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First Results from the SOHO Ultraviolet Coronagraph Spectrometer
Romoli, M.; Raymond, J. C.; Naletto, G. +23 more
The SOHO Ultraviolet Coronagraph Spectrometer (UVCS/SOHO) is being used to observe the extended solar corona from 1.25 to 10 R⊙ from Sun center. Initial observations of polar coronal holes and equatorial streamers are described. The observations include measurements of spectral line profiles for HI Lα and Lβ, Ovi 1032 Å and 1037 Å, Mgx 625 Å, Fexi…
EIT Observations of the Extreme Ultraviolet Sun
Michels, D. J.; Gurman, J. B.; Berghmans, D. +32 more
The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrume…
First Results of the SUMER Telescope and Spectrometer on SOHO - I. Spectra and Spectroradiometry
Vial, J. -C.; Grewing, M.; Wilhelm, K. +16 more
SUMER - the Solar Ultraviolet Measurements of the Emitted Radiation instrument on the Solar and Heliospheric Observatory (SOHO) - observed its first light on January 24, 1996, and subsequently obtained a detailed spectrum with detector B in the wavelength range from 660 to 1490 Å (in first order) inside and above the limb in the north polar corona…
Composition of Coronal Streamers from the SOHO Ultraviolet Coronagraph Spectrometer
Romoli, M.; Raymond, J. C.; Naletto, G. +24 more
The Ultraviolet Coronagraph Spectrometer on the SOHO satellite covers the 940-1350 Å range as well as the 470-630 Å range in second order. It has detected coronal emission lines of H, N, O, Mg, Al, Si, S, Ar, Ca, Fe, and Ni, particularly in coronal streamers. Resonance scattering of emission lines from the solar disk dominates the intensities of a…
Structure and Rotation of the Solar Interior: Initial Results from the MDI Medium-L Program
Kosovichev, A. G.; Hoeksema, J. T.; Scherrer, P. H. +31 more
The medium-l program of the Michelson Doppler Imager instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to ∽ 300. The data for the program are partly processed on board because only about 3% of MDI observations can be transmitted continuously to the ground. The on-board data processing, the …
First Results from VIRGO, the Experiment for Helioseismology and Solar Irradiance Monitoring on SOHO
Gough, Douglas; Domingo, Vicente; Appourchaux, Thierry +19 more
First results from the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) on the ESA/NASA Mission SOHO (Solar and Heliospheric Observatory) are reported. The observations started mid-January 1996 for the radiometers and sunphotometers and near the end of March for the luminosity oscillation imager. The performance of all t…
First Results of the SUMER Telescope and Spectrometer on SOHO - II. Imagery and Data Management
Grewing, M.; Wilhelm, K.; Marsch, E. +13 more
SUMER - Solar Ultraviolet Measurements of Emitted Radiation - is not only an extreme ultraviolet (EUV) spectrometer capable of obtaining detailed spectra in the range from 500 to 1610 Å, but, using the telescope mechanisms, it also provides monochromatic images over the full solar disk and beyond, into the corona, with high spatial resolution. We …
EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection
Llebaria, A.; St. Cyr, O. C.; Michels, D. J. +31 more
We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the p…
Polar Plume Anatomy: Results of a Coordinated Observation
Plunkett, S. P.; Thompson, B. J.; Gurman, J. B. +5 more
On 7 and 8 March 1996, the SOHO spacecraft and several other space- and ground-based observatories cooperated in the most comprehensive observation to date of solar polar plumes. Based on simultaneous data from five instruments, we describe the morphology of the plumes observed over the south pole of the Sun during the SOHO observing campaign. Ind…
Time-Distance Helioseismology with the MDI Instrument: Initial Results
Kosovichev, A. G.; Hoeksema, J. T.; Scherrer, P. H. +10 more
In time-distance helioseismology, the travel time of acoustic waves is measured between various points on the solar surface. To some approximation, the waves can be considered to follow ray paths that depend only on a mean solar model, with the curvature of the ray paths being caused by the increasing sound speed with depth below the surface. The …