Abstract Cold plasma distribution in the ionosphere‐plasmasphere system governs wave‐particle interactions, plasma energization and loss, and radio wave propagation. A longstanding observational gap at altitudes ∼ ${\sim} $800–8,000 km has largely prevented studying the coupled dynamics of the two regions. Here, we show that observations by JAXA’s Arase mission can bridge this gap. Electron densities inferred from the upper hybrid resonance frequencies measured by Arase are highly consistent with radio occultation profiles from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission, with a median difference of ∼ ${\sim} $5%. Using the combined COSMIC‐Arase data set, we provide a convenient way to reconcile the two regions in empirical models based on the analytical Chapman function inversion for scale height. Our results enable studying fundamental questions about the ionosphere‐plasmasphere coupling, their transition, and life cycle of cold plasma in near‐Earth space.
Observations from the Little Bunker
Last updated: December 08, 2025 04:14 PM
Atmospheric CO₂
427.2 ppm
+17.6
ppm/year
Atmospheric CH₄
1930.95 ppb
+-3.5
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
World Population
8.1 billion
+67
million/year