Wave-like processes in the ionospheric F region that accompanied rocket launches from the Baikonur site

Results of the observations performed using the wave-like disturbance (WLD) method at iono-spheric altitudes of 100–500 km during ten Soyuz and Proton rocket launches (RLs) in 2003–2005 have been analyzed. The observations were performed with the Kharkov incoherent scatter radar. It has been confirmed that WLDs propagated at a velocity of 560–740 m/s were observed reliably. Disturbances propagated at a higher velocity of several kilometers per second were observed indefinitely. Disturbances caused by RLs were most clearly defined at altitudes of 150–350 km. Rocket launches cased either enhancement or suppression of WLDs in the ionosphere. The relative amplitude of WLDs usually varied within 3–30%.     

Geomagnetic field paleointensity in the cretaceous from Upper Cretaceous rocks of Georgia

A representative collection of Upper Cretaceous rocks of Georgia (530 samples from 24 sites) is used for the study of magnetic properties of the rocks and the determination of the paleodirection and paleointensity (H _an) of the geomagnetic field. Titanomagnetites with Curie points of 200–350°C are shown to be carriers of natural remanent magnetization (NRM) preserving primary paleomagnetic information during heatings to 300–350°C. The characteristic NRM component of the samples is identified in the interval 120–350°C. The Thellier and Thellier-Coe methods are used for the determination of H _an meeting modern requirements on the reliability of such results. New paleointensity determinations are obtained and virtual dipole magnetic moment (VDM) values are calculated for four sites whose stratigraphic age is the Upper Cretaceous (Cenomanian-Campanian). It is shown that, in the interval 99.6–70.6 Ma, the VDM value was two or more times smaller than the present value, which agrees with the majority of H _an data available for this time period. According to our results, the H _an value did not change at the boundary of the Cretaceous normal superchron.     

Small-scale heterogeneities below the Lanzhou CTBTO seismic array,from seismic wave field fluctuations

Seismic wave field fluctuations below Lanzhou Comprehensive Test Ban Treaty Organization seismic array are determined and interpreted to describe the scattering characteristics of the crust beneath the northeastern margin of Qinghai–Tibet plateau in China. The frequency-dependent intensities of the mean and fluctuation wave fields are analyzed for 21 deep (206–632 km depth) teleseismic events. The observed wave field fluctuations in the frequency range 0.5–2.5 Hz can be explained by the scattering of the teleseismic P wave front at random media-type structures. The stable and narrow range of the fluctuation parameters from these teleseismic events indicates evidence for scattered seismic phases which are generated inside the crust. The reasonable structural models contain heterogeneities with 1–3% velocity fluctuations and 2.4–8.2 km correlation lengths in the crust with 53 km thickness.     

Possible relation of emergencies during spacecraft launches from the Plesetsk site to high-latitude geomagnetic disturbances

The relation of the series of carrier rocket emergency launches to geomagnetic activity and season is statistically analyzed. The data on the successful and emergency launches of more than ten types of different carrier rockets from the Plesetsk site for about 40 years (from 1966 to 2005) have been processed. It has been indicated that the relative number of emergencies during launches in summer is more than twice as high as in other seasons. An additional summer factor is statistically related to high-latitude geomagnetic activity. The effect remains unclear.     

