BRIGHTNESS VARIATIONS OF Mg Ib BRIGHT FEATURES     

Dara  H.C.  Koutchmy  S.  Zachariadis  Th.G.  Alissandrakis  C.E. 《Solar physics》2001,198(2):313-324

We study the temporal intensity variations of Mgib bright features and investigate the corresponding Hα velocity pattern. The network bright features are well visible in the continuum, in images averaged over the duration of the observations (130 min). We detected `flashing' bright features, which appear and disappear within two to five minutes, while the rest of the bright features undergo small variations of either their shape and/or their intensity. A power spectrum analysis reveals a 10-min oscillation for approximately half of the stable bright features. The 5-min oscillations are detected mainly at the network boundaries, where stable bright features are located, while 3-min oscillations coincide with few bright features, but are also quite intense inside the network cells. The majority of bright features are associated with Hα downflows. The downflow is very intense at the location of `flashing' bright features.  相似文献   

About the foreshortening effect on sunspot umbral dots     

A. Adjabshirzadeh  S. Koutchmy 《Solar physics》1982,75(1-2):71-74

Using high-resolution pictures of the core of a unipolar sunspot observed with several cos values, we studied the center limb effect on the form of the bright umbral dots. The ratio of the apparent sizes in radial and tangential direction do not show the foreshortening effect typically observed in granular structures.On leave from University of Tabriz, Iran.Observational part of this work was done during a stay of S.K. at Sacramento Peak Observatory, U.S.A., as NRC Resident Research Associate.  相似文献   

Chromospheric heating by electric currents induced by fluctuating magnetic elements     

Paul Lorrain  Serge Koutchmy 《Solar physics》1998,178(1):39-42

We refer to two papers by Goodman (1995, 1996) on the heating of the chromosphere by large-scale electric currents, and to our paper (Lorrain and Koutchmy, 1993) on magnetic elements. Goodman assumes that the dynamo that runs a magnetic element stops operating at t = 0. From then on, the magnetic field decays exponentially, and the induced currents heat the chromosphere. The time constants calculated by Goodman disagree with the observed values, possibly because he disregards the driving dynamo. Also, he assumes static conditions, but his magnetic force density appears suddenly when the dynamo stops, and it is about equal to the gravitational force density. The magnetic force acts downward and fluctuations in the current flowing through the magnetic element should induce vertical oscillations at the photosphere. This point should be investigated further.  相似文献   

About the prominence heating mechanisms during its eruptive phase     

Filippov  B.  Koutchmy  S. 《Solar physics》2002,208(2):283-295

Recent EUV observations reveal that the `image' of the prominence overlaying coronal emission sometimes suddenly changes from absorption of EUV radiation to emission during the eruptive phase. This change reveals fast heating of the plasma within the prominence. We propose a kinetic mechanism of heating the fluid particles that transforms magnetic energy of the pre-eruptive magnetic configuration stored in the filament electric current into heat through collision processes of counteracting flows. The shape of the flux that the filament is made of should include upward concave segments to provide the counter flows within the erupting prominence. A typical twisted flux rope easily meets this requirement. Gas dynamic calculations are offered in addition to permit a quantitative evaluation of the relevant parameters and their time variations.  相似文献   

On the visible shape of the cold plasma jets in the solar chromosphere     

I. S. Veselovsky  L. Třírsková  S. Koutchmy 《Solar physics》1994,153(1-2):237-243

Lines of equal optical thickness are calculated for cold plasma jets propagating in the simplest magnetic configuration. The paraxial approximation is used in the case of jets directed along the axis of a magnetic dipole. The results explain the apparently convergent as well as divergent shapes of the jets in a divergent magnetic configuration.  相似文献   

Study of the June 30, 1973 trans-polar coronal hole     

Serge Koutchmy 《Solar physics》1977,51(2):399-407

Radially and tangentially polarized pictures of the solar corona obtained near 4500 Å during the 30 June, 1973 solar total eclipse have been used to derive a model of a trans-polar coronal hole. The hole is identified by using OSO-7 EUV spectroheliograms. The line of sight coincides with the privileged plan of the hole over the N-polar region. A new method of absolute calibration is used. The Saito (1970) method is applied to determine the electron densities. Extrapolated values of densities down to the surface are lower than have ever been observed although derived hydrostatic temperatures are certainly not: N _e × 10⁷ cm^–3 and T = 2 × 10⁶ K. The morphological peculiarities of polar regions are considered.On leave from Institut d'Astrophysique, CNRS, Paris as NRC Research Associate.  相似文献   

Observation of global 160-min infrared (differential) intensity variation of the Sun     

V. A. Kotov  S. Koutchmy  O. Koutchmy 《Solar physics》1983,82(1-2):21-35

The method developed and the instrument designed for detecting variations of the solar limb darkening at the atmospheric transparency window of the solar opacity minimum region of λ 1.65 μ are described. This differential technique proved to be successful in rejecting undesirable low frequency noises due to the atmosphere and to the instrument. Analysis of observations made in 1977, 1978, and 1981 indicates the persistance of global fluctuations of the IR differential, center-to-limb intensity at the wellknown 160 min period with an average amplitude of about ± 2 × 10^-4 in units of the ‘average Sun’ intensity near 1.65 μm.  相似文献   

Optical detection of space debris using a large achromatic coronograph     

S. Koutchmy  C. Nitschelm 《Astrophysics and Space Science》1988,143(1):45-49

The space debris detectin will become greater and greater in the near future with the space debris enhancing. We introduce a theoretical approach of this problem assuming the using of a new generation large coronograph. We get some interesting — and alarming — results about the great probability to be able to observe space debris with this new ground-based large coronograph.  相似文献   

Observations and discussions concerning ‘high’ polarization features in the solar corona     

Serge Koutchmy  Kenneth H. Schatten 《Solar physics》1971,17(1):117-128

Photographic observations were obtained of the radial and tangential polarization of the solar corona for the 1970, March 7, solar eclipse. The corona was photographed using a neutral density filter and rotating linear polaroid sectors to allow the polarization structure to be seen from 1 to 6 solar radii. Anomalously high polarizations were found for structures with the E-tangential intensity being predominantly larger than the E-radial intensity. These structures are generally filamentary in nature and radial in direction. One case with a high radial polarization was also found. The photographs were calibrated accurately against the Earth shine from the Moon. Possible source mechanisms are discussed that may explain this new component in the solar corona. Most sources may be ruled out on physical grounds. One possibility appears to be synchrotron radiation from 10 GeV electrons in a 0.4 G field. The existence of these electrons, however, is unlikely in that spacecraft observations at 1 AU do not confirm their presence.  相似文献   

On the origin of the prolate solar chromosphere     

Filippov  Boris  Koutchmy  Serge 《Solar physics》2000,196(2):311-320

A simple geometric model is proposed to explain the recently reported effect of the prolateness of the solar chromosphere. We assume that a specific dynamical part of the solar atmosphere above the 2 Mm level, being a mixture of moving up and down jets of chromospheric matter with the coronal plasma between them, is responsible for the solar prolateness. Due to the dynamic nature of this layer, the magnetic field is considered to play a very important role in the density distribution with the height, guiding the mass flows along the field lines. The difference of the magnetic field topology in the polar and the equatorial regions leads to different heights of the chromospheric limb. Calculations show a satisfactory coincidence with observations when the mean separation between opposite polarity concentrations is about 9 Mm. The possible observational signature of this network in low photospheric and chromospheric layers is discussed.  相似文献