5:15 PM - 7:15 PM
[PPS06-P05] Intensity variation of sulfur ion and sodium emission lines near Io based on Pirka telescope observations
Intense volcanic activity frequently occurs on Jupiter's moon Io. The volcanic activity causes the eruption of sulfur oxides, potassium chloride, and sodium chloride into Io's atmosphere (Redwing et al. 2022). In addition to volcanic eruptions, sublimation from the Ioʼs surface is also thought to be responsible for the influx of sulfur oxides into the Ioʼs atmosphere. These materials then scatter into space, and the ionization and neutralization of these scattered materials create a plasma torus or neutral cloud around Io's orbit. Although many optical observations of materials released and dispersed from the Ioʼs atmosphere have been made (Yoneda et al. 2025, Morgenthaler et al. 2024), the differences in time variability of material of volcanic and sublimation origin immediately after the release have not been clarified.
The purpose of this study is to clarify the distinctions of the behavior in the chemical changes in materials from different volcanoes and sublimation origins that have escaped from the Ioʼs atmosphere based on the Pirka telescope observations. Using the multispectral imager (Watanabe et al. 2012) installed on the Pirka telescope, we conducted imaging observations at the 589 nm sodium emission line and the 672.5 nm sulfur ion emission line from September to November 2024. In order to estimate the intensity variation of these emission lines, we conducted the subtraction of the scattered emission from Jupiter and aperture photometry in the region of one Jupiter radius centered on Io. Aperture photometry was also conducted in the region on the opposite side of Io. We define Period 1 as spanning from September 29 to October 17, and Period 2 from October 17 to November 25. In the aperture photometry near Io, the 589 nm data showed an intensity decrease of about 30% of the September 29 brightness during Period 1, followed by a rebound to approximately 75% during Period 2. Similarly, the 672.5 nm data decreased to about 80% of the September 29 brightness during Period 1 and increased to approximately 130% during Period 2. The aperture photometry results for the region opposite Io remained unchanged from the 589 nm data during Period 1, but increased to approximately 170% during Period 2. However, the 672.5 nm data showed about 30% decrease in Period 1 and about 120% increase in Period 2. The origin and variations are discussed based on the brightness obtained during the observation period.
The purpose of this study is to clarify the distinctions of the behavior in the chemical changes in materials from different volcanoes and sublimation origins that have escaped from the Ioʼs atmosphere based on the Pirka telescope observations. Using the multispectral imager (Watanabe et al. 2012) installed on the Pirka telescope, we conducted imaging observations at the 589 nm sodium emission line and the 672.5 nm sulfur ion emission line from September to November 2024. In order to estimate the intensity variation of these emission lines, we conducted the subtraction of the scattered emission from Jupiter and aperture photometry in the region of one Jupiter radius centered on Io. Aperture photometry was also conducted in the region on the opposite side of Io. We define Period 1 as spanning from September 29 to October 17, and Period 2 from October 17 to November 25. In the aperture photometry near Io, the 589 nm data showed an intensity decrease of about 30% of the September 29 brightness during Period 1, followed by a rebound to approximately 75% during Period 2. Similarly, the 672.5 nm data decreased to about 80% of the September 29 brightness during Period 1 and increased to approximately 130% during Period 2. The aperture photometry results for the region opposite Io remained unchanged from the 589 nm data during Period 1, but increased to approximately 170% during Period 2. However, the 672.5 nm data showed about 30% decrease in Period 1 and about 120% increase in Period 2. The origin and variations are discussed based on the brightness obtained during the observation period.