排序方式： 共有20条查询结果，搜索用时 46 毫秒
1.
Solar Physics - A curved filament in a decaying active region (AR&;nbsp;8329) was observed on 9 September 1998 with a combination of several instruments. The main data base is a 4-hour long time... 相似文献
2.
3.
Earlier studies of quiescent prominences claim that there is a systematic downward directed motion of the small-scale structure.
Disk observations, on the other hand, have detected mass motions both upwards and downwards. The earlier high-resolution observations
of limb prominences have been re-examined using local cross-correlation techniques for measurements of motion perpendicular
to the line of sight. The new measurements reveal flow speeds and directions that are in good agreement with current Doppler
measurements on the disk. 相似文献
4.
Observations of two quiescent filaments show oscillatory variations in Doppler shift and central intensity of the He i 10830 Å line.The oscillatory periods range from about 5 to 15 min, with dominant periods of 5, 9, and 16 min. The 5-min period is also detected in the intensity variations, after correction for atmospheric effects. Doppler shifts precede intensity variations by about one period. The possibility that the oscillations are Alfvén waves is discussed.The Doppler signals of the filament form fibril-like structures. The fibrils are all inclined at an angle of about 25° to the long axis of the filament. The magnetic field has a similar orientation relative to the major direction of the filament, and the measured Doppler signals are apparently produced by motions along magnetic flux tubes threading the filament.The measured lifetimes of the small-scale fibrils of quiescent disk filaments are very likely a combined effect of intensity modulations and reshuffling of the structures. 相似文献
5.
Oddbjørn Engvold 《Solar physics》1976,49(2):283-295
The fine structure of nonspot prominences are studied from H filtergrams. The size of the smallest prominence structures increases with height above the chromosphere. Some prominences contain structures close to 1/2 arc second, which is the spatial resolution in the present data. The effective thickness of many nonspot prominences ranges between 4 × 107 cm and 1.5 × 108 cm. An apparent downward directed motion is observed in the majority of the prominences. No preferred direction of the motion is seen in regions composed of comparatively large diffuse structures. Some bright threads are visible for 1 hr and longer. Bright knots have an average observed lifetime of about 8 min. The process of condensation and subsequent destruction of prominence fine structure appears to take place on a very short time scale compared to the life time of the regions where prominences may exist. The observed H brightness of the prominences in the present data may be accounted for as scattered chromospheric radiation. 相似文献
6.
Oddbjørn Engvold 《Solar physics》1978,56(1):87-106
High spatial resolution spectral observations of five hedgerow prominences were made in H, He i D3 and Ca ii H and K.The observed relations between the lines were not the same in all prominences. The Ca ii H and K lines were 2–4 times brighter relative to H and D3 than predicted theoretically. The optical thickness of H was less than for the H and K lines, the H was optically thin in medium faint prominence structures. Faint structures appeared slightly hotter than bright structures.On leave from Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, Oslo 3, Norway. 相似文献
7.
It is the objective of the present study to establish an absolute scale for flows in the solar transition region in observations obtained with the UVSP/SMM. By use of the polar limbs as reference one finds that the downflows range between 3 and 10 km s–1. The brighter regions show the largest downward flows.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
8.
The interaction between small-scale magnetic fields and horizontal photospheric flows has been studied from observations of high angular resolution
obtained with the Lockheed narrowband filter in the Swedish Vacuum Solar Telescope at La Palma. The measured magnetic flux density (B
) is in the range from a detection limit of 10 G to about 500 G, showing a good correspondence with the filigree. The magnetic flux elements take part in the local flows towards downdrafts at the supergranulation cell boundaries. The measured flux density, as well as the associated filigree intensity, decrease as the structures approach the downdrafts, presumably as a result of increased tilting and possibly submergence of flux into the downdrafts. 相似文献
9.
The nature of thin, highly inclined threads observed in quiescent prominences has puzzled solar physicists for a long time. When assuming that the threads represent truly inclined magnetic fields, the supporting mechanism of prominence plasma against gravity has remained an open issue. This paper examines the levitation of prominence plasma exerted by weakly damped MHD waves in nearly vertical magnetic flux tubes. It is shown that the wave damping, and resulting `radiation pressure', caused predominantly by ion-neutral collisions in the `cold' prominence plasma, may balance the acceleration of gravity provided the oscillation frequency is 2 rad s–1 (f0.5 Hz). Such short wave periods may be the result of small-scale magnetic reconnections in the highly fragmentary magnetic field of quiescent prominences. In the proposed model, the wave induced levitation acts predominantly on plasma – neutral gas mixtures. 相似文献
10.
High resolution observations of quiescent filaments show oscillations that are strongly tied to their fine threads. It is shown that neither slow nor fast MHD modes may account for the observations, which rather are in accordance with Alfvén waves. 相似文献