Artykuły w czasopismach: „Geomagnetic induction”

1

Lilley, F. E. M. "Geomagnetic induction: the study of geomagnetic induction physics". Exploration Geophysics 17, nr 1 (marzec 1986): 22–24. http://dx.doi.org/10.1071/eg986022.

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Trichtchenko, L., i D. H. Boteler. "Modelling of geomagnetic induction in pipelines". Annales Geophysicae 20, nr 7 (31.07.2002): 1063–72. http://dx.doi.org/10.5194/angeo-20-1063-2002.

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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)

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3

Leonov, M., i Yu Otruba. "Measurement of the difference in the geomagnetic induction between the magnetometer pillars of the geomagnetic observatory of the Ukrainian Antarctic Akademik Vernadsky station". Ukrainian Antarctic Journal, nr 1 (2021): 16–23. http://dx.doi.org/10.33275/1727-7485.1.2021.662.

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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.

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4

Chamalaun, F. H., i P. Cunneen. "The canning basin geomagnetic induction anomaly". Australian Journal of Earth Sciences 37, nr 4 (grudzień 1990): 401–8. http://dx.doi.org/10.1080/08120099008727940.

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Everett, M. E., i A. Schultz. "Geomagnetic induction in eccentrically nested spheres". Physics of the Earth and Planetary Interiors 92, nr 3-4 (grudzień 1995): 189–98. http://dx.doi.org/10.1016/0031-9201(95)03036-6.

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Falayi, E. O., A. B. Rabiu, O. S. Bolaji i R. S. Fayose. "Response of ionospheric disturbance dynamo and electromagnetic induction during geomagnetic storm". Canadian Journal of Physics 93, nr 10 (październik 2015): 1156–63. http://dx.doi.org/10.1139/cjp-2014-0461.

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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.

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7

Ádám, A., J. Verõ i J. Szendrõi. "Solar eclipse effect on geomagnetic induction parameters". Annales Geophysicae 23, nr 11 (21.12.2005): 3487–94. http://dx.doi.org/10.5194/angeo-23-3487-2005.

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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.

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8

Ingham, M. R. "Geomagnetic induction studies in central New Zealand". Exploration Geophysics 17, nr 1 (marzec 1986): 35–36. http://dx.doi.org/10.1071/eg986035.

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9

Parkinson, W. D. "Low Frequency Geomagnetic Variations and Induction Studies". Exploration Geophysics 24, nr 2 (czerwiec 1993): 145–46. http://dx.doi.org/10.1071/eg993145.

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Martinec, Z. "Geomagnetic induction in multiple eccentrically nested spheres". Geophysical Journal International 132, nr 1 (27.02.2002): 96–110. http://dx.doi.org/10.1046/j.1365-246x.1998.00392.x.

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Plotkin, V. V. "Geomagnetic induction responses of anisotropic conducting mantle". Russian Geology and Geophysics 55, nr 10 (październik 2014): 1229–38. http://dx.doi.org/10.1016/j.rgg.2014.09.009.

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12

Flores, C., i R. C. Bailey. "Geomagnetic induction soundings over the Michigan Basin". Physics of the Earth and Planetary Interiors 48, nr 1-2 (wrzesień 1987): 142–52. http://dx.doi.org/10.1016/0031-9201(87)90117-8.

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Sun, J., A. Kelbert i G. D. Egbert. "Ionospheric current source modeling and global geomagnetic induction using ground geomagnetic observatory data". Journal of Geophysical Research: Solid Earth 120, nr 10 (październik 2015): 6771–96. http://dx.doi.org/10.1002/2015jb012063.

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14

Wang, Xiao Mao. "Study on Variation Rate Characters of Mid-to-Low Latitude Area Geomagnetic Field during Geomagnetic Storms". Applied Mechanics and Materials 448-453 (październik 2013): 2125–31. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.2125.

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Geomagnetic field changes acutely during geomagnetic storms. According to Faraday's law of electromagnetic induction, the change of the geomagnetic field produces geomagnetically induced current (GIC) in power grid, which directly damages the power equipment and threatens safe operation of power grid. The more dramatically geomagnetic field changes, the bigger geomagnetically induced current in power grid becomes, and thus, the greater harm it brings to power grid. In this paper, based on the H and D components of recent geomagnetic storm data measured by several mid-to-low latitude geomagnetic observatories, the variation law of the amplitude of north-south and east-west geomagnetic component change rate (dX/dt and dY/dt) pulse with geomagnetic latitude was analyzed when geomagnetic field changed very severely. Finally, the possibilities of power grid in different direction affected by GIC with the change of latitude were discussed. The analysis results will contribute to the evaluation, measurement and control of GIC in Chinese current and future power grid.

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15

Arora, B. R., P. B. V. Subba Rao, N. B. Trivedi, A. L. Padilha i I. Vitorello. "Appraisal of electromagnetic induction effects on magnetic pulsation studies". Annales Geophysicae 19, nr 2 (28.02.2001): 171–78. http://dx.doi.org/10.5194/angeo-19-171-2001.