基于中国地磁台网地磁子夜均值数据对地磁急变的分析

为探索地磁长期变化中地磁急变事件的识别方法,分析地磁急变的特征,本文基于多个地磁台站子夜均值数据,利用线性拟合方法计算了地磁场X,Y和Z三个分量的年变率,对近年来发生的地磁急变事件进行了识别和分析。结果显示:Y分量能对分析时段内已报道的地磁急变事件进行很好的识别,其中1999年的地磁急变事件,在我国区域内发生的时间可能为1998年,此外2017年可能存在一个新的地磁急变事件;Z分量年变率整体变化平缓,2001年和2013年前后发生两次显著的地磁年变率变化,并且分别早于2003年和2014年两次显著的地磁急变事件时间,这与下地幔的高电导率层对不同分量地磁信号从核幔边界传播至地表过程中的延迟作用有关;X分量年变率出现多次地磁急变事件特征,其变化与D_st指数年变率变化具有相关性,可利用其去除X分量年变率中存在的外部空间电流体系影响成分,更可靠地辅助Y分量对地磁急变事件进行识别。总体上,地磁子夜均值数据年变率的空间分布与基于第12代国际地磁参考场（IGRF12）模型计算的地磁数据年变率的空间分布所呈现的变化特征在总趋势上具有一致性,表明地磁台站子夜均值数据能够反映我国区域地球主磁场的变化特征,而分别由子夜均值数据和IGRF12模型计算的2003年Y分量年变率空间分布均存在的显著局部特征,可能与地磁急变事件的区域特征有关。      

Geomagnetic reversals in the paleozoic: A transitional field,polarity bias,and mantle convection

The paper analyzes previously published results of studies of detailed records of geomagnetic reversals in sedimentary and volcanic sequences of the Paleozoic in the Siberian and Eastern European platforms. It is shown that the processes of geomagnetic reversals, both in the Early Paleozoic and at the end of this era, are well described by a model in which the transitional field is controlled by an equatorial dipole. During a reversal, this dipole maintained a magnetic field at the Earth’s surface whose intensity amounted to about 20% of the intensity before and after the reversal. The equatorial dipole existed before and during the reversal and was responsible for the deviation from antipodality of paleomagnetic poles of adjacent polarity chrons (the so-called reversal bias). The position of the equatorial dipole axis during the Paleozoic correlates with the supposed geometry of convective motions in the mantle at that time.     

Geomagnetic field intensity during the Plio-Pleistocene derived from the thermo-remanence of porcellanites and palaeo-slags (Czechoslovakia)

Summary The present paper deals with the derivation of the intensity of the geomagnetic field in the Plio-Pleistocene, Central Europe. The intensity was derived from the thermo-remanence of porcellanites and palaeo-slags. These rocks represent a common product of intense thermal alteration of loams due to spontaneous combustion of coal seams. Porcellanites and palaeo-slags show outstanding palaeomagnetic properties, their remanent magnetization is of thermo-remanent origin and they were mineralogically stabilized under natural conditions in the geological past, during the coal combustion. It was found, that the intensity of the geomagnetic field during the Plio-Pleistocene oscillated about the value of the present-day intensity.     

Geomagnetic field from the Earth's core: Its westward drift rate and some probable global-tectonics implications

Summary Sets of virtual poles corresponding to sets of geomagnetic field values at equidistant points, lying along circles of latitude, were defined on the basis of the 1980 IGRF extending to degree and order 8. Certain places on the Earth's surface yield virtual poles lying very close together. The segments of the virtual pole paths, corresponding to these places, have a large curvature. The mentioned places of the Earth's surface are supposed to be areas with a low rate of the westward drift. They form continuous zones that show a certain relation to global-tectonics features.

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Penetration of electric field from the near ground atmospheric layer to the ionosphere

A mathematical model has been proposed for describing quasi-stationary atmospheric electric fields with approximate, but fairly accurate allowance for ionospheric conductivity. It is shown that some well-known models of electric field penetration from the Earth into the ionosphere have been deemed inadequate, though they work well in the atmosphere below 50 km. In these models, the arbitrarily specified boundary condition in the upper boundary of the atmosphere omits the existing good conductor or adds not existent conductor. The maximum possible field in our model is far less than in models where ionospheric conductivity is not taken into account, but vastly larger than in models based on the approximation with infinite Pedersen conductivity in the upper ionosphere.     

Short-period fluctuations in the atmospheric electric field over the ocean

Fluctuations of short period in the atmospheric electric field were studied through the measurements of electric field and space charge density on the Mid-Pacific Ocean. The amplitude of fluctuation is about one third of the mean electric field, and the period mainly ranges from 2 to 5 min. The fluctuations are considered to be under the influence of spatial and temporal variation of space charge layer that possibly originates from the electrode effect above the sea surface. The unit of electrical irregularities in the atmosphere above the ocean has horizontal scale of the order of 1.5 km and indicates a tendency to become large as the wind speed increases. The vertical scale of space charge layer is estimated at several tens meters.     

