Search Publications
A tailward moving current sheet normal magnetic field front followed by an earthward moving dipolarization front
Goldstein, M. L.; Walsh, B. M.; Moore, T. E. +5 more
A case study is presented using measurements from the Cluster spacecraft and ground-based magnetometers that show a substorm onset propagating from the inner to outer plasma sheet. On 3 October 2005, Cluster, traversing an ion-scale current sheet at the near-Earth plasma sheet, detected a sudden enhancement of Bz, which was immediately …
Survey of Saturn auroral storms observed by the Hubble Space Telescope: Implications for storm time scales
Nichols, J. D.; Cowley, S. W. H.; Meredith, C. J.
We examine the ultraviolet images of Saturn obtained by the Hubble Space Telescope (HST) between 1997 and 2013 for the presence of auroral storm signatures, consisting of 2060 individual images over 74.4 h of exposure time. We find 12 storm intervals in these data, identified by bright high-latitude auroras spanning the dawn sector, which previous…
Observed decline in Titan's thermospheric methane due to solar cycle drivers
Waite, J. H.; Perryman, R.; Bell, J. M. +1 more
We present Cassini Ion and Neutral Mass Spectrometer observations of Titan's N2 and CH4 from Cassini flybys of Titan spanning the time period from 2004 to 2013 representing 9 years of in situ neutral density observations. This data reveal an upward trend in CH4 mixing ratios during the extended solar minimum encoun…
Variations of the 3-D coronal magnetic field associated with the X3.4-class solar flare event of AR 10930
Chen, P. F.; Yan, Yihua; Wang, Huaning +2 more
The variations of the 3-D coronal magnetic fields associated with the X3.4-class flare of active region 10930 are studied in this paper. The coronal magnetic field data are reconstructed from the photospheric vector magnetograms obtained by the Hinode satellite and using the nonlinear force-free field extrapolation method developed in our previous…
What flare and CME parameters control the occurrence of solar proton events?
Moon, Y. -J.; Park, Jinhye
In this study we examine the occurrence probabilities of solar proton events (SPEs) and their peak fluxes depending on both flare and coronal mass ejection (CME) parameters: flare peak flux, longitude, impulsive time, CME linear speed, and angular width. For this we use the NOAA SPEs, their associated X-ray flares, and CME from 1997 to 2011. We di…
Temporal and spatial scales of a high-flux electron disturbance in the cusp region: Cluster observations
Dunlop, Malcolm; Fazakerley, Andrew; Torkar, Klaus +4 more
Using the Cluster multispacecraft observations, we analyze a long-duration field-aligned high-flux electron disturbance in the cusp region on 30 September 2001. All four Cluster spacecraft observed the same disturbance in which both the upward and downward electrons are observed and the electron flux was 1 order of magnitude higher than usual in t…
Transient small-scale structure in the main auroral emission at Jupiter
Bonfond, B.; Palmaerts, B.; Grodent, D. +2 more
The main auroral emission at Jupiter results from the ionosphere-magnetosphere coupling current system associated with the corotation breakdown of iogenic plasma in the current sheet. The morphology and brightness of the main auroral emission are generally suggested to be stable during time intervals of the order of an hour. Here we reveal a trans…
The relationship between sawtooth events and O+ in the plasma sheet
Dandouras, I.; Klecker, B.; Kistler, L. M. +4 more
In order to study the relationship between sawtooth events and the composition of the plasma sheet, we perform a superposed epoch analysis (SEA) of the O+ concentration inside the near-Earth plasma sheet during sawtooth events and substorms sorted by different geomagnetic storm phases, using Cluster/Composition Distribution Function dat…
Turbulence in the Earth's cusp region: The k-filtering analysis
Dunlop, Malcolm; Cao, Jin-Bin; Fu, Huishan +2 more
On 13 April 2002, four Cluster spacecraft with separations up to 127 km measured similar turbulence in the exterior cusp during northward interplanetary magnetic field (IMF) Bz. Both the power spectra of magnetic and electric field fluctuations resemble the classical Kolmogorov power law, with the scaling f-1.7 under the prot…
An empirical model for the plasma environment along Titan's orbit based on Cassini plasma observations
Rymer, Abigail M.; Smith, H. Todd
Prior to Cassini's arrival at Saturn, the nitrogen-rich dense atmosphere of Titan was considered as a significant, if not dominant, source of heavy ions in Saturn's magnetosphere. While nitrogen was detected in Saturn's magnetosphere based on Cassini observations, Enceladus instead of Titan appears to be the primary source. However, it is difficul…