Search Publications
Probing Supergranular Flow in the Solar Interior
Woodard, M. F.
Helioseismic correlation data computed from SOHO MDI high-resolution Doppler images were inverted for solar subsurface supergranular flow, using an improved forward model. The statistical error of the inversion is set by the stochastic nature of solar wave excitation, which limits the detection of supergranular flow with these data to the first 4 …
Taylor scale and effective magnetic Reynolds number determination from plasma sheet and solar wind magnetic field fluctuations
Walker, R. J.; Dasso, S.; Matthaeus, W. H. +2 more
Cluster data from many different intervals in the magnetospheric plasmas sheet and the solar wind are employed to determine the magnetic Taylor microscale from simultaneous multiple point measurements. For this study we define the Taylor scale as the square root of the ratio of the mean square magnetic field (or velocity) fluctuations to the mean …
A Cluster measurement of fast magnetic reconnection in the magnetotail
Escoubet, C. P.; Balogh, A.; Dandouras, I. +11 more
Fast reconnection is crucial to magnetospheric substorms, solar and stellar flares and fusion plasmas. Ultimate confirmation of fast reconnection must be achieved by multi-spacecraft detections of the reconnection rate itself and associated dimensions of the diffusion region. Here we report a multi-spacecraft measurement of fast reconnection rate …
A Comprehensive Study of the Initiation and Early Evolution of a Coronal Mass Ejection from Ultraviolet and White-Light Data
Romoli, M.; Bemporad, A.; Poletto, G. +1 more
In this work we analyze simultaneous UV and white-light (WL) observations of a slow CME that occurred on 2000 January 31. Unlike most CMEs studied in the UV so far, this event was not associated with a flare or filament eruption. Based on vector magnetograph data and magnetic field models, we find that field disruption in an active region (AR) was…
Structure and dynamics of the class I young stellar object L1489 IRS
Hogerheijde, M. R.; Jørgensen, J. K.; Brinch, C. +1 more
Context: During protostellar collapse, conservation of angular momentum leads to the formation of an accretion disc. Little is known observationally about how and when the velocity field around the protostar shifts from infall-dominated to rotation-dominated.
Aims: We investigate this transition in the low-mass protostar L1489 IRS, which is kn…
Confirming the Detection of an Intergalactic X-Ray Absorber toward PKS 2155-304
Canizares, Claude R.; Yao, Yangsen; Fang, Taotao
We present new observations of PKS 2155-304 with the Chandra Low Energy Transmission Grating (LETG), using the Advanced CCD Imaging Spectrometer (ACIS). We confirm the detection of an absorption line plausibly identified as O VIII Lyα from a warm-hot intergalactic medium associated with a small group of galaxies along the line of sight, as origina…
The Color-Magnitude Distribution of Field Galaxies to z~3: The Evolution and Modeling of the Blue Sequence
van Dokkum, Pieter G.; Franx, Marijn; Labbé, Ivo +7 more
Using deep NIR VLT ISAAC and optical HST WFPC2 imaging in the HDF-S and MS 1054-03, we study the rest-frame UV-to-optical colors and magnitudes of galaxies to z~3. Unlike the present day, there is no evidence for a red sequence at z~3, but there does appear to be a well-defined CMR for blue galaxies at all redshifts, with more luminous galaxies ha…
Gravity field and interior of Rhea from Cassini data analysis
Iess, Luciano; Tortora, Paolo; Rappaport, Nicole J. +5 more
The Cassini spacecraft encountered Rhea on November 26, 2005. Analysis of the Doppler data acquired at and around closest approach yields the mass of Rhea and the quadrupole moments of its gravity field with unprecedented accuracy. We obtained GM=153.9395±0.0018 kms which corresponds to a density of 1232.8±5.4 kgm. Our results for J and C are (7.9…
Electron dynamics and cross-shock potential at the quasi-perpendicular Earth's bow shock
Lefebvre, Bertrand; Schwartz, Steven J.; Fazakerley, Andrew F. +1 more
The evolution of the electron distribution function through quasi-perpendicular collisionless shocks is believed to be dominated by the electron dynamics in the large-scale coherent and quasi-stationary magnetic and electric fields. We investigate the electron distributions measured on board Cluster by the Plasma Electron and Current Experiment (P…
What is the origin of the soft excess in active galactic nuclei?
Done, Chris; Sobolewska, Małgorzata A.
We investigate the nature of the soft excess below 1 keV observed in active galactic nuclei. We use the XMM-Newton data of the low-redshift, optically bright quasar, PG 1211+143, and we compare it with the narrow-line Seyfert 1 galaxy, 1H 0707-495, which has one of the strongest soft excesses seen. We test various ideas for the origin of the soft …