共查询到20条相似文献，搜索用时 15 毫秒
1.
V. V. Adushkin A. A. Spivak V. A. Kharlamov 《Izvestiya Physics of the Solid Earth》2014,50(2):215-221
The instrumental observations of geomagnetic variations in the middle latitudes are analyzed. The main periodicities are revealed in the background local variations of the magnetic field of the Earth. Besides the 27–29-day variations, which are associated with the rotation of the Sun around its axis, also the harmonic components with periods of ～1, 6–8, 13–14, 57–60 days, and about a year are identified. It is shown that the periodicities in the background variations are both regular and sporadic. The peculiarities in the time behavior of some spectral components of geomagnetic variations are established. 相似文献
2.
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
3.
V. I. Perminov A. I. Semenov I. V. Medvedeva N. N. Pertsev V. A. Sukhodoev 《Geomagnetism and Aeronomy》2018,58(1):127-134
Long-term series of midnight temperature in the mesopause region have been obtained from spectral observations of hydroxyl airglow emission (OH(6-2) λ840 nm band) at the Tory station (52° N, 103° E) in 2008–2016 and Zvenigorod (56° N, 37° E) station in 2000–2016. On their basis, the Lomb-Scargle spectra of the variations in the period range from ~12 days to ~11 years have been determined. Estimates of the amplitudes of statistically significant temperature fluctuations are made. The dominant oscillations are the first and second harmonics of the annual variation, the amplitudes of which are 23–24 K and 4–7 K, respectively. The remaining variations, the number of which was 16 for the Tory and 22 for Zvenigorod stations, have small amplitudes (0.5–3 K). Oscillations with combinational frequencies, which arise from modulation of the annual variation harmonics, are observed in a structure of the variation spectra in addition to interannual oscillations (periods from ~2 to ~11 years) and harmonics of the annual variation (up to its tenth harmonic). 相似文献
4.
E. L. Afraimovich S. V. Voeykov A. B. Ishin N. P. Perevalova Yu. Ya. Ruzhin 《Geomagnetism and Aeronomy》2008,48(5):674-679
The variations in the total electron content (TEC), obtained from the data of 11 ground-based GPS stations in the region (5°S–80°N; 110–160°E) in the period August 2–15, 2006, have been analyzed in order to search for possible ionospheric manifestations of the SAOMAI powerful typhoon (August 5–11, 2006) near the south-eastern coast of China. The global TEC maps (GIM) have also been used. In the region of the typhoon action during the magnetic storm of August 7, 2006, an intensification of the TEC variations in the evening local time within the 32–128 min periods range was detected. However, this effect was most probably caused by the dynamics of the irregular structure of the equatorial anomaly and by the disturbed geomagnetic situation (Kp ～ 3–6, Dst varied from ?74 to ?153 nT). The analysis of the diurnal variations in the absolute values of TEC and TEC variations with periods of 2–25 min did not reveal a substantial increase in the intensity and changes in the spectrum of the TEC variations in the period of typhoon action as compared to the adjacent days. Thus, we failed to detect ionospheric disturbances unambiguously related to the SAOMAI typhoon. 相似文献
5.
Yu. N. Koren’kov N. A. Koren’kova F. S. Bessarab V. S. Lechshenko 《Geomagnetism and Aeronomy》2017,57(4):451-460
The results of analysis of variations in the sporadic layer critical frequency (foEs) for winter periods of 2008–2010 in which sudden stratospheric warmings were observed are presented in the paper. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) by a Parus digital ionosonde under the usual sounding regime with an interval of 15 min. Daily mean values of foEs were used for the analysis. Solar and geomagnetic activity remained low during the periods under study, making it possible to relate the quasiwave time variations in foEs to the parameters of stratospheric warmings. The results of spectral analysis performed on the basis of continuous wavelet transform showed that, during all warmings occurring in 2008–2010, time variations in foEs show the presence of wave processes with a period of an order of 5 days and longer ones with a period of ~10—11 days. These periods coincide with characteristic periods of planetary waves observed in the atmosphere during sudden stratospheric warnings. 相似文献
6.
A spectral analysis of the diurnal variations in the geomagnetic field horizontal component, observed at Kamchatka and Barrow polar observatory in September–October 1999, has been performed. The complete set of oscillations of thermal tidal atmospheric waves with T = 24, 12, 8, and 4 h has been detected in the variation spectral power (Sq) at Kamchatka, and only the fundamental harmonic with T = 24 h has been distinguished at Barrow. The above periods vary in both directions relative to stable maximums during strong geomagnetic disturbances. The relative spectral intensity at subharmonics also vary toward the fundamental harmonic with a period of 24 h. In the frequency band 0.5–3 h (IGW periods), the maximal intensity in the background spectra is observed at T ～ 2 h and increases by an order of magnitude with increasing geomagnetic activity at both Kamchatka and Barrow. A day before earthquakes, the intensity of this maximum is below the rms background values, and the spectra widen toward the region of periods shorter than 2 h. A similar effect was previously observed in the power spectra of the diurnal variations in the quasistatic electric field and VLF noise, simultaneously measured in September–October 1999. 相似文献
7.
