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1.
本文通过MHD理论研究了细磁流通管在二维静止平衡介质中的运动.用地球磁尾中的一维细丝来表示流通管,通过数值模拟可以得到细丝随时间变化的一些性质.重联产生的细丝磁场比周围磁场偶极性更强,运动时表现出了很强的地向流.结果还显示了阿尔芬波、慢激波等MHD波从磁层的赤道面传播到地球电离层上并部分地反射回来.细丝在电离层上的足点的赤道向运动滞后于赤道面上的地向运动.虽然在模拟中细丝的初始等离子体压强低于周围压强,但是当它开始迅速向地球方向运动时,它的等离子体压强很快上升到与周围压强相当,甚至有时候大于周围压强的值. 相似文献
2.
The structure, configuration, dynamics, and solar sources of the near-Earth MHD disturbance of the solar wind on November 20, 2003, is considered. The disturbances of October 24 and November 22 after flares from the same AR 10484 (10501) are compared. The velocity field in the leading part of the sporadic disturbance is for the first time studied in the coordinate system stationary relative to the bow shock. A possible scenario of the physical processes in the course of this solar-terrestrial storm is discussed in comparison with the previously developed scenario for the storm of July 15, 2000. It has been indicated that (1) the near-Earth disturbance was observed at the sector boundary (HCS) and in its vicinities and (2) the disturbance MHD structure included: the complicated bow shock, wide boundary layer with reconnecting fields at a transition from the shock to the magnetic cloud, magnetic cloud with a magnetic cavity including packed substance of an active filament, and return shock layer (supposedly). It has been found out that the shock front configuration and the velocity field are reproduced at an identical position of AR and HCS relative to the Earth on November 20 and 24. It has been indicated that the maximal magnetic induction in the cloud satisfied the condition B m = (8πn 1 m p)1/2(D ? NV1), i.e., depended on the dynamic impact on the cloud during all three storms [Ivanov et al., 1974]. When the disturbance was related to solar sources, the attention has been paid to the parallelism of the axes of symmetry of the active filament, transient coronal hole, coronal mass ejection, zero line of the open coronal field (HCS), and the axis of the near-Earth magnetic cloud: the regularity previously established in the scenario of the storm of July 15, 2000 [Ivanov et al., 2005]. It has been indicated that the extremely large B m value in the cloud of October 20 was caused by a strong suppression of the series of postflare shocks reflected from the heliospheric streamer. 相似文献
3.
The difficulties associated with calculating the parameters of the interplanetary magnetic field (IMF) from solar magnetic data have been considered. All conventional calculation patterns and available input databases have been analyzed from a unified standpoint. It has been shown that these assumptions and limitations cannot affect the general structure and dependence on cycle of solar and interplanetary data. At the same time, the measured solar field values are underestimated as a result of the magnetograph signal saturation effect. It has been shown that the correction should depend on the heliocentric observation latitude and cycle phase. The correction method responsible for good agreement between the calculated and measured values has been proposed. The created database makes it possible to quantitatively calculate the magnetic fields in the solar wind near the Earth. 相似文献
4.
The solar magnetic field B s at the Earth’s projection onto the solar-wind source surface has been calculated for each day over a long time interval (1976–2004). These data have been compared with the daily mean solar wind (SW) velocities and various components of the interplanetary magnetic field (IMF) near the Earth. The statistical analysis has revealed a rather close relationship between the solar-wind parameters near the Sun and near the Earth in the periods without significant sporadic solar and interplanetary disturbances. Empirical numerical models have been proposed for calculating the solar-wind velocity, IMF intensity, and IMF longitudinal and B z components from the solar magnetic data. In all these models, the B s value plays the main role. It is shown that, under quiet or weakly disturbed conditions, the variations in the geomagnetic activity index Ap can be forecasted for 3–5 days ahead on the basis of solar magnetic observations. Such a forecast proves to be more reliable than the forecasts based on the traditional methods. 相似文献
5.
