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1.
V. M. Bogod V. Garimov G. B. Gelfreikh K. R. Lang R. F. Willson J. N. Kile 《Solar physics》1995,160(1):133-149
Solar radio and microwave sources were observed with the Very Large Array (VLA) and the RATAN-600, providing high spatial resolution at 91 cm (VLA) and detailed spectral and polarization data at microwave wavelengths (1.7 to 20 cm - RATAN). The radio observations have been compared with images from the Soft X-ray Telescope (SXT) aboard theYohkoh satellite and with full-disk phoptospheric magnetic field data from the Kislovodsk Station of the Pulkovo Observatory. The VLA observations at 91 cm show fluctuating nonthermal noise storm sources in the middle corona. The active regions that were responsible for the noise storms generally had weaker microwave emission, fainter thermal soft X-ray emission, as well as less intense coronal magnetic fields than those associated with other active regions on the solar disk. The noise storms did, however, originate in active regions whose magnetic fields and radiation properties were evolving on timescales of days or less. We interpret these noise storms in terms of accelerated particles trapped in radiation belts above or near active regions, forming a decimetric coronal halo. The particles trapped in the radiation belts may be the source of other forms of nonthermal radio emission, while also providing a reservoir from which energetic particles may drain down into lower-lying magnetic structures.Presented at the CESRA-Workshop on Coronal Magnetic Energy Release at Caputh near Potsdam in May 1994. 相似文献
2.
In the present work a statistical analysis of long-lived microbursts (MBs) in the decimetric wavelength range was performed
for the first time. Long-lived microbursts at decimetric wavelengths were observed with one-dimensional scans on the RATAN-600
radio telescope in intensity and circular polarization with a sensitivity of about 5 – 10 Jy. MBs have fluxes in the range
of 0.001 – 0.1 s.f.u. and polarization degrees of 10 – 100%, and the duration of individual bursts is about 1 – 2 s. Microbursts
and background sources exist for several days and appear at the sites of prolonged energy release. In this work MBs were compared
with noise storms (NSs) in the metric wavelength range. Our analysis shows with high confidence that MBs are manifestation
of NSs in the decimetric wavelength range. The reason for the significant difference in flux between MBs and NSs could be
because MBs (unlike NSs) are related to incoherent generation of Langmuir waves. The nature of the MB emission is similar
to the smoothly varying (background) emission of the NSs, butthe MB emission is impulsive because of the high rate of pitch-angle
diffusion. 相似文献
3.
A method is presented for the direct measurement of the heights of the radio emission of solar active regions when they are located at the limb in order to reconstruct the vertical structure of the magnetic field in solar active regions. The method involves an analysis of radio source positions in the scans based on high frequency resolution one-dimensional centimeter-wave measurements performed on the RATAN-600 radio telescope. Radio sources are difficult to identify at many frequencies when observed at the limb at zero position angle because of abrupt signal variations at the solar limb. To eliminate edge effects on the scan, special observing periods are used (near vernal and autumnal equinoxes), when the source at the limb is located far from the scan edge because of the large position angle of the Sun. As a result of these observations, the spectra of relative heights are constructed for a number of sources for the period from 2007 through 2012. Source heights are shown to generally increase with wavelength. The height difference between the 5 and 2 cm emission is equal to 5.2 ± 2.0 Mm, and the corresponding height difference between the 8 and 2 cm emission is equal to 9.6 ± 3.0 Mm. It is shown that such characteristics can be obtained for a field generated by a dipole submerged under the photosphere at a depth of 17 Mm irrespective of the possible reduction of relative altitudes to absolute altitudes. 相似文献
4.
V. G. Eselevich V. M. Bogod I. V. Chashey M. V. Eselevich Yu. I. Yermolaev 《Geomagnetism and Aeronomy》2009,49(1):133-135
The solar sources of the magnetic storms of November 8 and 10, 2004, are analyzed. The preliminary results of such an analysis [Yermolaev et al., 2005] are critically compared with the results of the paper [Tsurutani et al., 2008], where solar flares were put in correspondence with these magnetic storms. The method for determining solar sources that cause powerful magnetospheric storms is analyzed. It has been indicated that an optimal approach consists in considering coronal mass ejections (CMEs) as storm sources and accompanying flares as additional information about the location of CME origination. 相似文献
5.