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Abstract. The quantification of wave polarization characteristics of ULF waves from the geomagnetic field variations is done under ‘a priori’ assumption that fields of internal induced currents are in-phase with the external inducing fields. Such approximation is invalidated in the regions marked by large lateral conductivity variations that perturb the flow pattern of induced currents. The amplitude and phase changes that these perturbations produce, in the resultant fields at the Earth’s surface, make determination of polarization and phase of the oscillating external signals problematic. In this paper, with the help of a classical Pc5 magnetic pulsation event of 24 March 1991, recorded by dense network of magnetometers in the equatorial belt of Brazil, we document the nature and extent of the possible influence of anomalous induction effects in the wave polarization of ULF waves. The presence of anomalous induction effects at selected sites lead to an over estimation of the equatorial enhancement at pulsation period and also suggest changes in the azimuth of ULF waves as they propagate through the equatorial electrojet. Through numerical calculations, it is shown that anomalous horizontal fields, that result from induction in the lateral conductivity distribution in the study region, vary in magnitude and phase with the polarization of external source field. Essentially, the induction response is also a function of the period of external inducing source field. It is further shown that when anomalous induction fields corresponding to the magnitude and polarization of the 24 March 1991 pulsation event are eliminated from observed fields, corrected amplitude in the X and Y horizontal components allows for true characterisation of ULF wave parameters.Key words. Geomagnetism and paleomagnetism (geomagnetic induction) – Ionosphere (equatorial ionosphere) – Magnetospheric physics (magnetosphere-ionosphere interactions)

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16

Doumbia, Vafi, Kouadio Boka, Nguessan Kouassi, Oswald Didier Franck Grodji, Christine Amory-Mazaudier i Michel Menvielle. "Induction effects of geomagnetic disturbances in the geo-electric field variations at low latitudes". Annales Geophysicae 35, nr 1 (4.01.2017): 39–51. http://dx.doi.org/10.5194/angeo-35-39-2017.

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Abstract. In this study we examined the influences of geomagnetic activity on the Earth surface electric field variations at low latitudes. During the International Equatorial Electrojet Year (IEEY) various experiments were performed along 5° W in West Africa from 1992 to 1995. Among other instruments, 10 stations equipped with magnetometers and telluric electric field lines operated along a meridian chain across the geomagnetic dip equator from November 1992 to December 1994. In the present work, the induced effects of space-weather-related geomagnetic disturbances in the equatorial electrojet (EEJ) influence area in West Africa were examined. For that purpose, variations in the north–south (Ex) and east–west (Ey) components of telluric electric field were analyzed, along with that of the three components (H, D and Z) of the geomagnetic field during the geomagnetic storm of 17 February 1993 and the solar flare observed on 4 April 1993. The most important induction effects during these events are associated with brisk impulses like storm sudden commencement (ssc) and solar flare effect (sfe) in the geomagnetic field variations. For the moderate geomagnetic storm that occurred on 17 February 1993, with a minimum Dst index of −110 nT, the geo-electric field responses to the impulse around 11:00 LT at LAM are Ex = 520 mV km−1 and Ey = 400 mV km−1. The geo-electric field responses to the sfe that occurred around 14:30 LT on 4 April 1993 are clearly observed at different stations as well. At LAM the crest-to-crest amplitude of the geo-electric field components associated with the sfe are Ex = 550 mV km−1 and Ey = 340 mV km−1. Note that the sfe impact on the geo-electric field variations decreases with the increasing distance of the stations from the subsolar point, which is located at about 5.13° N on 4 April. This trend does not reflect the sfe increasing amplitude near the dip equator due the high Cowling conductivity in the EEJ belt.

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17

Sokol-Kutylovskii, O. L. "The measurement of a weak alternating magnetic field in unshielded space". Metrologiya, nr 1 (31.05.2021): 46–59. http://dx.doi.org/10.32446/0132-4713.2021-1-46-59.

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In connection with attempts to use various types of sensors for measuring weak magnetic fields in geophysics, magnetobiology, and medicine in an unshielded space, the problem of comparing the results of these measurements arose. The issues of measuring a weak alternating magnetic field by various magnetic induction sensors in an unshielded space in the absence of obvious geomagnetic variations are considered. It is shown that the amplitude of natural geomagnetic noise in a quiet geomagnetic field in the absence of geomagnetic variations has a random character; therefore, gradient methods for measuring a weak alternating magnetic field are limited from below by the level of natural geomagnetic noise. The influence of the size of sensors of a weak alternating magnetic field on the results of measurements of broadband random geomagnetic noise is noted.

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18

Weiss, Chester J. "An overset grid method for global geomagnetic induction". Geophysical Journal International 198, nr 1 (23.04.2014): 8–24. http://dx.doi.org/10.1093/gji/ggu108.

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Neska, Anne, Jan Tadeusz Reda, Mariusz Leszek Neska i Yuri Petrovich Sumaruk. "On the relevance of source effects in geomagnetic pulsations for induction soundings". Annales Geophysicae 36, nr 2 (7.03.2018): 337–47. http://dx.doi.org/10.5194/angeo-36-337-2018.

