Generation of equatorial plasma bubble after the 2022 Tonga volcanic eruption.

Equatorial plasma bubbles are a phenomenon of plasma density depletion with small-scale density irregularities, normally observed in the equatorial ionosphere. This phenomenon, which impacts satellite-based communications, was observed in the Asia-Pacific region after the largest-on-record January 15, 2022 eruption of the Tonga volcano. We used satellite and ground-based ionospheric observations to demonstrate that an air pressure wave triggered by the Tonga volcanic eruption could cause the emergence of an equatorial plasma bubble.

Cross-Energy Couplings from Magnetosonic Waves to Electromagnetic Ion Cyclotron Waves through Cold Ion Heating inside the Plasmasphere.

Using a novel wave-particle interaction analysis, we show observational evidence of energy transfer from fast magnetosonic waves (MSWs) to low-energy protons in the magnetosphere. The analysis clearly indicates that the transferred proton energies are further converted to excite electromagnetic ion cyclotron waves. Since MSWs are excited by hot ions, cross-energy coupling of ions occurs through MSWs.

Volcanic history in the Smythii basin based on SELENE radar observation.

Elucidation of the subsurface structure in the Smythii basin on the moon is important for understanding lunar volcanic history. Two lava units (Units 1 and 2) cover this basin. The spatial subsurface structure below Unit 2 is unknown.

Visualization of rapid electron precipitation via chorus element wave-particle interactions.

Chorus waves, among the most intense electromagnetic emissions in the Earth's magnetosphere, magnetized planets, and laboratory plasmas, play an important role in the acceleration and loss of energetic electrons in the plasma universe through resonant interactions with electrons. However, the spatial evolution of the electron resonant interactions with electromagnetic waves remains poorly understood owing to imaging difficulties. Here we provide a compelling visualization of chorus element wave-particle interactions in the Earth's magnetosphere.

Lunar radar sounder observations of subsurface layers under the nearside maria of the Moon.

Observations of the subsurface geology of the Moon help advance our understanding of lunar origin and evolution. Radar sounding from the Kaguya spacecraft has revealed subsurface layers at an apparent depth of several hundred meters in nearside maria. Comparison with the surface geology in the Serenitatis basin implies that the prominent echoes are probably from buried regolith layers accumulated during the depositional hiatus of mare basalts.