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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.
Frédéric Ouattara Christine Amory-Mazaudier 《Journal of Atmospheric and Solar》2009,71(17-18):1736-1748
Legrand and Simon [1989. Solar cycle and geomagnetic activity: a review for geophysicists. Part I. The contributions to geomagnetic activity of shock waves and of the solar wind. Annales Geophysicae 7(6), 565–578] classified one century (1868–1978) of geomagnetic activity, using the Mayaud's Aa index, in four classes related to solar activity: (1) the magnetic quiet activity due to slow solar wind flowing around the magnetosphere, (2) the recurrent activity related to high wind speed solar wind, (3) the fluctuating activity related to fluctuating solar wind and (4) the shock activity due to shock events (CME). In this paper, we use this classification to analyse the solar–geomagnetic activity from 1978 to 2005. We found that during the last three decades the level of geomagnetic quiet activity estimated by Aa indices is decreasing: 2003 is the year of the smallest level of quiet geomagnetic activity since 1868. We compare Legrand and Simon's classification with new in situ solar wind data [Richardson, I.G., Cliver, E.W., Cane, H.V., 2000. Sources of geomagnetic activity over the solar cycle: relative importance of coronal mass ejections, high-speed streams, and slow solar wind. Journal of Geophysical research 105(A8), 18,200–18,213; Richardson, I.G., Cane, H.V., 2002. Sources of geomagnetic activity during nearly three solar cycles (1972–2000). Journal of Geophysical Research 107(A8), 1187] and find a rather good agreement. The differences are only due to minor definitions of the extent of the classes. An attempt is made at defining a more precise standard classification of solar phenomena and at defining time scales of these to understand more precisely the geomagnetic signatures of solar activity. 相似文献
3.
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
4.
The method for searching statistical relations between different solar wind parameters and the aa index of geomagnetic activity, which formed the basis for restoring the average annual values of some of these parameters (indicating that the solar coronal magnetic field increased by not more than 10% during the last century), has been proposed. 相似文献
5.
6.
The relation of the fluxes of relativistic electrons in geostationary orbit during magnetic storms to the state of the magnetosphere and variations in the solar wind parameters is studied based on the GOES satellite data (1996–2000). It has been established that, in ～52–65% of all storms, the fluxes of electrons with energies higher than 0.6 and 2 MeV during the storm recovery phase are more than twice as high as the electron fluxes before a storm. It has been indicated that the probability of such cases is closely related to the prestorm level of fluxes and to a decrease in fluxes during the storm main phase. It has been found that the solar wind velocity on the day of the storm main phase and the geomagnetic activity indices at the beginning of the storm recovery phase are also among the best indicators of occurrence of storms with increased fluxes at the storm recovery phase. 相似文献
7.
The average annual values of the electric field and parameters of the solar wind and IMF from our time to 1868 have been estimated
based on the statistical relation between the aa index of geomagnetic activity and the interplanetary medium parameters. This estimation indicates that the relative variations
during the 20th century were observed in the electric field (25 ± 3%), the IMF vector component transverse with respect to
the velocity (16 ± 3%), and the solar wind plasma velocity (9 ± 1%, 37 ± 4 km/s). The modulus of the IMF vector radial component
increased by 9.0 ± 2.5% during this period. 相似文献
8.
The correlation between total ozone content lower thermosphere horizontal wind parameters, and standard indices of solar activity
and geomagnetic activity has been studied. The satellite measurements of TOC for five observatories in Central Europe and
the lower thermosphere wind measurements for Collm observatory (Germany) were used for 1996–2003. The quasi-periodic structure
of these variations and the correlation between the corresponding periodograms were also studied. The quantitative evaluation
of the statistically significant correlations and common periodicities were revealed. 相似文献
9.
