Table1_The temporal variability of Io’s hotspots.docx

We investigate the variability of the power emission of Io’s hotspots by using recent Juno/JIRAM infrared observations. The Jovian Infrared Auroral Mapper (JIRAM) is an imaging spectrometer which began observing Jupiter in August 2016. Although observing Jupiter’s moons is not its primary objective, JIRAM can use the frequent opportunities to observe Io (up to once per orbit) to gather infrared images and spectra of its surface. The present study uses the data acquired by JIRAM during the last 2 years, including the location and morphology of Io’s hotspots, and the temporal variability of the total output. A new photometric model for the hotspots and the dayside surface has been developed, which permits us to disentangle the temporal variability from the changes in the observation geometry. While the latitudinal dependence of the power output is not well constrained, low-latitude hotspots show a significantly more intense temporal variability and greater temperature.

本研究借助近期朱诺号（Juno）/红外极光成像仪（JIRAM，Jovian Infrared Auroral Mapper）的红外观测数据，探究木卫一（Io）热点的热辐射功率变化特性。木星红外极光成像仪是一款成像光谱仪，于2016年8月起开展木星观测工作。尽管观测木星卫星并非其核心观测目标，但JIRAM可借助每轨道周期至多一次的观测契机，获取木卫一表面的红外影像与光谱数据。本研究采用JIRAM近两年来采集的观测数据，涵盖木卫一热点的位置、形貌特征以及总辐射功率的时间变化特性。我们针对热点与日照面构建了全新的光度学模型，借此将热辐射的时间变化特性与观测几何参数的变化分离开来。尽管目前热辐射功率的纬度依赖性尚未得到充分约束，但低纬度热点展现出显著更强的时间变化性与更高的温度。