09:30 〜 09:45
[MGI26-03] 衛星データ同化による太陽高エネルギー粒子のモデリング
キーワード：太陽高エネルギー粒子、多点衛星観測、輸送方程式
Solar Energetic Particles (SEPs) are high-energy charged particles ranging from a few keV to several GeV, generated by energetic phenomena on the Sun and subsequently ejected into interplanetary space (Reams 1999). Understanding their origin and dynamics is of great interest to space plasma physics and related fields. Additionally, accurate prediction of the SEP profile is crucial for space weather operations, as SEPs exceeding 10 MeV pose primary threats to the space environment, including radio communication failures, malfunction and degradation of equipment onboard aircraft and satellites, and radiation exposure of astronauts during extravehicular activities. This is expected to grow in importance as human activities expand beyond the Earth's magnetosphere.
In-situ satellites have been deployed to measure SEPs in the heliosphere, providing information on their acceleration and transport from the Sun. Currently, many satellites are operating to measure SEPs at different radii and longitudes, giving a valuable opportunity to integrate multi-satellite observations with theoretical and numerical studies for comprehensive understanding of SEP physics.
On 30 March, 2022, a large solar flare along with subsequent coronal mass ejections led to a SEP event, which was observed simultaneously by the BepiColombo and STEREO-A satellites at 0.6 and 1.0 AU, respectively. Fortunately, both satellites were positioned approximately along the same interplanetary magnetic field line, giving a good opportunity to investigate SEP transport processes. In this study, we numerically model the SEP intensity profile between 0.6 and 1.0 AU using the focused transport equation along the field line (Ruffolo 1995). By employing the observation data at 0.6 AU as input, the model predicts the SEP profile at 1.0 AU for direct comparison with the observation. To estimate the mean free path, a key transport parameter, we assimilate the observation data at 1.0 AU into the model. The results suggest that the mean free path shortens over time, indicating that scattering gradually affects the SEP transport. This interpretation is qualitatively supported by the independent observation of increasing magnetic field fluctuations at 1.0 AU.
In-situ satellites have been deployed to measure SEPs in the heliosphere, providing information on their acceleration and transport from the Sun. Currently, many satellites are operating to measure SEPs at different radii and longitudes, giving a valuable opportunity to integrate multi-satellite observations with theoretical and numerical studies for comprehensive understanding of SEP physics.
On 30 March, 2022, a large solar flare along with subsequent coronal mass ejections led to a SEP event, which was observed simultaneously by the BepiColombo and STEREO-A satellites at 0.6 and 1.0 AU, respectively. Fortunately, both satellites were positioned approximately along the same interplanetary magnetic field line, giving a good opportunity to investigate SEP transport processes. In this study, we numerically model the SEP intensity profile between 0.6 and 1.0 AU using the focused transport equation along the field line (Ruffolo 1995). By employing the observation data at 0.6 AU as input, the model predicts the SEP profile at 1.0 AU for direct comparison with the observation. To estimate the mean free path, a key transport parameter, we assimilate the observation data at 1.0 AU into the model. The results suggest that the mean free path shortens over time, indicating that scattering gradually affects the SEP transport. This interpretation is qualitatively supported by the independent observation of increasing magnetic field fluctuations at 1.0 AU.