共查询到20条相似文献，搜索用时 31 毫秒
1.
The velocity field in the region of quiescent filaments has been studied based on the observations performed at Sayan Solar
Observatory. The spectral observations of the velocity field have been performed simultaneously at two levels of the solar
atmosphere in lines Hβ (λ = 486.1 nm, the chromosphere) and FeI (λ = 486.3 nm, the photosphere). The character of stable and
oscillatory plasma motions in different filament parts at two levels of the solar atmosphere have been analyzed based on the
maps of two-dimensional velocity distribution. 相似文献
2.
A fractal analysis of narrowband images of the chromosphere and transition layer has been performed in order to study regimes of turbulence and their variations during time-varying processes in active regions. The NOAA 10039 and 10050 activity complexes on July 31, 2002, were observed at Baikal astrophysical observatory of ISZF SO RAN in the H-α line using a chromospheric telescope equipped with a Halle birefringent filter (BF) with a passband of 0.5 Å. Images of the same activity complexes in the spectral band centered at the FeXI 171 Å line, obtained at TRACE space observatory, have been processed using the same technique. The method of structure functions has been used to compute the time series of the scaling parameters. The power spectra of two-dimensional images have been used to compute the time variations in the fractal dimension of the considered activity complex. It has been indicated that the parameters of a multifractal structure (intermittent turbulence) demonstrate jump-like and quasiperiodic time variations correlating with flares. These variations were detected in the H-α and FeXI 171 Å lines of the transition zone, using the ground-based and onboard measurements, which demonstrates that they are of the solar origin. 相似文献
3.
Francesca Zuccarello Salvatore L. Guglielmino Viviana Battiato Lidia Contarino Daniele Spadaro Pado Romano 《Acta Geophysica》2009,57(1):15-23
This work aims to describe some aspects relevant to the emergence of magnetic structures on the solar surface. Using high
resolution photospheric and chromospheric data, besides than EUV images acquired by space telescopes, the dynamics of rising
flux tubes is studied. It is shown that, for both long-lived and short-lived magnetic regions, the flux tubes are initially
characterized by a high rising velocity, which eventually decreases as the region develops. Other results concern the timeline
of the active regions appearance in the atmospheric layers and the asymmetries in plasma downflows between preceding and following
legs of the flux tubes. These results are briefly discussed in the light of most recent models. 相似文献
4.
The prevailing heat transfer processes—convection in the photosphere and wave propagation in the chromosphere—are principally different. Despite this fact, there is a direct link between these processes: it is precisely convective photospheric flows that excite intense Alfven waves in the chromosphere. A physical model explaining the effect of strong chromospheric and coronal heating is improved in this work. The model is based on synchronous propagation and interaction in the chromosphere of photospheric spicules and Alfven waves. The results of observations of the last decade and the analytical solution of the equations of magnetohydrodynamics are used. It is established that the heating of the solar atmospheric plasma proceeds not in the corona but in the upper chromosphere. 相似文献
5.
Franz-Ludwig Deubner 《地球物理与天体物理流体动力学》2013,107(1-4):153-172
Abstract The most recent observational activities and results in the field of solar oscillations are reviewed. We address the dynamics and structure of the solar interior and of the atmosphere up to the transition layer, while global, local and atmospheric oscillations are being discussed. The topics of this review include: line width and amplitude limits of the p-modes; cycle variations of frequencies and amplitudes; internal solar rotation rate; p-mode absorption in spots and antipodal focussing of p-modes; diagnostics in the UV and in the IR; phase diagnostics in the atmosphere; chromospheric bright points. 相似文献
6.
