Search Publications

Status of the SOLAR2000 Solar Irradiance Model

Tobiska, W. K.

Extreme-Ultraviolet Flare Loop Emissions in an Eruptive Event

Qiu, Jiong; Wang, Haimin; Chae, Jongchul +1 more

The TRACE/BBSO joint campaign on 27 September 1998 observed an eruptive flare event which lasted for half an hour. The observation covered several ultraviolet (UV) and extreme-ultraviolet (EUV) lines and Hα center and off-band emissions with very high spatial resolution. We find the EUV emissions in different stages of the flare display different …

Multiple Scattering of Hydrogen Lyα Radiation in the Coma of Comet Hyakutake (C/1996 B2)

Keller, H. U.; Combi, M. R.; Meier, R. R. +1 more

The Goddard High Resolution Spectrograph on board the Hubble Space Telescope measured hydrogen Lyα (H Lyα) line profiles at different locations around the coma of comet Hyakutake (C/1996 B2) in 1996 April. The spectral resolution of about 4 km s^-1 (Doppler velocity, FWHM) was significantly better (by a factor of 2-3) than any previous m…

Internal Rotation of the Sun as Inferred from GONG Observations

Gavryusev, V. G.; Gavryuseva, E. A.; di Mauro, M. P.

Helioseismology is a direct and most informative method of studying the structure and dynamics of the Sun. Determining the internal differential rotation of the Sun requires that the frequencies of its eigentones be estimated with a high accuracy, which is possible only on the basis of continuous long-term observations. The longest quasi-continuou…

The Sun and the Solar Wind Close to the Sun

Suess, S. T.

One of the benefits of the Ulysses, SOHO, and YOHKOH missions has been a strong stimulus to better understand the magnetohydrodynamic processes involved in coronal expansion. Three topics for which this has been especially true are described here. These are: (i) The observed constancy of the radial interplanetary magnetic field strength (as mapped…

Bias in velocity determinations from full-disk solar observations

Strous, L. H.

Estimates for the global solar surface velocity field can be obtained from time series of full-disk solar images. However, bias is introduced by mistakes in the assumptions about the geometry of the observations, and by imperfections in the optical system. I investigate many sources of bias and determine their first-order influence on the measured…

Extragalactic novae

Shara, Michael M.

Novae are expected to form in all stellar systems with a binary population. Detection of extragalactic novae provides direct evidence of close binary populations and possible spatial variations in those populations. Comparison of extragalactic novae with their local counterparts can yield valuable tests of close binary evolution theory. I report e…

Ulysses observations of sector boundaries at aphelion

Forsyth, R.; Reisenfeld, D.; Roth, M. +1 more

We study a sample of sector boundaries observed by Ulysses near its early 1998 aphelion at 5.4 AU. We relate these sector boundaries to solar wind structure seen by Wind at 1 AU, guided by a hydrodynamic simulation. For each Ulysses sector boundary we are able to identify a corresponding 1 AU sector boundary, except when strong transients are pres…

Magnetic flux rope ejection: observation at 304Å and comparison with recent models

Delannée, C.

With one example of a coronal mass ejection observed with SOHO//EIT and LASCO we demonstrate the main characteristic of this kind of event: its flux rope nature. These events are commonly responsible for magnetic clouds approaching the Earth. Near the solar surface, the different structures expected during the ejection of a flux rope are observed:…

Solar large-scale emitting chains: some CME-associated events

Chertok, I. M.

Transient large-scale emitting chains and threads, associated with several coronal mass ejections (CMEs), are analyzed by the SOHO//EIT, TRACE, Yohkoh//SXT, Nobeyama Radioheliograph, and some other imaging data. It is illustrated that a pronounced evolution of the chains and threads in the EUV, soft X-ray, microwave, and other ranges can occur man…