The preliminary results of solar filaments distinguished in daily H-alpha observations at Kodaikanal (1912–2002) are presented. To mark the boundaries of solar filaments, methods based on automated procedures of marking low-contrast objects on the solar disk, as well as editing of the marked boundaries in a semiautomated manner, were developed. The characteristics of solar filaments were analyzed. Latitudinal diagrams of filaments number in 15–23 activity cycles were constructed. As is shown, one maximum in the filament latitudinal distribution may be clearly distinguished during activity cycles in both hemispheres. This maximum is located slightly higher (θ ~ 25°–30°) than the sunspot distribution maximum (θ ~ 14°–17°). However, there are no other local maxima related to the zonal structure of the large-scale magnetic field (Makarov and Sivaraman, 1989). 相似文献
6.
N. Ya. Maksimov 《Geomagnetism and Aeronomy》2006,46(5):635-637
A comparison of the time variations in the geomagnetic field characteristics (the u and aa indices of geomagnetic activity) with the variation in the solar magnetic dipole inclination shows close agreement between these variations. The linear correlation coefficients between the u and aa indices, the u index and solar magnetic dipole inclination, and the aa index and solar magnetic dipole inclination are 0.93, 0.45, and 0.49, respectively. This makes it possible to extend studying the IMF evolution in the 11-year cycle of solar activity to the 170-year period beginning from 1835. It has been indicated that the time variation in the heliospheric current sheet (HCS) surface deviation from the solar magnetic equator plane, calculated based on the actual HCS configuration, is in good agreement with the time variation in the amplitude of the Fourier series second harmonics in a harmonic analysis of the series of daily data on the IMF sign in the vicinity of the Earth. The linear correlation coefficient is 0.9 in this case. 相似文献
7.
向日面磁层顶在平静太阳风条件下,处于10RE（RE为地球半径）左右．但在异常的太阳风条件下,即南向行星际磁场很强和（或）太阳风的动压很大时,会被压缩,甚至到达同步轨道附近．集中分析2001年4月11日的磁暴事件,研究当磁层顶发生强烈压缩以后。在地球空间和地面上产生的磁场影响．磁层顶位形选取Shue（1998）模型计算．当把计算结果与GOESl0卫星的观测数据对比时发现：磁层顶在强的太阳风条件下的确会被压缩到同步轨道以内．Shue（1998）模型的预测基本正确,通常的漏报可能是由于预报的位置误差所致．实际磁层顶电流片的位置和强度与我们假设的理想磁层顶间断面计算结果基本吻合．在分析大磁暴过程时,磁层顶压缩使磁层顶电流对于中低纬度地磁场扰动有突出的贡献,在2001年4月事件中,这个贡献可以大于50nT,占主相的1／6左右．这一贡献可以使Dst指数产生相应的误差． 相似文献
8.
High-performance computational models are required to make the real-time or faster than real-time numerical prediction of adverse space weather events and their influence on the geospace environment. The main objective in this article is to explore the application of programmable graphic processing units (GPUs) to the numerical space weather modeling for the study of solar wind background that is a crucial part in the numerical space weather modeling. GPU programming is realized for our Solar-Interplanetary-CESE MHD model (SIP-CESE MHD model) by numerically studying the solar corona/interplanetary solar wind. The global solar wind structures are obtained by the established GPU model with the magnetic field synoptic data as input. Meanwhile, the time-dependent solar surface boundary conditions derived from the method of characteristics and the mass flux limit are incorporated to couple the observation and the three-dimensional (3D) MHD model. The simulated evolution of the global structures for two Carrington rotations 2058 and 2062 is compared with solar observations and solar wind measurements from spacecraft near the Earth. The MHD model is also validated by comparison with the standard potential field source surface (PFSS) model. Comparisons show that the MHD results are in good overall agreement with coronal and interplanetary structures, including the size and distribution of coronal holes, the position and shape of the streamer belts, and the transition of the solar wind speeds and magnetic field polarities. 相似文献
9.