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Abstract. This study is an attempt to close a gap between recent research on geomagnetic pulsations and their usage as source signals in electromagnetic induction soundings (i.e., magnetotellurics, geomagnetic depth sounding, and magnetovariational sounding). The plane-wave assumption as a precondition for the proper performance of these methods is partly violated by the local nature of field line resonances which cause a considerable portion of pulsations at mid latitudes. It is demonstrated that and explained why in spite of this, the application of remote reference stations in quasi-global distances for the suppression of local correlated-noise effects in induction arrows is possible in the geomagnetic pulsation range. The important role of upstream waves and of the magnetic equatorial region for such applications is emphasized. Furthermore, the principal difference between application of reference stations for local transfer functions (which result in sounding curves and induction arrows) and for inter-station transfer functions is considered. The preconditions for the latter are much stricter than for the former. Hence a failure to estimate an inter-station transfer function to be interpreted in terms of electromagnetic induction, e.g., because of field line resonances, does not necessarily prohibit use of the station pair for a remote reference estimation of the impedance tensor.

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Falayi, E. O., J. O. Adepitan i O. A. Oyebanjo. "Geomagnetic field H, Z, and electromagnetic induction features of coronal mass ejections in association with geomagnetic storm at African longitudes". Canadian Journal of Physics 96, nr 6 (czerwiec 2018): 654–63. http://dx.doi.org/10.1139/cjp-2017-0460.

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The largest geomagnetic disturbance caused by a coronal mass ejection (CME) of solar cycle 24 recorded on both 17 March and 22 June 2015 with minimum disturbance storm time values of −223 and −195 nT, respectively, was investigated. This study examines the effect of CME on Earth’s geomagnetic field, which includes the time derivatives of horizontal (H) and vertical (Z) components of the geomagnetic field and the rate of induction ΔZ/ΔH at African longitudes (AAE, MBO, HBK, HER, and TAM). The results demonstrated enhancement of dH/dt and dZ/dt in the daytime over the equatorial zone (AAE and MBO) and mid-latitudes (TAM, HER, and HBK) on 17 March 2015. Nighttime enhancement was observed on 22 June 2015 over the equatorial zones and mid-latitudes. Wavelet spectrum approach is used to investigate ΔZ/ΔH variation observed at AAE, MBO, HBK, HER, and TAM. The CME may have influence on time derivatives of geomagnetic field H, Z, and electromagnetic induction at the African longitudes, which may be associated with perturbations in electric fields and currents in the equatorial and low-latitude magnetic field linked with the changes in magnetospheric convection.

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Regi, Mauro, Antonio Guarnieri, Stefania Lepidi i Domenico Di Mauro. "Signature of Tidal Sea Level in Geomagnetic Field Variations at Island Lampedusa (Italy) Observatory". Remote Sensing 14, nr 24 (7.12.2022): 6203. http://dx.doi.org/10.3390/rs14246203.

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In this work, we analyze the geomagnetic field measurements collected from 2017 to 2020 at the Italian observatories of Lampedusa and Duronia (an island and inland site, respectively) for investigating a possible signature of the tidal sea water level changes on the local magnetic variations. We obtain the following main results: (a) evidence of the geomagnetic power spectral peaks at the solar and lunar tidal main frequencies at both sites is found; (b) by using a robust fit procedure, we find that the geomagnetic field variations at Lampedusa are strongly influenced by the lunar tidal variations in the sea level, while at Duronia, the main effects on the geomagnetic field variations are associated with diurnal solar ionospheric tides; (c) a single-station induction arrows (SSIAs) investigation reveals different behaviors between Lampedusa and Duronia. Specifically, Lampedusa shows that the induction arrows in different frequency ranges point toward different directions with different amplitudes, probably related to the surrounding regions with different water depths, while Duronia shows a persistent coast effect, with the induction arrows pointing toward the Adriatic sea; and (d) a Superposed Epoch Analysis reveals, only for Lampedusa, a close relationship between SSIAs with a frequency of >2 mHz (<1.3 mHz) and the sea level variations driven by the astronomical O1 tide, indicating an amplitude intensification of ∼4×10−3 (∼5×10−3) and an azimuthal angle increment of ∼3∘ ( ∼9∘), in correspondence to a 1 cm sea level increase.

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Pulkkinen, A., A. Thomson, E. Clarke i A. McKay. "April 2000 geomagnetic storm: ionospheric drivers of large geomagnetically induced currents". Annales Geophysicae 21, nr 3 (31.03.2003): 709–17. http://dx.doi.org/10.5194/angeo-21-709-2003.

