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Revisiting Iapetus following recent Cassini observations
Mendis, D. A.; Axford, W. I.
The recent observations of the Saturnian satellite Iapetus by the Cassini spacecraft support the theory proposed by us, over three decades ago, explaining the large brightness asymmetry between the leading and trailing faces of this synchronous satellite. Here we will revisit the question of the observed brightness variations, with orbital phase, …
Similarities and Dissimilarities between the Variations of CME and Other Solar Parameters at Different Heliographic Latitudes and Time Scales
Kane, R. P.
From the LASCO CME (Coronal Mass Ejection) catalog, the occurrence frequencies of all CMEs (all strong and weak CMEs, irrespective of their widths) were calculated for 3-month intervals and their 12-month running means determined for cycle 23 (1996 - 2007) and were compared with those of other solar parameters. The annual values of all-CME frequen…
Pulsations of auroral kilometric radiation at Pc1 frequencies
Pickett, Jolene; Hanasz, Jan; Schreiber, Roman +1 more
Cases of AKR pulsations at frequencies 1 to 4 Hz, typical for Pc1 geomagnetic pulsations, were observed from four Cluster spacecraft. 15 events were found in years 2001-2005, with 14 occurring in a recovery phase of a strong magnetic storm. In a studied event of 22 June 2003 the AKR pulses show positive frequency drifts, corresponding to the earth…
The Tilted Solar Dipole as Observed and Modeled during the 1996 Solar Minimum
Raouafi, N. -E.; Petrie, G. J. D.; Norton, A. A.
We examine the tilt of the solar magnetic dipole away from the rotational axis near the 1996 solar minimum. A persistent tilted dipole may result from an MHD instability acting on the toroidal bands in the solar interior. Nonaxisymmetric eruption of sunspots has been predicted by dynamo theory and observed in sunspot location patterns. The decay o…
Near-infrared polarization images of the Orion proplyds
Eckart, A.; Ott, T.; Rost, S.
Aims: The aim is to study structure and polarization properties of the stars and planet systems in the active Orion H II-region.
Methods: We performed AO-assisted high-resolution imaging polarimetry on selected Orion proplyds close to the Trapezium stars in the J, H, and K bands. Differential polarimetric images of one of the largest and brigh…
Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations
Taylor, M. G. G. T.; Denton, M. H.
Moments calculated from the ion distributions (~0-40 keV) measured by the Cluster Ion Spectrometry (CIS) instrument are combined with data from the Cluster Flux Gate Magnetometer (FGM) instrument and used to characterise the bulk properties of the plasma in the near-Earth magnetosphere over five years (2001-2005). Results are presented in the form…
Fueling QSOs: the relevance of mergers
Canalizo, G.; Schweizer, F.; Lacy, M. +4 more
To study the relevance of mergers for the fueling of QSOs, we are currently conducting an HST imaging campaign of a sample of QSO host galaxies classified as ellipticals in the literature. Here, we present results from a study of the first five QSO host galaxies imaged with HST/ACS. For the majority of objects, strong signs of interactions such as…
Latitude Dependence of the Variations of Sunspot Group Numbers (SGN) and Coronal Mass Ejections (CMEs) in Cycle 23
Kane, R. P.
The 12-month running means of the conventional sunspot number Rz, the sunspot group numbers (SGN) and the frequency of occurrence of Coronal Mass Ejections (CMEs) were examined for cycle 23 (1996 - 2006). For the whole disc, the SGN and Rz plots were almost identical. Hence, SGN could be used as a proxy for Rz, for which latitude data are not avai…
Plasma transport along discrete auroral arcs and its contribution to the ionospheric plasma convection
Fazakerley, A. N.; Nilsson, H.; Buchert, S. +6 more
The role of intense high-altitude electric field (E-field) peaks for large-scale plasma convection is investigated with the help of Cluster E-field, B-field and density data. The study covers 32 E-field events between 4 and 7 RE geocentric distance, with E-field magnitudes in the range 500 1000 mV/m when mapped to ionospheric altitude. …
Low heat conduction in white dwarf boundary layers?
Burwitz, V.; Liu, F. K.; Meyer, F. +1 more
Context: X-ray spectra of dwarf novae in quiescence observed by Chandra and XMM-Newton provide new information on the boundary layers of their accreting white dwarfs.
Aims: Comparison of observations and models allows us to extract estimates for the thermal conductivity in the accretion layer and reach conclusions on the relevant physical proc…