Search Publications
Formation and Evolution of the Large-Scale Magnetic Fields in Venus' Ionosphere: Results From a Three Dimensional Global Multispecies MHD Model
Luhmann, Janet; Toth, Gabor; Nagy, Andrew +2 more
Large-scale magnetic fields have been observed in Venus' ionosphere by both the Pioneer Venus Orbiter (PVO) and Venus Express spacecraft. In this study, we examine the formation and evolution of the large-scale magnetic field in the Venus ionosphere using a sophisticated global multispecies Magnetohydrodynamics (MHD) model that has been developed …
Identifying Active Kelvin-Helmholtz Vortices on Saturn's Magnetopause Boundary
Delamere, P. A.; Johnson, J. R.; Burkholder, B. L. +1 more
For ∼2,000 Cassini magnetopause encounters, we analyse plasma and magnetic fields. The boundary can be unstable to the Kelvin-Helmholtz instability (KHI), which can drive large-scale flows identifiable in plasma measurements. Bulk flow reversed from the expected direction near the magnetopause can indicate vorticity associated with active KH, and …
Momentum and Pressure Balance of a Comet Ionosphere
Nilsson, H.; Goetz, C.; Richter, I. +3 more
We calculate the momentum flux and pressure of ions measured by the Ion Composition Analyzer (ICA) on the Rosetta mission at comet 67P/Churyumov-Gerasimenko. The total momentum flux stays roughly constant over the mission, but the contributions of different ion populations change depending on heliocentric distance. The magnetic pressure, calculate…
Electron Acceleration in a Magnetotail Reconnection Outflow Region Using Magnetospheric MultiScale Data
Khotyaintsev, Yuri V.; Graham, Daniel B.; Vaivads, Andris +3 more
We study Magnetospheric MultiScale observations in the outflow region of magnetotail reconnection. We estimate the power density converted via the three fundamental electron acceleration mechanisms: Fermi, betatron, and parallel electric fields. The dominant mechanism, both on average and the peak values, is Fermi acceleration with a peak power de…
Is Nightside Outflow Required to Induce Magnetospheric Sawtooth Oscillations
Zhang, Binzheng; Brambles, Oliver J.; Lotko, William +1 more
Ionospheric outflow plays an important role in the mass coupling between the ionosphere and the coupled solar wind-magnetosphere system. Previous modeling studies have shown that outflowing ionospheric ions may induce magnetospheric sawtooth oscillations through mass loading of the magnetotail, stretching the magnetic field lines, and reducing nig…
Singing Comet Waves in a Solar Wind Convective Electric Field Frame
Goetz, C.; Taylor, M. G. G. T.; Plaschke, F.
The cometary plasma environment at low gas production rates is dominated by highly compressional, large-amplitude magnetic field waves in the 10-100 mHz range. They are thought to be caused by an ion-Weibel instability due to a cross-field current, which is caused by the cometary ions that are accelerated along the solar wind convective electric f…
Low-Frequency Radio Observations of the "Quiet" Corona During the Descending Phase of Sunspot Cycle 24
Ramesh, R.; Kumari, A.; Kathiravan, C. +3 more
We carried out a statistical study of the "quiet" solar corona during the descending phase of the Sunspot Cycle 24 (i.e., January 2015 to May 2019) using data obtained with the Gauribidanur RAdioheliograPH (GRAPH) at 53 and 80 MHz simultaneously. Our results show that the equatorial (east-west) diameters of the solar corona at the above two freque…
Boulder Fall Activity in the Jezero Crater, Mars
Vijayan, S.; Mangold, N.; Bhardwaj, Anil +5 more
Jezero crater is the landing site for the Mars 2020 Perseverance rover. We report 63 boulder fall tracks within the crater using High-Resolution Imaging Science Experiment (HiRISE) images. The boulder tracks have both fresh and faded morphologies similar to those reported elsewhere on Mars, but reported for the first time in Jezero crater. We comb…
The Ice Content of the Dorsa Argentea Formation From Radar Sounder Data
Plaut, Jeffrey J.; Whitten, Jennifer L.; Campbell, Bruce A.
The Dorsa Argentea Formation (DAF) is an extensive Hesperian plains unit in the south polar region of Mars that was once ice rich and may still contain a substantial fraction of water ice. Given its 3.5-Ga age, the possibility for massive ice in the DAF has significant implications for the preservation of volatiles during large obliquity changes. …
Simultaneous Observation of Negatively and Positively Charged Nanograins at Comet 67P/Churyumov-Gerasimenko
Goldstein, R.; Goetz, Charlotte; LLera, K. +1 more
Observations near comet 67P by Rosetta show evidence of charged nanograins. Specifically, the ion and electron sensor (IES) observed negative particles with energy/charge (E/q) consistent with charged nanograins. However, theory predicts that both polarities should be present. On 19 September 2014, IES detected positively and negatively charged pa…