We study the annual frequency of occurrence of intense geomagnetic storms (Dst < –100 nT) throughout the solar activity cycle for the last three cycles and find that it shows different structures. In cycles 20 and 22 it peaks during the ascending phase, near sunspot maximum. During cycle 21, however, there is one peak in the ascending phase and a second, higher, peak in the descending phase separated by a minimum of storm occurrence during 1980, the sunspot maximum. We compare the solar cycle distribution of storms with the corresponding evolution of coronal mass ejections and flares. We find that, as the frequency of occurrence of coronal mass ejections seems to follow very closely the evolution of the sunspot number, it does not reproduce the storm profiles. The temporal distribution of flares varies from that of sunspots and is more in agreement with the distribution of intense geomagnetic storms, but flares show a maximum at every sunspot maximum and cannot then explain the small number of intense storms in 1980. In a previous study we demonstrated that, in most cases, the occurrence of intense geomagnetic storms is associated with a flaring event in an active region located near a coronal hole. In this work we study the spatial relationship between active regions and coronal holes for solar cycles 21 and 22 and find that it also shows different temporal evolution in each cycle in accordance with the occurrence of strong geomagnetic storms; although there were many active regions during 1980, most of the time they were far from coronal holes. We analyse in detail the situation for the intense geomagnetic storms in 1980 and show that, in every case, they were associated with a flare in one of the few active regions adjacent to a coronal hole. 相似文献
10.
The solar wind–magnetosphere coupled system is characterized by dynamical processes. Recent works have shown that nonlinear couplings and turbulence might play a key role in the study of solar wind–magnetosphere interaction processes.Within this framework, this study presents a statistical analysis aimed to investigate the relationship between solar wind MHD turbulence and geomagnetic activity at high and low latitudes as measured by the AE and SYM-H indices, respectively. This analysis has been performed for different phases of solar cycle 23. The state of turbulence was characterized by means of 2-D histograms of the normalized cross-helicity and the normalized residual energy. The geomagnetic response was then studied in relation to those histograms.The results found clearly show that, from a statistical point of view, solar cycle 23 is somewhat peculiar. Indeed, good Alfvénic correlations are found unexpectedly even during solar activity maximum. This fact has implications on the geomagnetic response as well since a statistical relationship is found between Alfvénic fluctuations and auroral activity. Conversely, solar wind turbulence does not seem to play a relevant role in the geomagnetic response at low latitudes. 相似文献
11.
The relation of the long-period variations in the midnight and noon values of the critical frequency of the ionospheric F 2 layer at three midlatitude stations (Irkutsk, Moscow, and Boulder) to the daily mean index of geomagnetic activity in years of different solar activity has been studied. It has been found that the correlation coefficients between the above parameters depend on time of day, season, and solar activity level. The correlation coefficients are higher at night than in the daytime, especially at low solar activity. The highest absolute values of the correlation coefficient most often appear during equinoxes: April–May and September–October. It has been shown that the variability of the critical frequencies of the midlatitude ionospheric F 2 layer depends not only on geomagnetic activity but also (to a considerable degree) on the effect of the lower atmosphere. 相似文献
12.
A very strong magnetic storm of May 15, 2005, was caused by an interplanetary magnetic cloud that approached the Earths’ orbit. The sheath region of this cloud was characterized by a high solar wind density (～25–30 cm?3) and velocity (～850 km/s) and strong variations (to ～20 nT) in the interplanetary magnetic field (IMF). It has been indicated that an atypical bay-like geomagnetic disturbance was observed during the initial phase of this storm in a large longitudinal region at high latitudes: from the morning to evening sectors of the geomagnetic local time. Increasing in amplitude, the magnetic bay rapidly propagated to the polar cap latitudes up to the geomagnetic pole. An analysis of the global space-temporal dynamics of geomagnetic pulsations in the frequency band 1–6 mHz indicated that most intense oscillations were observed in the morning sector in the region of the equivalent ionospheric current at latitudes of about 72°–76°. The wavelet structure of magnetic pulsations in the polar cap and fluctuations in IMF was generally similar to the maximum at frequencies lower than 4 mHz. This can indicate that waves directly penetrated into the polar cap from the solar wind. 相似文献
13.
