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The linear force-free field in a spherical shell using a new method to determine the coefficients of the eigenfunction expansion
Bromage, B. J. I.; Clegg, J. R.; Browning, P. K. +2 more
The linear force-free field of a plasma in between spherical shells is found allowing for inhomogeneous boundary conditions. A three-dimensional solution is found by analysis and used as a benchmark to test a solution in terms of an expansion of eigenfunctions where the coefficients are determined by a new method. Alternative methods are also appl…
Towards Understanding Solar Convection and Activity - (Invited Review)
Gough, Douglas
The dynamics of the large-scale eddies which advect angular momentum through the convection zone is controlled in a significant way by the boundary conditions, which, if they are not modelled adequately, do not lead to a distribution of angular velocity that is consistent with observation. The transition boundary layer separating the convection zo…
A model for accelerated density enhancements emerging from coronal streamers in Large-Angle and Spectrometric Coronagraph observations
Cargill, Peter J.; Schmidt, Joachim M.
Recent Large-Angle and Spectrometric Coronagraph (LASCO) white light observations, ranging between 2RS and 32RS, trace accelerated density enhancements in the vicinity of the Sun which can be detected as enhancement in the intensity of the Thomson scattered light. One interpretation of these observed density enhancements is t…
SWAN/SOHO H Cell Measurements: The First Year
Bertaux, Jean-Loup; Lallement, Rosine; Quémerais, Eric +3 more
We present here an analysis of one year of data obtained by the SWAN instrument on board the SOHO spacecraft orbiting around the L1 Lagrange point at 1.5 × 106 km sunward from Earth. This instrument is measuring the interplanetary Lyman ca background due to solar photons backscattered by hydrogen atoms in the interplanetary medium. The …
Interstellar Gas in the NGC 4410 Galaxy Group
Smith, Beverly J.
We present new radio continuum, 21 cm H I, and 2.6 mm CO data for the peculiar radio galaxy NGC 4410A and its companion NGC 4410B and compare with available optical and X-ray maps. Our radio continuum maps show an asymmetric double-lobed structure, with a high surface brightness lobe extending 3.6‧ (~100 kpc) to the southeast and a 6.2‧ (~180 kpc)…
An analytical model to predict the particle flux on spacecraft in the solar system
Jehn, R.
In this paper an analytical meteoroid flux model is presented which extends from 1 to 10 AU and covers a mass range from 10 -18 to 1 g. The basic flux curve of the model by Grün et al. (1985, Icarus 62, 244-272.) is modified by an analytical multiplication factor in order to approximate the meteoroid flux as predicted by the five-popula…
A Synoptic View of the Subphotospheric Horizontal Velocity Flows in the Sun
Hill, F.; González Hernández, I.; Bogart, R. S. +3 more
Ring diagram analysis, a technique of local helioseismology, has been applied to 120 regions of 15deg×15deg over the solar surface in order to study the mass motions in the upper layers of the convection zone. The horizontal flows from ~0.95 Rsolar up to the surface have been investigated in a region spanning 360
Possible emission lines from the gaseous beta Pictoris disk
Feldman, P. D.; Lecavelier des Etangs, A.; Ferlet, R. +6 more
We present the results of exploratory HST observations to detect the emission lines of ions in the beta Pictoris disk with the spectrograph slit placed off the star. Possible emission lines from Fe II have been detected at ~10-14erg cm-2 s-1 at 0.5'' from beta Pictoris, which would suggest a total Fe II density of …
Simultaneous SOHO andYohkoh Observations of a Small Solar Active Region
Siegmund, O. H. W.; Fisher, G. H.; Acton, L. W. +2 more
We present new results from observations of a small active region taken with the SUMER spectrograph and Extreme Ultraviolet Imaging Telescope (EIT) on SOHO and with the Soft X-Ray Telescope (SXT) on Yohkoh. The SUMER study features line and continuum emission covering a wide range of temperatures and includes the density-sensitive O IV] λ1400 mult…
Simulations and Mitigation of Pile-Up in XMM CCD Instruments
Lumb, D. H.
Simulations of the XMM EPIC instruments are presented. They suggest the correct operating mode must be chosen to ensure that spectral analysis of the data is not compromised by `pile-up' effects. The performance is contrasted with the CHANDRA AXAF CCD Imaging Spectrometer, showing how the higher effective area but better over-sampling of its mirro…