Science Archives Publication System

Origin and Evolution of Coronal Streamer Structure During the 1996 Minimum Activity Phase

DOI: 10.1086/304467 Bibcode: 1997ApJ...485..875W

Llebaria, A.; Michels, D. J.; Paswaters, S. E. +17 more

We employ coronal extrapolations of solar magnetograph data to interpret observations of the white-light streamer structure made with the LASCO coronagraph in 1996. The topological appearance of the streamer belt during the present minimum activity phase is well described by a model in which the Thomson-scattering electrons are concentrated around…

1997 • The Astrophysical Journal

SOHO 110

Detection of Zonal Shear Flows beneath the Sun's Surface from f-Mode Frequency Splitting

DOI: 10.1086/310708 Bibcode: 1997ApJ...482L.207K

Kosovichev, A. G.; Schou, J.

We report on the first successful measure of the zonal variations of the Sun's differential rotation (so-called torsional oscillations) by helioseismology. Using new helioseismic data from the Michelson Doppler Imager on board SOHO, we have detected zonal flow bands with velocity variation of 5 m s^-1 at a depth of 2-9 Mm beneath the sur…

1997 • The Astrophysical Journal

SOHO 109

SUMER Observations Confirm the Dynamic Nature of the Quiet Solar Outer Atmosphere: The Internetwork Chromosphere

DOI: 10.1086/310836 Bibcode: 1997ApJ...486L..63C

Judge, P. G.; Wilhelm, K.; Carlsson, Mats

On 1996 March 12, during the commissioning phase of the SOHO mission, we obtained observations of the quiet-Sun with the SUMER instrument. The observations were sequences of 15-20 s exposures of ultraviolet emission-line profiles and of the neighboring continua. These data contain signatures of the dynamics of the solar chromosphere that are uniqu…

1997 • The Astrophysical Journal

SOHO 109

RAPID - The Imaging Energetic Particle Spectrometer on Cluster

DOI: 10.1023/A:1004994202296 Bibcode: 1997SSRv...79..399W

Livi, S.; Grande, M.; Woch, J. +30 more

1997 • Space Science Reviews

Cluster 106

Hubble Space Telescope Images of the HH 111 Jet.

DOI: 10.1086/118509 Bibcode: 1997AJ....114..757R

Hartigan, Patrick; Bally, John; Reipurth, Bo +2 more

We have observed the classic Herbig-Haro jet HH 111 with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope (\HST) through narrow-band filters isolating Hα and [S II]lambda lambda6716 ,6731 emission. The new images fully resolve the body of the jet into a series of small bow shocks, which we conclude form as fast jet material …

1997 • The Astronomical Journal

eHST 106

Resolving the Helium Lyman-alpha Forest: Mapping Intergalactic Gas and Ionizing Radiation at z~3

DOI: 10.1086/118366 Bibcode: 1997AJ....113.1495H

Anderson, Scott F.; Hogan, Craig J.; Rugers, Martin H.

We present a new, high resolution HST/GHRS spectrum of quasar Q0302-003, and use the He(+) Lyman-alpha absorption, together with a high resolution Keck spectrum of the HI Lyman-alpha forest, to probe the distribution and ionization state of foreground gas just below the quasar redshift z~ 3.3. Within ~ 4000 km/sec of the quasar redshift the spectr…

1997 • The Astronomical Journal

eHST 105

NGC 2419, M92, and the age gradient in the galactic halo

DOI: 10.1086/118533 Bibcode: 1997AJ....114.1030H

Bond, Howard E.; Stetson, Peter B.; Richer, Harvey B. +7 more

The WFPC2 camera on HST has been used to obtain photometry of the low-metallicity ([Fe/H] =-2.14), outer-halo globular cluster NGC 2419. Our color-magnitude diagram in (V, V-I) reaches V_lim =~ 27.8, clearly delineating the subgiant and turnoff region and about three magnitudes of the unevolved main sequence. A differential fit of the NG…

1997 • The Astronomical Journal

Hipparcos eHST 104

High-Velocity Flows in an Active Region Loop System Observed with the Coronal Diagnostic Spectrometer (Cds) on SOHO

DOI: 10.1023/A:1004950330900 Bibcode: 1997SoPh..175..511B

Harrison, R. A.; Kjeldseth-Moe, O.; Brekke, P.

EUV spectra of coronal loops above an active region show clear evidence of strong dynamical activity. We present an example where the Ov 629 Å line, formed at 240 000 K, is shifted from its reference position corresponding to line-of-sight velocities greater than 50 km s^-1 with the shift extending over a large fraction of a loop. The ob…

1997 • Solar Physics

SOHO 104

Scattered Nuclear Continuum and Broad Hα in Cygnus A

DOI: 10.1086/310675 Bibcode: 1997ApJ...482L..37O

Fosbury, R. A. E.; Miller, J. S.; Ogle, P. M. +3 more

We have discovered scattered broad Balmer emission lines in the spectrum of Cygnus A, using the Keck II Telescope. Broad Hα appears in polarized flux from components on either side of the nucleus and, to a lesser extent, in the nucleus. The full-width at half-maximum of broad Hα is 26,000 km s^-1, comparable to the widest emission lines …

1997 • The Astrophysical Journal

eHST 103

Electron Densities in the Solar Polar Coronal Holes from Density-Sensitive Line Ratios of Si VIII and S X

DOI: 10.1086/310668 Bibcode: 1997ApJ...482L.109D

Wilhelm, K.; Schühle, U.; Lemaire, P. +5 more

We derive electron densities as a function of height in the north and south polar coronal holes from a forbidden spectral line ratio of Si VIII. Si VIII is produced at about 8 × 10⁵ K in ionization equilibrium. We also derive densities from a similar line ratio of S X (1.3 × 10⁶ K). The spectra were obtained with the Solar Ul…

1997 • The Astrophysical Journal

SOHO 102