White-Light Coronal Dark Threads and Density Fine Structure

November, L. J.; Koutchmy, S.

doi:10.1086/177528

Cited by 94 publications

(71 citation statements)

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“…The outer helmet streamer structure is often seen in white-light eclipse observations. A unique set of high resolution, white-light images of the solar corona were obtained with the 3.6 m Canada-France-Hawaii Telescope on Mauna Kea during the eclipse of July 11, 1991 (Koutchmy et al 1994, November andKoutchmy 1996). The images show arcades of concentric, fine-scale, dark and bright looplike structures extending above a small prominence at the limb.…”

Section: Cavitiesmentioning

confidence: 99%

Observations of Filament Structure and Dynamics

Engvold¹

1998

International Astronomical Union Colloquium

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Abstract. Past and recent observations of spatial and temporal variations in fine structure of solar prominences/filaments are reviewed. Magnetic fields permeate the prominence plasma and play a decisive role in shaping the fine structure and its dynamics. Consequently, the shape, orientation, and possibly the strength, of the magnetic field may be inferred from the observed sub-structures. The review discusses possible physical implications of small-scale structures in the low-/? prominence plasma.

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Section: Cavitiesmentioning

confidence: 99%

Observations of Filament Structure and Dynamics

Engvold¹

1998

International Astronomical Union Colloquium

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“…Because of the high level of structuring in the corona, as shown on high resolution coronal images, the observed broadening shows the integration effects along the line of sight. However, depending on the importance of waves, one can look for a signature at different heights, keeping in mind that the hydrostatic pressure scale (see November and Koutchmy, 1996) is of the order of 100 Mm in a 2×10 6 K corona (or two times less, in a presumably more inner 1×10 6 K corona). Observations usually have a spatial resolution significantly better than this scale, and their resolution is often comparable or similar to the typical scale of variations of the coronal magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Analysis of non-thermal velocities in the solar corona

Contesse¹,

Koutchmy²,

Viladrich³

2004

Ann. Geophys.

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Abstract. We describe new ground-based spectroscopic observations made using a 40-cm aperture coronagraph over a whole range of radial distances (up to heights of 12 above the limb) and along four different heliocentric directions N, E, S and W. The analysis is limited to the study of the brightest forbidden emission line of Fe XIV at 530.3 nm, in order to reach the best possible signal-to-noise ratio. To make the results statistically more significant, the extracted parameters are averaged over the whole length of the slit, and measurements are repeated fives times at each position; the corresponding dispersions in the results obtained along the slit are given. Central line profile intensities and full line widths (FWHM) are plotted and compared to measurements published by other authors closer to the limb. We found widths and turbulent (non-thermal) velocities of significantly higher values above the polar regions, especially when a coronal hole is present along the line of sight. We do not see a definitely decreasing behaviour of widths and turbulent velocities in equatorial directions for larger radial distances, as reported in the literature, although lower values are measured compared to the values in polar regions. The variation in the high corona is rather flat and a correlation diagram indicates that it is different for different regions and different radial distances. This seems to be the first analysis of the profiles of this coronal line, up to large heights above the limb for both equatorial and polar regions.

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“…In all cases considered here, the interaction distance is much shorter than the inhomogeneity length scales, L n = (1-5) ×10 8 cm, observed as white and dark threads (November & Koutchmy 1996). These threads are embedded in a smooth coronal background for which L n > 10 9 cm.…”

Section: (B) High Level Coronamentioning

confidence: 79%

Nonlinear interaction of kinetic Alfvén waves and radio waves in the solar corona

Sirenko

Voitenko

Goossens

2002

A&A

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Abstract. This paper investigates the nonlinear interaction of short wavelength kinetic Alfvén waves (KAWs) with extraordinary (x-) and ordinary (o-) mode radio waves using two fluid magnetohydrodynamics. The focus is on the interaction of a preexistent KAW with an ordinary electromagnetic wave, giving rise to an extraordinary electromagnetic wave. The equation governing the time evolution of the amplitude of the excited x-mode is derived. The growth time of the x-mode wave is determined and the corresponding interaction distance is computed for active regions in the low corona and for high corona. The nonlinear coupling appears to be quite efficient for reasonable amplitudes of KAWs in the corona, B A /B 0 = 0.02-0.2. We suggest that this process provides a new possibility for the detection and remote sensing of coronal kinetic Alfvén waves by means of radio observations.

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White-Light Coronal Dark Threads and Density Fine Structure

Cited by 94 publications

References 0 publications

Observations of Filament Structure and Dynamics

Observations of Filament Structure and Dynamics

Analysis of non-thermal velocities in the solar corona

Nonlinear interaction of kinetic Alfvén waves and radio waves in the solar corona

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