A. E. Levitin L. I. Gromova S. V. Gromov L. A. Dremukhina 《Geomagnetism and Aeronomy》2014,54(3):292-299
A new method for determining geomagnetic activity based on calculation of the hourly amplitudes of geomagnetic field variations at ground-based observatories has been developed. Observations performed in 2009, when unusually low solar and geomagnetic activity was registered, were used as a reference level. The described method was used to estimate the energy of local geomagnetic activity; such energy is estimated for observatories in the Earth’s Northern and Southern hemispheres, and a total estimation is made for both hemispheres and for the entire Earth’s surface during large magnetic storms. These are used to compare characteristics of magnetic storm intensity based on the classical Kp and Dst indices and calculated energy estimate. 相似文献
10.
A brief overview of the observation results of filament interactions on the Sun both from the Earth and from space at the TRACE, SOHO, STEREO, Hinode, and Yohkoh stations in white light, Hα, extreme UV (EUV), X rays, and a radio range is presented. Various filament collision cases, where filaments merge (or do not merge) or change their forms as a result of reconnection, are considered. Filament interactions are associated with flares, filament eruptions, and coronal mass ejections. The theoretical aspects of the observed phenomena are also considered. 相似文献
11.
A new exact analytical solution of the magnetohydrostatic problem describes the equilibrium of a solitary, dense-cool solar filament maintained against the gravity by magnetic force in hot solar corona at heights up to 20–40 Mm. The filament is assumed to be uniform along the axis (the translation symmetry). The magnetic field of the filament has the helical structure (magnetic flux rope) with a typical strength of a few Gauss in the region of minimal temperature (about 4000 K). The model can be applied to the quiescent prominence of both normal and inverse magnetic polarity.
相似文献12.
Plasma and magnetic field data from the Helios 1/2 spacecraft have been used to investigate the structure of magnetic clouds (MCs) in the inner heliosphere. 46 MCs were identified in the Helios data for the period 1974–1981 between 0.3 and 1 AU. 85% of the MCs were associated with fast-forward interplanetary shock waves, supporting the close association between MCs and SMEs (solar mass ejections). Seven MCs were identified as direct consequences of Helios-directed SMEs, and the passage of MCs agreed with that of interplanetary plasma clouds (IPCs) identified as white-light brightness enhancements in the Helios photometer data. The total (plasma and magnetic field) pressure in MCs was higher and the plasma- lower than in the surrounding solar wind. Minimum variance analysis (MVA) showed that MCs can best be described as large-scale quasi-cylindrical magnetic flux tubes. The axes of the flux tubes usually had a small inclination to the ecliptic plane, with their azimuthal direction close to the east-west direction. The large-scale flux tube model for MCs was validated by the analysis of multi-spacecraft observations. MCs were observed over a range of up to 60° in solar longitude in the ecliptic having the same magnetic configuration. The Helios observations further showed that over-expansion is a common feature of MCs. From a combined study of Helios, Voyager and IMP data we found that the radial diameter of MCs increases between 0.3 and 4.2 AU proportional to the distance, R, from the Sun as R0.8 (R in AU). The density decrease inside MCs was found to be proportional to R–2.4, thus being stronger compared to the average solar wind. Four different magnetic configurations, as expected from the flux-tube concept, for MCs have been observed in situ by the Helios probes. MCs with left-and right-handed magnetic helicity occurred with about equal frequencies during 1974–1981, but surprisingly, the majority (74%) of the MCs had a south to north (SN) rotation of the magnetic field vector relative to the ecliptic. In contrast, an investigation of solar wind data obtained near Earths orbit during 1984–1991 showed a preference for NS-clouds. A direct correlation was found between MCs and large quiescent filament disappearances (disparition brusques, DBs). The magnetic configurations of the filaments, as inferred from the orientation of the prominence axis, the polarity of the overlying field lines and the hemispheric helicity pattern observed for filaments, agreed well with the in situ observed magnetic structure of the associated MCs. The results support the model of MCs as large-scale expanding quasi-cylindrical magnetic flux tubes in the solar wind, most likely caused by SMEs associated with eruptions of large quiescent filaments. We suggest that the hemispheric dependence of the magnetic helicity structure observed for solar filaments can explain the preferred orientation of MCs in interplanetary space as well as their solar cycle behavior. However, the white-light features of SMEs and the measured volumes of their interplanetary counterparts suggest that MCs may not simply be just H-prominences, but that SMEs likely convect large-scale coronal loops overlying the prominence axis out of the solar atmosphere. 相似文献
13.
