Gotowa bibliografia na temat „Geomagnetic induction”

Abstract. Geomagnetic field variations induce telluric currents in pipelines, which modify the electrochemical conditions at the pipe/soil interface, possibly contributing to corrosion of the pipeline steel. Modelling of geomagnetic induction in pipelines can be accomplished by combining several techniques. Starting with geomagnetic field data, the geoelectric fields in the absence of the pipeline were calculated using the surface impedance derived from a layered-Earth conductivity model. The influence of the pipeline on the electric fields was then examined using an infinitely long cylinder (ILC) model. Pipe-to-soil potentials produced by the electric field induced in the pipeline were calculated using a distributed source transmission line (DSTL) model. The geomagnetic induction process is frequency dependent; therefore, the calculations are best performed in the frequency domain, using a Fourier transform to go from the original time domain magnetic data, and an inverse Fourier transform at the end of the process, to obtain the pipe-to-soil potential variation in the time domain. Examples of the model calculations are presented and compared to observations made on a long pipeline in the auroral zone.Key words. Geomagnetism and paleomagnetism (geo-magnetic induction)

The article describes the features of measurements of spatial inhomogeneities of the geomagnetic field between the pillars of magnetometers in the measuring pavilion, which were carried out at the geomagnetic observatory of the Ukrainian Antarctic Akademik Vernadsky station in 2015. Some preliminary results of these measurements are also given. The concept of the timescaled value of the geomagnetic field induction is introduced, which is convenient for compensating for time changes of the real geomagnetic induction and bringing it to one reference level of induction. The differences in geomagnetic induction between pillars are obtained as the differences in time-scaled values of the geomagnetic induction on the pillars. The technique allows comparing long-term series of measurements of field inhomogeneities at important points in space. The main objectives are to increase the accuracy of measurements of local inhomogeneities of the geomagnetic field in the measuring pavilion of the geomagnetic observatory of the Ukrainian Antarctic Akademik Vernadsky station and to determine the differences in the geomagnetic induction between the pillars on which the magnetometer sensors are installed. Obtaining numerical values of the differences in the geomagnetic induction between the pillars as objective criteria needed to assess the accuracy of the data in the final processing of geomagnetic observatory data. The method of comparison of two series of data is used: one obtained by the scalar magnetometer installed in the observatory as a mandatory stationary device, and the other obtained during measurements with a mobile magnetometer at the desired points in space. Compensation of temporal changes of the geomagnetic field by time-scaling the measurement readings of the mobile magnetometer relative to one reference value and thus, bringing them to one selected and fixed time epoch. Special geometric scheme of mobile measurements in the space around the pillars with magnetometer sensors or at important points in space. A rough estimate of method errors. Based on the analysis of the obtained data, the efficiency of the method and its acceptable potential accuracy were confirmed. We obtained approximate numerical values of the differences in the geomagnetic field induction between the pillars on which the magnetometer sensors are installed. Further increase in the accuracy of determining these differences is possible using modern devices of high accuracy and GPS-synchronization of mobile measurements.

During geomagnetic storms, the direct penetration of magnetospheric convection electric field and the ionospheric disturbance dynamo (IDD) take place in the ionosphere. In this paper, we studied variability of IDD and electromagnetic induction (EMI) at different latitudinal sectors during the geomagnetic storms on 7 and 8 September 2002 and 20 and 21 November 2003 with high solar wind speed due to coronal mass ejection. This investigation employs geomagnetic field components (H and Z), the geomagnetic indices (Dst, AL, and AU), solar wind speed (Vx), and interplanetary magnetic field (Bz). It was observed that the H component of geomagnetic field decreases across latitudes, and varies with Vx, Bz, Dst, AL, and AU indices throughout the difference phases of the storm. Our result demonstrated the dominance of the IDD during the nighttime compared to the daytime. This implies that neutral dynamic wind is greater at night than during the day. Higher ratio ΔZ/ΔH is observed at nighttime because of the reduction on the E region conductivity, which allowed F region electric fields to dominate.

Abstract. The 11 August 1999 total solar eclipse had been studied using a large array of stations in Central Europe (Bencze et al., 2005). According to the result of this study, the amplitudes of the field line resonance (FLR)-type pulsations decreased in and around the dark spot by about a factor of 2, and this decrease moved with the velocity of the dark spot in the same direction. This decrease was interpreted as a switch-off of the FLR-type pulsations, due to a change in the eigenperiod of the field line as a consequence of a change in the charged particle distribution along the field line. An effect was also found in the phase of the (magnetic or electric) perpendicular components. At the Nagycenk (NCK) observatory lying in the zone of totality, both magnetic and electric records were available. The magnetotelluric (MT) sounding curve computed by the usual method for the eclipse interval (08:00-14:00 UT) fits the previously known standard curve extremely well. During the eclipse, however, impedance values in the FLR period range were highly scattered. The scatter remained as long as the eclipse lasted. Coherence values between magnetic and electric components decreased significantly. In contrast, an earlier similar switch-off of the FLR-type activity on the same day did not cause a similar scatter, in spite of a comparably low coherence. Thus, the lack of FLR-type activity disturbed the usual MT connection between the magnetic and electric components during the eclipse. The induction vector (tipper), especially its real part, shows a clear effect of the eclipse in the FLR period range (24-29 s), too. Both at NCK and at Bad Bergzabern (BBZ, westernmost station and longest FLR period), a definite decrease in the real tipper was ascertained during the totality. The average direction of the tipper did not change. Concerning both parameters, a random effect cannot fully explain the observed phenomena. The scatter of the EM induction parameters is most likely due to the switch-off of the FLR activity. The possibility of such an effect should be considered in induction studies. Pilipenko and Fedotov (1993) supposed an opposite effect and emphasised lower quality data, if resulting from FLR-type pulsations, while we claim high quality data just from such an activity.