G. I. Druzhin V. N. Uvarov V. A. Mullayarov V. I. Kozlov A. A. Korsakov 《Geomagnetism and Aeronomy》2010,50(2):211-218
The effect of the solar eclipse that occurred on August 1, 2008, on the level of the natural electro-magnetic emission signals
in the ELF-VLF range, simultaneously observed at Kamchatka and in Yakutsk, and the variations in the amplitude and phase of
signals from the VLF radiostations, registered in Yakutsk, has been considered. The VLF radiostations in Krasnodar, Novosibirsk,
and Khabarovsk successively emitted signals at frequencies of 11 905, 12 649, and 14 880 Hz. Based on the observations of
the signals from these radiostations, it has been established that the signal amplitudes and phases increased by 3–5% and
30°–45° when the signals crossed the lunar shadow region. The synchronous registration of the ELF-VLF noise emission indicated
that a bay-like increase and the following decrease in the emission to the background level was observed at both receiving
points during the eclipse from ∼1000 to 1130 UT. This effect was registered at frequencies of 0.6–5.6 kHz in Yakutsk and at
lower (30–200 Hz) and higher (2.5–11 kHz) frequencies at Kamchatka. In this case the noise emission intensity maximum was
observed when the lunar shadow maximally approached the registration point. At higher frequencies, the emission maximum was
observed simultaneously at both points (at 1100 UT) but with a delay relative to the maximum at lower frequencies. The possible
causes of the appearance of the solar eclipse effects in the natural ELF-VLF emission are considered. 相似文献
7.
The contribution of global magnetospheric oscillations to magnetic disturbance during magnetospheric storms is studied. The
bases of magnetic data from the INTERMAGNET global network in combination with the interplanetary and intramagnetospheric
measurements of the magnetic field and plasma and the sets of the Kp, Dst, and AE indices are used for this purpose. The most favorable conditions in the solar wind and magnetosphere for generation of global
Pc5 have been revealed. The contribution of these oscillations to the variations in the magnetic disturbance level, characterized
by the AE index, has been estimated. The findings confirm that magnetospheric MHD oscillations participate in the processes of energy
income from the solar wind and energy dissipation in the magnetosphere. 相似文献
8.
The challenges of ‘standard’ model of solar flares motivated by new observations with the spacecrafts and ground-based telescopes are presented. The most important problems are in situ heating of photospheric and chromospheric loop footpoints up to the coronal temperatures without precipitating particle beams accelerated in the corona, and the sunquakes which are unlikely to be explained by the impact of highenergy particles producing hard X-ray emission. There is also the long-standing ‘number problem’ in the physics of solar flares. It is shown that modern observations favored an important role of the electric currents in the energy release processes in the low solar atmosphere. Particle acceleration mechanism in the electric fields driven by the magnetic Rayleigh-Taylor instability in the chromosphere is proposed. The electric current value I ≥ 1010 A, needed for the excitation of super-Dreicer electric fields in the chromosphere is determined. It is shown that both Joule dissipation of the electric currents and the particles accelerated in the chromosphere can be responsible for in situ heating of the low solar atmosphere. Alternative model of the solar flare based on the analogy between the flaring loop and an equivalent electric circuit which is good tool for the electric current diagnostics is presented. Interaction of a current-carrying loop with the partially-ionized plasma of prominence in the context of particle acceleration is considered. The role of plasma radiation mechanism in the sub-THz emission from the chromosphere is discussed. 相似文献
9.
