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Abstract Magnetotail current sheet (CS) flapping is a universal plasma phenomenon observed at multiple planets, yet its triggering mechanisms remain poorly understood outside of Earth. At Mars, single‐spacecraft observations have also reported tail flapping, but the processes responsible for its onset have never been identified. In this study, we investigate the potential correlation between magnetic reconnection and magnetotail flapping using multipoint measurements from Mars Atmosphere and Volatile EvolutioN (MAVEN) and Tianwen‐1 (TW‐1) missions. We analyze an example event in which MAVEN observed a reconnection‐associated CS crossing in the near tail while TW‐1 simultaneously detected CS flapping further downtail. A statistical survey of joint observations from November 2021 to February 2024 identifies that about two‐thirds of TW‐1 flapping events coincide with reconnection signatures observed by MAVEN. Multiple magnetic flux ropes were also detected before or during flapping intervals, similar to previous observations at Earth, suggesting that reconnection‐generated magnetic flux ropes may propagate tailward and drive plasma instabilities that trigger the tail flapping at Mars. These results provide the first multipoint evidence of a potential statistical correlation between magnetic reconnection and magnetotail flapping at Mars, enabling us to explore the potential triggering mechanism of magnetotail flapping. Our findings also offer new insights into Martian magnetotail dynamics and broaden the comparative understanding of this fundamental plasma process across planetary environments.
Volatile loss from exoplanetary atmospheres and its possible implications for the longevity of habitable surface conditions is a topic of vigorous debate currently. The vast majority of the habitable zone terrestrial-like exoplanets known to date orbit low-mass M- and K-dwarf stars and are subject to the conditions drastically different to those of terrestrial planets in the Solar System. In particular, they orbit far closer to their host stars than similar planets around G-dwarfs similar to the Sun. Therefore they receive higher X-ray and UV fluxes, even though luminosities of M- and K-dwarfs are lower than those of heavier stars. Furthermore, due to their slower evolution, M-dwarfs retain high activity on the gigayear timescales. The combination of these two effects has led to claims that most terrestrial planets orbiting M-dwarfs may have their atmospheres stripped from the higher X-ray and UV fluxes of their host stars. Opposing this are researchers who point out that volatile inventories for terrestrial exoplanets are ill-constrained, and hence, they may be able to “weather the storm” of these higher X-ray and UV fluxes. In this article, we focus on exploring volatile loss in the upper atmospheres of terrestrial planets in our solar system and applications to those in exoplanetary systems around stars of different types.
Ions with mass-to-charge ratios from 2 to 150 have been measured in the Martian ionosphere by the Neutral Gas and Ion Mass Spectrometer (NGIMS) onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Among these, protonated species at 31, 33, and 41 atomic mass units (amu) are observed at densities significantly higher than those predicted by photochemical models. In this study, we combine photochemical modelling with NGIMS measurements to investigate these discrepancies in the dayside ionosphere of Mars. For 41 amu ions, the photochemical model predicts ArH+ densities more than one order of magnitude lower than NGIMS measurements. For 31 and 33 amu ions, modelled densities of HNO+ and HO2+ are three orders of magnitude lower than observed values. We find that the vertical profiles reveal striking similarities among (a) the 31, 32, and 33 amu channels and (b) the 41, 42, 43, and 44 amu channels, which cannot be fully explained by interlinked chemical pathways and contributions from oxygen isotopes. Instead, we suggest that instrumental effects, specifically mass channel cross-talk from the strong 32 and 44 amu, provide a plausible explanation for the anomalously high densities reported at 31, 33, and 41 amu.
Auroral kilometric radiation (AKR), Earth's strongest radio emission, has long been associated with discrete auroras and electrons near a few kilo-electron volt (keV) range. However, auroras also occur in diffuse forms with broader electron energies, raising the question of why AKR has not been observed above diffuse auroras or linked to electrons outside the kilo-electron volt population. Comprehensive AKR source distributions have remained elusive because of observational limitations, and their local-time coverage remains largely unknown. Using spacecraft measurements, we identify a "radio oval" above the optical auroral oval, spanning the full local-time range, where AKR is emitted over both discrete and diffuse auroras. The AKR source electrons display diverse precipitation features, including monoenergetic (peak flux at 3.82 kilo-electron volts), broadband (1.34 kilo-electron volts), low-energy (0.47 kilo-electron volts), and diffuse types (>1 kilo-electron volt). These results reveal that the cyclotron maser instability-the mechanism driving AKR-can arise in diverse plasma environments, broadening our understanding of both AKR generation and auroral complexity.
The Jupiter and Icy Moons Explorer (JUICE) mission of the European Space Agency (ESA) will investigate the Jovian system with multiple instruments over several years, beginning in early 2031. This paper describes the historical context and state of knowledge, as well as JUICE’s scientific goals and measurement techniques of the satellites that will not be encountered in close flybys. These include the large volcanically active moon Io, the four small inner moons Metis, Adrastea, Amalthea, and Thebe, and the numerous small Irregular (outer) moons. JUICE will provide multiple opportunities to observe Io from relatively remote distances of hundreds of thousands of kilometers. These observations will enable monitoring of Io’s surface for changes, and for the study of its neutral clouds and plasma torus. Io observations will be performed with the four optical remote sensing instruments and with the Particle Environment Package. For the small inner moons it is planned to obtain complete geographic longitude (scales up to 8 km/px), solar-phase and multi-color coverage, oblique polar views, and UV to near-IR spectra. Astrometric measurements will also be performed. The Irregular moons will mostly appear unresolved to the JUICE instruments. Nonetheless, long-duration disk-integrated lightcurves will be acquired to derive rotation periods, object dimensions, pole-axis orientations, and colors for most objects for the first time. From these data, convex-shape models will be generated and phase curves determined. Furthermore, the precision of the orbital elements will be improved via accurate astrometry. UV and near-IR measurements will be attempted for the largest of these objects.
