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1.
Results on the spectral analysis using geomagnetic field at three low latitude stations and the planetary magnetic activity
index have shown peaks in the power densities in a broad band centred around 146-day period. This periodic behaviour appears
to be close to that shown by the solar flare activity index for the same interval. It is suggested that the geoeffectiveness
of the flare activity signal in different phases of the solar cycle can be better worked out using long series of ground-based
geomagnetic data. 相似文献
2.
G. K. Rangarajan 《Journal of Earth System Science》1991,100(1):49-54
From maximum entropy spectral analysis (MESA) of short lengths ofAa indices of geomagnetic activity, the characteristics of the strength of the 27-day and 13.5-day signals for each of the solar
cycles 11 to 21 are highlighted. It is shown that the 13.5-day signal is a near permanent feature in geomagnetic activity.
The Hale-cycle (22 yr) effect could be seen in the average magnitude of the 27-day signal with greater strengths in the even
cycles. No clear annual variation in the strength is noticed, contrary to some earlier known results. 相似文献
3.
火山活动对南半球平流层气候异常变化的影响 总被引：5，自引：0，他引：5
文中利用逐次滤波法分析结果表明 ,火山活动能引起平流层较大幅度增温 ,对于南半球 70hPa高空气候异常变化的影响超过了总方差的 1 6 % ;火山活动影响最显著的高度是平流层 70hPa约1 5～ 2 2km高空 ,由此高度向上或向下 ,火山活动的影响都逐渐减小 ;火山活动引起平流层大气升温的同时还将引起对流层大气降温 ,其分界线大致位于对流层顶 30 0hPa附近。平流层高空气候异常变化还具有显著的 2 2a变化周期和 1 1a变化周期 ,分析认为是大气温度场对太阳磁场磁性 2 2a周期和太阳黑子 1 1a周期变化的响应 ,其方差贡献率超过 8%。 相似文献
4.
Long period variations in the occurrence of prolonged intervals of calm magnetic field conditions are studied using index
Ap of magnetic activity. The solar-cycle variation in occurrence is compared with the sunspot number. Anomalous behaviour
for solar cycle 20, observed in other solar parameters, are shown to be manifested in the occurrence frequency of quiet intervals.
Spectral characteristics of occurrence indicates a dominant long period variation of about 30 years and a more feeble 11-year
oscillation 相似文献
5.
To study the characteristic of plasma bubbles in the topside ionosphere during the solar minima, we have analyzed a large
database of post-sunset plasma density measurement acquired during ∼5104 equatorial crossings made by Defense Meteorological
Satellite Program (DMSP) F14 in 2005. On 675 of these crossings, equatorial plasma bubbles (EPBs) events were observed as
intervals of depleted and irregular plasma densities that degrade communication and navigation signals. We have analyzed these
EPB events to study their distributions with month, season and longitude. To test for possible dependence of EPB occurrence
at topside altitudes on the level of magnetic activity, we compared the distributions of one year database with those of Kp
index at the time of equatorial crossings by the DMSP satellites. We also examined the response of the evening sector, low-latitude
ionosphere during eight magnetic storms with minimum Dst ≤ −100 nT. We observed that EPBs occurred regularly during geomagnetic
storms, especially in the initial and main phases but can be suppressed sometimes for days, after prolonged activity during
recovery phases. These results are discussed according to the other reported results. 相似文献
6.
We study the effect of solar activity on the incidence of myocardial infarction deaths (MID) in Mexico. We work with 129,917 cases along 1996–1999, grouping the data by sex and age, and considering the solar cycle phases. At higher frequencies the circaseptan is the most persistent periodicity in MID occurrence. During solar minimum the circaseptan period is not detectable compared with solar maximum. During Forbush decreases and geomagnetic activity, most cases present a higher average MID occurrence. Furthermore the MID rate is higher as the level of the geomagnetic perturbation increases. Male MID rates are in general higher than female rates and the difference increases as the geomagnetic perturbation increases. The age group with the lowest MID incidence is 25 to 44 years, the age group of 65 years is the most vulnerable. We conclude that solar activity does affect MID at low geomagnetic latitudes and that the solar maximum is the most hazardous time for MID incidence. 相似文献
7.
