Search Publications
Hinode Solar Optical Telescope Observations of the Source Regions and Evolution of "Type II" Spicules at the Solar Polar Limb
Moore, Ronald L.; Sterling, Alphonse C.; DeForest, Craig E.
We examine solar spicules using high-cadence Ca II data of the north pole coronal hole region, using the Solar Optical Telescope (SOT) on the Hinode spacecraft. The features we observe are referred to as "Type II" spicules by De Pontieu et al. in 2007. By convolving the images with the inverse-point-spread function for the SOT Ca II filter, we are…
Short-term Solar Flare Level Prediction Using a Bayesian Network Approach
Huang, Xin; Yu, Daren; Wang, Huaning +3 more
A Bayesian network approach for short-term solar flare level prediction has been proposed based on three sequences of photospheric magnetic field parameters extracted from Solar and Heliospheric Observatory/Michelson Doppler Imager longitudinal magnetograms. The magnetic measures, the maximum horizontal gradient, the length of neutral line, and th…
The Kelvin-Helmholtz instability at Mercury: An assessment
Korth, H.; Blomberg, L. G.; Slavin, J. A. +2 more
The Kelvin-Helmholtz instability is believed to be an important means for the transfer of energy, plasma, and momentum from the solar wind into planetary magnetospheres, with in situ measurements reported from Earth, Saturn, and Venus. During the first MESSENGER flyby of Mercury, three periodic rotations were observed in the magnetic field data po…
C, N and O abundances in red clump stars of the Milky Way
Ilyin, I.; Edvardsson, B.; Tautvaišienė, G. +2 more
The Hipparcos orbiting observatory has revealed a large number of helium-core-burning ‘clump’ stars in the Galactic field. These low-mass stars exhibit signatures of extra mixing processes that require modelling beyond the first dredge-up of standard models. The 12C/13C ratio is the most robust diagnostic of deep mixing becau…
Fast Contraction of Coronal Loops at the Flare Peak
Wang, Haimin; Liu, Rui
On 2005 September 8, a coronal loop overlying the active region NOAA 10808 was observed in TRACE 171 Å to contract at ~100 km s-1 at the peak of an X5.4-2B flare at 21:05 UT. Prior to the fast contraction, the loop underwent a much slower contraction at ~6 km s-1 for about 8 minutes, initiating during the flare preheating pha…
Detection of high-velocity material from the wind-wind collision zone of Eta Carinae across the 2009.0 periastron passage
Gull, T. R.; Nielsen, K. E.; Madura, T. I. +15 more
We report near-infrared spectroscopic observations of the Eta Carinae massive binary system during 2008-2009 using the CRIRES spectrograph mounted on the 8 m UT 1 Very Large Telescope (VLT Antu). We detect a strong, broad absorption wing in He i λ10833 extending up to -1900 km s-1 across the 2009.0 spectroscopic event. Analysis of archi…
Deriving Metallicities from the Integrated Spectra of Extragalactic Globular Clusters Using the Near-infrared Calcium Triplet
Spitler, Lee R.; Forbes, Duncan A.; Brodie, Jean P. +3 more
The Ca II triplet (CaT) feature in the near-infrared has been employed as a metallicity indicator for individual stars as well as integrated light of Galactic globular clusters (GCs) and galaxies with varying degrees of success, and sometimes puzzling results. Using the DEIMOS multi-object spectrograph on Keck we obtain a sample of 144 integrated …
Unusual Trends in Solar P-Mode Frequencies During the Current Extended Minimum
Hill, F.; Jain, K.; Tripathy, S. C. +1 more
We investigate the behavior of the intermediate-degree mode frequencies of the Sun during the current extended minimum phase to explore the time-varying conditions in the solar interior. Using contemporaneous helioseismic data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI), we find that the changes in reson…
Swift/XRT observations of unidentified INTEGRAL/IBIS sources
Bird, A. J.; Fiocchi, M.; Landi, R. +4 more
The most recent IBIS/ISGRI survey, i.e. the fourth one, lists 723 hard X-ray sources, many still unidentified, i.e. lacking an X-ray counterpart or simply not studied at lower energies, i.e. below 10keV. In order to overcome this lack of X-ray information, we cross-correlated the list of IBIS sources included in the fourth IBIS catalogue with the …
Ion transport in Titan's upper atmosphere
Dougherty, M. K.; Wahlund, J. -E.; Ågren, K. +4 more
Based on a combined Cassini data set including Ion Neutral Mass Spectrometer, Radio Plasma Wave Science, and Magnetometer measurements made during nine close encounters of the Cassini spacecraft with Titan, we investigate the electron (or total ion) distribution in the upper ionosphere of the satellite between 1250 and 1600 km. A comparison of the…