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Observations and Impacts of the 10 September 2017 Solar Events at Mars: An Overview and Synthesis of the Initial Results
Holmström, M.; Luhmann, J. G.; Halekas, J. S. +8 more
On 10 September 2017, some of the strongest solar activity occurred in association with active region 12673 (AR2673), including an X-class solar flare and a fast coronal mass ejection. Although AR2673 was not centrally facing Mars, the activity impacted the local space weather conditions at Mars. We give an overview of observations obtained from t…
Titan's Meteorology Over the Cassini Mission: Evidence for Extensive Subsurface Methane Reservoirs
Le Mouélic, S.; Rodriguez, S.; Sotin, C. +15 more
Cassini observations of Titan's weather patterns over >13 years, almost half a Saturnian year, provide insight into seasonal circulation patterns and the methane cycle. The Imaging Science Subsystem and the Visual and Infrared Mapping Spectrometer documented cloud locations, characteristics, morphologies, and behavior. Clouds were generally mor…
Observations of the Proton Aurora on Mars With SPICAM on Board Mars Express
Rodriguez, L.; Montmessin, F.; Ritter, B. +2 more
We report observations of the proton aurora at Mars, obtained with the Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet spectrograph on board Mars Express between 2004 and 2011. This is a third type of UV aurora that is discovered on Mars, in addition to the discrete and diffuse nightside aur…
H+/O+ Escape Rate Ratio in the Venus Magnetotail and its Dependence on the Solar Cycle
Fedorov, A.; Barabash, S.; Futaana, Y. +3 more
A fundamental question for the atmospheric evolution of Venus is how much water-related material escapes from Venus to space. In this study, we calculate the nonthermal escape of H+ and O+ ions through the Venusian magnetotail and its dependence on the solar cycle. We separate 8 years of data obtained from the ion mass analyz…
MARSIS Observations of the Martian Nightside Ionosphere During the September 2017 Solar Event
Gurnett, D. A.; Halekas, J. S.; Kopf, A. J. +5 more
We present topside ionospheric sounding on the nightside of Mars during the September 2017 solar event by Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express along with complementary dayside observations from Mars Atmosphere and Volatile EvolutioN (MAVEN). The MARSIS and MAVEN observations during the event sug…
Models of Saturn's Equatorial Ionosphere Based on In Situ Data From Cassini's Grand Finale
Wahlund, J. -E.; Waite, J. H.; Cravens, T. E. +8 more
We present new models of Saturn's equatorial ionosphere based on the first in situ measurements of its upper atmosphere. The neutral spectrum measured by Cassini's Ion and Neutral Mass Spectrometer, which includes substantial methane, ammonia, and organics in addition to the anticipated molecular hydrogen, helium, and water, serves as input for un…
Intense Current Structures Observed at Electron Kinetic Scales in the Near-Earth Magnetotail During Dipolarization and Substorm Current Wedge Formation
Lavraud, B.; Malykhin, A. Yu.; Grigorenko, E. E. +4 more
We use data from the 2013-2014 Cluster Inner Magnetosphere Campaign, with its uniquely small spacecraft separations (less than or equal to electron inertia length, <fi>λ</fi>e), to study multiscale magnetic structures in 14 substorm-related prolonged dipolarizations in the near-Earth magnetotail. Three time scales of dipolar…
Responses of the Martian Magnetosphere to an Interplanetary Coronal Mass Ejection: MAVEN Observations and LatHyS Results
Holmström, M.; Luhmann, J. G.; Chaufray, J. -Y. +12 more
The Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft observed a strong interplanetary coronal mass ejection (ICME) reaching Mars on 13 September 2017. In this work we analyze the interaction between such an extreme event and the Martian-induced magnetosphere by means of Laboratoire Atmosphères, Milieux et Observations Spatiales Hybrid Sim…
Electron Distributions in Kinetic Scale Field Line Resonances: A Comparison of Simulations and Observations
Hull, A. J.; Chaston, C. C.; Johnson, J. R. +1 more
Observations in kinetic scale field line resonances, or eigenmodes of the geomagnetic field, reveal highly field-aligned plateaued electron distributions. By combining observations from the Van Allen Probes and Cluster spacecraft with a hybrid kinetic gyrofluid simulation we show how these distributions arise from the nonlocal self-consistent inte…
Thermal Structure and Composition of Saturn's Upper Atmosphere From Cassini/Ion Neutral Mass Spectrometer Measurements
Waite, J. Hunter; Hörst, S. M.; Perry, M. E. +4 more
Analysis of measurements of the H2 density in Saturn's equatorial thermosphere indicates temperatures from 340 to 370 K. The deepest measurements, obtained during Cassini's final plunge into the atmosphere, measure the thermospheric temperature profile. The measurements are well fit by a Bates profile with an exospheric temperature of 3…