Long and short term relationships between solar wind velocity and geomagnetic field at low latitudes
G. K. Rangarajan 《Journal of Earth System Science》1984,93(4):343-351
Solar wind velocity control of low latitude geomagnetic field both on long and short term basis is studied. It is shown that
semiannual averages of the low latitude field is inversely related to solar wind velocity and that there is a dominant local
time dependence of the relationship. Strongest correlation are confined to the local afternoon hours. It is also shown that
for a duration when the solar wind velocity exhibits significant recurrent pattern the low latitude geomagnetic field also
depicts strong solar synodic rotation periodicity of 27 days with significant coherence with velocity. The low latitude field
on a short term basis is influenced by variable solar wind velocity with a delay of about 1–2 days. During the period of systematic
recurrent pattern in solar wind velocity even the quiet-time night field at equatorial and low latitudes show a strong dependence
on velocity indicative of the solar wind control of the quiet-time proton belt encompassing the earth. 相似文献
8.
Jaroslav Střeštïk 《Central European Journal of Geosciences》2009,1(2):152-156
It is known that solar wind velocity fluctuates regularly with a period of about 1.3 years. This periodicity (and other signals with periods near to 1.1 and 0.9 years) has also been observed in biological data. The variation is a temporary feature, mostly being observed in the early 1990s. Here, the occurrence of these periodic signals in solar and geomagnetic activity between 1932 and 2005 has been investigated. The signal with 1.3 year period is present in geomagnetic activity only in a short interval after 1990 and to a lesser extent around 1942. At other times the signal is very weak or not present at all. Other periods are much lower amplitude and appear only sporadically throughout the time investigated. A connection between these periods and solar cycles (e.g. different even or odd cycles) has not been proven. It is possible that there is a long-term periodicity in the occurrence of the 1.3 year period but the time series data available is insufficient to confirm this. There are no such periodicities in solar activity. In order to gain a greater understanding of these periodic signals, we should search for their origin in interplanetary space. 相似文献
9.
E. Giannaropoulou M. Papailiou H. Mavromichalaki M. Gigolashvili L. Tvildiani K. Janashia P. Preka-Papadema Th. Papadima 《Natural Hazards》2014,70(2):1575-1587
Over the last few years, various researches have reached the conclusion that cosmic ray variations and geomagnetic disturbances are related to the condition of the human physiological state. In this study, medical data concerning the number of incidents of different types of cardiac arrhythmias for the time period 1983–1992, which refer to 1902 patients in Tbilisi, Georgia, were used. The smoothing method and the Pearson r-coefficients were used to examine the possible effect of different solar and geomagnetic activity parameters and cosmic ray intensity variations on the different types of arrhythmias. The time interval under examination was separated into two different time periods, which coincided with the polarity reversal of the solar magnetic field occurred in the years 1989–1990, and as a result, a different behavior of all the above-mentioned parameters as well as of the different types of arrhythmias was noticed during the two time intervals. In addition, changing of polarity sign of the solar magnetic field was found to affect the sign of correlation between the incidence of arrhythmias and the aforementioned parameters. The primary and secondary maxima observed in the solar parameters during the solar cycle 22, also appeared in several types of arrhythmias with a time lag of about 5 months. 相似文献
10.
11.
中生代地球系统与核—幔边界动力学研究进展 总被引：3，自引：1，他引：2
本文介绍了９０年以来地球物理学在地球磁场方面的研究成果,揭示了２００－１００Ｍａ全球低的地球磁场古强度;１２４－８３Ｍａ低的极性反转频率以及１７０－１１０Ｍａ近乎停滞的真极移。 相似文献
12.
