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Observations of Transition Region Plasma
Brekke, Pâl
Recent space missions have changed our view of the solar transition region. In particular the ESA/NASA Solar and Heliospheric Observatory (SOHO) and NASA's TRACE satellite have provided a unique opportunity to explore the solar atmosphere in detail. The combination of high spatial, spectral and temporal observations has made it possible to derive …
Electron density and temperature structure of two limb active regions observed by SOHO-CDS
Young, P. R.; Mason, H. E.; Landi, E. +1 more
The analysis of two active regions on the limb using observations from SOHO-CDS allows us to determine the electron density and temperature distribution of the coronal emission. We find that the active regions have hot cores (3×106 K) with larger cooler (106 K) loop structures extending above the limb. The electron number den…
SOHO Observations of the Structure and Dynamics of Sunspot Region Atmospheres
Kjeldseth-Moe, O.; Haugan, S. V. H.; Brekke, P. +2 more
We present results from a study of the spatial distributions of line emission and relative line-of-sight velocity in the atmosphere above 17 sunspot regions, from the chromosphere, through the transition region and into the corona, based on simultaneous observations of ten EUV emission lines with the Coronal Diagnostic Spectrometer - CDS on SOHO. …
Multi-wavelength observations of the onset phase of a coronal mass ejection
Thompson, B. J.; Inhester, B.; Harrison, R. A. +6 more
The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Te…
Anomalous Line Shifts From Local Intensity Gradients on the Soho/cds NIS Detector
Haugan, S. V. H.
Line shifts for some emission lines on the SOHO/CDS NIS detector appear to be strongly correlated with local intensity gradients along the slit in a way that seems impossible to explain with a physical solar model. Line widths also show a correlation with local intensity gradients. The most plausible instrumental explanation seems to be an ellipti…
Evidence for non-potential magnetic fields in the quiet Sun
Chae, Jongchul; Woodard, M. F.
A comparison of BBSO Hα centerline filtergrams and videomagnetograms was made to investigate the existence of non- potential magnetic fields in the quiet Sun near magnetic network. We use the fibril structure in the Hα images as a proxy for the horizontal chromospheric magnetic field which we compare with the horizontal field obtained by potential…
Oscillations of the upper chromosphere
Vial, J. -C.; Bocchialini, K.; Lemaire, P. +2 more
Variations of intensity and wavelength in several UV lines have been observed with the SUMER spectroheliometer onboard SOHO, and they have been analysed to obtain oscillation spectra and phase differences between lines of different ions. Lines intensities of neutral or singly ionized atoms (with temperature of formation ≤ 30 000 K) exhibit an incr…
Multiple-Thread Model of a Prominence Observed by SUMER and EIT on SOHO
Wilhelm, K.; Schmieder, B.; Dammasch, I. E. +1 more
A quiescent polar crown prominence was observed at Meudon in Hα and Ca ii lines, and by EIT and SUMER on board SOHO in UV lines from 9 to 10 March 1996. SUMER observed the prominence continuously in a scanning mode between 21:40 UT on 9 March, and 18:13 UT on 10 March, in the nitrogen line N v (λ1238) with a 1 arc sec2 resolution. Altog…
Structure and Dynamics of Interconnecting Loops and Coronal Holes in Active Longitudes
Kosovichev, A. G.; Scherrer, P. H.; Benevolenskaya, Elena E.
Using SOHO/MDI and SOHO/EIT data we study properties and dynamics of interconnected active regions, and the relations between the photospheric magnetic fields and coronal structures in active longitudes during the beginning of solar cycle 23. The emergence of new magnetic flux results in appearance of new interconnecting loops. The existence of st…
Dynamics of polar plumes observed at the 1998 February 26 eclipse
Gurman, J. B.; Lites, B. W.; Elmore, D. F. +5 more
This paper presents first observations of dynamics of the white-light solar corona detected during the few minutes of totality of a solar eclipse. Perturbations of a polar plume associated with an embedded `jet' structure observed simultaneously at 195 Å with the EUV Imaging Telescope (EIT) aboard the SOHO spacecraft lead to estimates of the elect…