Search Publications
A new model of total solar irradiance based on sunspot areas
Walton, Stephen R.; Preminger, Dora G.
We show that daily sunspot area can be used in a simple model to reconstruct daily variations in the total solar irradiance, S. The model assumes that all fluctuations in S are correlated with the emergence of sunspots on the solar disk. Cotemporal data for S and sunspot area are analysed to extract the finite impulse response function that descri…
An update on the ring exosphere and plasma disc of Saturn
Ip, W. -H.
A re-examination of the mass budget of the ring exosphere of Saturn - as prompted by the most recent Cassini measurements in the vicinity of the ring system - indicates that the corresponding number density could reach the level of 2-3 × 105 cm-3 at maximum. Such extended exospheric structure in equilibrium with a thin ring p…
Small rampart craters in an equatorial region on Mars: Implications for near-surface water or ice
Jaumann, R.; Neukum, G.; Hauber, E. +3 more
Small onset diameters (1 km) of rampart craters were identified in High Resolution Stereo Camera (HRSC) imagery in the equatorial region of the Valles Marineris plateaus. This is in contrast to previous global studies based on Viking imagery, which showed onset diameters in the range of 4 km to 7 km in equatorial regions. The observed small rampar…
A nightside source of Saturn's kilometric radiation: Evidence for an inner magnetosphere energy driver
Gurnett, D. A.; Kurth, W. S.; Cecconi, B. +5 more
During Cassini's orbit insertion about Saturn, the spacecraft passed within 1.4 Rs of the planet passing from dayside into the nightside region. During this nightside passage, the onboard Radio and Plasma Wave (RPWS) instrument surprisingly detected Saturn kilometric radiation (SKR). Prior to this encounter, it was believed that SKR ori…
Cluster electron observations of the separatrix layer during traveling compression regions
Balogh, A.; Fazakerley, A. N.; Owen, C. J. +2 more
We present Cluster 4-point observations of electrons during traveling compression regions (TCRs) on 19 September 2001. The electron and |B| signatures vary with distance from the plasma sheet, confirming that transient plasma sheet bulges propagate past Cluster. TCRs with |B| increases have either no electron signature, or unidirectional ~1 keV el…
Variability in Saturn's bow shock and magnetopause from Pioneer and Voyager: Probabilistic predictions and initial observations by Cassini
Russell, C. T.; Dougherty, M. K.; Neubauer, F. M. +2 more
Probability distributions for the location of the Saturnian bow shock and magnetopause have been derived by extrapolating observations of dynamic solar wind pressures to the position of Saturn's orbit. These observations are those made by the Pioneer 11, Voyager 1 and 2 spacecraft near Saturn's orbit and by the Ulysses spacecraft near its aphelion…
Ion composition variations in the plasma sheet observed by Cluster/RAPID
Zong, Q. -G.; Daly, P. W.; Ruan, P. +5 more
Based on the energetic particle measurements obtained by Cluster/RAPID (Research with Adaptive Particle Imaging Detectors), ion composition variations in the plasma sheet have been investigated. By comparing observations during quiet and storm intervals, it is found that, in addition to the enhanced energy density for all ion species, the ratio of…
Relating near-Earth observations of an interplanetary coronal mass ejection to the conditions at its site of origin in the solar corona
Balogh, A.; van Driel-Gesztelyi, L.; Lucek, E. +7 more
A halo coronal mass ejection (CME) was detected on January 20, 2004. We use solar remote sensing data (SOHO, Culgoora) and near-Earth in situ data (Cluster) to identify the CME source event and show that it was a long duration flare in which a magnetic flux rope was ejected, carrying overlying coronal arcade material along with it. We demonstrate …
Interplanetary shocks unconnected with earthbound coronal mass ejections
Tappin, S. J.; Howard, T. A.
An associated study by Howard and Tappin (2005) identified 7 Earthbound forward shocks (of which 3 were geoeffective) which were not connected with any detectable coronal mass ejection activity along the Sun-Earth line. This largely unexplored result lends evidence to the fact that some large interplanetary transients are not detected by coronagra…
Detecting sub-glacial aquifers in the north polar layered deposits with Mars Express/MARSIS
Gurnett, D. A.; Farrell, W. M.; Plaut, J. J. +1 more
The penetration of the MARSIS radar signal into the polar ice mass is modeled to determine the capability of the instrument to locate sub-glacial aquifers. As a ground penetrating radar, the orbiting MARSIS transmits a signal >1 W between 1-5 MHz. In this work we will investigate the effect of ice reflective and conductive losses on the radar-d…