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
14.
N. A. Zolotukhina 《Geomagnetism and Aeronomy》2006,46(6):688-700
Disturbances in the solar wind density, geomagnetic field, and magnetospheric plasma density and fluxes are analyzed. The disturbances have the same sign and are close to each other in time. They accompany the process of amplitude modulation of Pc1 geomagnetic pulsations during the recovery phase of the moderate magnetic storm of April 10–11, 1997. The magnetospheric disturbances were recorded by ground-based observatories and on spacecraft in all local time sectors with insignificant time delays. It is concluded that in this case variations in the geomagnetic field and magnetospheric plasma density are primary, whereas the amplitude modulation of Pc1, 2 is a secondary manifestation of fast magnetosonic (FMS) waves that are generated during the interaction between the magnetosphere and solar wind density irregularities. 相似文献
15.
The F-region peak electron densities NmF2 measured during daytime quiet geomagnetic conditions at low solar activity on January 22, 2008, April 8, 1997, July 12, 1986, and October 26, 1995, are compared. Ionospheric parameters are measured by the ionosonde and incoherent scatter radar at Millstone Hill and calculated with the use of a 1D nonstationary ionosphere–plasmasphere model of number densities and temperatures of electrons and ions at middle geomagnetic latitudes. The formation of the semiannual anomaly of the midlatitudinal NmF2 under daytime quiet geomagnetic conditions at low solar activity is studied. The study shows that the semiannual NmF2 anomaly occurs due to the total impact of three main causes: seasonal variations in the velocity of plasma drift along the geomagnetic field due to the corresponding variations in the components of the neutral wind velocity; seasonal variations in the composition and temperature of the neutral atmosphere; and the dependence of the solar zenith angle on a number of the day in the year at the same solar local time. 相似文献
16.
R. I. Crickmore 《Annales Geophysicae》1994,12(10-11):1101-1113
Thermospheric winds on a total of 237 nights have been studied for the effects due to geomagnetic activity, solar flux, and season. The observations have been made from 1988 to 1992 by a Fabry-Perot interferometer (FPI) operating at Halley (75.5°S, 26.6°W), Antarctica. This is the first statistical study of thermospheric winds near the southern auroral zone. The main factor affecting the wind velocities is the geomagnetic activity. Increases in activity cause an increase in the maximum equatorward wind, and cause the zonal wind in the evening to become more westward. Smaller changes in the mean wind occur with variations in season and solar flux. The small variation with solar flux is more akin to the situation found at mid-latitudes than at high latitudes. Since the geomagnetic latitude of Halley is only 61°, it suggests that the variability of the wind with solar flux may depend more on geomagnetic than geographic latitude. These observations are in good agreement with the empirical Horizontal Wind Model (HWM90). However, comparisons with predictions of the Vector Spherical Harmonic Model (VSH) show that for low geomagnetic activity the predicted phases of the two components of the wind closely resemble the observations but the modelled amplitudes are too small by a factor of two. At high geomagnetic activity the major differences are that modelled zonal velocity is too westward in the evening and too eastward after 04 UT. The modelled ion densities at the F-region peak are a factor of up to 9 too large, whilst the predicted mean value and diurnal variation of the altitude of the peak are significantly lower than those observed. It is suggested that these differences result from the ion loss rate being too low, and an inaccurate model of the magnetic field. 相似文献
17.
