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1.
The effect of the high-speed stream following the corotating interaction region on the geomagnetic activities 总被引：1，自引：0，他引：1
S. Watari 《Annales Geophysicae》1997,15(6):662-670
The high-speed stream following the corotating interaction regions (CIRs) was analyzed. As a result of the analysis, it is found that the geomagnetic field is continuously disturbed in the high-speed stream in question. The geomagnetic disturbances with long duration recurred several rotations between December 1993 and June 1994. These disturbances were associated with a large recurrent coronal hole expanding from the south pole of the Sun. High-speed solar wind from this coronal hole was observed by the IMP-8 satellite during this period. However, the observed intensities of the geomagnetic disturbances were different for each recurrent period. This is explained by the seasonal effect. The disturbed geomagnetic condition continued in the highspeed stream after the passage of the CIRs. The long duration of these disturbances can be explained by the continuous energy input into the Earths magnetosphere from the high-speed regions following the CIRs. This kind of long-duration geomagnetic disturbance in association with coronal holes has been observed in the declining phase of other solar cycles. The relation between the coronal-hole area and the maximum solar-wind velocity is not good for the well-developed large coronal hole analyzed here. 相似文献
2.
冕洞是太阳风高速流的源区.当冕洞出现在中低纬区域时,太阳风高速流会扫过地球并引发地球空间环境扰动,如地磁暴和高能电子暴等.在太阳活动周下降年和低年,这种类型的扰动占据主导地位.因此,冕洞高速流的到达时间、峰值时间、峰值强度和持续时间等,是空间天气预报的重要内容.本文基于2010年5月到2016年12月的SDO/AIA太阳极紫外图像以及1AU处ACE和WIND卫星的太阳风观测数据,确定了160个冕洞-太阳风高速流事件,定量计算了他们的特征参数,包括冕洞与太阳风高速流的开始时间、峰值时间、峰值强度和结束时间,分析了各个特征参数的分布规律,对冕洞-高速流之间的关系进行了统计研究,并提出了一种新的预报方法,为基于冕洞成像观测的太阳风高速流的精准预报提供了依据. 相似文献
3.
The excitation of long-period irregular pulsations in the 2.0–6.0 mHz range (ipcl pulsation series) in the Earth’s magnetosphere, depending on the set of solar wind plasma and IMF parameters, has been studied experimentally. It has been found that burst regimes are observed when the solar wind dynamic pressure and velocity are higher than V ∼ 320 km/s and P ∼ 1 nPa, respectively. It has been indicated that the dynamics of the ipcl pulsation intensity and fractal structure largely depend on the solar wind plasma velocity and magnetic pressure, respectively. An analysis of the relationship between the appearance of ipcl pulsation burst series and large-scale solar wind streams and polar coronal holes made it possible to identify solar geoeffective regions, which can cause solar wind streams and Alfvén waves that promote the generation of burst regimes. On the basis of the studied conditions of the interplanetary medium, favourable for the excitation of ipcl pulsation burst series, and generalization of morphological patterns, the possible mechanisms of their generation have been considerded. It has been demonstrated that ipcl burst regimes are most probably generated as wind instability in hydrodynamics (the Miles-Phillips mechanism). The Miles-Phillips instability is related to different factors in the solar wind stream, among which turbulence, the threshold velocity value, and pressure fluctuations play a defining role. Precisely these regularities are typical of the ipcl burst regime generation conditions. 相似文献
4.
The regularities of the variations in the IMF B z component have been studied based on the data on the solar wind streams and their solar sources. Isolated solar wind streams such as magnetic clouds and shock layers before them, undisturbed heliospheric current sheets (HCSs), leading edges and bodies of high-speed streams from coronal holes (HSSs from CHs) have been considered. It has been revealed that each type of isolated streams in the interplanetary medium has it own features in the variations in the value and direction of the B z component related to the stream immanent properties and conditions of propagation in the interplanetary plasma. The appearance of the southward B z component is obligatory for all these streams which are, therefore, geoeffective. 相似文献
5.
Ellen G. Zweibel 《地球物理与天体物理流体动力学》2013,107(3-4):317-331
Abstract We apply the MHD energy principle to the stability of a magnetized atmosphere which is bounded below by much denser fluid, as is the solar corona. We treat the two fluids as ideal; the approximation which is consistent with the energy principle, and use the dynamical conditions that must hold at a fluid-fluid interface to show that if vertical displacements of the lower boundary are permitted, then the lower atmosphere must be perturbed as well. However, displacements which do not perturb the coronal boundary can be properly treated as isolated perturbations of the corona alone. 相似文献
6.
Geomagnetic disturbances in the Canadian region are compared with their solar and heliospheric sources during the decline phase of solar activity, when recurrent solar wind streams from low-latitude coronal holes were clearly defined. A linear correlation analysis has been performed using the following data: the daily and hourly indices of geomagnetic activity, solar wind velocity, and coronal hole area. The obtained correlation coefficients were rather low between the coronal hole areas and geomagnetic activity (0.17–0.48), intermediate between the coronal hole areas and the solar wind velocity (0.40–0.65), and rather high between the solar wind velocity and geomagnetic activity (0.50–0.70). It has been indicated that the correlation coefficient values can be considerably increased (by tens of percent in the first case and about twice in the second case) if variations in the studied parameters related to changes in the ionosphere (different illumination during a year) and variations in the heliolatitudinal shift of the coordinate system between the Earth, the Sun, and a spacecraft are more accurately taken into account. 相似文献
7.
