Search Publications
Plasma Properties in Coronal Funnels
Mann, G.; Marsch, E.; Hackenberg, P.
A two dimensional model of the transition region and the lower corona, based on the idea that the magnetic flux is strongly concentrated at the boundaries of the supergranular convection cells, has been proposed by Gabriel in 1976. The plasma moves along the open magnetic field lines, which define the the so-called "funnel," and eventually builds …
The nature of the sharp-lined A1V star HD 72660
Varenne, O.
In order to specify the nature of the sharp-lined A1V star HD 72660, its effective temperature and surface gravity have been determined using two different methods. First, the ultraviolet energy distribution of HD 72660 has been compared with that of the normal A0 star HD 10939 and with the predictions of two model atmospheres. Secondly, the param…
Searching for Signal in Noise by Random-Lag Singular Spectrum Analysis
Henney, C. J.; Ulrich, R. K.; Bertello, L. +2 more
Singular spectrum analysis, a technique to detect oscillations in short and noisy time series, was first developed for geophysical applications. This work offers a generalization for long and noisy time series in astrophysical applications. The motivating problem is the detection of low-amplitude solar oscillations.
A mode filter for plasma waves in the Hall-MHD approximation
Glassmeier, K. -H.; Motschmann, U.; Vocks, C.
A filter method is presented which allows a qualitative and quantitative identification of wave modes observed with plasma experiments on satellites. Hitherto existing mode filters are based on the MHD theory and thus they are restricted to low frequencies well below the ion cyclotron frequency. The present method is generalized to cover wave mode…
Increasing the Visibility of Solar Oscillations
Toutain, T.; Jefferies, S. M.; Toner, C. G.
Recent calculations by Toutain, Berthomieu, & Provost predict that low-degree p- and g-modes should produce large continuum intensity perturbations close to the solar limb. Analysis of 72 hr of spatially resolved, full-disk, continuum intensity images of the Sun--obtained with the Solar Oscillations Investigation/Michelson Doppler Imager instr…
The CaII-M_v Correlation (Wilson-Bappu Effect) Calibrated by HIPPARCOS Parallaxes
Wallerstein, George; Machado-Pelaez, Laura; Gonzalez, Guillermo
We have used Hipparcos parallaxes to derive absolute visual magnitudes of G, K, and M stars with Ca II emission line widths previously measured by O. C. Wilson. A linear relationship similar to the one derived originally by Wilson & Bappu and improved by Lutz & Kelker was found from M_v=+7 to -2. For stars brighter than M_v=-2 a substantia…
Numerical simulation of the dust flux on a spacecraft in orbit around an aspherical cometary nucleus - I
Fulle, M.; Rodionov, A. V.; Crifo, J. F.
This study is the first investigation of the dust collection by a spacecraft orbiting a cometary nucleus, which is based on a physically consistent ab-initio model of the dust distribution in the vicinity of an aspherical comet nucleus. The homogeneous bean-shaped nucleus of Crifo & Rodionov (1997a) is used, with updated parameter values adapt…
Martian North Polar Cap 1996-1997
Iwasaki, Kyosuke; Parker, Donald C.; Larson, Steve +1 more
In order to investigate the interannual variability of the regression of the martian north polar cap, the regression of the martian north polar cap during the 1996-1997 apparition is examined utilizing measurements with CCD images.
The regression of the north polar cap in 1996-1997 as determined from our measurements is in excellent agreement…Analysis of the oscillations in HST observations of the quiescent SU UMa type dwarf nova WZ Sagittae
Horne, Keith; Wood, Janet H.; Welsh, William F. +2 more
An analysis of the UV oscillations in WZ Sge is presented, in which we obtain the oscillation amplitude spectra. We find a strong 27.9-s oscillation in our Hubble Space Telescope (HST) UV and zeroth-order light curves as well as weaker oscillations at 28.4s in the UV and 29.1s in the zeroth order. We find that the main oscillation amplitude spectr…
UVCS/SOHO Observations of H I Lyman Alpha Line Profiles in Coronal Holes at Heliocentric Heights Above 3.0 R⊙
Cranmer, S. R.; Ciaravella, A.; Noci, G. +7 more
The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) has been used to measure spectral line profiles for H I Lyα in the south polar coronal hole at projected heliocentric heights from 3.5 to 6.0 R⊙ during 1998 January 5 11. Observations from 1.5 to 2.5 R⊙ were made for comparison. T…