О влиянии экстремальной геомагнитной активности на точность проведения геофизических исследований в северных регионах

The auroral zone is the region surrounding the geomagnetic north and south poles and is where the largest and most frequent disturbances in the Earth's magnetic field are experienced. Since the accuracy of magnetic MWD directional surveys are affected by geomagnetic disturbances, surveying wells in the auroral zone is challenging. Development of industry practices to enable accurate surveying and safe operations in these areas is therefore important. The objective of this study is to investigate how the geomagnetic field parameters declination, dip angle and total magnetic field intensity are influenced by magnetic disturbances in the auroral zone. This is done by analysing the statistical properties of data from 20 land-based magnetic observatories and variometer stations in Alaska, Greenland, and Scandinavia, all located in the auroral zone. The results are used to estimate models for magnetic field disturbance variations as function of distance and direction. Additionally, methods and correction procedures to reduce azimuth uncertainty using data from distant monitoring stations are presented. Uncritical use of data from monitoring stations can result in uncertain azimuth measurements. In cases where data from more than one nearby monitoring stations are available, the challenge is often related to identifying which stations that provide the most accurate corrections. As will be shown, important criteria for the selection of monitoring stations are not only limited to directions and distances, but also the position of the ionospheric current relative to the rig-location. Procedures and methods for how to predict the positions of ionospheric currents are presented. The datasets analysed in this study contain measured deviations from the quiet mean for periods with low, moderate and high geomagnetic activity. Station-pairs with mutual distances ranging from 150km to 850km are considered. The general trends are that magnetic data from station-pairs located along the east-west direction are more correlated than data from stations located along north-south, and that differences in magnetic fluctuations between station-pairs are lower east-west than north-south. This accounts for all distances, directions, and disturbance levels.

We study the ionospheric convection that prevails during the passage of a magnetic cloud past the Earth. For the cloud studied here, January 13‐15, 1988, the ionospheric convection was measured almost continually in cross sections of the polar cap and auroral zone by the Defense Meteorological Satellite Program (DMSP) polar‐orbiting satellite. In turn, the conditions in the magnetic cloud are like those of a controlled laboratory experiment: First, the magnetic field changes smoothly and slowly on time scales much longer than the expected ionospheric response time, ensuring that the external interplanetary conditions giving rise to any ionospheric flow pattern are known to unprecedented accuracy. Second, over the longer time scale of the magnetic cloud passage, the magnetic field vector rotates by over 180° such that the magnetic cloud divides into two intervals of northward (Bz > 0) and southward (Bz < 0) pointing interplanetary magnetic field (IMF) of 11 and 18 hours duration, respectively. During the former interval our observations show that (1) for strongly northward IMF (Bz > 18 nT) the convection in one (the southern) hemisphere is characterized by a two‐cell convection pattern confined to high latitudes (≥ 75°) with sunward flow over the pole (“reverse” two‐cell convection). (2) The strength of the flows (∼1 km/s) is comparable to that seen under southward IMF later. (3) Superimposed on this convection pattern there are clear dawn‐dusk asymmetries associated with a one‐cell convection component whose sense depends on the polarity of the magnetic cloud's large east‐west magnetic field component. (4) Whilst the flows in the southern hemisphere are ordered into a well‐defined convection pattern, the flows in the northern hemisphere are very irregular, varying on short spatial scales. When the cloud's magnetic field turns southward the following observations were made: (1) The convection is characterized by a two‐cell pattern extending to lower latitudes (∼50°) with antisunward flow over the pole (“standard” two‐cell convection). (2) There is no evident interhemisphere difference in the structure and strength of the convection. (3) Superimposed dawn‐dusk asymmetries in the flow pattern are observed which are only in part attributable to the east‐west component of the magnetic field. (4) A dawn‐dusk asymmetry in the latitude of the convection reversal boundary also exists, which is most pronounced in the northern hemisphere (up to 10° difference). We study the transition from a reverse to standard two‐cell convection pattern and find that because of the large By component of the magnetic field inside the magnetic cloud, this transition actually takes place before the external field turns southward. It occurs when the magnetic shear angle between the subsolar magnetospheric field and the magnetic field of the magnetic cloud is ∼70°. We consider the effect of the Bz component of the cloud magnetic field on the size of the open field line region or polar cap, inferred from the convection pattern. We argue that the long‐term variation in the polar cap size is determined by the temporal gradient of the Bz component. We investigate the strength of the ionospheric convection, parameterized by the maximum potential difference across the convection pattern, as a function of the Bz component of the cloud magnetic field, extending the range of similar investigations. For strongly northward IMF a potential difference of 60‐80 kV is observed across the reverse two‐cell convection pattern. For southward IMF the potential difference across the standard two‐cell convection pattern changes almost linearly with Bz, attaining its maximum value of ∼180 kV at the extreme value of Bz = −19 nT reached in this cloud.

