Search Publications
Jupiter's Dark Polar Region as Observed by the Hubble Space Telescope During the Juno Approach Phase
Nichols, J. D.; Bunce, E. J.; Swithenbank-Harris, B. G.
We present an analysis of Jupiter's dark polar region, previously described as a crescent-shaped region devoid of emission along the dawnside poleward of the main oval. Using ultraviolet images obtained by the Hubble Space Telescope between days of year 137 and 176, coupled with interplanetary data captured during the approach phase of the NASA Ju…
Magnetic Field Observations on Cassini's Proximal Periapsis Passes: Planetary Period Oscillations and Mean Residual Fields
Dougherty, M. K.; Cowley, S. W. H.; Bunce, E. J. +4 more
We analyze periapsis pass magnetic field data from the final 23 orbits of the Cassini spacecraft at Saturn, uniquely encompassing auroral, subauroral, ring region, and intra-ring field lines, to determine the planetary period oscillations (PPOs) and mean residual fields in these regions. Dual modulation by northern and southern PPO systems is foun…
Reconstruction of Local Magnetic Structures by a Modified Radial Basis Function Method
Semenov, V. S.; Tsyganenko, N. A.; Andreeva, V. A. +2 more
Local magnetic structures in space environments, in particular, those in the diffusion region such as magnetic nulls or separators, are very difficult to identify by satellite measurements but important for understanding of magnetic reconnection. Multi-spacecraft missions such as Cluster or MMS, however, provide an opportunity to reconstruct the f…
Efficacy of Electric Field Models in Reproducing Observed Ring Current Ion Spectra During Two Geomagnetic Storms
Kistler, L. M.; Mouikis, C. G.; Matsui, H. +4 more
We use the UNH-IMEF, Weimer 1996, https://doi.org/10.1029/96GL02255 and Volland-Stern electric field models along with a dipole magnetic field to calculate drift paths for particles that reach the Van Allen Probes' orbit for two inbound passes during two large geomagnetic storms. We compare the parti…
Energy Spectral Properties of Hydrogen Energetic Neutral Atoms Emitted From the Dayside Atmosphere of Mars
Barabash, S.; Futaana, Y.; Wurz, P. +3 more
The energy spectrum of hydrogen energetic neutral atoms (HENAs) emitted from the dayside atmosphere of Mars reveals the physical processes of their origin and provides means for remote sensing on the Mars plasma environment. We first compile all available energy spectra of sunward flowing HENA using high-energy resolution data from the neutral par…
Signatures of Magnetic Separatrices at the Borders of a Crater Flux Transfer Event Connected to an Active X-Line
Eastwood, J. P.; Lavraud, B.; Dunlop, M. W. +7 more
In this paper, we present Magnetospheric Multiscale (MMS) observations of a flux transfer event (FTE) characterized by a clear signature in the magnetic field magnitude, which shows maximum at the center flanked by two depressions, detected during a period of stable southward interplanetary magnetic field. This class of FTEs are called "crater-FTE…
Abnormal Subauroral Ion Drifts (ASAID) and Pi2s During Cross-Tail Current Disruptions Observed by Polar on the Magnetically Quiet Days of October 2003
Horvath, Ildiko; Lovell, Brian C.
In this study we further investigate the development of abnormal subauroral ion drifts/polarization streams (ASAID/ASAPS) during the magnetically quiet days of 9-10 October 2003. Our main aim is to provide direct observational evidence verifying that the Defense Meteorological Satellite Program F15 detected quiet-time ASAID/ASAPS features develope…
Direct Measurement of Low-Energy Electron Foreshock Beams
Soucek, Jan; Píša, David; Santolík, Ondrej
Electrostatic plasma waves above and below the local electron plasma frequency represent a characteristic feature of the foreshock region. These waves are known to be generated by electron beams originating from the bow shock and their spectrum varies from narrowband intense waves close to foreshock edge to weaker broadband emissions further downs…
Machine Learning Analysis of Jupiter's Far-Ultraviolet Auroral Morphology
Milan, S. E.; Nichols, J. D.; Kamran, A.
We present the first principal component analysis of Jupiter's far-ultraviolet auroras, in order to identify the most repeatable sources of variation in the auroral morphology. We show that the most recurrent source of variance is emission just poleward of the statistical oval on the dawnside. Further significant repeatable sources of variance are…
Solar Wind Dynamic Pressure Upstream From Saturn: Estimation From Magnetosheath Properties and Comparison With SKR
Thomsen, M. F.; Jackman, C. M.; Lamy, L.
An analytical method is developed by which measurements made by the Cassini spacecraft in Saturn's magnetosheath can be used to infer the upstream solar wind parameters, specifically the solar wind speed (Vsw) and the dynamic pressure (Pd). The method is validated by comparing the results with other estimates of these parameters, includ…