MHD Aspects of Coronal Transients

Symposium - International Astronomical Union ◽

10.1017/s007418090006770x ◽

1980 ◽

Vol 91 ◽

pp. 263-277 ◽

Cited By ~ 1

Author(s):

U. Anzer

Keyword(s):

Solar Corona ◽

Time Scales ◽

White Light ◽

Solar Flares ◽

Great Length ◽

X Ray

If one defines coronal transients as events which occur in the solar corona on rapid time scales (≲ several hours) then one would have to include a large variety of solar phenomena: flares, sprays, erupting prominences, X-ray transients, white light transients, etc. Here we shall focus our attention on the latter two phenomena; solar flares have been discussed at great length in a recent Skylab workshop and IAU Colloqium No. 44 was devoted to the study of prominences. Coronal transients, in the narrower sense, were first seen with the instruments on board of Skylab, both in the optical and the X-ray part of the spectrum.

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Flaring Coronal Structures

International Astronomical Union Colloquium ◽

10.1017/s0252921100025367 ◽

1994 ◽

Vol 144 ◽

pp. 227-234

Author(s):

T. Watanabe

Keyword(s):

Solar Corona ◽

Magnetic Reconnection ◽

Time Scales ◽

Solar Flares ◽

Initial Phase ◽

X Ray ◽

Ionized Plasmas ◽

First Time ◽

Coronal Structures

AbstractThe highlights of the Japanese solar mission,Yohkoh, are presented, with emphasis on flaring structures in the solar corona. Definitive evidences of the magnetic reconnection in the solar corona are observationally confirmed for the first time. New insights in the location of hard X-ray sources are obtained. Completely blueshifted line emissions from highly ionized plasmas are seen at the very initial phase of solar flares. It is revealed that the solar corona is very dynamic in various time scales in X-ray intensities. Ample evidences of numerous flare-like activity like microflares and X-ray jets conclude that they are also the manifestation of the magnetic reconnection.

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Optical Evidence for Plasma Ejections and Waves in the Solar Corona

Symposium - International Astronomical Union ◽

10.1017/s0074180900234414 ◽

1974 ◽

Vol 57 ◽

pp. 323-332 ◽

Cited By ~ 6

Author(s):

A. Bruzek

Keyword(s):

Solar Corona ◽

White Light ◽

Solar Disk ◽

Dense Plasma ◽

Radio Bursts ◽

X Ray ◽

Imperfect Knowledge ◽

Optical Evidence ◽

Made In

Plasma ejections and waves in the solar corona are almost exclusively flare associated phenomena. Ejections of relatively cool and dense plasma are frequently observed in Hα whereas observations in coronal light (visible, EUV- and X-radiation) are still rather scarce. Occurrence of coronal waves is so far best known from their effects on the Hα chromosphere and, of course, from the production of radio bursts. Only in relatively few cases have observations been made in coronal lines and in coronal continuum by ground based as well as by satellite borne equipment. We may expect, however, that the white light coronagraph and the X-ray telescopes on board of the Skylab will detect quite a number of events in front of the solar disk and high in the solar corona and will considerably increase and improve our imperfect knowledge and understanding of coronal ejections and waves as it is presented in this review.

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Reconnection Driven Coronal Transients

Symposium - International Astronomical Union ◽

10.1017/s0074180900067796 ◽

1980 ◽

Vol 91 ◽

pp. 317-321 ◽

Cited By ~ 2

Author(s):

G. W. Pneuman

Keyword(s):

Physical Process ◽

White Light ◽

Solar Flares ◽

X Ray ◽

Wide Range ◽

Chromospheric Emission ◽

Coronal Transient

The association of coronal transients with two-ribbon solar flares is well established. During the Skylab period, every two-ribbon flare when observed close enough to the limb was accompanied by a coronal transient. Flares do not occur with all transients, however many of these transients are associated with soft X-ray enhancements in the corona similar to but less energetic than the intense X-ray loops that occur with two-ribbon flares [cf. MacCombie and Rust (1979) for a review]. The eruption of a filament seems to be the ingredient common to all these events - more so than flares. For these reasons, we consider this class of phenomena, regardless of whether a flare occurs or not, to be exhibiting a common physical process. To produce chromospheric emission requires a substantial amount of energy. Hence, one should expect chromospheric flares to be associated with only the most energetic phenomena. Nevertheless, the most comprehensive observations covering a wide range of wavelengths (Hα, EUV, X-ray, radio, white light) are available for the large two-ribbon flares, and the study of these events sheds the most light on the mechanism which produces coronal transients.

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CORRELATION OF HARD X-RAY AND WHITE LIGHT EMISSION IN SOLAR FLARES

The Astrophysical Journal ◽

10.3847/0004-637x/816/1/6 ◽

2015 ◽

Vol 816 (1) ◽

pp. 6 ◽

Cited By ~ 33

Author(s):

Matej Kuhar ◽

Säm Krucker ◽

Juan Carlos Martínez Oliveros ◽

Marina Battaglia ◽

Lucia Kleint ◽

...

Keyword(s):

White Light ◽

Solar Flares ◽

Light Emission ◽

White Light Emission ◽

X Ray

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FeXIV Line Emission Polarization of the July 11, 1991 Solar Corona

International Astronomical Union Colloquium ◽

10.1017/s0252921100026002 ◽

1994 ◽

Vol 144 ◽

pp. 541-547

Author(s):

J. Sýkora ◽

J. Rybák ◽

P. Ambrož

Keyword(s):

High Resolution ◽

Solar Corona ◽

Emission Line ◽

Solar Eclipse ◽

White Light ◽

Preliminary Analysis ◽

Line Emission ◽

Total Solar Eclipse ◽

Degree Of Polarization ◽

High Resolution Images

AbstractHigh resolution images, obtained during July 11, 1991 total solar eclipse, allowed us to estimate the degree of solar corona polarization in the light of FeXIV 530.3 nm emission line and in the white light, as well. Very preliminary analysis reveals remarkable differences in the degree of polarization for both sets of data, particularly as for level of polarization and its distribution around the Sun’s limb.

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Some Problems in Understanding the Solar Corona

International Astronomical Union Colloquium ◽

10.1017/s025292110002491x ◽

1994 ◽

Vol 144 ◽

pp. 1-9

Author(s):

A. H. Gabriel

Keyword(s):

Solar Corona ◽

Solar Atmosphere ◽

Theoretical Modelling ◽

Total System ◽

Major Advance ◽

X Ray ◽

Proper Perspective ◽

Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

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White-Light Coronal Structures: Streamers and CMEs

International Astronomical Union Colloquium ◽

10.1017/s0252921100025045 ◽

1994 ◽

Vol 144 ◽

pp. 82

Author(s):

E. Hildner

Keyword(s):

Emission Line ◽

Electron Density ◽

White Light ◽

Coronal Mass Ejections ◽

X Rays ◽

Solar Cycles ◽

Temperature Function ◽

X Ray ◽

Eclipse Observations ◽

Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

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