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Abstract. Geomagnetically induced currents (GIC) flowing in technological systems on the ground are a direct manifestation of space weather. Due to the proximity of very dynamic ionospheric current systems, GIC are of special interest at high latitudes, where they have been known to cause problems, for example, for normal operation of power transmission systems and buried pipelines. The basic physics underlying GIC, i.e. the magnetosphere – ionosphere interaction and electromagnetic induction in the ground, is already quite well known. However, no detailed study of the drivers of GIC has been carried out and little is known about the relative importance of different types of ionospheric current systems in terms of large GIC. In this study, the geomagnetic storm of 6–7 April 2000 is investigated. During this event, large GIC were measured in technological systems, both in Finland and in Great Britain. Therefore, this provides a basis for a detailed GIC study over a relatively large regional scale. By using GIC data and corresponding geomagnetic data from north European magnetometer networks, the ionospheric drivers of large GIC during the event were identified and analysed. Although most of the peak GIC during the storm were clearly related to substorm intensifications, there were no common characteristics discernible in substorm behaviour that could be associated with all the GIC peaks. For example, both very localized ionospheric currents structures, as well as relatively large-scale propagating structures were observed during the peaks in GIC. Only during the storm sudden commencement at the beginning of the event were large-scale GIC evident across northern Europe with coherent behaviour. The typical duration of peaks in GIC was also quite short, varying between 2–15 min.Key words. Geomagnetism and paleo-magnetism (geomagnetic induction) – Ionosphere (ionospheric disturbances) – Magnetospheric physics (storms and substorms)

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Sulic, D. M. "Guiding of whistler-mode waves with frequencies above one half of the gyrofrequency in the magnetosphere". Serbian Astronomical Journal, nr 159 (1999): 11–15. http://dx.doi.org/10.2298/saj9959011s.

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Ray-tracing calculations show that a trough, L = 4.6, located in the region outside the plasmapause is capable to guide whistler-mode waves in frequency range 0.5fBmin?0.64fBmin, from one hemisphere to the other. From an initial position rays propagate in unducted mode up to h ? 14000 km where they are trapped inside the trough. Propagation along the trough is possible only with great shifting of wave normal direction in respect to the direction of the geomagnetic induction B, following the variations of the magnitude of the ambiental geomagnetic induction, or those of ratio f/fB. On leaving the trough rays propagate in unducted mode downward in the magnetosphere.

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Yiliang Guan, Ling Zhang, Xiaona Dong, Xiliang Li, Zhicai Wang i Haitao Yin. "Geomagnetic Induction Vectors Reveal Tectonic Electrical Characteristics of Shandong Province, China, Using a Geomagnetic Array". Geomagnetism and Aeronomy 63, nr 4 (sierpień 2023): 503–12. http://dx.doi.org/10.1134/s0016793222600485.

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Irrgang, Christopher, Jan Saynisch-Wagner i Maik Thomas. "Depth of origin of ocean-circulation-induced magnetic signals". Annales Geophysicae 36, nr 1 (29.01.2018): 167–80. http://dx.doi.org/10.5194/angeo-36-167-2018.

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Abstract. As the world ocean moves through the ambient geomagnetic core field, electric currents are generated in the entire ocean basin. These oceanic electric currents induce weak magnetic signals that are principally observable outside of the ocean and allow inferences about large-scale oceanic transports of water, heat, and salinity. The ocean-induced magnetic field is an integral quantity and, to first order, it is proportional to depth-integrated and conductivity-weighted ocean currents. However, the specific contribution of oceanic transports at different depths to the motional induction process remains unclear and is examined in this study. We show that large-scale motional induction due to the general ocean circulation is dominantly generated by ocean currents in the upper 2000 m of the ocean basin. In particular, our findings allow relating regional patterns of the oceanic magnetic field to corresponding oceanic transports at different depths. Ocean currents below 3000 m, in contrast, only contribute a small fraction to the ocean-induced magnetic signal strength with values up to 0.2 nT at sea surface and less than 0.1 nT at the Swarm satellite altitude. Thereby, potential satellite observations of ocean-circulation-induced magnetic signals are found to be likely insensitive to deep ocean currents. Furthermore, it is shown that annual temporal variations of the ocean-induced magnetic field in the region of the Antarctic Circumpolar Current contain information about sub-surface ocean currents below 1000 m with intra-annual periods. Specifically, ocean currents with sub-monthly periods dominate the annual temporal variability of the ocean-induced magnetic field. Keywords. Electromagnetics (numerical methods) – geomagnetism and paleomagnetism (geomagnetic induction) – history of geophysics (transport)

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Pinçon, Jean-Louis, Michel Menvielle i Laszlo Szarka. "Geomagnetic induction study using the NetLander network of magnetometers". Planetary and Space Science 48, nr 12-14 (październik 2000): 1261–70. http://dx.doi.org/10.1016/s0032-0633(00)00108-2.

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Velímský, J., i C. C. Finlay. "Effect of a metallic core on transient geomagnetic induction". Geochemistry, Geophysics, Geosystems 12, nr 5 (maj 2011): n/a. http://dx.doi.org/10.1029/2011gc003557.

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Pulkkinen, A., i M. Engels. "The role of 3-D geomagnetic induction in the determination of the ionospheric currents from the ground geomagnetic data". Annales Geophysicae 23, nr 3 (30.03.2005): 909–17. http://dx.doi.org/10.5194/angeo-23-909-2005.

