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The Dust Halo of Saturn’s Largest Icy Moon, Rhea
Coates, A. J.; Krupp, N.; Woch, J. +32 more
Saturn’s moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn’s magnetosphere. The Cassini spacecraft’s in situ observations reveal that energetic electrons are depleted in the moon’s vicinity. The absence of a substantial exosphere implies that Rhea’s magnetospheric int…
Dynamics of Saturn's South Polar Vortex
Fletcher, Leigh N.; West, Robert A.; Porco, Carolyn C. +9 more
We present observations of Saturn's south polar vortex (SPV) showing that it shares some properties with terrestrial hurricanes: cyclonic circulation, warm central region (the eye) surrounded by a ring of high clouds (the eye wall), and convective clouds outside the eye. The polar location and the absence of an ocean are major differences. It also…
Chromospheric Alfvénic Waves Strong Enough to Power the Solar Wind
Schrijver, C. J.; Ichimoto, K.; De Pontieu, B. +11 more
Alfvén waves have been invoked as a possible mechanism for the heating of the Sun's outer atmosphere, or corona, to millions of degrees and for the acceleration of the solar wind to hundreds of kilometers per second. However, Alfvén waves of sufficient strength have not been unambiguously observed in the solar atmosphere. We used images of high te…
The Process of Tholin Formation in Titan’s Upper Atmosphere
Coates, A. J.; Young, D. T.; Waite, J. H. +4 more
Titan’s lower atmosphere has long been known to harbor organic aerosols (tholins) presumed to have been formed from simple molecules, such as methane and nitrogen (CH4 and N2). Up to now, it has been assumed that tholins were formed at altitudes of several hundred kilometers by processes as yet unobserved. Using measurements …
Evidence for Alfvén Waves in Solar X-ray Jets
Weber, M.; Golub, L.; Kano, R. +11 more
Coronal magnetic fields are dynamic, and field lines may misalign, reassemble, and release energy by means of magnetic reconnection. Giant releases may generate solar flares and coronal mass ejections and, on a smaller scale, produce x-ray jets. Hinode observations of polar coronal holes reveal that x-ray jets have two distinct velocities: one nea…
Chromospheric Anemone Jets as Evidence of Ubiquitous Reconnection
Matsumoto, Takuma; Shibata, Kazunari; Nishizuka, Naoto +19 more
The heating of the solar chromosphere and corona is a long-standing puzzle in solar physics. Hinode observations show the ubiquitous presence of chromospheric anemone jets outside sunspots in active regions. They are typically 3 to 7 arc seconds = 2000 to 5000 kilometers long and 0.2 to 0.4 arc second = 150 to 300 kilometers wide, and their veloci…
Coronal Transverse Magnetohydrodynamic Waves in a Solar Prominence
Lites, B. W.; Ichimoto, K.; Shibata, K. +10 more
Solar prominences are cool 104 kelvin plasma clouds supported in the surrounding 106 kelvin coronal plasma by as-yet-undetermined mechanisms. Observations from Hinode show fine-scale threadlike structures oscillating in the plane of the sky with periods of several minutes. We suggest that these represent Alfvén waves propagat…
Subsurface Radar Sounding of the South Polar Layered Deposits of Mars
Gurnett, Donald A.; Stofan, Ellen R.; Frigeri, Alessandro +21 more
The ice-rich south polar layered deposits of Mars were probed with the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express orbiter. The radar signals penetrate deep into the deposits (more than 3.7 kilometers). For most of the area, a reflection is detected at a time delay that is consistent with an interface between th…
Tracking Solar Gravity Modes: The Dynamics of the Solar Core
García, Rafael A.; Turck-Chièze, Sylvaine; Mathur, Savita +5 more
Solar gravity modes have been actively sought because they directly probe the solar core (below 0.2 solar radius), but they have not been conclusively detected in the Sun because of their small surface amplitudes. Using data from the Global Oscillation at Low Frequency instrument, we detected a periodic structure in agreement with the period separ…
Martian Atmospheric Erosion Rates
Barabash, Stas; Lundin, Rickard; Fedorov, Andrei +1 more
Mars was once wet but is now dry, and the fate of its ancient carbon dioxide atmosphere is one of the biggest puzzles in martian planetology. We have measured the current loss rate due to the solar wind interaction for different species: Q(O+) = 1.6·1023 per second = 4 grams per second (g s-1), Q(O2…