2025-06-27
セミナー

PPARCセミナー (2025/06/30)

PPARCセミナー (2025/06/30)

(1)

[Name]

Rentaro Sugawara

[Title]

Long-Term Identification and Latitudinal Distribution Analysis of Jovian nKOM Using Juno Waves Data

[Abstract]

Narrow-band kilometric radiation (nKOM) is a distinct type of Jovian radio emission originating near the Io plasma torus, typically exhibiting narrow frequency bands and periodic structures. Although its magnetic latitude dependence has been suggested, long-term variations remain poorly understood.
In this study, we focus on the identification of nKOM events using dynamic spectra from Juno’s radio wave observations. Events are manually selected based on visual criteria such as narrowband signatures and temporal pairings, followed by frequency-wise threshold detection using smoothed intensity profiles. This semi-manual approach allows us to isolate reliable nKOM occurrences across different observation periods.
By compiling a detailed event database, we aim to explore the magnetic latitude distribution and long-term evolution of nKOM, shedding light on magnetospheric dynamics such as plasma injections or density variations.

(2)

[Name]

Masato Kagitani

[Title]

Daytime observation of Mercury’s exosphere with Tohoku 60-cm telescope adaptive optics at Haleakala observatory

[Abstract]

We present the visible adaptive-optics system T60-AO, developed for the Tohoku 60-cm telescope at Haleakala observatory to provide ground support for BepiColombo’s Mercury mission (orbit insertion in 2026). Mercury’s sodium exosphere varies on minute time-scales though conventional slit-scans need ~1 h per global map. Combining a high-dispersion (R = 67 000) integral-field spectrograph with T60-AO enables two-dimensional Na D-line spectroscopy every few minutes in daylight, essential because Mercury remains within 25° of the Sun. The 12 × 12 MEMS deformable mirror and 11 × 11 Shack–Hartmann sensor improve daytime spatial resolution FWHM from 3.5–7″ to <1.5″. We summarize these on-sky results and the system’s readiness for continuous monitoring of Mercury’s dynamic exosphere.