata K. Mohanty
Participating Researchers: Dr. Pravata K. Mohanty, Prof. Sunil K. Gupta, Dr. Mohamed
Rameez, Dr. B. Hari Haran, Dr. Meeran Zuberi, Prof. Akitoshi Oshima, Prof. Toshiyuki
Nonaka, Prof. Koichi Tanaka.
Summary of Research Result：A large area (560 m2) muon telescope based onproportional counters of dimension 6m x 6m x 0.1m each, has been operating in Ooty,
India since 2000 as a part of the GRAPES-3 air shower array with the joint efforts of theIndian and Japanese scientists. The muon telescope records about 4 billion muons every
day, providing an unprecedented high sensitivity in the measurements of the Galactic
cosmic ray modulation, caused by the dynamically changing solar activities. A similar
configuration muon telescope is being operated at the Akeno observatory, Japan, butwith an area of about 15% of the GRAPES-3 muon telescope. The two muon telescopes
have an overlapping field of view of 20% and can provide complementary observations on
the space weather. Visits to Japan by Indian researchers or vice versa was not possible
in the fiscal year 2021 due to the continued covid pandemic and carry over of theapproved budget to fiscal year 2022 was requested. However, regular analysis meetingsand discussions were conducted in virtual mode involving researchers from the Indianand Japan side. An investigation on the solar diurnal anisotropy in the cosmic ray flux
using 21 years of data (2001-2021) recorded by the GRAPES-3 muon telescope wascarried out. Dependence of solar diurnal anisotropy amplitude on the interplanetary
magnetic field was studied and a strong correlation has been observed. The results areunder finalization. The diurnal anisotropy is observed by the ground based detectors as atime variation with a period of 24 hour. However, using the high statistics GRAPES-3data, a spatial map of the diurnal anisotropy could be produced, demonstrating that thediurnal anisotropy is an anisotropy effect in the heliosphere.
The upgrade of the GRAPES-3 muon telescope at Ooty is under progress which will
double the total area for muon observation. It is expected to be completed within a year’stime. The expansion would enhance the GRAPES-3 capability for solar modulation
studies as well as cosmic ray composition and gamma ray studies. The data acquisition
system (DAQ) of the Akeno muon telescope is very old causing breaks in the data
recording, hence it needs to be upgraded. Development efforts for new and efficientelectronics and DAQ for the GRAPES-3 new muon telescope were undertaken in the last
few years and successfully achieved. As a part of the proposal, the Ooty group is helping
out in the upgrade of the DAQ system of the Akeno muon telescope from the outdated
PCI interface to TCP/IP interface which would enable uninterrupted observation ofmuon data. The fabrication of the required system is under progress and will be delivered
to the concerned Japanese researchers for installing in the Akeno muon telescope.

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