K. G. Ivanov 《Geomagnetism and Aeronomy》2011,51(3):287-298
This paper considers the MHD structure and configuration of near-Earth interplanetary disturbances during the heliospheric
extrastorm of November 2004, taking into account the effect of the IMF sector structure and using the measurements of near-Earth
satellites. During three successive disturbance intervals, the Earth entered, remained and left a relative narrow positive
sector with flare-active region 10696, which generated a series of shocks and an active transequatorial filament. It has been
indicated that the MHD structure and configuration of near-Earth disturbances substantially and specifically (for each position)
depend on the IMF sector structure and interactions between shocks and sector boundaries, filaments, and magnetic clouds in
these three different positions. Specifically, this manifested itself in multiple crossings of sector boundaries and considerable
deformations of magnetic clouds. It has been indicated that the models of circular clouds are applied with limitations under
the considered conditions. 相似文献
14.
短临预报是目前地震预测的难点,通过对2013年甘肃岷县漳县MS6.6地震发生日期的研究,发现发生日期7月22日是节气、低点位移、异年倍七律和朔望共同作用的时间点。据此,本文用一些基于可能触发地震发生的非传统方法的时间预测方法,回顾性地讨论了甘肃岷县漳县MS6.6地震发生日期的临震日期预测问题。通过对岷县漳县MS6.6地震研究,认为在地震短临日期的预测上。一些非传统方法虽然在机理上还有待研究,但在统计上多次证明该方法具有预测准确性的效能。要基于传统方法与非传统方法结合,才能对临震预测的时间逼近,同时提出今后预测临震时间的思路:多因素不断拦截法。 相似文献
15.
E. S. Belenkaya 《Geomagnetism and Aeronomy》2014,54(3):287-291
When the effect of a solar wind dynamic pressure pulse on the magnetospheric and ionospheric dynamics is studied, it is usually difficult to detect the effect of a sudden change in the density against the background of the other varying solar wind parameters, which often play a most pronounced role. Cases in which the solar wind plasma density gradient dominated in the dynamics of the different parameters of an interplanetary medium and its magnetic field are considered in this work. Variations in the Earth’s dayside magnetopause current caused by a change in the solar wind ion density are presented for two such cases (February 11 and January 11, 1997) based on the method developed by us previously. Variations in the dayside magnetopause current for collisions of the magnetosphere with corotating interacting flows in January 2004, studied in detail by us previously, are also presented for Saturn. The estimates are comparable with the current values in the transitional three-dimensional current systems of Saturn that were previously calculated by us. 相似文献
16.
I. N. Myagkova M. I. Panasyuk Yu. I. Denisov V. V. Kalegayev A. V. Bogomolov V. O. Barinova D. A. Parunakyan L. I. Starostin 《Geomagnetism and Aeronomy》2011,51(7):897-901
The study of variations in the electron flux in the outer Earth radiation belt (ERB) and their correlations with solar processes
is one of the important problems in the experiment with the Electron-M-Peska instrument onboard the CORONAS-Photon solar observatory.
Data on relativistic and subrelativistic electron fluxes obtained by the Electron-M-Peska in 2009 have been used to study
the outer ERB dynamics at the solar minimum. Increases in outer ERB relativistic electron fluxes, observed at an height of
550 km after weak magnetic disturbances induced by high-velocity solar wind arriving to the Earth, have been analyzed. The
geomagnetic disturbances induced by the high-velocity solar wind and that resulted in electron flux variations were insignificant:
there were no considerable storms and substorms during that period; however, several polar ground-based stations observed
an increase in wave activity. An assumption has been made that the wave activity caused the variations in relativistic electron
fluxes. 相似文献
17.
