Volcanic gases, primarily composed of SO2, SO, and S, originating from Io are ionized through interactions with magnetospheric plasma, forming a dense plasma region known as the Io plasma torus. Ion pickup serves as the most significant energy source for the plasma torus though, the spatial distribution of the pickup region and its temporal variability remain poorly understood. Measuring ion distributions with sufficient spatial resolution enables the derivation of ion temperatures and temperature anisotropy, being closely related to the influx of fresh pickup ions.Since 2014, we have carried out ground-based observations of sulfur ion emissions ([SII] 671.6 nm and 673.1 nm) from the Io plasma torus at the Haleakal Observatory in Hawaii, utilizing Tohoku 60-cm telescope. The telescope is equipped with a monochromatic imager and a coronagraph, enabling us to observe the distribution of singly charged sulfur ions with a spatial resolution as fine as 0.03 Jovian radii. This unique setup has allowed us to track changes in the torus structure with high spatial and temporal precision.Over the past six years, our observations revealed five significant peaks in [SII] brightness. For three of these events, we observed that the [SII] ribbon scale height began to increase shortly after the brightness peaks. This phenomenon likely indicates a rise in ion temperature, driven by volcanic outbursts on Io that introduce fresh ions into the torus. Such findings provide critical insights into the dynamic nature of the Io plasma torus and its response to volcanic activity.In this presentation, we will review past and ongoing remote sensing projects, present the latest observational results from our multi-year campaign, and discuss future plans for supporting upcoming space missions.

The formation of massive stars in dense and cold molecular clouds is a fundamental problem in star formation. In this work, we studied three compact massive star-forming regions, M8E, RAFGL 6366S, and IRAS 18317-0513, to investigate the environment of massive star formation, specifically the possibility of a local feedback process. Our new mid-infrared observations using miniTAO/MAX38 at 31 and 37 mu m resolved individual objects in each region and allowed us to obtain their individual luminosities and masses. Together with existence/absence of ultra-compact H II regions, it is suggested that less-massive objects are more evolved than the more-massive objects in two out of the three regions. Because the objects that are more massive evolve faster, those that are less massive form earlier. This formation trend of local mass-sequential star was first suggested in 0.1 pc-scale massive star-forming regions. Therefore, feedback, such as outflows, jets, or radiative heating, from previously formed lower-mass young stellar objects might affect the environment of parental clouds and lead to next-generation massive young stellar objects.

Io's atmosphere is predominately SO2 that is sustained by a combination of volcanic outgassing and sublimation. The loss from the atmosphere is the main mass source for Jupiter's large magnetosphere. Numerous previous studies attributed various transient phenomena in Io's environment and Jupiter's magnetosphere to a sudden change in the mass loss from the atmosphere supposedly triggered by a change in volcanic activity. Since the gas in volcanic plumes does not escape directly, such causal correlation would require a transient volcano-induced change in atmospheric abundance, which has never been observed so far. Here we report four observations of atmospheric SO2 and NaCl from the same hemisphere of Io, obtained with the IRAM NOEMA interferometer on 11 December 2016, 14 March, 6 and 29 April 2017. These observations are compared to measurements of volcanic hot spots and Io's neutral and plasma environment. We find a stable NaCl column density in Io's atmosphere on the four dates. The SO2 column density derived for December 2016 is about 30% lower compared to the SO2 column density found in the period of March to April 2017. This increase in SO2 from December 2016 to March 2017 might be related to increasing volcanic activity observed at several sites in spring 2017, but the stability of the volcanic trace gas NaCl and resulting decrease in NaCl/SO2 ratio do not support this interpretation. Observed dimmings in both the sulfur ion torus and Na neutral cloud suggest rather a decrease in mass loading in the period of increasing SO2 abundance. The dimming Na brightness and stable atmospheric NaCl furthermore dispute an earlier suggested positive correlation of the sodium cloud and the hot spot activity at Loki Patara, which considerably increased in this period. The environment of Io overall appears to be in a rather quiescent state, preventing further conclusions. Only Jupiter's aurora morphology underwent several short-term changes, which are apparently unrelated to Io's quiescent environment or the relatively stable atmosphere.

We report on the spatial distribution of a neutral oxygen cloud surrounding Jupiter's moon Io and along Io's orbit observed by the Hisaki satellite. Atomic oxygen and sulfur in Io's atmosphere escape from the exosphere mainly through atmospheric sputtering. Some of the neutral atoms escape from Io's gravitational sphere and form neutral clouds around Jupiter. The extreme ultraviolet spectrograph called EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) installed on the Japan Aerospace Exploration Agency's Hisaki satellite observed the Io plasma torus continuously in 2014–2015, and we derived the spatial distribution of atomic oxygen emissions at 130.4 nm. The results show that Io's oxygen cloud is composed of two regions, namely, a dense region near Io and a diffuse region with a longitudinally homogeneous distribution along Io's orbit. The dense region mainly extends on the leading side of Io and inside of Io's orbit. The emissions spread out to 7.6 Jupiter radii (RJ). Based on Hisaki observations, we estimated the radial distribution of the atomic oxygen number density and oxygen ion source rate. The peak atomic oxygen number density is 80 cm−3, which is spread 1.2 RJ in the north‐south direction. We found more oxygen atoms inside Io's orbit than a previous study. We estimated the total oxygen ion source rate to be 410 kg/s, which is consistent with the value derived from a previous study that used a physical chemistry model based on Hisaki observations of ultraviolet emission ions in the Io plasma torus.

