Akeno Muon Observations: Japan-India Collaborative Research on Near-Earth Space in 2024

Ground-based observations of cosmic rays provide one of the most effective methods for investigating the effects of solar activity in near-Earth space. The Akeno muon telescope, which employs a detection technique and energy threshold similar to those of the GRAPES-3 muon telescope,serves as a complementary observation system. The field of view of the Akeno telescope overlaps by approximately 20% with that of GRAPES-3 at a distance of 25 Earth radii. By utilizing the multidirectional observation capabilities of both muon telescopes—located in Japan and India—it becomes possible to resolve the global anisotropy of cosmic rays and its precise temporal and spatial evolution. Such observations not only advance our understanding of the fundamental mechanisms governing cosmic ray propagation in the interplanetary magnetic field (IMF) but also contribute to the early detection of solar activity-induced phenomena. From June 2024 to June 2025, a large number of solar flares, coronal mass ejections, and geomagnetic storms were recorded. During this period, both the Akeno and GRAPES-3 telescopes successfully captured multiple variations in cosmic ray intensity associated with these solar events, including several clear Forbush Decreases. This report presents an overview of these observations without interpretation, demonstrating the effectiveness of the joint observation system for space weather monitoring.