Search Publications
Ultraviolet Hubble Space Telescope Observations of the Jet in M87
Zepf, Stephen E.; Waters, Christopher Z.
We present new ultraviolet photometry of the jet in M87 obtained from Hubble Space Telescope (HST) WFPC2 imaging. We combine these ultraviolet data with previously published photometry for the knots of the jet in radio, optical, and X-ray and fit three theoretical synchrotron models to the full data set. The synchrotron models consistently overpre…
The disrupted molecular envelope of Frosty Leo
Sahai, R.; Sánchez Contreras, C.; Alcolea, J. +2 more
We present maps of CO emission in the protoplanetary nebula Frosty Leo. Observations of the rotational transitions 12CO J=2{-}1 and 1 0 have been obtained with the IRAM interferometer and the OVRO array. The molecular envelope of Frosty Leo is found to be complex and compact; most of the gas extends ⪉6´´ and shows a structure that is ve…
The Martian atmosphere above great volcanoes: Early planetary Fourier spectrometer observations
Grassi, D.; Ignatiev, N. I.; Zasova, L. V. +4 more
This work reports the first observations of the Martian atmosphere returned by the planetary Fourier spectrometer (PFS) on board of Mars express (MEX) satellite in the vicinity of the greatest volcanic domes of the planet. Two of the early MEX orbits have already covered the region of Olympus Mons and Ascraeus Mons. These measurements are very sim…
Helium Abundance in High-Temperature Solar Flare Plasmas
Landi, E.; Feldman, U.; Laming, J. M.
In the present work we use emission from dense plasmas late in the decay phase of flares, while the plasmas are still hot [(2-4)×106 K], to determine the absolute helium abundance in flaring solar corona. To achieve this, we make use of intensity ratios of H I and He II lines and of intensity ratios between the He II lines and the brems…
Three Criteria to Discriminate between Elementary and Composite Coronal Loops
Aschwanden, Markus J.
In this Letter, we establish three simple criteria to discriminate between elementary and composite loop structures, based on observations from high-resolution (TRACE) and low-resolution (EIT) imagers. Both data sets contain triple-filter data with a temperature diagnostic in the range of T~0.7-2.8 MK, which we use for forward-fitting of a differe…
Resolving the enigmatic solar wind disappearance event of 11 May 1999
Janardhan, P.; Tokumaru, M.; Kojima, M. +2 more
On 11 and 12 May 1999, the Earth was engulfed by an unusually low-density (<1 cm-3) and low-velocity (<350 km s-1) solar wind for a period of over 1 day. Extensive studies of this unusual event that occurred during Carrington rotation 1949 (CR1949), using both ground-based and space-based in situ observations, have not …
Stability of the inner source pickup ions over the solar cycle
Geiss, J.; McComas, D. J.; Schwadron, N. A. +2 more
Inner source pickup ions (PUIs) were discovered and are observed by Ulysses. They are thought to be generated by solar wind interaction with dust grains near the Sun. From previous work, four constraints were derived on inner source PUIs from observations near solar minimum: (1) the composition resembles the solar wind; (2) the distribution functi…
Multipoint observations of transient reconnection signatures in the cusp precipitation: A Cluster-IMAGE detailed case study
Budnik, E.; Berchem, J.; Escoubet, C. P. +10 more
This paper uses 90 min of Cluster multipoint data at ∼5 RE altitude together with global dayside imaging data provided by the IMAGE-SI-12 instrument to analyze the northern cusp crossed on 14 July 2001, during a period of high solar wind pressure Psw and strongly duskward interplanetary magnetic field (IMF). Simultaneous obse…
Global structure of the out-of-ecliptic solar wind
Burlaga, L. F.; Sheeley, N. R.; Wang, Y. -M. +1 more
We use the observed photospheric field maps and the wind speed observed from Ulysses to study the out-of-ecliptic solar wind. The model calculates the wind speed from the rate of magnetic flux tube expansion factors using a conversion function that is determined by least squares fit of all currently available data from Ulysses. Using the best fit …
FUSE Observations of DB White Dwarfs
Kruk, J. W.; Chayer, P.; Petitclerc, N. +2 more
We present a comprehensive analysis of the far-ultraviolet spectra of three DB white dwarfs secured with the FUSE observatory. Transitions associated with various carbon ions are detected in all three objects. Atmospheric parameters are first redetermined on the basis of an analysis of archival data available, and the abundance of carbon, together…