The finest white-light coronal features     

Serge Koutchmy  Olivier Bouchard  Jean Mouette  Olga Koutchmy 《Solar physics》1993,148(1):169-172

An attempt to detect the finest white-light coronal features observed with a large optical telescope was made at the July 11, 1991 Solar Total Eclipse. A few selected results taken from the video-CCD high speed observations obtained at the prime focus of the Canada-France-Hawaï-Telescope (CFHT) with a red coronal interference filter are presented. The smallest (sub-arsec) detected and/or resolved coronal features are shown. The methods that were used to extract them from the noisy and seeing-limited images taken from video frames are described.  相似文献   

Velocity pattern of small scale magnetic fields     

H. C. Dara  C. E. Alissandrakis  S. Koutchmy 《Solar physics》1990,126(2):403-406

High resolution observations of horizontal proper motions, as well as vertical Doppler velocities measured over two selected regions of small scale magnetic elements show a coherent behaviour. In a region with two opposite polarities, approching with a velocity of 0.4 km s^-1, the material in between moves downwards with a velocity of 0.10 to 0.45 km s^-1; while in a region with two peaks of the same polarity, moving apart with a velocity of 0.3 km s^-1, the material in between moves predominantly upwards, with a velocity of up to 0.3 km s^-1.  相似文献   

Jet phenomena above null points of the coronal magnetic field     

B. Filippov  S. Koutchmy  L. Golub 《Geomagnetism and Aeronomy》2009,49(8):1109-1112

Short-lived plasma jets of various scales, from giant X-ray jets more than 300 Mm in extent to numerous small jets with sizes typical of macrospicules, are the phenomena observed in the solar corona in extreme ultraviolet and X-ray emission. Small jets are particularly prominent in polar coronal holes. They are close neighbors of tiny bright loops and coincide in time with their sudden brightening and increase in size. The geometric shape of the jets and their location suggest that they arise near singular null points of the coronal magnetic field. These points appear in coronal holes due to the emergence of small bipolar or unipolar magnetic structures within large-scale unipolar cells. Polar jets show a distinct vertical plasma motion in a coronal hole that introduces significant momentum and mass into the solar wind flow. Investigating the dynamics of polar jets can elucidate certain details in the problem of fast solar wind acceleration.  相似文献   

Atmospheric Emission Layers according to Photographic Observations from the International Space Station     

Platov  Yu. V.  Koutchmy  S.  Nikolayshvili  S. Sh. 《Geomagnetism and Aeronomy》2019,59(3):351-355

Geomagnetism and Aeronomy - Photographic and video observations made by astronaut Thomas Pesquet (European Space Agency) during the 51st expedition to the International Space Station (ISS) contain...  相似文献   

Improved SOT (Hinode mission) high resolution solar imaging observations: 2—Photometric properties of sunspot umbral dots     

H. Goodarzi  S. Koutchmy  A. Adjabshirizadeh 《Astrophysics and Space Science》2016,361(11):366

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Étude hydrodynamique du grand jet coronal ne observé à l'éclipse du 7 Mars 1970     

S. Koutchmy 《Solar physics》1972,24(2):373-384

A Hydrodynamical Study of the Large NE Coronal Streamer Observed during the 7th March Eclipse. The photometry of the large coronal streamer located on the N-E limb of the Sun observed on the 7th March 1970 in Mexico has been performed using compensated plates in unpolarized light as well as in tangentially and radially polarized light. The measured polarizations permit us to locate the streamer in space using a generally used method. The density distribution in the core of the streamer and for r > 1.5 R is given as well as the half-widths of the density distribution perpendicular to the axis of the streamer. Densities n(r) in the 1(R ) < r < 1.5(R ) region are obtained assuming hydrostatic equilibrium (4) for 1.5 < r < 2.The axial values of n(r) are given which agree with those of others models. The values of parameters for the model given are tabulated.The variation of the expansion velocity has been derived from the hydrodynamical continuity equation. This velocity becomes supersonic [v > 150(km s^–1)] above the height of minimum cross section of the streamer, r = 3.5 (R ). This result is verified by a simple calculation based on the observed curvature of the streamer's stalk. The velocity corresponding to the garden hose effect considered has a lower value equal to 60(km s^–1). The radial distribution of the expansion velocity is shown. Our model allows us to extrapolate in order to obtain the value of v(r) at the Sun's surface. This value, v 0.07 (km s^–1) can be compared with the value of the differential rotation velocity of the foot of the streamer. The values of the corpuscular flux of the streamer are calculated [F=2.4 × 10³⁴( s^-1] and agree with the value of the flux corresponding to the density enhancements of the solar wind, measured in situ. This shows the importance of large streamers for the coronal expansion processus.  相似文献   

