Search Publications
Does the tachocline show solar cycle related changes?
Basu, Sarbani; Schou, Jesper
The tachocline at the base of the convection zone is generally believed to be the seat of the solar dynamo. Here we investigate whether the tachocline shows any detectable change using several 72 day time-series of the Michelson Doppler Imager (MDI) Medium-l data. We do not find any clear evidence of change with time.
The SOHO-Stellar Connection
Ayres, Thomas R.
The `solar- stellar connection' bridges the daytime and nighttime communities; an essential link between the singular, but detailed, views of our Sun, and the broad, but coarse, glimpses of the distant stars. One area in particular - magnetic activity - has profited greatly from the two way traffic in ideas. In that spirit, I present an evolutiona…
VLA, SOHO and TRACE Observations of Nonthermal Burst Activity, Coronal Mass Ejections, and EUV Transient Events
Willson, Robert F.
Very Large Array (VLA) observations of the Sun at 91 and 400 cm wavelength have been used to investigate the radio signatures of EUV heating events and coronal mass ejections (CMEs) detected by SOHO and TRACE. Our 91 cm observations show the onset of Type I noise storm emission about an hour after an EUV ejection event was detected by EIT and TRAC…
The Occurrences of Coronal Mass Ejection at Solar Minimum and their Association with Surface Activity
Simnett, G. M.; Lewis, D. J.
We have developed a non-subjective technique for recording the occurrences of coronal mass ejection (CME) in data recorded by the Large Angle Spectrometric Coronagraph experiment (LASCO) aboard the Solar and Heliospheric Observatory spacecraft (SOHO). We have found evidence for, and quantified, an asymmetry in the apparent longitudes at which mass…
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…
Solar rotation in the subphotospheric layers
González Hernández, I.; Patrón, J.
The solar rotation rate at latitudes 0°, 15° and 30° has been inferred by averaging the results of 120 regions of 15°×15°, which have been studied over a total area of about 75° in latitude and 360° in longitude. A local helioseismology technique, the ring diagram analysis method, has been used to analyse the horizontal velocity vectors from about…
SERTS-97 Measurements Of Relative Wavelength Shifts In Coronal Emission Lines Across A Solar Active Region
Thompson, W. T.; Davila, J. M.; Thomas, R. J. +1 more
We used slit spectra from the 18 November 1997 flight of Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-97) to measure relative wavelength shifts of coronal emission lines as a function of position across NOAA active region 8108. The shifts are measured relative to reference wavelengths derived from spectra of the…
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 …
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…
Electron density diagnostics for solar ultraviolet lines of O V
Doyle, J. G.; Keenan, F. P.; O'Shea, E. +1 more
We determine the electron densities for a range of solar features using new calculations for the O v line ratio, R=I(λ761.1)/I(λ760.4), in conjunction with observational data obtained with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory (SOHO). The densities obtained from this di…