In has an atmosphere produced by volcanism and sublimation of frosts deposited around active volcanoes. However, the time variation of atomic oxygen escaping Io's atmosphere is not well known. In this paper, we show a significant increase in atomic oxygen around to during a volcanic event. Brightening of Io's extended sodium nebula was observed in the spring of 2015. We used the Hisaki satellite to investigate the time variation of atomic oxygen emission around lo during the same period. This investigation reveals that the duration of atomic oxygen brightness increases from a volcanically quiet level to a maximum level during the same approximate time period of 30 days as the observed sodium brightness. On the other hand, the recovery of the atomic oxygen brightness from the maximum to the quiet level (60 days) was longer than that of the sodium nebula decreasing (40 days). Additionally, a dawn-dusk asymmetry of the atomic oxygen emission is observed. (C) 2017 Elsevier Inc. All rights reserved.

Meeting Information: SPICA Science Conference from Exoplanets to Distant Galaxies: SPICA's New Window on the Cool Universe (June 18-21, 2013. Ito Hall, the University of Tokyo), Bunkyou-ku, Tokyo, Japan

The spatial and temporal variations of planetary atmospheric phenomena (e.g., auroras on Jupiter and Io, as well as the polarization of expolanetary atmospheres) are extremely complicated. Indeed, the wide range of these phenomena, and the cross-scale coupling processes that exist between them, means that is difficult to understand their underlying mechanisms. To study and understand such planetary atmospheric phenomena it is therefore essential to perform continuous and flexible monitoring with a suitable telescope. From previous studies it is known that Jupiter’s auroras are generated by two separate mechanisms: a rapid 10-hour rotation of the magnetic field (known as the ‘internal source’) and the variation of the solar wind (known as the ‘external source’).1 Although much effort has been made to determine which of these sources plays the major role in causing the spatial and temporal variations of Jupiter’s auroras, the mechanism has still not been resolved.2 In addition, it has been shown that active volcanoes on Io (a moon of Jupiter) intermittently inject large amounts of gases into the magnetosphere and can modulate the auroral activity.3 Past studies have also revealed that the light from exoplanet host stars is polarized with the variation period of the planet’s orbital motion. This result suggests that the polarization is caused by Rayleigh scattering in the exoplanetary atmosphere.4 The examples of exoplanetary atmospheres that have so far been studied, however, have been very limited. Further observations are thus required to fully characterize the atmospheres of different types of exoplanets. Figure 1. The 60cm Cassegrain and Coude telescope (T60) installed at the summit of Mount Haleakala, Hawaii.

The satellite Io which has many active volcanos supplies volcanic gases to the Jovian magnetosphere with a typical rate of 1 ton/sec and has is a primary source of plasmas in the magnetosphere. Change in the volcanic activity would cause change in plasma supply rate to the magnetosphere and could affect structure of the magnetosphere and dynamics occurring in it. However, responses of the magnetosphere to the plasma supply rate change is still not fully understood. The extreme ultraviolet (EUV) spectroscope, EXCEED, onboard the HISAKI satellite made observations of Io plasma torus and Jovian northern aurora from the end of Nov. 2014 to middle of May 2015 continuously. On middle of Jan. 2015, HISAKI detected gradual increase in intensity of S + emission lines and decrease of S 3+ ones in the plasma torus. The S+ intensity showed a maximum around the end of Feb. and S 2+ and S 3+ intensities also showed maxima subsequently. Simultaneous ground based observation of the sodium nebula showed increase of the emission intensity from the middle of Jan. to Feb. These observations suggest that the volcanic activity enhancement started at the middle of Jan. and increase neutral atom and ion densities in the Io torus. Change in radial structure of the plasma torus was also detected. The intensity of S + ion began to increase around the orbit of Io (6 Jovian radii). The

Jupiter’s sodium nebula, which originates from Io’s volcanic gas, shows variations in its brightness due to the volcanic activity on Io. Imaging observation of D-line brightness in the sodium nebula was performed from 2013 through 2015 in a conjunction with the HISAKI mission. The D-line brightness of the sodium nebula had been stably faint and dim until January 2015, but it showed a distinct enhancement from February through March, 2015. The brightness increased by three times during this enhancement. Details in variations of Jupiter’s sodium nebula are shown in this paper.