Seminar Title: OTSO (v1.3.0+) – Functions and Applications

Seminar Information:
Date: 4 September 2026
Time: 13:30–14:30
Location: Room 221, Research Institute Building II
Speaker: Nicholas Larsen, Institute for Space–Earth Environmental Research, Nagoya University
Language: English

Abstract:
The Earth is constantly bombarded by a salvo of energetic charged particles known as cosmic rays (CRs). These particles pose several hazards to human activities, including contributing to biological radiation exposure and causing damage to aircraft, satellites, and other space-based infrastructure. Fortunately, the Earth's magnetic field provides a natural shield against CRs by deflecting lower-energy charged particles and permitting access primarily to those with sufficiently high energies. The ability of a CR to reach a particular location on Earth depends strongly on its energy and direction of arrival, as well as on the state of the Earth's magnetosphere at the time. Determining the CR energies required to access specific locations on Earth requires computationally intensive simulations of particle transport through the magnetosphere. Understanding and quantifying geomagnetic shielding aids in assessing radiation hazards, planning space missions, developing and constraining cosmogenic isotope production models, and interpreting CR measurements made by ground-based instruments. More broadly, such calculations have applications across space-weather research, atmospheric physics, radiation dosimetry, and CR transport modelling. OTSO is an open-source computational tool developed to perform these calculations using state-of-the-art magnetospheric models. It was developed to provide a modern, open-source alternative to historically used proprietary programs that are no longer actively maintained. In this seminar, I will introduce the OTSO framework, discuss the problems it is designed to address and the functions it can perform, and highlight recent applications of the tool in CR and space-weather research.