Search Publications
Correlation between ground-based observations of substorm signatures and magnetotail dynamics
Lester, M.; Owen, C. J.; Dunlop, M. +8 more
We present a substorm event study using the four Cluster spacecraft in combination with ground-based instruments, in order to perform simultaneous observations in the ionosphere and magnetotail. We show good correlation between substorm signatures on the ground and in the magnetotail, even though data from the northern-ground and southern-tail hem…
Bouncing ion clusters in the plasma sheet boundary layer observed by Cluster-CIS
Lundin, R.; Dandouras, I.; RèMe, H. +10 more
We report on ion beams injected into the plasma sheet boundary layer (at or near the separatrix) at distances >39 RE and up to 169 RE that bounced several times back and forth (up to three echoes) while remaining in coherent bunches before thermalizing in the central plasma sheet. These bouncing ion clusters (BIC) interact…
HST Imaging of MEGA Microlensing Candidates in M31
Crotts, Arlin P. S.; Kuijken, Konrad; Widrow, Lawrence M. +5 more
We investigate HST/ACS and WFPC2 images at the positions of five candidate microlensing events from a large survey of variability in M31 (MEGA). Three closely match unresolved sources, and two produce only flux upper limits. All are confined to regions of the color-magnitude diagram where stellar variability is unlikely to be easily confused with …
Reverse convection and cusp proton aurora: Cluster, polar and image observation
Zong, Q. -G.; Daly, P. W.; Mende, S. B. +4 more
On April 21, 2001 an interplanetary CME started to interact with the magnetosphere when CLUSTER spacecraft were travelling in the cusp region. This interaction produced a strong magnetic storm ( Dst = 103 nT) at Earth. Cusp proton aurora was caused by the leading phase of the CME. Cusp proton aurora generally appear during northward IMF…
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…
On the Nature of the Unidentified X-ray/γ-ray Sources Igr J18027–1455 and Igr J21247+5058
Mirabel, I. F.; Combi, J. A.; Ribó, M.
We present a multiwavelength study of the environment of the unidentified X-ray/γ-ray sources IGR J18027–1455 and IGR J21247 + 5058, recently discovered by the IBIS/ISGRI instrument, onboard the INTEGRAL satellite. The main properties of the sources found inside their position error circles, give us clues about the nature of these high-energy sour…
Rapid X-Ray Variability of Seyfert 1 Galaxies
Iwasawa, K.; Vaughan, S.; Fabian, A. C.
The rapid and seemingly random fluctuations in X-ray luminosity of Seyfert galaxies provided early support for the standard model in which Seyferts are powered by a supermassive black hole fed from an accretion disc. However, since EXOSAT there has been little opportunity to advance our understanding of the most rapid X-ray variability. Observatio…
Photon scattering in the solar ultraviolet lines of HeI and HeII
Jordan, C.; Houdebine, E. R.; Smith, G. R.
Observations made with the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SOHO) are used to investigate the behaviour of the intensities of the emission lines of HeI, HeII and OIII at the quiet Sun-centre and at θ= 60° towards the equatorial limb. The aim is to examine the possible effects of photon scatterin…
Solar wind velocity measurements near the sun using Ulysses radio amplitude correlations at two frequencies
Plettemeier, D.; Bird, M. K.; Efimov, A. I. +4 more
Measurements of solar wind velocity have been derived from simultaneous coronal sounding observations of radio amplitude scintillations at both S-band and X-band during the solar conjunction of the Ulysses spacecraft in August 1991. The signal amplitude was recorded with an averaging time of 1 s. A cross-correlation analysis between S- and X-band …
Double Star, Cluster, and ground-based observations of magnetic reconnection during an interval of duskward oriented IMF: preliminary results
Balogh, A.; Davies, J. A.; Wild, J. A. +3 more
We present a space- and ground-based study exploiting data from the coordinated Cluster and Double Star missions in order to investigate dayside magnetic reconnection under BY+ dominated IMF conditions. In-situ observations of magnetosheath flux transfer events combined with measurements of pulsed poleward and dawnward directed flows in…