Magneto-ionospheric effects of the solar eclipse of March 20, 2015, over Kharkov

The results of observations of disturbances in the lower and middle ionosphere and in the geomagnetic field accompanying the partial solar eclipse over Kharkov are presented. The ionospheric effects have been studied with the use of an ionosonde and measurements of the phase and amplitude of a radio signal with a frequency of 66.(6) kHz on the Moscow–Kharkov route, and the effects in the magnetic field have been analyzed with the help of a magnetometer–fluxmeter in the range of periods from 1 to 1000 s. Disturbances in both the lower and middle ionosphere, as well as in the geomagnetic field, have been detected. The observation results have been compared with the results of a simulation of physical processes accompanying the solar eclipse. A good agreement has been found between observational and modeling results.     

Luminescence dating of the top of a deep water core from the NESTOR site near the Hellenic Trench,east Mediterranean Sea

In the present study, the uppermost 3 cm of muddy, seabed sediment was collected from a deep-sea sediment core, drilled from a water depth of 4 km, near the deepest site of the Mediterranean Sea, outside Pylos, Greece. The core was divided into 7 layer samples, each 3–4 mm thick, in order to get an independent age assessment for each one using luminescence dating; from polymineral coarse grains in the range 30–60 μm. Between 11 and 22 aliquots were measured for each sample using the optically stimulated luminescence, single-aliquot regenerative-dose analysis. The estimated mean equivalent dose values had an uncertainty less than 3% and resulted in optical ages ranging from 3.5 to approximately 5 ka, with uncertainties lying between 5.5 and 7.4%. Multiple-aliquot, thermoluminescence-based, additive-dose, total bleaching approach provided equivalent doses with typical errors of 10–15% and ages in the range of 3.6 and 9.4 ka, with uncertainties up to 17%. Single-aliquot optical ages are shown to be relatively successful, due to their consistency with AMS ¹⁴C radiocarbon ages, obtained from Planktonic foraminifera from the same core. Luminescence dates for the topmost 1.5 cm indicate a substantial mix and post burial disturbance of the surface sediment. Below the topmost 1.5 cm, both luminescent approaches indicate ages which increase smoothly with depth. The concordant OSL and TL age estimates for the sample O5, in conjunction with specific luminescence properties and its major-element geochemical chemistry content, suggest that it was heated during the Santorini volcanic eruption. Deposition rates of 8.6–18.9 cm over 10 ka below the sample O5, provided by optical ages, exhibit an excellent level of agreement with the accumulation rate of 7–18 cm over 10 ka at the sea bottom, already reported for the site under study.     

The role of site effects in the comparison between code provisions and the near field strong motion of the Emilia 2012 earthquakes

A damaging seismic sequence hit a wide area mainly located in the Emilia-Romagna region (Northern Italy) during 2012 with several events of local magnitude \(\hbox {M}_\mathrm{l} \ge 5\) , among which the \(\hbox {M}_\mathrm{l}\) 5.9 May 20 and the \(\hbox {M}_\mathrm{l}\) 5.8 May 29 were the main events. Thanks to the presence of a permanent accelerometric station very close to the epicentre and to the temporary installations performed in the aftermath of the first shock, a large number of strong motion recordings are available, on the basis of which, we compared the recorded signals with the values provided by the current Italian seismic regulations, and we observed several differences with respect to horizontal components when the simplified approach for site conditions (based on Vs30 classes) is used. On the contrary, when using the more accurate approach based on the local seismic response, we generally obtain a much better agreement, at least in the frequency range corresponding to a quarter wavelength comparable with the depth of the available subsoil data. Some unresolved questions still remain, such as the low frequency behaviour ( \(<\) 1 Hz) that could be due either to complex propagation at depth larger than the one presently investigated or to near source effects, and the behaviour of vertical spectra whose recorded/code difference is too large to be explained with the information currently available.     

