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1.
The structure of the photospheric magnetic field during solar flares is examined using echelle spectropolarimetric observations. The study is based on several Fe i and Cr i lines observed at locations corresponding to brightest Hα emission during thermal phase of flares. The analysis is performed by comparing magnetic-field values deduced from lines with different magnetic sensitivities, as well as by examining the fine structure of I±V Stokes-profiles’ splitting. It is shown that the field has at least two components, with stronger unresolved flux tubes embedded in weaker ambient field. Based on a two-component magnetic-field model, we compare observed and synthetic line profiles and show that the field strength in small-scale flux tubes is about 2?–?3 kG. Furthermore, we find that the small-scale flux tubes are associated with flare emission, which may have implications for flare phenomenology. 相似文献
2.
D. N. Rachkovsky T. T. Tsap V. G. Lozitsky 《Journal of Astrophysics and Astronomy》2005,26(4):435-445
We analyse different observational data related to the problem of intrinsic magnetic field strength in small-scale fluxtubes
outside sunspots. We conclude that the kG range of fluxtube fields follows from not only classical line ratio method, but
also from other old and new techniques. For the quiet regions on the Sun, the most probable mode of such fields has a magnetic
field strength of 1.2–1.5 kG assuming the rectangular field profile. To best interpret the observations, a weak background
field between fluxtubes should be assumed, and its magnetic field strength is expected to increase with the filling factor
of fluxtubes. The alternative point of view about subkilogauss fluxtube fields is critically examined, and possible sources
of different conclusions are presented. 相似文献
3.
E. S. Andriets N. N. Kondrashova E. V. Kurochka V. G. Lozitsky 《Bulletin of the Crimean Astrophysical Observatory》2012,108(1):1-3
We investigate the photosphere parameters of a 2N/M2 solar flare that occurred in the NOAA 9077 active area on 18 July, 2000 before its maximum. We use Echelle Zeeman spectrograms obtained in orthogonal circular polarizations by means of a solar spectrograph of the astronomical observatory of Kiev National University, Ukraine (Kurochka, E.V., et. al, 1980). The photosphere is simulated by SIR software (Ruiz Cobo, B. and del Toro Inesta, J.C., 1992). The model of the flare??s photosphere is characterized by a two-component structure, including a magnetic flux tube and its nonmagnetic environment. For both components, we obtain the height distribution of the following parameters: temperature, magnetic field density and line-of-sight velocity. The temperature in the magnetic flux tube increases to approximately 5100 K in the upper photosphere layer of 250?C400 km. The magnetic field intensity decreases sharply from 2600 G (lower photosphere) to 100 G (middle photosphere) with a gradient of about 12 G/km. The model of the nonmagnetic environment differs slightly from the model of undisturbed photosphere. 相似文献
4.
E. V. Kurochka V. G. Lozitsky O. B. Osyka 《Kinematics and Physics of Celestial Bodies》2008,24(4):215-222
An M4.1/1B solar flare on November 5, 2004, is investigated. The Stokes I ± V profiles of nine photospheric Fe I, Fe II, Sc II, and Cr II lines are studied for three instants of this flare (11 h 35 m , 11 h 39 m , and 11 h 45 m UT). The magnetic fields in the flare were measured in two ways: using the center-of-gravity method and by comparing the observed profiles with the theoretical ones computed with Baranovsky’s code. Analysis of the profiles reveals that the magnetic field strength peaked in the upper photosphere (logτ500 = ?2.7) at the flare maximum (11 h 35 m ); this peak was smeared and shifted into the deeper photospheric layers as the flare evolved. The semiempirical model of the flare has two layers with an enhanced temperature: in the upper and middle photosphere. These layers also shifted deep into the photosphere as the flare evolved. The turbulent velocities at the distribution maximum increased by almost a factor of 5 compared to those in the undisturbed photosphere, while the plasma density both increased and decreased by a factor of 3–6. 相似文献
5.
E. A. Baranovsky V. G. Lozitsky V. P. Tarashchuk 《Kinematics and Physics of Celestial Bodies》2009,25(5):254-259
The spectra of two powerful flares with approximately the same intensities in the optical region but with different spectral
features and power in other regions are studied. One of them is the unique flare which occurred on October 28, 2003, importance
X17.2/4B, ranking third in magnitude among the recorded flares. Another occurred on September 1, 1990, 3B importance. The
flares vary in the Balmer decrement. The flare of October 28, 2003, has a ratio of I(Hβ)/I(Hα) = 1.47. This is the largest value for solar flares ever observed. The flares also differ in magnitude of the D Na I lines emission: the emission of the flare of October 28, 2003, is substantially larger than that of the other flare.