《Journal of Atmospheric and Solar》2000,62(14):1251-1255
We report here preliminary results of a mission analysis for a space weather monitoring system that provides continuous transmission of solar wind conditions 0.10 A.U. upstream from Earth. The system is based on four platforms that are phased into eccentric heliocentric orbits but, from the perspective of a fixed Sun–Earth line, the spacecraft appear to orbit Earth. This system offers a 10× improvement in reporting solar wind plasma and magnetic field characteristics beyond similar platforms located at the Lagrangian L-1 point. We describe launch and energy considerations, along with a preliminary analysis of communication requirements. The Space Weather Diamond offers significant potential for scientific insight into problems requiring coordinated observations from multiple vantage points by providing the ability to separate spatial from temporal variations. We discuss examples for payloads including both in situ and remote sensing instrumentation. 相似文献
18.
A long series of the known Π index of the solar corona structure has been proposed. It seems that this index, which characterizes the limb extension of polar coronal plume systems, is of importance because it is related to the large-scale polar solar magnetic flux. Solar corona photographs and drawings during total solar eclipses, collected for 13 solar activity cycles from different sources (78 eclipses), as well as H-alpha map data on the drift of the high-latitude belt of filaments before polarity reversal of the polar magnetic field have been used. Daily solar corona images, obtained on the SOHO spacecraft (using an EIT ultraviolet telescope), have been additionally used. 相似文献
19.
Catherine Constable 《Surveys in Geophysics》2016,37(1):27-45
The natural spectrum of electromagnetic variations surrounding Earth extends across an enormous frequency range and is controlled by diverse physical processes. Electromagnetic (EM) induction studies make use of external field variations with frequencies ranging from the solar cycle which has been used for geomagnetic depth sounding through the 10\(^{-4}\)–10\(^4\) Hz frequency band widely used for magnetotelluric and audio-magnetotelluric studies. Above 10\(^4\) Hz, the EM spectrum is dominated by man-made signals. This review emphasizes electromagnetic sources at \(\sim\)1 Hz and higher, describing major differences in physical origin and structure of short- and long-period signals. The essential role of Earth’s internal magnetic field in defining the magnetosphere through its interactions with the solar wind and interplanetary magnetic field is briefly outlined. At its lower boundary, the magnetosphere is engaged in two-way interactions with the underlying ionosphere and neutral atmosphere. Extremely low-frequency (3 Hz–3 kHz) electromagnetic signals are generated in the form of sferics, lightning, and whistlers which can extend to frequencies as high as the VLF range (3–30 kHz).The roughly spherical dielectric cavity bounded by the ground and the ionosphere produces the Schumann resonance at around 8 Hz and its harmonics. A transverse resonance also occurs at 1.7–2.0 kHz arising from reflection off the variable height lower boundary of the ionosphere and exhibiting line splitting due to three-dimensional structure. Ground and satellite observations are discussed in the light of their contributions to understanding the global electric circuit and for EM induction studies. 相似文献
20.
本文用19个行星际扰动事件为样本,采用三维运动学模式研究暗条消失事件（简称FD事件）与行星际瞬变扰动间的关系．太阳上的扰动源取行星际扰动前2-5d以内的所有FD事件,用势场模式计算得到的源表面磁场为背景,模拟每个扰动在行星际中的传播及其相互作用过程,观察扰动到达地球的时间和扰动大小．从模拟的结果来看,FD事件与行星际扰动事件有较好的对应关系,说明FD事件是行星际瞬变事件的一类重要的太阳源．19个事件中有2个没有对应的FD事件,5个模拟结果与观测结果相差较大,其余12个模拟结果与实际观测符合很好．这与过去这方面的工作有所不同,我们具体模拟了每个扰动事件的传播过程,同时考虑了扰动间的相互作用,包括扰动与共转流之间的相互作用,为太阳-行星际-地磁链天气过程的预报奠定了基础． 相似文献