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Abstract. The geomagnetic field variations measured at the surface of the Earth are composed of both internal and external parts. The external field arises from the sources in the magnetosphere and ionosphere, whereas the internal field is generated by the currents induced within the Earth. The internal part may in some situations comprise a notable part of the measured total field and thus a blind usage of geomagnetic field recordings potentially produces significant errors to estimated ionospheric currents. In this paper the role of geomagnetic induction in auroral ionospheric studies is investigated by modeling the induction using simultaneously the realistic ionospheric source and a realistic three-dimensional Earth conductivity structure. The modeling results imply that the effects of the lateral ground conductivity anomalies on ionospheric equivalent current patterns are, though clearly detected, less severe than anticipated for fields varying with periods from 5 to 120min. However, the amplification of the determined currents caused by induction is significant, leading to an overestimation of up to 30% of the main current flow intensities, with the overestimation increasing sharply when moving away from the region of the main flow. In addition to the 3-D modeling, a simple method is introduced to help estimate the internal contribution to the measured variations of the IL index (local variant of the AL index). A test with the 26 June 1998 substorm event indicates that the method can help to extract the internal contribution from the IL index.

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Vanhamäki, H., A. Viljanen i O. Amm. "Induction effects on ionospheric electric and magnetic fields". Annales Geophysicae 23, nr 5 (28.07.2005): 1735–46. http://dx.doi.org/10.5194/angeo-23-1735-2005.

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Abstract. Rapid changes in the ionospheric current system give rise to induction currents in the conducting ground that can significantly contribute to magnetic and especially electric fields at the Earth's surface. Previous studies have concentrated on the surface fields, as they are important in, for example, interpreting magnetometer measurements or in the studies of the Earth's conductivity structure. In this paper we investigate the effects of induction fields at the ionospheric altitudes for several realistic ionospheric current models (Westward Travelling Surge, Ω-band, Giant Pulsation). Our main conclusions are: 1) The secondary electric field caused by the Earth's induction is relatively small at the ionospheric altitude, at most 0.4 mV/m or a few percent of the total electric field; 2) The primary induced field due to ionospheric self-induction is locally important, ~ a few mV/m, in some "hot spots", where the ionospheric conductivity is high and the total electric field is low. However, our approximate calculation only gives an upper estimate for the primary induced electric field; 3) The secondary magnetic field caused by the Earth's induction may significantly affect the magnetic measurements of low orbiting satellites. The secondary contribution from the Earth's currents is largest in the vertical component of the magnetic field, where it may be around 50% of the field caused by ionospheric currents. Keywords. Geomagnetism and paleomagnetism (geomagnetic induction) – Ionosphere (electric fields and currents)

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Noh, Kyubo, Ki Ha Lee, Seokmin Oh, Soon Jee Seol i Joongmoo Byun. "Numerical evaluation of active source magnetics as a method for imaging high-resolution near-surface magnetic heterogeneity". GEOPHYSICS 82, nr 5 (1.09.2017): J27—J38. http://dx.doi.org/10.1190/geo2016-0435.1.

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We have evaluated a geophysical method that uses a low-frequency magnetic source to image subsurface magnetic heterogeneity. This active source approach can be used to image magnetic features at higher resolutions than the conventional passive geomagnetic method. Importantly, this frequency-domain active source approach is independent of the effects of remanent magnetization, which complicates the interpretation of geomagnetic data. We carried out forward modeling of frequency-domain electromagnetic (EM) data and we found that, at frequencies of a few hertz, the magnetostatic response due to the induced magnetization dominates the EM induction response. The result suggests that it is possible to make magnetic interpretation of low-frequency EM data without having to consider the conductivity structure and the corresponding EM induction effect. We compare the anomalous magnetic responses with magnetic noise components and find that the proposed active source magnetic (ASM) method has a depth of investigation of approximately 300 m. Free-space field and inductive noise are considered as the most important issues affecting the depth of investigation. We also determine the potential for linear interpretation of magnetic heterogeneity under 0.1 SI by showing that the low-frequency magnetic response can be approximated by a linear magnetic response. In our synthetic experiments, inversion of the ASM data shows a marked enhancement in resolution, with no effect of the remanent magnetization, in contrast to geomagnetic inversion. These results show that the ASM method is a useful geophysical tool, especially when high-resolution imaging of magnetic susceptibility is required or where strong remanent magnetization complicates the magnetic interpretation.

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Varlamov, Ilya, Stanislav Parnikov, Igor Ievenko, Dmitry Baishev i Kazuo Shiokawa. "Registration of synchronous geomagnetic pulsations and proton aurora during the substorm on March 1, 2017". EPJ Web of Conferences 254 (2021): 02012. http://dx.doi.org/10.1051/epjconf/202125402012.