Geomagnetic field intensity in the first millennium BC from data on ceramics of the Los Villares archaeological monument (Spain)

The geomagnetic field variation pattern in the second and third quarters of the first millennium BC is obtained from data on ceramic material sampled in the Los Villares multilayer archaeological monument (Spain). The analysis of available data on the geomagnetic field variation in Spain over the last seven millennia shows that it is similar to the geomagnetic variation pattern observed in other Eurasian regions. The amplitude of the “fundamental” (8000-yr) oscillation (≈20 μT) estimated from the Spain data exceeds significantly its amplitudes in other regions, which supports the previously noted tendency to a westward increase in the amplitude of the fundamental oscillation.     

Geomagnetic field: Contribution of higher harmonics to the variations of virtual pole positions

Summary On the basis of the 1945 IGRF two sets of virtual geomagnetic poles have been computed and compared. The first set refers to a realistic model of the field; these virtual poles are all located in the north polar area. The second set refers to an artificial field containing higher harmonics only; these virtual poles are distributed over the Earth's surface as a whole. However both sets of virtual poles yield similar distributions of values of their space (and probably also time) variations.     

Geomagnetic field mapping from a satellite: Spatial power spectra of the geomagnetic field at various satellite altitudes relative to natural noise sources and instrument noise

For a low-level geomagnetic satellite survey, for which the motion of the satellite converts spatial variation into temporal variation, the limit on accuracy may well be background temporal fluctuations. The sources of the temporal fluctuations are current systems external to the Earth and include currents induced in the Earth due to these sources. The internal sources consist primarily of two components, the main geomagnetic field with sources in the Earth's core and a crustal geomagnetic field.Power spectra of the vertical geomagnetic field internal component that would be observed by a spacecraft in circular orbit at various altitudes, due to satellite motion through the spatially varying geomagnetic field, are compared to power spectra of the natural temporal fluctuations of the geomagnetic field vertical component (natural noise) and to the power spectrum for typical fluxgate magnetometer instrument noise. The natural noise is shown to be greater than this typical instrument noise over the entire frequency range for which useful measurements of the geomagnetic field may be made, for all geomagnetic latitudes and all times. Thus there would be little benefit in reducing the instrument noise below the typical value of 10^?4 gamma² Hz^?1 plus a 1/f component of 10 milligamma rms decade^?1.For a given satellite altitude, there is a maximum frequency above which the natural noise is greater than the power spectrum of the crustal geomagnetic field vertical component. Below this maximum frequency, the situation is reversed. This maximum frequency depends on geomagnetic latitude (and to a lesser extent on time of day and season of year), being lower in the auroral zone than at lower latitudes. The maximum frequency is also lower at higher satellite altitudes. The maximum frequency determines the spatial resolution obtainable on a magnetic field map. The spatial resolution (for impulses) obtainable at low latitudes for a 100-km satellite altitude (possibly achievable by tethering a small satellite at this altitude to a space vehicle at a higher altitude) is 60 km, while at the auroral zone the obtainable spatial resolution is 100 km. At the higher satellite altitude of 300 km the obtainable spatial resolution is 230 km at low latitudes and 530 km at the auroral zone. At 500-km satellite altitude, the obtainable spatial resolution is 500 km at low latitudes, while maps cannot be made at all for the auroral zone unless the data are selected for “quiet” days.For the lower satellite altitudes, greater spatial resolution can be obtained than at higher altitudes. Furthermore since the crustal geomagnetic field power spectrum is larger at lower altitudes, the relative error due to the natural noise is less than for higher altitudes.     

