Distance of flight of cosmic-ray muons to study dynamics of the upper muosphere

Abstract

The Earth can be divided by main layers, including the atmosphere, geosphere (solid Earth), and biosphere, depending on its predominant component. In this work, the layer of the Earth which constantly contains a high concentration of muons ( ∼ 8×1012 muons) and its upper border are respectively defined as the muosphere and muopause. The altitude of the muosphere spans from the lower stratosphere to the upper crust of the Earth. In order to study its dynamics, the muopause height was spatiotemporally studied with a new kind of technique called the distance of flight (DOF), which utilizes variations in the muon's decay length. In this work, (A) numerical modeling was performed, and it was clarified that seasonal variations in the cosmic muon flux are predominantly ruled by muopause dynamics; (B) the muon data were compared with the balloon-based measurement results, and it was confirmed that muopause dynamics are closely related to lower-stratospheric height variations. Since the muopause is the region spanning the area between the upper troposphere and the lower stratosphere, the potential of the current distant of flight (DOF) approach needs to be further investigated by cross-comparing related case studies and other atmospheric climate datasets.