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Data of synchronous geomagnetic pulsations and proton aurora registrations were analyzed during the substorm on March 1, 2017 at Zhigansk (L=4.5, induction magnetometer), Maimaga (L=4, all-sky imager and Yakutsk (L = 3.3, induction magnetometer) stations, simultaneously with satellite measurement of EMIC waves. Ground-based registration of proton aurora is very difficult due to the fact that their intensity is much lower than the aurora intensity caused by precipitations of electrons, but in the event of substorm activity at the zenith of Maimaga station, a narrow (1 degree in latitude) proton arc was observed. Irregular pulsations of the diminishing periods (IPDPs) in the range of Pc1 geomagnetic pulsations associated with the injection of energetic protons were recorded simultaneously at Zhigansk and Yakutsk stations. This is the first report when STEVE (Strong Thermal Emission Velocity Enhancement) was observed in the course of a substorm with the onset at 12:45 UT after the decay of Pc1-associated proton arc. It is shown that the proton arc and geomagnetic pulsations are a consequence of ion-cyclotron instability in the area of the outer plasmasphere overlapping by energetic protons.

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32

Falayi, E. O., O. O. Ogundile, J. O. Adepitan i A. A. Okusanya. "Solar quiet variation of the horizontal and vertical components of geomagnetic field using wavelet analysis". Canadian Journal of Physics 97, nr 4 (kwiecień 2019): 450–60. http://dx.doi.org/10.1139/cjp-2018-0034.

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The solar quiet (Sq) variations of horizontal and vertical (SqH and SqZ) components of the geomagnetic field obtained from both the Northern Hemisphere and Southern Hemisphere of the International Real-Time Magnetic Observatory Network (INTERMAGNET) during solar maximum year 2001 were investigated. The results show enlargement of the SqH component of the geomagnetic field during the daytime, attributed to equatorial electrojet (EEJ) current closer to the geomagnetic equator at the electrojet stations (BNG and MBO), which are produced from large eastward flow of the current. It was observed that SqZ is positive at the southward and negative at the northward hemispheres. SqZ is amplified at HER and HBK around the daytime. Wavelet power spectrum based approach was employed to analyse the SqH, SqZ, and rate of induction (SqZ/SqH) time series in a sequence of time scaling from January to December. The higher energy of SqH and SqZ of the wavelet coefficients is noticeable at high frequency. The monthly variation rate of induction (SqZ/SqH) analyses during the Sq variations are associated with the influence of equatorwards penetration of electric fields from the field-aligned current, Earth conductivity, effect of the ocean, and ionospheric conductivity.

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33

Petersons, H. F. "Electromagnetic Induction in the Earth Using Long Period Geomagnetic Variations". Exploration Geophysics 24, nr 2 (czerwiec 1993): 157–59. http://dx.doi.org/10.1071/eg993157.

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Boteler, D. H. "A new versatile method for modelling geomagnetic induction in pipelines". Geophysical Journal International 193, nr 1 (22.01.2013): 98–109. http://dx.doi.org/10.1093/gji/ggs113.

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35

Bayanjargal, G. "The Study of Westward Drift in the Main Geomagnetic Field". International Journal of Geophysics 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/202763.

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We have obtained a solution for the velocity of westward drift from the induction equation in which an approach for main geomagnetic field was built. Distribution functionsB(r, t) entered into the induction equation have been built by the observatories' data in North America and the Europe from 1991 to 2006. The longitudinal −0.123 degree/year and latitudinal 0.068 degree/year drifts were defined in North America. And the longitudinal −0.257 degree/year drift was defined in Europe from 1991 to 2006. These drifts are similar to results of other studies.

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36

Viljanen, A., A. Pulkkinen, O. Amm, R. Pirjola i T. Korja. "Fast computation of the geoelectric field using the method of elementary current systems and planar Earth models". Annales Geophysicae 22, nr 1 (1.01.2004): 101–13. http://dx.doi.org/10.5194/angeo-22-101-2004.

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Abstract. The method of spherical elementary current systems provides an accurate modelling of the horizontal component of the geomagnetic variation field. The interpolated magnetic field is used as input to calculate the horizontal geoelectric field. We use planar layered (1-D) models of the Earth's conductivity, and assume that the electric field is related to the local magnetic field by the plane wave surface impedance. There are locations in which the conductivity structure can be approximated by a 1-D model, as demonstrated with the measurements of the Baltic Electromagnetic Array Research project. To calculate geomagnetically induced currents (GIC), we need the spatially integrated electric field typically in a length scale of 100km. We show that then the spatial variation of the electric field can be neglected if we use the measured or interpolated magnetic field at the site of interest. In other words, even the simple plane wave model is fairly accurate for GIC purposes. Investigating GIC in the Finnish high-voltage power system and in the natural gas pipeline, we find a good agreement between modelled and measured values, with relative errors less than 30% for large GIC values. Key words. Geomagnetism and paleomagnetism (geomagnetic induction; rapid time variations) – Ionosphere (electric field and currents)

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37

Белецкий, Александр, Aleksandr Beletsky, Равиль Рахматулин, Ravil Rakhmatulin, Татьяна Сыренова, Tatyana Syrenova, Роман Васильев i in. "Preliminary results of simultaneous recording of auroral and geomagnetic pulsations at the ISTP SB RAS station Istok". Solar-Terrestrial Physics 5, nr 2 (28.06.2019): 39–44. http://dx.doi.org/10.12737/stp-52201906.