A. V. Mordvinov 《Astronomy Reports》2006,50(11):936-943
The asymmetry of the magnetic field of the Sun and its manifestation in the interplanetary magnetic field (IMF) are studied. The dominant magnetic polarity of the radial component of the IMF alternates from cycle to cycle, but with an overall systematic dominance of polarity directed toward the Sun. The global asymmetry is also manifest in the component of the IMF perpendicular to the plane of the solar equator. The dominance of positive values of B z together with an appreciable linear trend in the cumulative sum of this quantity is interpreted as a manifestation of a relic solar magnetic field. The strength of this relic magnetic field near the Earth is estimated to be 0.048 ± 0.015 nT, based on the growth of the linear component of the cumulative sum of B z . Time intervals, in which negative values of the B z component of the IMF dominate and enhanced geomagnetic activity is observed, are identified. Our analysis of solar and heliospheric magnetic fields in an integrated representation has enabled us to compare various types of measurements and estimate their stability. 相似文献
13.
A. Aldahan G. Possnert S. J. Johnsen H. B. Clausen E. Isaksson W. Karlen M. Hansson 《Journal of Earth System Science》1998,107(2):139-147
We report in this study the distribution of10Be in the top 40 m of the Renland ice core (East Greenland) and in a 30 m long core from DML (Dronning Maud Land, Antarctica)
for the period 1931–1988. The two sites show differences in10Be content, the Antarctica site showing smaller variance and a lower average10Be annual flux. Similarly, the average accumulation rate (cm water equivalent year−1) is higher in the Renland relative to DML. The variability in accumulation (precipitation) rates seems to explain part of
the difference in10Be flux between the two polar sites. Cyclic fluctuations of10Be flux correlate with the 11-year sunspot number and cosmic ray intensity than with the aa index (perturbation of the geomagnetic
activity by the solar wind). Our data corroborate10Be cyclic fluctuation pattern from the Dye 3 ice core and confirm a promising potential for correlation of global and local
events. 相似文献
14.
Mohamed Sharif Berguig Mohamed Hamoudi Jean Louis Lemouël Yves Cohen 《Arabian Journal of Geosciences》2013,6(4):1063-1072
In this work, we report a global mapping of vector lunar magnetic field based on new method of separation of internal and external fields. The magnetic measurements collected during the lifetime of lunar prospector (LP) extended mission during 1999 were strongly disturbed by the solar wind, a period which coincided with a maximum of the 23 cycle activity. The multiscale wavelength external fields were analyzed using spherical harmonic transform. The external field determined by inversion was then removed from each magnetic field component for each half orbit. To map the vector magnetic crustal anomalies, all LP magnetometer data collected at low altitudes in the three different lunar environments: (1) geomagnetic tail, (2) solar wind, and (3) geomagnetic sheath were processed using this new approach. The results obtained using these selection criteria allow us to get a global coverage of the lunar surface by the vector magnetic field at variable spacecraft low altitudes. To validate our mapping, we have developed and applied a method based on properties of potential fields functions. This method can be used to determine both horizontal north and east components using only vertical component. The validated lunar internal magnetic measurements obtained at variable spacecraft altitudes were then continued to a common altitude of 30 km using an inverse method. This mapping confirms firstly the nature of the crustal sources of lunar magnetic field and clearly shows that the strongest concentrations of anomalies are associated with high albedo and/or located antipodal to large young basins (Orientale, Serenitatis, Imbrium, and Crisium) of age about 3.9 Ga. 相似文献
15.
Chashei I. V. Tyul’bashev S. A. Subaev I. A. Chernyshova A. I. 《Astronomy Reports》2019,63(5):409-419
Astronomy Reports - Solar and geomagnetic data demonstrate that, at the decay phase of solar activity in 2016, the dominating role in strong geomagnetic perturations was played by long-lived... 相似文献
16.