L. I. Miroshnichenko J. A. Pérez-Peraza V. M. Velasco-Herrera J. Zapotitla E. V. Vashenyuk 《Geomagnetism and Aeronomy》2012,52(5):547-560
Using modern wavelet analysis techniques, we have made an attempt to search for oscillations of intensity of galactic cosmic rays (GCR), sunspot numbers (SS) and magnitudes of coronal index (CI) implying that the time evolution of those oscillations may serve as a precursor of Ground Level Enhancements (GLEs) of solar cosmic rays (SCR). From total number of 70 GLEs registered in 1942–2006, the four large events — 23 February 1956, 14 July 2000, 28 October 2003, and 20 January 2005 — have been chosen for our study. By the results of our analysis, it was shown that a frequency of oscillations of GCR decreases as time approaches to the event day. We have also studied a behaviour of common periodicities of GCR and SCR within the time interval of individual GLE. The oscillations of GLE occurrence rate (OR) at different stages of the solar activity (SA) cycle is of special interest. We have found some common periodicities of SS and CI in the range of short (2.8, 5.2, 27 and 60 days), medium (0.3, 0.5, 0.7, 1.3, 1.8 and 3.2 years) and long (4.6 and 11.0 years) periods. Short and medium periodicities, in general, are rather concentrated around the maxima of solar cycles and display the complex phase relations. When comparing these results with the behaviour of OR oscillations we found that the period of 11 years is dominating (controlling); it is continuous over the entire time interval of 1942–2006, and during all this time it displays high synchronization and clear linear ratios between the phases of oscillations of η, SS and CI. It implies that SCR generation is not isolated stochastic phenomena characteristic exclusively for chromospheric and/or coronal structures. In fact, this process may have global features and involve large regions in the Sun’s atmosphere. 相似文献
10.
Running waves at the chromospheric level (Hα) in sunspots are studied. Propagating 3-min oscillations are shown to be typical
of many spots. Presumably, they propagate along the vertical magnetic-field lines. Their propagation speed is measured. According
to our analysis, the 5-min oscillations propagating in the penumbral chromosphere are not a continuation of the 3-min umbral
oscillations. The wavelength and propagation speed of the running penumbral waves are determined. 相似文献
11.
We study the mutual relation of sunspot numbers and several proxies of solar UV/EUV radiation, such as the F10.7 radio flux, the HeI 1083 nm equivalent width and the solar MgII core-to-wing ratio. It has been noted earlier that the relation between these solar activity parameters changed in 2001/2002, during a large enhancement of solar activity in the early declining phase of solar cycle 23. This enhancement (the secondary peak after the Gnevyshev gap) forms the maximum of solar UV/EUV parameters during solar cycle 23. We note that the changed mutual relation between sunspot numbers and UV/EUV proxies continues systematically during the whole declining phase of solar cycle 23, with the UV/EUV proxies attaining relatively larger values for the same sunspot number than during the several decennia prior to this time. We have also verified this evolution using the indirect solar UV/EUV proxy given by a globally averaged f0(F2) frequency of the ionospheric F2 layer. We also note of a simultaneous, systematic change in the relation between the sunspot numbers and the total solar irradiance, which follow an exceptionally steep relation leading to a new minimum. Our results suggest that the reduction of sunspot magnetic fields (probably photospheric fields in general), started quite abruptly in 2001/2002. While these changes do not similarly affect the chromospheric UV/EUV emissions, the TSI suffers an even more dramatic reduction, which cannot be understood in terms of the photospheric field reduction only. However, the changes in TSI are seen to be simultaneous to those in sunspots, so most likely being due to the same ultimate cause. 相似文献
12.
The specific features in the development of an X1 solar flare, which occurred on September 22, 2011, and was registered with the Atmospheric Imaging Assembly (AIA) device onboard the Solar Dynamics Observatory (SDO) in the UV line (λ = 304 Å, He II), are analyzed. During the flare, which lasted about 12 h, cold plasma was sucked up with an increasing velocity from a very distant region into the low-lying hot region of flare energy release along a flat helical trajectory. This phenomenon fundamentally differs from a surge ejection, when matter previously ejected from the flare region returns to the flare hot zone under the action of gravity. Suction of cold plasma “from outside” into the hot flare region is interpreted in the scope of the rope flare mechanism, according to which an extremely inhomogeneous plasma density distribution in the cross-section originates in an emerging magnetic rope. In the region with a sharply decreased density (which is the suction region), the drift velocity in the current chanel can reach the ion thermal velocity, which inevitably results in the excitation of plasma turbulence and anomalous resistance, i.e., in the development of a flare. 相似文献
13.
