Search Publications
Waves in the solar transition region
Doyle, J. G.; Banerjee, D.; O'Shea, E. +1 more
The power spectra for line intensities of several lines formed in the upper transition region around 100000 to 250000 K are presented. A period of ∼5 min is clearly present in lines due to Oiii, Oiv, and Ov. In one dataset a period approaching 10 min is present for ∼40 min. The size of the emitting features is limited to ∼7 arc sec squared. In all…
Comparison of Prominences in Hα and He II 304 Å
Wang, Haimin; Chae, Jongchul; Gurman, Joseph B. +1 more
In this letter, we bring attention to prominences which show different morphology in Hα and He ii 304 Å, as observed simultaneously by BBSO and EIT on board SOHO. Those two lines have been thought to represent similar chromospheric structures although they are formed at significantly different temperatures. We give two examples representing two ki…
Joint Nancay Radioheliograph and LASCO Observations of Coronal Mass Ejections - II. The 9 July 1996 Event
Llebaria, A.; Michels, D. J.; Schwenn, R. +10 more
The development of a coronal mass ejection on 9 July 1996 has been analyzed by comparing the observations of the LASCO/SOHO coronagraphs with those of the Nancay radioheliograph. The spatial and temporal evolution of the associated radioburst is complex and involves a long-duration continuum. The analysis of the time sequence of the radio continuu…
SOHO Observations of the Connection Between Line Profile Parameters in Active and Quiet Regions and the Net Red Shift in EUV Emission Lines
Harrison, R. A.; Wilhelm, K.; Fredvik, T. +5 more
We present high spatial and spectral resolution observations of one active and one quiet-Sun region, obtained with CDS and SUMER on SOHO. The connections between the line profile parameters are studied and a systematic wavelength shift towards the red with increasing peak line intensity (line broadening) is detected. The large scatter in the data …
The Solar Minimum Active Region 7978, Its X2.6/1B Flare, CME, and Interplanetary Shock Propagation of 9 July 1996
Michels, D. J.; Paswaters, S. E.; Koomen, M. J. +21 more
The first X-class flare in four years occurred on 9 July 1996. This X2.6/1B flare reached its maximum at 09:11 UT and was located in active region 7978 (S10° W30°) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio…
The Geometric Spreading of Coronal Plumes and Coronal Holes
Wu, S. T.; Poletto, G.; Suess, S. T. +2 more
The geometric spreading in plumes and in the interplume region in coronal holes is calculated, using analytic and numerical theoretical models, between 1.0 and 5.0 R⊙. We apply a two-scale approximation that permits the rapid local spreading at the base of plumes (fl) to be evaluated separately from the global spreading (f
Filament Observations with SOHO Sumer/cds: The Behaviour of Hydrogen Lyman Lines
Heinzel, P.; Vial, J. -C.; Schmieder, B. +1 more
On 21 September 1996, a filament close to an area of enhanced network was observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer and Coronal Diagnostic Spectrometer (CDS). CDS provided intensity, Doppler shift and linewidth maps of the region in six lines whose temperature range covers 104 to 106…
EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO - II. Velocities and Line Profiles
Harrison, R. A.; Wilhelm, K.; Fredvik, T. +8 more
We have studied the dynamics in the sunspot transition region between the chromosphere and the corona and investigated the extension of the flow field into the corona. Based on EUV spectra of a medium size sunspot and its surroundings, NOAA 7981, observed with CDS and SUMER on SOHO, we derive line-of-sight velocities and study the line profiles fo…
SUMER Observations of the Evolution and the Disappearance of a Solar Prominence
Kucera, T. A.; Ofman, L.; Mouradian, Z. +1 more
The mechanisms that lead to the formation and the disappearance of prominences are poorly understood, at present. An arch-shaped prominence was observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on board the Solar and Heliospheric Observatory (SOHO) on 31 March-1 April 1996. The observations were performed a…
Joint Nançay Radioheliograph and LASCO Observations of Coronal Mass Ejections - I. The 1 July 1996 Event
Llebaria, A.; Michels, D. J.; Schwenn, R. +9 more
The development of a coronal mass ejection on 1 July 1996 has been analyzed by comparing the observations of the LASCO/SOHO coronagraph with those of the Nançay radioheliograph. This comparison brings new insight and very useful diagnosis for the study of CME events. It is shown that the initial instability took place in a small volume located abo…