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The paper presents the results on first synchronous observations of variations in auroral luminosity and geomagnetic field, made with high temporal resolution at the ISTP SB RAS high-latitude station Istok (70° N, 88° E) in September–December 2018. Auroras were recorded with all-sky camera, pulsations in the auroras were recorded by a photometer in four spectral ranges with silicon photomultipliers. Continuous monitoring of geomagnetic pulsations was performed using a LEMI-30 three-component induction magnetometer. Both synchronous bursts of auroras and magnetic field pulsations, as well as disturbances of auroras, not accompanied by disturbances in the geomagnetic field, were observed. We note that the photometer clearly recorded short-period (~20 min) variations in in auroral luminosity. At the same time, some instability of the photometer signal level occurred at sufficiently long time intervals. In the photometer data, there are powerful signal bursts, probably of a hardware nature. Nevertheless, the temporary distribution analysis of the registration moments (registration frequency) of signal bursts indicates the possible dependence of the burst registration frequency on the geomagnetic activity level.

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38

Белецкий, Александр, Aleksandr Beletsky, Равиль Рахматулин, Ravil Rakhmatulin, Татьяна Сыренова, Tatyana Syrenova, Роман Васильев i in. "Preliminary results of simultaneous recording of auroral and geomagnetic pulsations at the ISTP SB RAS station Istok". Solnechno-Zemnaya Fizika 5, nr 2 (28.06.2019): 42–48. http://dx.doi.org/10.12737/szf-52201906.

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The paper presents the results on first synchronous observations of variations in auroral luminosity and geomagnetic field, made with high temporal resolution at the ISTP SB RAS high-latitude station Istok (70° N, 88° E) in September–December 2018. Auroras were recorded with all-sky camera, pulsations in the auroras were recorded by a photometer in four spectral ranges with silicon photomultipliers. Continuous monitoring of geomagnetic pulsations was performed using a LEMI-30 three-component induction magnetometer. Both synchronous bursts of auroras and magnetic field pulsations, as well as disturbances of auroras, not accompanied by disturbances in the geomagnetic field, were observed. We note that the photometer clearly recorded short-period (~20 min) variations in in auroral luminosity. At the same time, some instability of the photometer signal level occurred at sufficiently long time intervals. In the photometer data, there are powerful signal bursts, probably of a hardware nature. Nevertheless, the temporary distribution analysis of the registration moments (registration frequency) of signal bursts indicates the possible dependence of the burst registration frequency on the geomagnetic activity level.

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39

Rokityansky, I., V. Babak i A. Tereshin. "Geomagnetic activity impact on the results of the induction vector calculations". Geofizicheskiy Zhurnal 37, nr 6 (29.09.2017): 86–98. http://dx.doi.org/10.24028/gzh.0203-3100.v37i6.2015.111173.

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Fernberg, P. A., C. Samson, D. H. Boteler, L. Trichtchenko i P. Larocca. "Earth conductivity structures and their effects on geomagnetic induction in pipelines". Annales Geophysicae 25, nr 1 (1.02.2007): 207–18. http://dx.doi.org/10.5194/angeo-25-207-2007.

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Abstract. Anomalous, large pipe-to-soil potentials (PSP) have been observed along a natural gas pipeline in eastern Ontario, Canada, where there is a major geological contact between the highly resistive rocks of the Precambrian Shield to the west and the more conductive Paleozoic sediments to the east. This study tested the hypothesis that large variations of PSP are related to lateral changes of Earth conductivity under the pipeline. Concurrent and co-located PSP and magnetotelluric (MT) geophysical data were acquired in the study area. Results from the MT survey were used to model PSP variations based on distributed-source transmission line theory, using a spatially-variant surface geoelectric field. Different models were built to investigate the impact of different subsurface features. Good agreement between modelled and observed PSP was reached when impedance peaks related to major changes of subsurface geological conditions were included. The large PSP could therefore be attributed to the presence of resistive intrusive bodies in the upper crust and/or boundaries between tectonic terranes. This study demonstrated that combined PSP-MT investigations are a useful tool in the identification of potential hazards caused by geomagnetically induced currents in pipelines.

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41

Sekhar, E. Chandra, i B. R. Arora. "On the Source Field Geometry and Geomagnetic Induction in Southern India." Journal of geomagnetism and geoelectricity 46, nr 9 (1994): 815–25. http://dx.doi.org/10.5636/jgg.46.815.

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Viljanen, Ari. "Source Effect on Geomagnetic Induction Vectors in the Fennoscandian Auroral Region." Journal of geomagnetism and geoelectricity 48, nr 7 (1996): 1001–9. http://dx.doi.org/10.5636/jgg.48.1001.

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43

Banks, R. J., i J. N. Ainsworth. "Global induction and the spatial structure of mid-latitude geomagnetic variations". Geophysical Journal International 110, nr 2 (sierpień 1992): 251–66. http://dx.doi.org/10.1111/j.1365-246x.1992.tb00871.x.

