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- 검색키워드
- 저자 : Yuri E. Litvinenko (검색결과 4 건)
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COMMENTS ON MAGNETIC RECONNECTION MODELS OF CANCELING MAGNETIC FEATURES ON THE SUN
Yuri E. Litvinenko 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.3
Data analysis and theoretical arguments support magnetic reconnection in a chromospheric current sheet as the mechanism of the observed photospheric magnetic ux cancellation on the Sun. Flux pile-up reconnection in a Sweet{Parker current sheet can explain the observed properties of canceling mag- netic features, including the speeds of canceling magnetic fragments, the magnetic uxes in the fragments, and the ux cancellation rates, inferred from the data. It is discussed how more realistic chromospheric reconnection models can be developed by relaxing the assumptions of a negligible current sheet curvature and a constant height of the reconnection site above the photosphere.
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Chae, Jongchul,Litvinenko, Yuri E. American Astronomical Society 2017 The Astrophysical journal Vol.844 No.2
<P>The vertical propagation of nonlinear acoustic waves in an isothermal atmosphere is considered. A new analytical solution that describes a finite-amplitude wave of an arbitrary wavelength is obtained. Although the short-and long-wavelength limits were previously considered separately, the new solution describes both limiting cases within a common framework and provides a straightforward way of interpolating between the two limits. Physical features of the nonlinear waves in the chromosphere are described, including the dispersive nature of lowfrequency waves, the steepening of the wave profile, and the influence of the gravitational field on wavefront breaking and shock formation. The analytical results suggest that observations of three-minute oscillations in the solar chromosphere may reveal the basic nonlinear effect of oscillations with combination frequencies, superposed on the normal oscillations of the system. Explicit expressions for a second-harmonic signal and the ratio of its amplitude to the fundamental harmonic amplitude are derived. Observational evidence of the second harmonic, obtained with the Fast Imaging Solar Spectrograph, installed at the 1.6 m New Solar Telescope of the Big Bear Observatory, is presented. The presented data are based on the time variations of velocity determined from the Na I D2 and Ha lines.</P>
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RATES OF PHOTOSPHERIC MAGNETIC FLUX CANCELLATION MEASURED WITH <i>HINODE</i>
Park, Soyoung,Chae, Jongchul,Litvinenko, Yuri E. IOP Publishing 2009 ASTROPHYSICAL JOURNAL LETTERS - Vol.704 No.1
<P>Photospheric magnetic flux cancellation on the Sun is generally believed to be caused by magnetic reconnection occurring in the low solar atmosphere. Individual canceling magnetic features are observationally characterized by the rate of flux cancellation. The specific cancellation rate, defined as the rate of flux cancellation divided by the interface length, gives an accurate estimate of the electric field in the reconnecting current sheet. We have determined the specific cancellation rate using the magnetograms taken by the Solar Optical Telescope (SOT) aboard the Hinode satellite. The specific rates determined with SOT turned out to be systematically higher than those based on the data taken by the Michelson Doppler Imager (MDI) aboard the Solar and Heliospheric Observatory. The median value of the specific cancellation rate was found to be 8 x 10(6) G cm s(-1)-a value four times that obtained from the MDI data. This big difference is mainly due to a higher angular resolution and better sensitivity of the SOT, resulting in magnetic fluxes up to five times larger than those obtained from the MDI. The higher rates of flux cancellation correspond to either faster inflows or stronger magnetic fields of the reconnection inflow region, which may have important consequences for the physics of photospheric magnetic reconnection.</P>
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