Optical dating of a Paleolithic site near the eastern coastal region of Shandong,northern China

Many archaeological sites were excavated in China, but rarely in the adjacent coastal areas. An archaeological site at Huangniliang in the coastal area of Shandong Province, northern China was excavated in 2013. Abundant stone artifacts including hammers, cores, flakes, chunks, and retouched tools are found in the silty aeolian sediments. In this study, optically stimulated luminescence (OSL) technique was employed to establish the chronological framework of the site. Medium-grained (45–63 μm) quartz was extracted from six sediment samples for dating. The equivalent doses obtained with the single-aliquot regenerative-dose (SAR) protocol are shown to increase with depth. Three samples from the stone-tool containing layer yield OSL ages ranging from 54 ka to 59 ka, providing the earliest geochronological evidence for the presence of humans in the eastern coast of Shandong peninsula during the early period of Marine Isotope Stage (MIS) 3.     

Physical processes in the middle ionosphere accompanying the solar eclipse of January 4, 2011, in Kharkov

Aperiodic and quasi-periodic variations in the critical frequency of the F2 layer and Doppler frequency shift of radiowaves at vertical paths on the day of a partial (the magnitude was ～0.78) solar eclipse and on background days are analyzed. According to the experiment, the relative decrease in the electron concentration was 0.41 (0.46 according to calculations) and 0.50 (0.53 according to calculations) in the E region and in the lower part of the F region of the ionosphere. At a height of the main maximum of the electron concentration, the relative decrease in the electron concentration was 0.52 (0.51 according to calculations). It is shown that on the day of the eclipse and on the background day, the characteristics of wave disturbances within the height range 160–240 km were substantially different. Changes in the spectral composition began 30 min after the eclipse occurrence and, depending on the period, lasted from 2 to 4 h. The calculation results of the main parameters of the medium and signal correspond to the observational results.     

Geomagnetic results from Sabhawala,Yangi-Bazar and Alma-Ata in relation to the asthenosphere beneath the Pamir-Himalaya

An attempt is made to study the properties of the Mohorovi?i? discontinuity and the asthenosphere beneath the Pamir-Himalaya from the geomagnetic results obtained at Sabhawala (Dehra Dun), Yangi-Bazar (Tashkent) and Alma-Ata observatories, situated on its southern and northern flanks, in a narrow longitude zone.Medium-sized induction arrows (Wiese vectors) for night-time “bay” events at all the three stations are found to point northward. The northward orientation at Sabhawala indicates a subsurface concentration of induced currents in a step structure at the Moho to the south of Sabhawala and higher electrical conductivity in the Aravalli-Cambay region, where high heat flow and gravity values have also been reported, supporting an elevated asthenosphere, as against the one beneath the western Himalaya. The arrows at Yangi-Bazar and Alma-Ata also show an east-west current channelling in another step structure at the Moho to the south of these stations and north of the Pamir and the Tien Shan mountains.The Sq variations of the H, D and Z components at the three stations, lying close to the northern Sq ionospherics current focus, reveal the characteristic features, without reflecting any unusual asthenospheric conditions in the region.It is concluded that the orogenesis of the Pamir-Himalaya mountain system in terms of plate tectonics or block uplift is different from that of the Cordilleran and Andean mountains in North and South America respectively, where subsurface conductive structures have been delineated from geomagnetic observations by earlier workers.     

The decay of radar echoes from meteors with particular reference to their use in the determination of temperature fluctuations near the mesopause

The rate of decay of a radar echo from an ionised meteor train will be governed by the diffusion coefficient of the plasma and this in turn will depend on the temperature. Very recently the temperature fluctuations near the mesopause have been monitored by this means, by the recording of the decay times of underdense trains. The usual derivation of the precise expression relating the underdense echo decay time to the temperature contains two important assumptions, (i) that the train is created with a Gaussian ionisation profile, and (ii) that kinetic theory may be applied to calculate the diffusion coefficient. We investigate the effect of these assumptions, showing that the first assumption is unnecessary, an underdense backscatter echo decaying exponentially with a decay time equal to ²/(32²D), where is the wavelength and D the diffusion coefficient, indepndently of the initial distribution. However, the second assumption is shown to be incorrect, and whereas according to kinetic theory D\proptoT^1/2/, where T and are the atmospheric temperature and density, the correct result is D\proptoT/. This leads to an appreciable correction to the results for the temperature fluctuations.