14:45 〜 15:00
[PEM10-29] Prosecces of Earth's Atmospheric Expansion Caused by Solar Activity and Its effect on Orbits of CubeSats
キーワード：地球、大気、超小型衛星、地磁気嵐、極端紫外線
In this study, we investigate the relationship between solar activity and the Earth's atmospheric variations using GPS data from the X-ray astronomy CubeSat "NinjaSat" in LEO (Low Earth Orbit).
2024 was a year of very high solar activity.
During this period, the Earth's upper atmosphere experienced significant variations due to the increased solar activity which included some of the largest flares and CMEs in recorded history, accompanied by massive geomagnetic storms. Using a method that compares orbital altitude changes derived from NinjaSat's GPS data with those propagated from TLE (Two-Line Element) data provided by NORAD (North American Aerospace Defense Command), the dynamic effects of Earth's atmosphere is extracted, enabling a fine time-resolution analysis of solar activity and atmospheric variations.
This study statistically reveals a time-delayed response of the orbital altitude changes to the solar EUV radiation variations, with a delay for the EUV radiation in the shorter wavelength range (25.6-30.4 nm) and a delay for variations in the longer wavelength range (117.5-140.5 nm) at around 500 km altitude.
Additionally, by analyzing orbital altitude changes with the effects of EUV radiation removed, we investigate atmospheric density variations caused by extreme geomagnetic storms associated with intense solar flares and CMEs in May and October 2024. The analysis statistically demonstrates a response delay of 9.5 hours to high-energy proton fluxes caused by CMEs, providing a highly accurate indicator for predicting orbital altitude changes associated with severe geomagnetic storms. Furthermore, correlation analysis between orbital altitude changes, excluding the effects of solar EUV radiation, and geomagnetic disturbance indices in both polar and equatorial regions suggests contributions from auroral electrojet currents and equatorial ring currents, as well as Joule heating caused by atmospheric friction. The differences in response time reveal the timescale of the propagation of heated atmosphere from polar regions to low-latitude regions.
We find that under geomagnetic quiet conditions, the EUV radiation heating effect is dominant, while the Joule heating effect becomes more significant during extreme geomagnetic storms, causing the atmosphere to expand and increase the density at higher altitudes suddenly, as determined by calculating the heat input to the atmosphere.
This study serves as a foundation for future research on the effects of solar EUV radiation and geomagnetic disturbances on satellite orbits, aiming to accurately predict orbital altitude changes based on solar activity and geomagnetic disturbance indices.
2024 was a year of very high solar activity.
During this period, the Earth's upper atmosphere experienced significant variations due to the increased solar activity which included some of the largest flares and CMEs in recorded history, accompanied by massive geomagnetic storms. Using a method that compares orbital altitude changes derived from NinjaSat's GPS data with those propagated from TLE (Two-Line Element) data provided by NORAD (North American Aerospace Defense Command), the dynamic effects of Earth's atmosphere is extracted, enabling a fine time-resolution analysis of solar activity and atmospheric variations.
This study statistically reveals a time-delayed response of the orbital altitude changes to the solar EUV radiation variations, with a delay for the EUV radiation in the shorter wavelength range (25.6-30.4 nm) and a delay for variations in the longer wavelength range (117.5-140.5 nm) at around 500 km altitude.
Additionally, by analyzing orbital altitude changes with the effects of EUV radiation removed, we investigate atmospheric density variations caused by extreme geomagnetic storms associated with intense solar flares and CMEs in May and October 2024. The analysis statistically demonstrates a response delay of 9.5 hours to high-energy proton fluxes caused by CMEs, providing a highly accurate indicator for predicting orbital altitude changes associated with severe geomagnetic storms. Furthermore, correlation analysis between orbital altitude changes, excluding the effects of solar EUV radiation, and geomagnetic disturbance indices in both polar and equatorial regions suggests contributions from auroral electrojet currents and equatorial ring currents, as well as Joule heating caused by atmospheric friction. The differences in response time reveal the timescale of the propagation of heated atmosphere from polar regions to low-latitude regions.
We find that under geomagnetic quiet conditions, the EUV radiation heating effect is dominant, while the Joule heating effect becomes more significant during extreme geomagnetic storms, causing the atmosphere to expand and increase the density at higher altitudes suddenly, as determined by calculating the heat input to the atmosphere.
This study serves as a foundation for future research on the effects of solar EUV radiation and geomagnetic disturbances on satellite orbits, aiming to accurately predict orbital altitude changes based on solar activity and geomagnetic disturbance indices.