The power spectra of time variations in the electric field strength in the near-Earth’s atmosphere and in the geomagnetic field horizontal component, which were simultaneously observed at the Paratunka observatory (φ = 52°58.3′ N; λ = 158°14.9′ E) in September 1999, have been studied. The periods of the day (including sunrise, sunset, and night) have been considered. It has been indicated that oscillations with periods T ～ 2.0–2.5 h are present in the power spectra of these parameters during the day. The intensity of these oscillations increases noticeably and the oscillations in the band of periods T < 1 h increase simultaneously in the field strength power spectra at sunrise. The variations in the argument of the cross-spectrum of these parameters indicated that oscillations in the 2.0–2.5 h period band are caused by sources that are located above the ionospheric dynamo region; at the same time, oscillations in the 0.5–1 h period band are caused by sources in the lower atmosphere. A possible mechanism by which these oscillations are generated, related to the vortex motion of convective cells that originate at sunrise in the boundary atmospheric layer, is proposed. 相似文献
8.
V. N. Pogrebnoi V. P. Golovkov T. I. Zvereva E. L. Mozoleva S. Moldobekova 《Geomagnetism and Aeronomy》2010,50(4):536-541
The results of investigations of the latitudinal distribution of annual variation of the geomagnetic field level in the seasons
of 1964 (International Quiet Sun Year) using the data from 95 world magnetic observatories located at various longitudes in
the latitude range 83° N–90° S are reported. The latitudinal features of the X, Y, and Z components of the geomagnetic field have been analyzed. It has been shown that the amplitudes (summer-winter differences)
of the annual variation are maximal in the polar regions, decrease continuously to zero towards the equator, and are identical
for both the Northern and Southern hemispheres with a half-year delay (local summer). The amplitudes of the equinox-winter
difference in the equinox periods are smaller than those in summer, but are manifested simultaneously in the Northern and
Southern hemispheres. An equivalent circumpolar current system has been constructed, which is responsible for the annual variation
of the geomagnetic field level. Its parameters have been determined. 相似文献
9.
10.
Bogdan Grecu Cristian Neagoe Dragos Tataru Felix Borleanu Bogdan Zaharia 《Journal of Seismology》2018,22(5):1275-1292
We present the first detailed investigation of the background seismic noise recorded in the Romanian-Bulgarian cross-border region over 3 years (2012–2015). We used the power spectral densities probability density functions (PSD PDFs) to study the noise variations in the period domain (0.025–1 s) as well as in the secondary microseism band (2–10 s). Strong diurnal variations and an increase of the noise levels during working days were observed at high frequencies at all stations, thus confirming the anthropic origin of the noise at low periods. The noise variations observed at longer periods (>?1 s) are relatively small among the stations and are related to season changes. The dominant feature in the noise spectra between 2 and 10 s is the double-frequency peak (DFP) whose amplitude increases and changes during winter. For a specific interval, from 25th to 27th of January 2014, when a storm was reported in the Black Sea area, the maximum of the DFP shifted from larger periods (~?5.5 s) at stations far from the Black Sea towards smaller periods (~?1.8 s) at stations located on the coastline. The polarization analysis showed that the short period double-frequency microseisms originating from the Black Sea dominate during the winter month. Finally, we showed that site conditions vary due to noise variations related to weather conditions in the Black Sea or to changes in anthropogenic noise sources. 相似文献
11.
《Journal of Atmospheric and Solar》2002,64(8-11):1217-1228
Long period variations in the mesosphere wind have been observed for some time by ground-based radars. These planetary scale disturbances have reoccurring periods at or near 5–7, 10, and 16 days and at times dominate the wind field at mesospheric heights. Recently, due to the continuous operation of several of the MLT radars and the availability of measurements from the UARS satellite, it has been possible to compare observations during periods of large planetary wave activity. Wind measurements from four MLT radars; the meteor radars at Durham, NH (43°N,71°W) and Sheffield, UK (53°N,2°W) and MF radars at Urbana, IL (40°N,88°W) and Saskatoon, Canada (52°N,107°W) were compared with the HRDI measurements during intervals when 7-d planetary waves were present. Wind data from the HRDI instrument on UARS has been processed to show the latitudinal structure and the seasonal variation of the planetary scale wind variation. The phases and amplitudes of the waves as determined by both the satellite and the radars are in good agreement. The ground-based measurements show large modulation of tides by these long period components, and also show comparable responses of these low frequency components over thousands of kilometers. The satellite and the ground-based results both indicate a preponderance of wave occurrence during the equinoxes and at preferred latitudes. 相似文献
12.
