Variability of the auroral footprint of io detected by Juno‐JIRAM and modeling of the Io plasma torus

One of the auroral features of Jupiter is the emission associated with the orbital motion of its moon Io. The relative velocity between Io and the surrounding plasma trigger perturbations that travels as Alfvén waves along the magnetic field lines toward the Jovian ionosphere. These waves can accelerate electrons into the atmosphere and ultimately produce an auroral emission, called the Io footprint. The speed of the Alfvén waves—and hence the position of the footprint—depends on the magnetic field and on the plasma distribution along the field line passing through Io, whose SO2-rich atmosphere is the source of a dense plasma torus around Jupiter. Since 2016, the Jovian InfraRed Auroral Mapper (JIRAM) onboard Juno has been observing the Io footprint with a spatial resolution of ∼few tens of km/pixel. JIRAM detected evidences of variability in the Io footprint position that are not dependent on the System III longitude of Io. The position of the Io footprint in the JIRAM images is compared with the position predicted by a model of the Io Plasma Torus and of the magnetic field. This is the first attempt to retrieve quantitative information on the variability of the torus by looking at the Io footprint. The results are consistent with previous observations of the density and temperature of the Io Plasma Torus. However, we found that the plasma density and temperature exhibit considerable non-System III variability that can be due either to local time asymmetry of the torus or to its temporal variability

Stability of the Jupiter Southern Polar Vortices Inspected Through Vorticity Using Juno/JIRAM Data

The Jovian InfraRed Auroral Mapper (JIRAM) onboard the NASA Juno mission monitored the evolution of Jupiter’s polar cyclones since their first observation ever in February 2017. Data acquired by JIRAM have revealed cloudy cyclones organized in a complex, yet stable geometrical pattern at both poles. Several studies have investigated the dynamics and the structure of these cyclones, to understand the physical mechanisms behind their formation and evolution. In this work, we present vorticity maps deduced from the wind fields for the region poleward of ∼−80°, which has been extensively covered over the last four years of observations. The cyclonic features related to the stable polar cyclones are embedded in a slightly, but diffused anticyclonic circulation, in which short-living anticyclones emerge with respect to the surroundings. Although the general stability of both the cyclones and the whole system is strongly confirmed by this work, variations in the shape of the vortices, as well as changes in the local structures, have been observed

Five Years of Observations of the Circumpolar Cyclones of Jupiter

The regular polygons of circumpolar cyclones, discovered by Juno in 2017, are one of the most puzzling features of Jupiter. Here we show new recent global pictures of the North polar cyclones' structure. These are the first simultaneous images of the whole structure since 2017, and we find that it remained almost unperturbed, just like the South one. The observation of these long-lasting structures poses questions regarding the formation mechanism of cyclones, and on their vertical structure. Data by Juno/JIRAM infrared camera collected over the last 5 years show that cyclones migrate around what may seem like equilibrium positions, with timescales of a few months but, aside from that, the cyclones systems are very stable. Our analysis of the observations shows that the motion of cyclones around their equilibrium position is uncorrelated with their position if a barotropic approximation (β-drift) is assumed. Thus, a different dynamical explanation than the barotropic β-drift is needed to explain the stability of the observed features. Each cyclone has a peculiar morphology, which differs from the others and is stable over the observed lapse of time in most cases

Preliminary investigation of performance of thermoluminescent dosimeters for dose verification in brachytherapy

Brachytherapy represents the treatment of choice for many cancerous lesions, including skin tumours. Purpose of the study was to investigate the performance of thermoluminescent dosimeters of type 100, (TLD-100), for dose verification in high dose-rate treatment with a radioactive source of iridium-192. A set of TLDs-100 was calibrated with a 250 kVp X-ray beam in the dose range 0–5 Gy. Through a head and neck phantom, TLDs were fixed on districts corresponding to volumes of interest, including the target volume and some critical structures, then a single fraction of brachytherapy treatment was delivered. The dose measurements provided by TLDs were compared with the planned ones and the results were discussed in the light of limitations affecting the current treatment planning systems and critical aspects relating to brachytherapy implementation that still occurred in clinical settings. The findings of the study allow us to conclude that TLDs-100 show a good performance in the radiation field investigated and the use of so small, cheap and practical dosimetry system is potentially an optimal strategy of improving and standardizing the quality assurance protocol in brachytherapy