太阳风的动量涨落将通过磁层边界在磁尾激发磁流体力学波。快磁声波携带扰动能量传到等离子体片中,发展为激波,或者通过激波的相互作用而耗散能量,使等离子体加热。等离子体片中的随机费米加速机制,使麦克斯韦分布尾巴部分的高能量粒子被加速到更高能。在宁静态时,加热、加速与耗散过程平衡。当太阳风的动量或者其涨落较大时,整个加热和加速过程加剧,更多的高能粒子产生,并从等离子体片中逃逸,形成高速的等离子体流注入近地轨道和极区,表现为磁层亚暴过程。利用这种机制,可以解释地球磁层亚暴的定性特征。 相似文献
8.
The solar wind velocity and polarity of the B x-component of the interplanetary magnetic field have been analyzed for the first eight months of 2005. The interplanetary magnetic field had a four-sector structure, which persisted during nine Carrington rotations. Three stable clusters of a high-speed solar wind stream and one cluster of a low-speed stream were observed during one solar rotation. These clusters were associated with the interplanetary magnetic field sectors. The predicted solar wind velocity was calculated since July 2005 one month ahead as an average over several preceding Carrington rotations. The polarity of the B x-component of the interplanetary magnetic field was predicted in a similar way based on the concept of the sector structure of the magnetic field and its relation to maxima of the solar wind velocity. The results indicate a satisfactory agreement of the forecast for two rotations ahead in July–August 2005 and pronounced violation of agreement for the next rotation due to a sudden reconfiguration of the solar corona and strong sporadic processes in September 2005. 相似文献
9.
Lee S. Elson 《地球物理与天体物理流体动力学》2013,107(1):57-90
Abstract A primitive equation, solar driven, thermospheric model is derived which has applications to the neutral gas components on Mars and Venus. The full effects of molecular viscosity and thermal conductivity are included, necessitating the development of a combined analytic and numerical solution technique. The model is applied to Venus in order to understand how thermospheric rotation, if present, would affect the dynamics. Results indicate that rotation periods of eight days or less should be observable. Application of the model to Mars indicates that the perturbation solar heating and the atmospheric response have primarily a diurnal component for which typical temperature and zonal wind maximum amplitudes are 20 K and 30 m/sec respectively. Because of uncertainty in the solar heating efficiency, calculations were made varying this parameter by an order of magnitude. The results imply that the response due to solar forcing alone is probably too small to account for observed concentrations of the minor constituents CO and O. An upper limit estimate is made of the upward propagation of wave energy from the lower atmosphere and the resulting response of the thermosphere. 相似文献
10.
Short-lived plasma jets of various scales, from giant X-ray jets more than 300 Mm in extent to numerous small jets with sizes
typical of macrospicules, are the phenomena observed in the solar corona in extreme ultraviolet and X-ray emission. Small
jets are particularly prominent in polar coronal holes. They are close neighbors of tiny bright loops and coincide in time
with their sudden brightening and increase in size. The geometric shape of the jets and their location suggest that they arise
near singular null points of the coronal magnetic field. These points appear in coronal holes due to the emergence of small
bipolar or unipolar magnetic structures within large-scale unipolar cells. Polar jets show a distinct vertical plasma motion
in a coronal hole that introduces significant momentum and mass into the solar wind flow. Investigating the dynamics of polar
jets can elucidate certain details in the problem of fast solar wind acceleration. 相似文献
11.
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
12.
Barbara A. Emery Ian G. Richardson David S. Evans Frederick J. Rich 《Journal of Atmospheric and Solar》2009,71(10-11):1157-1175
We assess the contributions of various types of solar wind structures (transients, coronal hole high-speed streams (HSS), and slow-speed wind) to hourly average auroral electron power (Pe). The time variation of the solar wind velocity (Vsw) and Pe are determined by HSS, which contribute ～47% to Pe and Vsw. Transients contribute ～42% of Pe in solar maxima, and ～6% in solar minimum. Cross-correlations of Pe with Vsw|B| for negative Bz are significant. Pe exhibits solar rotational periodicities similar to those for Vsw, with strong 7- and 9-day periodicities in 2005–2008 and equinox semiannual periodicities in 1995–1999. 相似文献
13.
Polar and high latitude substorms and solar wind conditions 总被引：1，自引：0，他引：1
All substorm disturbances observed in polar latitudes can be divided into two types: polar, which are observable at geomagnetic latitudes higher than 70° in the absence of substorms below 70°, and high latitude substorms, which travel from auroral (<70°) to polar (>70°) geomagnetic latitudes. The aim of this study is to compare conditions in the IMF and solar wind, under which these two types of substorms are observable on the basis of data from meridional chain of magnetometers IMAGE and OMNI database for 1995, 2000, and 2006–2011. In total, 105 polar and 55 high latitude substorms were studied. It is shown that polar substorms are observable at a low velocity of solar wind after propagation of a high-speed recurrent stream during the late recovery phase of a magnetic storm. High latitude substorms, in contrast, are observable with a high velocity of solar wind, increased values of the Bz component of the IMF, the Ey component of the electric field, and solar wind temperature and pressure, when a high-speed recurrent stream passes by the Earth. 相似文献
14.