Quasi-periodic variations in the power of incoherent scattered signals, caused by wave disturbances of the electron concentration in the ionosphere, are analyzed for the day of a partial solar eclipse and for a background day. The windowed and adaptive Fourier transforms and the wavelet transform are used for spectral analysis. The spectral parameters of the wave disturbances at altitudes of 100–500 km in the 10–120 min period range differed significantly on the day of the solar eclipse and on the background day. Variations in the spectrum began near the onset of the phase of maximum disk occultation and continued no less than 2 h. The amplitude of time variations N was 2 × 109–4 × 1010 m?3, and the relative amplitude was 0.10–0.15. Wave disturbances have been compared for five solar eclipses; the comparison shows a noticeable variation in the spectrum of the wave disturbances during these events. 相似文献
14.
The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We have to observe and model the vector magnetic field to understand the structures and physical mechanisms of these solar activities. Vector magnetic fields on the photosphere are routinely observed via the polarized light, and inferred with the inversion of Stokes profiles. To analyze these vector magnetic fields, we need first to remove the 180° ambiguity of the transverse components and correct the projection effect. Then, the vector magnetic field can be served as the boundary conditions for a force-free field modeling after a proper preprocessing. The photospheric velocity field can also be derived from a time sequence of vector magnetic fields.Three-dimensional magnetic field could be derived and studied with theoretical force-free field models, numerical nonlinear force-free field models, magnetohydrostatic models, and magnetohydrodynamic models. Magnetic energy can be computed with three-dimensional magnetic field models or a time series of vector magnetic field. The magnetic topology is analyzed by pinpointing the positions of magnetic null points, bald patches, and quasi-separatrix layers. As a well conserved physical quantity,magnetic helicity can be computed with various methods, such as the finite volume method, discrete flux tube method, and helicity flux integration method. This quantity serves as a promising parameter characterizing the activity level of solar active regions. 相似文献
15.
T. I. Kaltman V. M. Bogod A. G. Stupishin L. V. Yasnov 《Geomagnetism and Aeronomy》2013,53(8):1030-1034
The physical conditions in the low corona and chromosphere of solar active regions are studied. A diagnostics technique based on multiwave observations in the centimeter range, photospheric magnetic field extrapolation, and radioemission calculations has been applied. The calculated spatial and spectral structure of the radioemission has been compared with RATAN-600 spectral-polarization observations with a high spatial resolution. The effect of the plasma physical parameters on the emission structure character in a complex magnetic field topology in active regions is analyzed. Modeling of the spectral singularities at a quasi-periodic propagation of the radioemission is presented. 相似文献
16.
A. A. Pevtsov 《Geomagnetism and Aeronomy》2016,56(8):972-977
We employ time sequences of images observed with a G-band filter (λ4305Å) by the Solar Optical Telescope (SOT) on board of Hinode spacecraft at different latitude along solar central meridian to study vorticity of granular flows in quiet Sun areas during deep minimum of solar activity. Using a feature correlation tracking (FCT) technique, we calculate the vorticity of granular-scale flows. Assuming the known pattern of vertical flows (upward in granules and downward in intergranular lanes), we infer the sign of kinetic helicity of these flows. We show that the kinetic helicity of granular flows and intergranular vortices exhibits a weak hemispheric preference, which is in agreement with the action of the Coriolis force. This slight hemispheric sign asymmetry, however, is not statistically significant given large scatter in the average vorticity. The sign of the current helicity density of network magnetic fields computed using full disk vector magnetograms from the Synoptic Optical Long-term Investigations of the Sun (SOLIS) does not show any hemispheric preference. The combination of these two findings suggests that the photospheric dynamo operating on the scale of granular flows is non-helical in nature. 相似文献
17.