Prominence fine structure     

J. B. Zirker  S. Koutchmy 《Solar physics》1990,127(1):109-118

The vertical fine structure in a quiescent prominence was modelled as an assembly of very narrow, optically thin threads. Random clusterings of the threads can account for the observed contrast and H line profiles of the fine structures. In this picture, each structure consists of a cluster of 7–20 elementary threads.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.NAS/NRC Research Associate, on leave from Institut d'Astrophysique, CNRS, Paris, France.  相似文献   

Small-scale motions over concentrated magnetic regions of the quiet Sun     

H. C. Dara  C. E. Alissandrakis  S. Koutchmy 《Solar physics》1987,109(1):19-29

We have used a 5.5 min time-sequence of spectra in the Fe i lines λ5576 (magnetically insensitive), λ6301.5 and λ6302.5 (magnetically sensitive) to study the association of concentrated magnetic regions and velocity in the quiet Sun. After the elimination of photospheric oscillations we found downflows of 100–300 m s ^?1, displaced by about 2″ from the peaks of the magnetic field; this velocity is comparable to downflow velocity associated with the granulation and of the same order or smaller than the oscillation amplitude. Quasi-periodic time variations of the vertical component of the magnetic field up to ± 40% were also found with a period near 250 s, close to the values found for the velocity field. Finally we report a possible association of intensity maxima at the line center with peaks of the oscillation amplitude.  相似文献   

Oscillations in solar jets observed with the SOT of Hinode: viscous effects during reconnection     

E. Tavabi  S. Koutchmy 《Astrophysics and Space Science》2014,352(1):7-15

Transverse oscillatory motions and recurrence behavior in the chromospheric jets observed by Hinode/SOT are studied. A comparison is considered with the behavior that was noticed in coronal X-ray jets observed by Hinode/XRT. A jet like bundle observed at the limb in Ca II H line appears to show a magnetic topology that is similar to X-ray jets (i.e., the Eiffel tower shape). The appearance of such magnetic topology is usually assumed to be caused by magnetic reconnection near a null point. Transverse motions of the jet axis are recorded but no clear evidence of twist is appearing from the highly processed movie. The aim is to investigate the dynamical behavior of an incompressible magnetic X-point occurring during the magnetic reconnection in the jet formation region. The viscous effect is specially considered in the closed line-tied magnetic X-shape nulls. We perform the MHD numerical simulation in 2-D by solving the visco-resistive MHD equations with the tracing of velocity and magnetic field. A qualitative agreement with Hinode observations is found for the oscillatory and non-oscillatory behaviors of the observed solar jets in both the chromosphere and the corona. Our results suggest that the viscous effect contributes to the excitation of the magnetic reconnection by generating oscillations that we observed at least inside this Ca II H line cool solar jet bundle.  相似文献   

Formation of a White-Light Jet Within a Quadrupolar Magnetic Configuration     

Boris Filippov  Serge Koutchmy  Ehsan Tavabi 《Solar physics》2013,283(1):143-156

The cadence and resolution of solar images have been increasing dramatically with the launch of new spacecraft such as STEREO and SDO. This increase in data volume provides new opportunities for solar researchers, but the efficient processing and analysis of these data create new challenges. We introduce a fuzzy-based solar feature-detection system in this article. The proposed system processes SDO/AIA images using fuzzy rules to detect coronal holes and active regions. This system is fast and it can handle different size images. It is tested on six months of solar data (1 October 2010 to 31 March 2011) to generate filling factors (ratio of area of solar feature to area of rest of the solar disc) for active regions and coronal holes. These filling factors are then compared to SDO/EVE/ESP irradiance measurements. The correlation between active-region filling factors and irradiance measurements is found to be very high, which has encouraged us to design a time-series prediction system using Radial Basis Function Networks to predict ESP irradiance measurements from our generated filling factors.  相似文献