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44

Nakahara, Mio, Akimasa Yoshikawa, Teiji Uozumi i Akiko Fujimoto. "Electromagnetic induction responses to geomagnetic disturbances at low-and-mid-latitudes". Journal of Physics: Conference Series 1152 (styczeń 2019): 012035. http://dx.doi.org/10.1088/1742-6596/1152/1/012035.

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45

Molteno, T. C. A., i W. L. Kennedy. "Navigation by Induction-Based Magnetoreception in Elasmobranch Fishes". Journal of Biophysics 2009 (18.10.2009): 1–6. http://dx.doi.org/10.1155/2009/380976.

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A quantitative frequency-domain model of induction-based magnetoreception is presented for elasmobranch fishes. We show that orientation with respect to the geomagnetic field can be determined by synchronous detection of electrosensory signals at harmonics of the vestibular frequency. The sensitivity required for this compass-sense mechanism is shown to be less than that known from behavioral experiments. Recent attached-magnet experiments have called into doubt the induction-based mechanism for magnetoreception. We show that the use of attached magnets would interfere with an induction-based mechanism unless relative movement between the electrosensory system and the attached magnet is less than 100 m. This suggests that further experiments may be required to eliminate induction as a basis for magnetoreception.

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46

Okhitina, Anna, Stepan Tkachev i Dmitry Roldugin. "Comparative Cost Functions Analysis in the Construction of a Reference Angular Motion Implemented by Magnetorquers". Aerospace 10, nr 5 (17.05.2023): 468. http://dx.doi.org/10.3390/aerospace10050468.

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This paper considers a construction procedure of a satellite reference angular motion in the vicinity of an unstable gravitational equilibrium position. The satellite is stabilized on the reference trajectory by the magnetic coils. The problem is solved in several stages. An optimization problem to be solved by the particle swarm optimization method is formulated at each stage. Cost functions are based on the linearized model analysis. The main stage is the construction of a special reference motion, which provides the minimum control torque projection on the geomagnetic induction vector. Optimal geomagnetic field dipole approximation for a given time interval is considered to reduce tracking errors. The paper compares combinations of different cost functions in terms of the terminal attitude accuracy in the presence of perturbations.

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Mulligan, Bryce, i Stanley Koren. "Geopsychology of instrumental aggression: daily concurrence of global terrorism and solar-geomagnetic activity (1970-2018)". Advances in Social Sciences Research Journal 8, nr 5 (2.06.2021): 487–99. http://dx.doi.org/10.14738/assrj.85.10266.

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Formal scientific study of the geopsychology of human aggression dates back at least a century and has consistently demonstrated a positive association between solar-geomagnetic activity and aggressive behaviour. Advances in the theories, methodologies, and practical applications of geopsychology could therefore contribute to collective efforts to comprehend, to forecast, and to develop interventions for aggressive behaviours such as those seen in terrorism. This requires a rigorous and precise estimate of the magnitude of association between solar-geomagnetic activity and aggression using a representative, contemporary sample of strictly-operationalized behaviour. Here we show that days in recent history (1970-2018) with the lowest levels of instrumental human aggression (number of casualty-associated terrorism incidents) also had the lowest levels of solar and geomagnetic activity, and that stepwise increases in human aggression were mirrored by progressive increases in solar activity. We used Bayesian methods robust to outliers and heterogeneity of variance to analyze the most comprehensive and contemporary global database of terrorism incidents available, which included more than 106,000 unique instances of instrumental aggression spanning 48 years. We conclude that there is a small, nonzero promotional effect of solar-geomagnetic activity on terrorism-related aggression. This may reflect the fact that solar-geomagnetic activity serves as a zeitgeber that coordinates the expression of instrumental aggression across an aggregation of susceptible individuals. We propose that many behaviours – even instrumental acts such as terrorism which are presumed to involve a degree of planning and intention – may be subject to subtle geopsychological induction or suppression.

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Orlyuk, M. I., T. P. Sumaruk, Yu P. Sumaruk i A. A. Romenets. "Valuation of induction current contribution to the secular variation of geomagnetic field (according to the data of Ukrainian geomagnetic observatories)". Geofizicheskiy Zhurnal 36, nr 2 (24.11.2014): 111–19. http://dx.doi.org/10.24028/gzh.0203-3100.v36i2.2014.116124.

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Shiokawa, K., R. Nomura, K. Sakaguchi, Y. Otsuka, Y. Hamaguchi, M. Satoh, Y. Katoh i in. "The STEL induction magnetometer network for observation of high-frequency geomagnetic pulsations". Earth, Planets and Space 62, nr 6 (czerwiec 2010): 517–24. http://dx.doi.org/10.5047/eps.2010.05.003.

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Demetrescu, C., M. Andreescu i T. Neştianu. "Induction model for the secular variation of the geomagnetic field in Europe". Physics of the Earth and Planetary Interiors 50, nr 3 (kwiecień 1988): 261–71. http://dx.doi.org/10.1016/0031-9201(88)90107-0.

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