E. N. Parker 《地球物理与天体物理流体动力学》2013,107(3-4):161-182
Abstract The relatively large resistivity in the solar photosphere and chromosphere softens the ideal tangential discontinuities of magnetostatic equilibrium into continuous transitions in field direction over scales of 0.1–10 km. This softening is communicated upward at the Alfvén speed into the active solar corona. The degree of softening is a vital part of the theory of magnetic heat input to the active X-ray corona, because the very low resistivity of the coronal gas provides effective dissipation only if the current sheets are reduced to a thickness of 10?2km. A close examination of the problem shows that the Alfvén transit time up into the corona is large compared to the characteristic time of 1 sec in which the coronal tangential discontinutities are formed. It also shows that the principal effect of the resistivity is to create a thin surface layer of fluid on adjacent flux bundles, which causes a general drift of the flux but does not directly broaden the current sheets higher up in the field. In fact the motions of the surface layers do not extend upwards beyond the first winding pattern at each end of a coronal loop. It appears that the photospheric and chromospheric resistivity is without striking consequences for magnetic heating in the corona. 相似文献
18.
风云二号卫星是我国研制的第一代静止业务气象卫星.本文针对风云二号C星/D星(FY-2C/D)太阳X射线探测数据与美国GOES系列卫星太阳X射线探测数据开展交叉比对,以检验FY-2C/D卫星数据的有效性.研究结果表明在X射线通量变化的时间特性以及通量大小等方面,FY-2C/D卫星探测结果与GOES系列卫星探测结果具有较好的一致性.对2004年11月—2010年6月期间85次耀斑事件X射线峰值流量的比对结果表明,FY-2C卫星与GOES系列卫星的探测结果在1~8 Å波段的相关系数为0.795,FY-2D卫星与GOES系列卫星的探测结果在0.5~3 Å和1~8 Å波段的相关系数分别为0.921和0.989,说明FY-2C/D卫星太阳X射线探测结果可信度较高,能够用于太阳X射线耀斑的监测、预警以及研究工作. 相似文献
19.
In this paper, we examine the nature of the main source of the sporadic solar wind on the Sun: coronal mass ejections (CMEs).
Analysis of data from Mark 3 and Mark 4, the Digital Prominence Monitor (MLSO), and STEREO (EUVI) spacecraft has revealed
the existence of two types of CMEs: gradual and impulse. They differ in the place, velocity, and angular size at the instant
of their emergence. The source of gradual CMEs is located in the corona, at a distance of 1.1 R
0 < R ≤ 1.7 R
0 from the center of the Sun. They start moving from a state of rest, having an angular size ≈15–65° (in the heliographic coordinate
system). Impulse CMEs are probably formed under the Sun’s photosphere. This may be due to the supersonic emergence of magnetic
tubes (ropes) from the convective zone. The possibility of this phenomenon has been demonstrated earlier in theory. The radial
velocity of such tubes at the photospheric level may be 100 km/s or higher; the minimum angular size is ∼1°. 相似文献
20.
O. M. Chugunova V. A. Pilipenko S. L. Shalimov M. Engebretson 《Geomagnetism and Aeronomy》2008,48(3):307-313
The variations in the daily average energy of geomagnetic pulsations and noise in the Pc3 (20–60 mHz) and Pc4 (10–19 mHz) frequency bands in the polar cap have been studied based on the data from P5 Antarctic station (corrected geomagnetic latitude ?87°) from November 1998 to November 1999. The daily average pulsation energy has been calculated using the method for detecting the wave packets, the spectral amplitude of which is higher than the threshold level, from the dynamic spectrum. A spectral analysis of the energy of pulsations and noise in the Pc3 and Pc4 bands, performed using the maximal entropy method, has revealed periodicities of 18 days in the local winter and 26, 13, and 7–9 days during the local summer. The simultaneous and coherent variations with periods of 26, 13, and 7–9 days in the solar wind velocity and IMF orientation indicate that the variations in the Pc3–4 wave energy in the polar cap at a sunlit ionosphere are mainly controlled by the parameters of the interplanetary medium. The variations in the Pc3–4 wave energy with a period of 18 days are observed only during the local winter and are supposedly related to the variations in the ionospheric conductivity modulated by planetary waves. 相似文献