N. G. Sergeeva E. Turunen O. F. Ogloblina S. M. Chernyakov 《Geomagnetism and Aeronomy》2009,49(5):682-689
The data, obtained using the methods of partial reflections and ionosphere vertical sounding on the Kola Peninsula and in Scandinavia, at Tumannyi (69.0° N, 35.7° E) and Sodankyla (67.37°N, 26.63°E) observatories, have been analyzed in order to detect earthquake responses. The strong earthquakes have been considered: one earthquake with a magnitude of 7.7 occurred at 0819:25 UT on July 17, 2006, on the western coast of Indonesia (9.33° S, 107.26° E), and another earthquake with a magnitude of 6.2 occurred 2253:59 UT on May 26, 2006, on Yava (7.94° S, 110.32° E). These earthquakes, the epicenters of which were located in the same region and at identical depths (10 km), were observed under quiet conditions in the geomagnetic field (ΣK p = 5.7 and 6.3) and during small solar flares. The response of the ionosphere to these flares was mainly observed in the parameters of the lower ionosphere in the D and E regions. It has been found out that the period of variations in the ordinary component of the partially reflected signal at altitudes of the E region increased before the earthquake that occurred on July 17, 2006. The f min variations at Sodankyla observatory started 20 h before the earthquake. The periods of these variations were 3–6 h. The same periods were found in the variations in other ionospheric parameters (foEs and h’Es). The variations in the ordinary component of partially reflected signals with periods of 2–5 hours were observed on the day of another earthquake (May 26, 2006). Internal gravity waves with periods of several hours, which can be related to the earthquakes, were detected in the amplitude spectra of the ordinary component of partially reflected signals and in other parameters in the lower ionosphere. 相似文献
13.
The influence of geomagnetic disturbances on electron density Ne at F1 layer altitudes in different conditions of solar activity during the autumnal and vernal seasons of 2003–2015, according to the data from the Irkutsk digital ionospheric station (52° N, 104° Е) is examined. Variations of Ne at heights of 150–190 km during the periods of twenty medium-scale and strong geomagnetic storms have been analyzed. At these specified heights, a vernal–autumn asymmetry of geomagnetic storm effects is discovered in all periods of solar activity of 2003–2015: a considerable Ne decrease at a height of 190 km and a weaker effect at lower levels during the autumnal storms. During vernal storms, no significant Ne decrease as compared with quiet conditions was registered over the entire analyzed interval of 150?190 km. 相似文献
14.
O. V. Kozyreva N. G. Kleimenova T. A. Kornilova K. Kauriste J. Manninen A. Ranta 《Geomagnetism and Aeronomy》2006,46(5):580-592
The spatial dynamics of geomagnetic variations and pulsations, auroras, and riometer absorption during the development of the main phase of the extremely strong magnetic storm of November 7–8, 2004, has been studied. It has been indicated that intense disturbances were observed in the early morning sector of auroral latitudes rather than in the nighttime sector, as usually takes place during magnetic storms. The unusual spatial dynamics was revealed at the beginning of the storm main phase. A rapid poleward expansion of disturbances from geomagnetic latitudes of 65°–66° to 74°–75° and the development of the so-called polar cap substorm with a negative bay amplitude of up to 2500 nT, accompanied by precipitation of energetic electrons (riometer absorption) and generation of Pi2–Pi3 pulsations, were observed when IMF B z was about ?45 nT. The geomagnetic activity maximum subsequently sharply shifted equatorward to 60°–61°. The spatial dynamics of the westward electrojet, Pi2–Pi3 geomagnetic pulsations, and riometer absorption was similar, which can indicate that the source of these phenomena is common. 相似文献
15.
Yu. N. Koren’kov F. S. Bessarab N. A. Koren’kova V. S. Leshchenko 《Geomagnetism and Aeronomy》2018,58(3):420-429
The study presents the results of the analysis of the F2-layer critical frequency variations obtained for the winter periods of 2008–2010, during which sudden stratospheric warmings were observed. The data were obtained at Kaliningrad ionospheric station (54.6° N, 20° E) with the Parus digital ionosonde in standard sounding mode. The mean daily foF2 values were used in the analysis. The results of spectral analysis based on continuous wavelet transform showed that, during all of the warmings that occurred in 2008–2010, the foF2 time variations demonstrated the presence of wave processes with periods of approximately 5?6 days, as well as more extended processes with periods of ~10?13 and 23?30 days. These periods coincide with the characteristic periods of planetary waves observed in the mesosphere during sudden stratospheric warmings, while the 13- and 30-day periods can be conditioned by the influence of the Sun. 相似文献
16.