The period of interplanetary, geomagnetic and solar disturbances of September 7–15, 2005, is characterized by two sharp increases of solar wind velocity to 1000 km/s and great Dst variation of the geomagnetic field (~140 nT). The time variations of theoretical and experimental geomagnetic thresholds observed during this strong geomagnetic storm, their connection with solar wind parameters and the Dst index, and the features of latitudinal behavior of geomagnetic thresholds at particular times of the storm were studied. The theoretical geomagnetic thresholds were calculated with cosmic ray particle tracing in the magnetic field of the disturbed magnetosphere described by Ts01 model. The experimental geomagnetic thresholds were specified by spectrographic global survey according to the data of cosmic ray registration by the global station network. 相似文献
18.
Using a simple time-lagged correlation technique, present study aims to identify the solar wind (SW) parameter, which is better associated with the ground magnetic field variations of shorter time duration near equator, during intense geomagnetic storms. It is found that out of all SW parameters, successively occurring enhancements in the SW dynamic pressure have substantial influence on the horizontal component of magnetic field at ground. Present analysis reveals a time lag of ~30–45 min between the SW pressure changes seen at L1 location and ground magnetic field variations, and hence providing a good approximation of an averaged propagation time during entire storm interval; the time lag varies with solar wind velocity. Separate study during day and nighttime suggests that the SW dynamic pressure enhancements recorded by the dayside outer magnetospheric satellite have impact on the ground horizontal magnetic field measurements near equator, irrespective of day or nighttime. 相似文献
19.
The geomagnetic observations, performed at the global network of ground-based observatories during the recovery phase of the superstrong magnetic storm of July 15–17, 2000 (Bastille Day Event, Dst = ?301 nT), have been analyzed. It has been indicated that magnetic activity did not cease at the beginning of the storm recovery phase but abruptly shifted to polar latitudes. Polar cap substorms were accompanied by the development of intense geomagnetic pulsations in the morning sector of auroral latitudes. In this case oscillations at frequencies of 1–2 and 3–4 mHz were observed at geomagnetic latitudes higher and lower than ～62°, respectively. It has been detected that the spectra of variations in the solar wind dynamic pressure and the amplitude spectra of geomagnetic pulsations on the Earth’s surface were similar. Wave activity unexpectedly appeared in the evening sector of auroral latitudes after the development of near-midnight polar substorms. It has been established that the generation of Pc5 pulsations (in this case at frequencies of 3–4 mHz) was spatially asymmetric about noon during the late stage of the recovery phase of the discussed storm as took place during the recovery phase of the superstrong storms of October and November 2003. Intense oscillations were generated in the morning sector at the auroral latitudes and in the postnoon sector at the subauroral and middle latitudes. The cause of such an asymmetry, typical of the recovery phase of superstrong magnetic storms, remains unknown. 相似文献
20.
M. I. Tyasto O. A. Danilova V. M. Dvornikov V. E. Sdobnov 《Geomagnetism and Aeronomy》2008,48(6):691-708
The time variations in the CR geomagnetic cutoff rigidity and their relation to the interplanetary parameters and the Dst index during a strong magnetic storm of November 18–24, 2003, have been analyzed. The Tsyganenko (Ts03) model of a strongly disturbed magnetosphere [Tsyganenko, 2002a, 2002b; Tsyganenko et al., 2003] have been used to calculate effective geomagnetic thresholds with the help of the method for tracing CR particle trajectories in the magnetospheric magnetic field. The geomagnetic thresholds have been calculated using the method of global spectrographic survey (GSS), based on the data from the global network of CR stations, and the results have been compared with the effective geomagnetic cutoff rigidities. The daily anisotropy of effective geomagnetic thresholds during the Dst variation minimum have been estimated. The relation of the theoretical and experimental geomagnetic thresholds, obtained using the GSS method, to the interplanetary parameters and Dst variation is analyzed. The Dst variations, IMF B z , and solar wind density are most clearly defined in the geomagnetic thresholds during this storm. The correlation between B y and experimental geomagnetic thresholds is higher than such a correlation between this parameter and theoretical thresholds by a factor 2–3, which suggests that a real dawn-dusk asymmetry during this storm was stronger than such an asymmetry represented by the Ts03 model. 相似文献