A. Nindos C. E. Alissandrakis G. B. Gelfreikh V. N. Borovik A. N. Korzhavin V. M. Bogod 《Solar physics》1996,165(1):41-59
We present two-dimensional solar maps at 2.7, 3.2, 4, and 8.2 cm computed from one-dimensional observations with the RATAN-600, using Earth rotation aperture synthesis techniques. Before the calculation of maps, the position of each scan was corrected with respect to the center of the solar disk and the scans were calibrated. The circular polarization scans were corrected for polarization cross-talk between the I and V channels. Subsequently, the quiet-Sun background emission was subtracted. After all corrections, a dirty map was computed by combining the scans at different position angles. The last step of the processing was an attempt to free the dirty map of the sidelobes, using the standard CLEAN procedure. The resolution of the clean maps at 2.7 cm was 0.5 by 6. Both active regions which were present on the solar disk were mapped. We studied the flux spectra of different types of sources: one was associated with a sunspot, the second was located over the neutral line of an active region, and the other was associated with the plage. The emission mechanism of the former was attributed to the gyroresonance process, while the short wavelength emission of the others was attributed to the free-free process. For the sunspot-associated source we estimated the magnetic field strengths at the base of the transition region and in the low corona. 相似文献
6.
V. N. Borovik G. B. Gelfreikh V. M. Bogod A. N. Korzhavin A. Krüger J. Hildebrandt S. Urpo 《Solar physics》1989,124(1):157-166
Recently recognized solar millimetre-wave off-limb sources are interpreted as a special phenomenon of long-duration post- and inter-flare emission at coronal altitudes. We present, for the first time, information about the brightness and polarization spectrum in the centimetre range for one such event of September 22, 1980 by means of RATAN-600 observations.The brightness temperatures observed favour the interpretation of the bulk of the emission by thermal optically thin bremsstrahlung. The degree of polarization measured (p 0.1–0.2 in the range 7.5–15 GHz) implies quite strong magnetic fields of about 300 ± 100 G at a height z > 3 × l04km above the photosphere and indicates a possible contribution of gyromagnetic radiation and/or optically thick bremsstrahlung at longer wavelengths. 相似文献
7.
On the basis of our multiwavelength observations made with the one-dimensional RATAN-600 radio telescope, we study the inversion
of the circular polarization in the solar microwave emission at different frequencies. The inversion is detected in the emission
of flare-producing active regions (FPARs) at various stages of their development, starting from the pre-flare stage. During
the latest 23rd solar cycle maximum, numerous FPARs revealed spectral inhomogeneities in their polarized microwave radiation
(Bogod and Tokhchukova, 2003, Astron. Lett.
29, 263). Here, we discuss a particular case of such inhomogeneities, the frequency-dependent double inversion of the sign of
circular polarization, which probably reflects some essential processes in FPARs. We consider several mechanisms for the double
inversion: linear interaction of waves in the region of a quasitransverse magnetic field, the propagation of waves through
a region of zero magnetic field, the scattering of radio waves on waves of high-frequency plasma turbulence, the influence
of the current fibrils on the propagation of the radio emission, and the magnetic “dips,” in which the direction of magnetic
field lines changes the sign relative to the observer. All of them have shortcomings, but the last mechanism explains the
observations the best. 相似文献
8.
The results of microwave observations of the polarized emission of active regionsmade with the RATAN-600 radio telescope are
used to develop the method for determining the structure of the magnetic field of these regions at coronal heights. About
1000-G-strong magnetic fields are observed in the solar atmosphere at rather high altitudes (from 10 to 25 Mm). This result
is confirmed fairly well by the ultraviolet observations of magnetic loops, it is consistent with earlier radio-astronomical
observations of the magnetic field at the height of the transition region, and it corresponds as well, if interpreted in terms
of the dipole magnetic field model, to the vertical gradients of the photospheric magnetic field. 相似文献
9.
The latitudinal distribution of sunspot groups over a solar cycle is investigated. Although individual sunspot groups of a solar cycle emerge randomly at any middle and low latitude, the whole latitudinal distribution of sunspot groups of the cycle is not stochastic and, in fact, can be represented by a probability density function of the distribution having maximum probability at about 15.5°. The maximum amplitude of a solar cycle is found to be positively correlated against the number of sunspot groups at high latitude (35°) over the cycle, as well as the mean latitude. Also, the relation between the asymmetry of sunspot groups and its latitude is investigated, and a pattern of the N-S asymmetry in solar activity is suggested. 相似文献
10.
We observed the structure of an off-limb prominence (4 October 1996) with a fan-beam resolution of RATAN-600 up to heights
of 0.4 R⊙ above the optical limb in the wavelength range 1.8–15 cm, in intensity and circular polarization. Multi-component structures
were discovered, and physical parameters of each component are discussed in conjunction with current theoretical models. 相似文献