The conducted archeomagnetic studies resulted in data on variations in the geomagnetic field intensity in the central East European Plain (Sakhtysh I site area, ? = 56°48′ N, λ = 40°33′ E) during the time interval of 5–3 ka BC. The geomagnetic field intensity varied mainly within the range of 30–60 μT. In the first half of the 5th millennium BC, the mean level of geomagnetic field intensity was about 35 μT. In the second half of the 5th–early 4th millennium BC, it rose to about 50 μT and then decreased again to reach a mean value of about 40 μT in the period of 4–3 ka BC. Comparison of the geomagnetic field intensity variation based on the obtained data and the data on the Caucasus region for the same time interval demonstrates a certain similarity. 相似文献
17.
Results from joint work between the Geophysical Institute (Sofia, Bulgaria), and the Geomagnetic Institute (Grocka, Yugoslavia) on the geomagnetic field variation in the prehistoric past are presented. Preliminary curves of variation of the three geomagnetic elements: declination, inclination and intensity are presented. The movement of the virtual pole position for the 6500 years time period B.C. is derived. The curves and the virtual pole positions provide a dating tool for archaeological purposes and determination of the periodicities in the geomagnetic secular variations in southeastern Europe. 相似文献
18.
The occurrence frequency of SAR arcs during 1997–2006 has been analyzed based on the photometric observations at the Yakutsk meridian (Maimaga station, corrected geomagnetic coordinates: 57° N, 200° E). SAR arcs appeared in 114 cases (～500 h) during ～370 nights of observations (～3170 h). The occurrence frequency of SAR arcs increases to 27% during the growth phase of solar activity and has a clearly defined maximum ～36% at a decline of cycle 23. The SAR arc registration frequency corresponds to the variations in geomagnetic activity in this solar cycle. The dates, UT, and geomagnetic latitudes of photometric observations are presented for 1997–2006. 相似文献
19.
Yu. Ya. Ruzhin V. E. Chertoprud G. S. Ivanov-Kholodnyi 《Geomagnetism and Aeronomy》2016,56(5):585-591
The influence of the earthquake probability diurnal variation on specific features in the weekend effect in global seismic activity is revealed. The dependence of the global earthquake number on the local time and its possible relation to a quiet solar diurnal variation (Sq) in the geomagnetic field have been considered in detail. It has been indicated that a stable diurnal effect, which has a maximum near midnight and a minimum near local noon, exists in the global seismicity of the Earth. The diurnal variation amplitude changes insignificantly during days of week and substantially decreases (by a factor of almost 3) on Saturday and Sunday. The weekend effect is not revealed during “local nights.” Since the daily effect of a quiet solar diurnal variation (Sq) should not depend on days of week, we arrive at the conclusion that the diurnal variation in global seismicity evidently contains the anthropogenic activity product. The Sunday effect in the earthquake number decreases over the course of time and is most probably real but weak and not stationary since weekly variations occur against a background (or under the action) of stronger variations, i.e., an increase in the earthquake number and diurnal variations. 相似文献
20.
通过甘肃省嘉峪关台地磁场观测资料,研究嘉峪关台、瓜州台磁静日地电场日变化的时频特征波;由地电场分钟值观测数据的时序叠加残差方法,研究嘉峪关、瓜州山的地电暴变化。结果表明:(1)两台地电场静日变化以两次起伏变化为主,无相位差,但两台之间日变幅差异较大;(2)地电场分量变化与地磁场正交分量变化显著相关;地电场与地磁场日变波形不同,极值时间有差异。2个台存在很明显的高频成分,在去除了高频变化后,其优势周期也相同,从大到小依次为12 h、8 h、24 h。地磁场H分量因存在磁暴影响,故高频变化较多,在去除了磁暴影响后,其优势周期从大到小依次为24 h、12 h、8 h;(3)当电磁暴扰动剧烈时,两台可以较清晰地记录到地电暴的完整变化。在发生电磁暴时,地电场与地磁场的相关性明显降低,且不同台、不同测向之间的变化幅度也不尽相同。两台东分量E_Y暴日的日变幅较静日明显增大,磁暴期间Y分量变化率与地电场东分量E_Y观测数据显著相关,由此说明:两台日变幅的不同与台站台址电导率有关,太阳风引起的电离层活动是引起了地电场日变化主因。引起电暴的原因可能不同于引起日变化的原因,主要是两台之间及不同测向之间的浅、深层电阻率和地质构造等诸多因素的结果。 相似文献