In this study, the relationship between the hourly changes of the ionospheric critic frequency values of F2 layers in low latitudes and geomagnetic activity is examined by using statistical methods. The ionospheric critical frequency data has been taken from the Manila (121.1° E, 14.7° N) ionosonde station. In order to investigate the effect of sun activity on ionospheric critical frequency, the data of 1981 when the sun was active and of 1985 when the sun was less active has been used. According to the Granger causality test results, on 5 % significance level, a causality relationship from disturbance storm time (Dst) index values to ionospheric critical frequency values direction has been observed. However, a causality relationship from ionospheric critical frequency values to Dst values has not been observed. From the results of cause-and-effect analysis, it is evaluated that the effect of a shockwave occurring in geomagnetic activity on ionospheric critical frequency continues along 72 h, that is, geomagnetic activity has a long-term effect on ionospheric critical frequency. The response of ionospheric critical frequency to geomagnetic activity substantially depends on seasons. This response is more observed especially in equinox period when the sun is active and in winter months. The increase in geomagnetic activity causes ionospheric critical frequency to decrease in night hours and increase in day hours. The same relationship has not been observed exactly, though observed very little in winter months, for 1985 when the sun was less active. 相似文献
17.
日地空间环境是人类生存发展的重要场所,太阳剧烈活动引起日地空间短时间尺度的变化,对人类社会带来严重影响和危害。本文简要介绍了空间天气学产生的背景和迅速发展的社会需求,当今国际合作研究的重大计划和进展,以及空间天气学研究的未来和展望。 相似文献
18.
显生宙以来,地磁场有7次频繁倒转间断,每次倒转伴随有相应的造山运动及岩浆活动。地磁场频繁变化,与之相伴的造山运动的发生,大陆与大洋的构造运动、生物的大量灭绝等,都与太阳系在银河系中的活动有关。 相似文献
19.
Ge Tongming Fan Limin Liu Jian Guangzhou Marine Geological Survey Ministry of Geology Mineral Resources of Chin Guangzhou 《《地质学报》英文版》1993,67(2):235-245
The presence of the reversals of the geomagnetic field within the Brunhes is indicated by paleomagnetic stuides on Cenozoic volcanic rocks in the Leizhou Peninsula, loess strata and Quaternary marine sediments in the Pearl River Mouth basin in China. These regional reversals occured at 0.58±0.13 Ma, 0.45 Ma and 0.47—0.48 Ma respectively according to the results of K-Ar isotopic dating and climatostratigraphic and biostratigraphic analyses. The reversals equivalent to the Emperor Event is suggested.The reversals revealed in different regions with various lithologic characters in China prove that the Emperor Event is a global reversal event rather than a geomagnetic excursion, and its confirmation will permit a precise definition of the Middle/Late Pleistocene boundary. 相似文献
20.
C. Panneerselvam C. Selvaraj K. Jeeva K. U. Nair C. P. Anilkumar S. Gurubaran 《Journal of Earth System Science》2007,116(3):179-186
Surface measurements of the atmospheric electrical parameters like Maxwell current, electric field and conductivity studied
at the Indian station, Maitri (70.75° S, 11.75° E, 117 m above mean sea level), Antarctica, during austral summer have been
analyzed for the years 2001 to 2004. A total of 69 days were selected which satisfied the ‘fairweather’ conditions, i.e.,
days with absence of high winds, drifting or falling snow, clouds, and fog effects. The diurnal variation curve of electric
field and vertical current averaged for 69 fairweather days is a single periodic with a minimum at 03:00 UT and a maximum
near 19:00 UT, which is very similar to the Carnegie curve. The correlation coefficient between these measured parameters
has a high value (more than 0.9) for all the days. During fairweather days the measured current and field variations are similar
and hence it is clear that the conductivity is more or less stable. During magnetically disturbed days, the dawn-dusk potential
drop has clear influences on the diurnal variation and it modifies the conductivity. Apart from the day-to-day variation in
low latitude thunderstorm activity, there are diurnal, seasonal, inter-annual variations in the electric potential and the
currents, as well as solar influences on the measured parameters. This study will help us to examine the impact of solar and
geophysical phenomena like solar flares, geomagnetic storms and substorms on the global electric circuit. 相似文献