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981.
The so-called zebra structures in radio dynamic spectra, specifically their frequencies and frequency drifts of emission stripes,
contain information on the plasma parameters in the coronal part of flare loops. This paper presents observations of zebra
structures in a microwave range. Dynamic spectra were recorded by Chinese spectro-polarimeters in the frequency band close
to the working frequencies of the Siberian Solar Radio Telescope. The emission sources are localized in the flare regions,
and we are able to estimate the plasma parameters in the generation sites using X-ray data. The interpretation of the zebra
structures in terms of existing theories is discussed. The conclusion has been arrived at that the preferred generation mechanism
of zebra structures in the microwave range is the conversion of plasma waves to electromagnetic emission on the double plasma
resonance surfaces distributed across a flare loop. 相似文献
982.
M. B. Martynov S. N. Alexashkin N. M. Khamidullina O. I. Orlov N. D. Novikova E. A. Deshevaya V. I. Trofimov 《Solar System Research》2011,45(7):593-596
The article presents an analysis of the Phobos-Grunt mission, a classification of its phases in terms of planetary protection,
and the main principles of activities management and definition of actions for fulfilling the planetary-protection requirements
developed by Committee on Space Research. 相似文献
983.
This is an analysis of the dependence of the flare activity of the well known flare star UV Ceti on the linear distance between
the components of this binary system. It is shown that its flaring activity clearly depends on the mutual distance of the
components, while this kind of variability is not seen in isolated flare stars. 相似文献
984.
We present the second part of the results of our work to investigate the atmospheric parameters and chemical composition of
southern-hemisphere Cepheids obtained by analyzing 24 spectra for eight bright Cepheids and three semiregular bright supergiants
taken with the 1.9-m telescope of the South African Astronomical Observatory. The chemical composition and atmospheric parameters
have been determined for S Cru, AP Pup, AX Cir, S TrA, T Cru, R Mus, S Mus, U Car, V382 Car, HD 75276, and R Pup. 相似文献
985.
The twin STEREO spacecraft have been observing the Sun since 2006. Even though STEREO has only been active during solar minimum
conditions so far, an important number of coronal mass ejections (CMEs) and their interplanetary counterparts (ICMEs) have
been observed. Many of the ICMEs can be linked back to the corresponding CMEs on the Sun through the combination of remote-sensing
and in situ observations. This paper aims to answer the question whether a CME observed by a coronagraph will be detected in situ by a spacecraft in a specific location in the heliosphere. We use a flux-rope-like model fit to the STEREO SECCHI/COR2 data
to obtain the direction of CME propagation and its geometrical configuration in three dimensions. Based on model parameters,
we then calculate their angular widths and determine whether they should have been detected by STEREO-A, STEREO-B, Wind or ACE. We compare the results with corresponding in situ observations of ICMEs. We find that predictions of ICME detections on the base of COR2 data generally match well the actual
in situ observations. 相似文献
986.
High-latitude interplanetary mass ejections (ICMEs) observed beyond 1 AU are not studied very often. They are useful for improving
our understanding of the 3D heliosphere. As there are only few such events registered by the Ulysses spacecraft, the task of detecting their solar counterparts is a challenge, especially during high solar activity periods,
because there are dozens coronal mass ejections (CMEs) registered by SOHO that might be chosen as candidates. We analyzed
a high-latitude ICME registered by the Ulysses spacecraft on 18 January 2002. Our investigation focused on the correlation between various plasma parameters that allow
the identification to be made of the ICME and its components such as the forward shock, the magnetic cloud and the reverse
shock. 相似文献
987.
V. R. MARTHI J. N. CHENGALUR Y. GUPTA G. C. DEWANGAN D. BHATTACHARYA 《Journal of Astrophysics and Astronomy》2011,32(4):451-455
We describe the serendipitous discovery of a very steep-spectrum radio point source in low-frequency Giant Metrewave Radio
Telescope (GMRT) images of the supernova remnant (SNR) G76.9+1.0. The steep spectrum, as well as the location of the point
source near the centre of this SNR confirm that this indeed is the pulsar J2022+3842. Archival Chandra X-ray data shows a point source coincident with the radio point source. However, no pulsed radio emission was detected despite
deep searches at 610 MHz and 1160 MHz – which can be understood to be due to temporal broadening of the pulses. Weak pulsed
emission has indeed been seen at 2 GHz with the Green Bank Telescope (GBT), establishing the fact that scattering is responsible
for its non-detection at low radio frequencies. We underline the usefulness of low-frequency radio imaging as a good technique
to prospect for pulsar candidates. 相似文献
988.
In this paper we summarize and analyze the results of observation of linear polarization of H
α emission for solar flares and moustaches obtained earlier. Basic structural and evolutional properties of the observed polarization
are formulated and presented. A conclusion is drawn that polarization data obtained from rough time and spatial averaging
of Stokes parameters distort the true picture of polarization of H
α emission in flares and moustaches. 相似文献
989.
B. E. Zhilyaev Yu. T. Tsap M. V. Andreev A. V. Stepanov Yu. G. Kopylova R. E. Gershberg M. N. Lovkaya A. V. Sergeev I. A. Verlyuk K. O. Stetsenko 《Kinematics and Physics of Celestial Bodies》2011,27(3):154-159
One of the most powerful and long-lived flares on the active red dwarf YZ CMi is considered. The flare was observed in the
U band at the Terskol Peak Observatory on February 9, 2008. During the formation of the flare over the course of 30 seconds,
the flare-induced stellar luminosity increased and became more than 180 times the preflare value. The total duration of the
flare was approximately one hour. At the flare maximum, quasi-periodic pulsations having a specified period of approximately
11 s, an initial modulation depth of 5.5%, and an exponential damping time of 29 s were discovered using wavelet analysis.
Assuming that the pulsations were caused by fast magnetohydrodynamic oscillations of a flare loop, the following parameters
were determined in the region of energy release using coronal seismology methods: plasma concentration (2 × 1010 cm−3), temperature (3 × 107 K), and magnetic field strength (0.015 T). 相似文献
990.
V. M. Malashchuk G. V. Rudenko N. N. Stepanian V. G. Fainshtein 《Bulletin of the Crimean Astrophysical Observatory》2011,107(1):60-66
By means of comparison of the positions of 665 observed coronal holes (CHs) and the structures of the magnetic field at different
heights, it was shown that 43% of the observed CHs are not associated with unipolar regions of the background field at the
photosphere. With height increasing from 1 to 2.5 solar radii, the structure of the magnetic field varies in 57% of all CHs.
In 16% of the cases, variations of the structure can be observed at heights as small as 2500–10 000 km. Comparison of the
positions of CHs with the longitudinal distribution of long-lived +/− and −/+ boundaries of the large-scale structure of the
magnetic field at all the heights was carried out. It was shown that CHs adjoin or intersect with the Hale boundaries half
as often as with those having the opposite distribution of the fields at both sides of the boundary. These results attest
to a closer connection between the CHs and the photospheric and subphotospheric fields than with coronal fields. The magnetic
fields of coronal structures can shield the coronal holes, thus creating “closed” CHs with a limited output of high-speed
solar wind streams. 相似文献