The chromosphere models of the flares are computed using the observed profiles of Balmer lines and D Na I lines. The satisfactory agreement of the calculated and observed profiles is obtained for the two-component models in
which a hot component occupies 6% of the area. The hot component of the chromosphere model is characterized with the dense
condensation available in the upper layers. For the flare of October 28, 2003, this condensation is located deeper and its
substance concentration is greater than that for another flare. The Hα line intensity for the model hot component alone is approximately 30 and the continuous spectrum intensity is approximately
3% of the undisturbed level. The photosphere model is computed using the observed profiles of photosphere lines for the flare
of October 28, 2003. It is found that very broad profiles of individual sigma-components of the Fe I λ 525.0 nm line may be
only explained by the presence of magnetic fields having different directions. A great difference is detected between values
of the magnetic field strength obtained in the splitting of sigma-components and those provided by simulation. 相似文献
6.
V. G. Lozitsky 《Astronomy Letters》2009,35(2):136-142
Strong (“kilogauss”) small-scale magnetic fields were detected outside a sunspot near the seismic source of the major X17.2/4B solar flare on October 28, 2003. Echelle Zeeman spectrograms of the flare were obtained with the horizontal solar telescope at the Astronomical Observatory of the Taras Shevchenko Kiev National University. Analysis of the Stokes I ± V profiles for the Fe I 5232.9, 5247.1, 5250.2, and 5397.1 Å lines has revealed a number of characteristic spectral features. These are indicative of both background fields with a strength of ≈300 G and small-scale fields with a strength of 1300–3100 G. Evidence for the presence of another small-scale field component of opposite polarity with a strength of 8–10 kG has been found. A redshift (downflow) with a velocity of 1 km s?1 was observed in the latter component. 相似文献
7.
I±V and I±Q profiles of nine spectral lines of Fei, Feii, and Hi in the 2B flare of 16 June 1989 have been analyzed. Two bright flare knots outside and inside of a spot were investigated. To measure the true magnetic field strength in the flare, two different methods were applied. In addition to these data, the magnetic field and thermodynamic conditions were determined using the non-LTE program for line profile synthesis. According to the measurements, the magnetic field in both flare knots changed in synchronism and non-monotonically, and reached its peak (nearly 1.6 kG for non-spot areas and approximately 4.0 kG for sunspot locations) at the time of flare peak. For the flare knot outside the spot, a background field component was also detected; the magnetic field in this component was found to have mixed polarity and remained practically unchanged during the flare. The non-LTE calculations show that the unique local magnetic field peak existed near the temperature minimum zone in the flare peak too. The observed perturbations do not exclude such phenomena as a magnetic field transient in flare. 相似文献
8.
Geomagnetism and Aeronomy - The double Hale cycle (about 44 years) was found in changes of power-law index for integral distributions of equivalent diameters of large groups of sunspots having... 相似文献
9.
V. P. Babij V. M. Efimenko V. G. Lozitsky 《Kinematics and Physics of Celestial Bodies》2011,27(4):191-196
Integral and differential distributions of sunspot diameters are studied for the last seven 11-year cycles of solar activity.
Data of the Greenwich catalogue, Pulkovo’s database, and the “Solniechnyie Dannyie” bulletin are used. We found that the average
index of integral distribution α is 6.0 for the diameters from 50 to 90 Mm and independent of the Wolf’s numbers, but it depends
on a cycle phase in the majority of cycles (four of seven), i.e., it is higher during the ascending phase, of intermediate
value during the maximum phase and minimum during the declining phase. Cycles 17, 18, and 22 behave differently: the index
α is either invariable with phase or the variations differ from the above ones. It turned out that cycles 17 and 18 are peculiar
by sunspot diameters, i.e., sunspots of up to 140–180 Mm in diameter, the largest over the last 80 years, have been observed.
Three assumptions concerning the nature of these gigantic sunspots have been proposed: (a) these sunspots occur due to changes
in differential rotation of the sun, (b) these sunspots are a certain independent statistical assembly formed in a sporadic
discrete region of the convective zone, and (c) these sunspots are surface “fragments” of the relict magnetic field of the
solar nucleus. 相似文献
10.
We present the results of magnetic field measurements in three active prominences, July 24, 1981, July 24, 1999, and July 12, 2004, obtained from observations with the echelle spectrograph of the horizontal solar telescope at the Astronomical Observatory of the Taras Shevchenko Kiev National University. The magnetic fields were measured from the Zeeman splitting of the I ± V profiles in the He I D3 and H?? lines in the atmosphere at heights from 3 to 14 Mm. Our measurements of the effective magnetic fields B eff from the shift of the profile centroids have shown that the magnetic fields averaged over the entrance slit area were within the range from ?600 to +1500 G. The amplitude values of the local fields have been estimated from the splitting of the bisectors of the central parts of the line profiles at 0.9 of the peak intensity. The corresponding fields B 0.9 have turned out to be approximately twice B eff and reached 4000 G in absolute value. Narrow (1?C2 Mm) height peaks at heights of 6?C11 Mm have been found in the height distributions of the magnetic field. We have found an interesting effect in two prominences-an anticorrelation between the magnetic field strengths measured from the D3 and H?? lines. 相似文献