Mitchell A. Berger 《地球物理与天体物理流体动力学》2013,107(1-2):79-104
Abstract The Cauchy-Schwarz inequality is employed to find geometry-independent limits on the magnetic helicity dissipation rate in a resistive plasma. These limits only depend upon the total energy of the plasma, the energy dissipation rate, and a mean diffusion coefficient. For plasmas isolated from external energy sources, limits can also be set on the minimum time necessary to dissipate a net amount of helicity ΔH. As evaluated in the context of a solar coronal loop, these limits strongly suggest that helicity decay occurs on a diffusion timescale which is far too great to be relevant to most coronal processes. Furthermore, rapid reconnection is likely to approximately conserve magnetic helicity. The dilliculties involved in determining the free energy residing in a magnetic structure (given the constraint of magnetic helicity conservation) are discussed. 相似文献
15.
Ulysses 是迄今为止第一次沿独特的日球纬度方向考察日球高纬度空间区域的飞船。本文描述了 Ulysses 飞船的部分主要观测结果,并进行了分析,在 Ulysses 飞船穿越太阳南,北极之前,科学家们提出了各种不同的太阳风速度、磁场等参量的纬向变化模型。分析表明,这些模型都不能解释 Ulysses 飞船的观测结果。Ulysses 飞船的观测对经典的太阳风理论提出了挑战,太阳风的加热与加速是一个远没有被解决的问题。观测与分析表明,经典热传导不可能驱动高速流,太阳风的加速伴随着加热的发生,而加热率大小可能与离子的回旋频率有关;太阳风的热源可能不是单一的形式,而且不同形式的热源对太阳的加热贡献大小与日球径向距离有关。本文讨论并分析了几种可能的太阳风加热与加速机制。 相似文献
16.
The event of March 12–19, 2009, when a moderately high-speed solar wind stream flew around the Earth’s magnetosphere and carried
millihertz ultralow-frequency (ULF) waves, has been analyzed. The stream caused a weak magnetic storm (D
st min = −28 nT). Since March 13, fluxes of energetic (up to relativistic) electrons started increasing in the magnetosphere. Comparison
of the spectra of ULF oscillations observed in the solar wind and magnetosphere and on the Earth’s surface indicated that
a stable common spectral peak was present at frequencies of 3–4 mHz. This fact is interpreted as evidence that waves penetrated
directly from the solar wind into the magnetosphere. Possible scenarios describing the participation of oscillations in the
acceleration of medium-energy (E > 0.6 MeV) and high-energy (E > 2.0 MeV) electrons in the radiation belt are discussed. Based on comparing the event with the moderate magnetic storm of
January 21–22, 2005, we concluded that favorable conditions for analyzing the interaction between the solar wind and the magnetosphere
are formed during a deep minimum of solar activity. 相似文献
17.
18.
Abstract A class of exact solutions to the steady, two-dimensional magnetohydrodynamic equations ina cylindrical geometry is presented. These may model both closed and open magnetic structures found in the solar atmosphere. For closed structures, it is found that increasing the flow speed causes the summit of the arcade of closed magnetic fieldlines to rise. Parameter ranges also exist where the solution has regions of open and closed field, and so the solutions may be relevant for modelling flows in solar magnetic structures such as coronal streamers, X-ray bright points coronal plumes and coronal holes. 相似文献
19.
The effect of the mutual orientation of the Poynting vector P of the electromagnetic energy density in the solar wind and the vector M of the Earth’s magnetic moment (taking into account its orbital and diurnal motions) on the geomagnetic activity has been
examined for the first time using the measurements of the solar wind parameters on the Earth orbit in 1963–2005. The component
P
m of the vector P along the vector M is shown to have a pronounced annual variation with the extrema in November and May and a diurnal variation with the extrema
at ∼6 and 18 UT. The phases of the variations are shown to be determined only by the geometric parameters and are independent
of the sign of the sector structure of the interplanetary magnetic field. The experimental data on the planetary and high-latitude
geomagnetic activity, which is a response to changes in the orientation of P relative to M, are presented. The power of the sources of the electromagnetic energy of the solar wind during strong geomagnetic disturbances
is also estimated. 相似文献
20.
The velocities of the stationary extra-ecliptic solar wind are analyzed depending on the heliolatitudes, heliocentric distances,
and solar activity. An analysis has been performed using the direct measurements of the solar plasma flux velocities onboard
Ulysses and the simultaneous ground-based IPS observations. The arguments for the hypothesis that primary high-speed (V ∼ 900 km/s) flows exist at the corona bottom and are directly related to the photosphere and solar magnetic fields are presented.
The possible mechanism by which high-speed streams are generated is generally considered. 相似文献