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31.
Einar Tandberg-Hanssen 《Solar physics》1970,15(2):359-371
We discuss the longitudinal component of the magnetic field, B
, based on data from about 135 quiescent prominences observed at Climax during the period 1968–1969. The measurements are obtained with the magnetograph which records the Zeeman effect on hydrogen, helium and metal lines. Use of the following lines, H; Hei, D3, Hei, 4471 Å; Nai, Di and D2, leads to the same value for the observed magnetic field component in these prominences. For more than half of the prominences their mean field, B
, satisfy the inequalities 3 G B
8 G, and the overall mean value for all the prominences is 7.3 G. As a rule, the magnetic field enters the prominence on one side and exits on the other, but in traversing the prominence material, the field tends to run along the long axis of the prominence.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
32.
The solar transition region in the neighbourhood of prominences has been studied from observations with the Ultraviolet Spectrometer and Polarimeter of NASA's Solar Maximum Mission satellite. Dopplergrams from observations of the transition-region lines Civ 1548 Å and Siiv 1393 Å, which are formed at about 105 K, give velocity amplitudes typically in the range ± 15 km s-1. Prominences are found to be located very close to dividing lines between areas of up- and down-draughts in the transition-region. The observed pattern suggests that the 105 K gas flows take place within arcades of magnetic loops, which most likely are part of the supporting magnetic structure for the prominence matter. An additional band of blue-ward Doppler shifts is frequently seen close to quiescent prominences. This may be the source of outward flowing matter along the helmet streamers above filament channels. 相似文献
33.
Using simultaneous observations of the same solar regions in the lines H and Civ 1548 Å, we have derived schematic models of closed magnetic lines from dynamical constraints. We conclude that the magnetic loops are closed at higher levels above facular than above non-facular regions. This result remains valid whatever are the assumed density models and even if we take into account the 3 min oscillations. The center-to-limb behaviour is well predicted by taking into account the relative opacity in chromosphere and transition region. 相似文献
34.
We describe briefly the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission and discuss data pertaining to the emissions observed in lines originating in the transition-region plasma, particularly during impulsive flares. The data pertain to lines from the following ions: SiII, CIV, OIV, SiIV, OV, and FeXXI. 相似文献
35.
A. I. Poland M. E. Machado C. J. Wolfson K. J. Frost B. E. Woodgate R. A. Shine P. J. Kenny C. C. Cheng E. A. Tandberg-Hanssen E. C. Bruner W. Henze 《Solar physics》1982,78(2):201-213
Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25–300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30–0.3 keV range. The ultraviolet observations were images with a 10 spatial resolution in the lines of O v (T
e 2.5 × 105 K) and Fe xxi (T
e 1.1 × 107 K). The hard X-ray and O v data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as material was ejected into the corona. Impulsive excitation was observed up to 30 000 km above the solar surface at specific points in the flare loop. The Fe xxi observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient. 相似文献
36.
J. B. Smith Jr. D. M. Speich R. M. Wilson E. Tandberg-Hanssen S. T. Wu 《Solar physics》1977,52(2):379-391
Skylab soft X-ray observations of two lower coronal limb events and corresponding H observations (Skylab and ground-based) are analyzed. We discuss the morphology and evolution of an eruptive prominence occurring on 21 August 1973, beginning (in H) at about 1300 UT and of a surge on 4 December 1973, beginning at about 1758 UT. For the eruptive prominence, measured X-ray flux is used in the determination of line-of-sight temperatures, emission measures, and electron densities. A peak temperature of 8.5 × l06 K and densities to 3.5 × l09 cm-3 are derived. A time-dependent, two-dimensional, single-fluid magnetohydrodynamic computer code has been used to simulate the coronal response to these prominences. We find that the coronal response to the observed eruptive prominence may be simulated with a density-dominated pressure pulse at the base of the corona ( 30000 km above photosphere), while a temperature pulse of short duration will simulate the coronal response to the surge. Approximately 1031 ergs and 1040 particles (or 1016 g) were deposited into the corona during the eruptive prominence event, while about 1029 ergs and 1038 particles (or 1014 g) were injected during the surge event. A shock wave formed ahead of the ejected material at about 70000 km above the photosphere in the eruptive prominence event and had a velocity of 275 km s-1 at 1.5 r
above the limb.Presently at NASA / Marshall Space Flight Center. 相似文献
37.
Polytropic solar wind flows in flow tubes whose cross-sectional area increases faster with radius than for a radial expansion have been studied by Kopp and Holzer (1976). Their use of a faster-than-radial expansion proved promising in analytically associating the high-speed streams observed near 1 AU with the relatively low values of electron densities observed in the lower corona. They could not, however, obtain quantitative agreement with observations. We have extended their work to include thermal conduction and have compared thermally conductive and polytropic flows in the lower corona for given high-speed conditions at 1 AU. The thermally conductive flows (calculated using the Spitzer (1962) thermal conductivity) do yield closer agreement with observations, although the predicted electron density is still too low and the predicted temperature is too high. We also considered a modified thermal conductivity which decreases more rapidly with increasing radius than does the Spitzer value. Again the results were improved, but the agreement could not be termed quantitative. We conclude that thermal conduction alone will not explain solar wind flows originating in coronal holes and that some other mechanism (such as wave pressure) is necessary. 相似文献
38.
We studied the morphology and spatial distribution of loops in an active region, using coordinated observations obtained with both the S082A XUV spectroheliograph and the S056 grazingincidence X-ray telescope on Skylab. The active region loops in the temperature range 5 × 105 –3 × 106 K fall basically into two distinctive groups: the hot loops with temperatures 2–3 × 106 K as observed in coronal lines and X-rays, and the relatively cool loops with temperature 5 × 105 –1 × 106 K as observed in transition-zone lines (Ne vii, Mg ix). The brightest hot coronal loops in the active region are mostly low-lying, compact, closely-packed, and show greater stability than the transition-zone loops, which are fewer in number, large, and slender. The observed aspect ratio of the hot coronal loops is in the range of 0.1 and 0.2, which are almost two orders of magnitude larger than those for the Ne vii loops. Brief discussion of the MHD stability of the loops in terms of the aspect ratio is presented. 相似文献
39.
S. T. Wu Y. Q. Hu S. Wang M. Dryer E. Tandberg-Hanssen 《Astrophysics and Space Science》1982,83(1-2):189-194
In this paper, a new ideal magnetohydrodynamic (MHD) model is used to examine the dynamical response of the upper solar atmosphere to injection of cold mass from the photosphere akin to a surge. A significant new physical phenomenon is revealed: the formation of an almost stationary loop prominence in the atmosphere as a consequence of the ejected material. Simultaneously with the formation of this new loop, the simulation exhibits MHD waves that propagate outward (i.e., away from the loop) to excite coronal material. It is conjectured that these waves may trigger a class of coronal disturbances. 相似文献
40.
During solar cycle No. 20 new insight into the flare-spray phenomenon has been attained due to several innovations in solar optical-observing techniques (higher spatial resolution cinema-photography, tunable pass-band filters, multi-slit spectroscopy and extended angular field coronagraphs). From combined analysis of 13 well-observed sprays which occurred between 1969–1974 we conclude that (i) the spray material originates from a preexisting active region filament which undergoes increased absorption some tens of minutes prior to the abrupt chromospheric brightening at the flare-start, and (ii) the spray material is confined within a steadily expanding, loop-shaped (presumably magnetically controlled) envelope with part of the material draining back down along one or both legs of the loop. 相似文献