A technology is proposed for calculating the strength and angular components of the vector of the induction of the Earth's magnetic field. The technology is based on the development of a three-dimensional model of the earth's crust and the calculation of the northern (∆ В а х ), eastern (∆ В а y ) and vertical (∆ В а z ) components of the anomalous magnetic field from it, which, together with the corresponding components ( В 0 х , В 0 y , В 0 z ) allow us to determine the total values of the В х -, В y -, В z -components of the Earth's magnetic field. With their use, the horizontal component (BH) of the geomagnetic field vector and the angles of its declination D and the inclination J are calculated. The values of the magnetic declination D in the territory of Ukraine for the epoch of 2010 are calculated (varies from –6 ° to +20 °) and the secular run for the period 2010—2015 (6.0—7.5 min/year). The contribution to the value of the magnetic declination D of its normal ( D 0 ) and anomalous (Δ D ) components is estimated. The accuracy of the calculated values of D is estimated by comparison with the measured values of magnetic declination at magnetic observatories and points of secular run. For most points, the difference is about 3—6 minutes. Currently, the results of calculating the magnetic declination D for the time interval of 2010—2015 are used by the state services of Ukraine (UkSATSE, Topographic Service of the APU) to ensure flight safety and compiling topographic maps.

In September 1859 the Colaba observatory measured the most extreme geomagnetic disturbance ever recorded at low latitudes related to solar activity: the Carrington storm. This paper describes a geomagnetic disturbance case with a profile extraordinarily similar to the disturbance of the Carrington event at Colaba: the event on 29 October 2003 at Tihany magnetic observatory in Hungary. The analysis of the H-field at different locations during the "Carrington-like" event leads to a re-interpretation of the 1859 event. The major conclusions of the paper are the following: (a) the global Dst or SYM-H, as indices based on averaging, missed the largest geomagnetic disturbance in the 29 October 2003 event and might have missed the 1859 disturbance, since the large spike in the horizontal component (H) of terrestrial magnetic field depends strongly on magnetic local time (MLT); (b) the main cause of the large drop in H recorded at Colaba during the Carrington storm was not the ring current but field-aligned currents (FACs), and (c) the very local signatures of the H-spike imply that a Carrington-like event can occur more often than expected.

Magnetic and electric field variations during geomagnetically active days over Turkey

Aims. We introduce a new model for coronal mass ejections (CMEs) that has been implemented in the magnetohydrodynamics (MHD) inner heliosphere model EUHFORIA. Utilising a linear force-free spheromak (LFFS) solution, the model provides an intrinsic magnetic field structure for the CME. As a result, the new model has the potential to predict the magnetic components of CMEs at Earth. In this paper, we present the implementation of the new model and show the capability of the new model. Methods. We present initial validation runs for the new magnetised CME model by considering the same set of events as used in the initial validation run of EUHFORIA that employed the Cone model. In particular, we have focused on modelling the CME that was responsible for creating the largest geomagnetic disturbance (Dst index). Two scenarios are discussed: one where a single magnetised CME is launched and another in which we launch all five Earth-directed CMEs that were observed during the considered time period. Four out of the five CMEs were modelled using the Cone model. Results. In the first run, where the propagation of a single magnetized CME is considered, we find that the magnetic field components at Earth are well reproduced as compared to in-situ spacecraft data. Considering a virtual spacecraft that is separated approximately seven heliographic degrees from the position of Earth, we note that the centre of the magnetic cloud is missing Earth and a considerably larger magnetic field strength can be found when shifting to that location. For the second run, launching four Cone CMEs and one LFFS CME, we notice that the simulated magnetised CME is arriving at the same time as in the corresponding full Cone model run. We find that to achieve this, the speed of the CME needs to be reduced in order to compensate for the expansion of the CME due to the addition of the magnetic field inside the CME. The reduced initial speed of the CME and the added magnetic field structure give rise to a very similar propagation of the CME with approximately the same arrival time at 1 au. In contrast to the Cone model, however, the magnetised CME is able to predict the magnetic field components at Earth. However, due to the interaction between the Cone model CMEs and the magnetised CME, the magnetic field amplitude is significantly lower than for the run using a single magnetised CME. Conclusions. We have presented the LFFS model that is able to simulate and predict the magnetic field components and the propagation of magnetised CMEs in the inner heliosphere and at Earth. We note that shifting towards a virtual spacecraft in the neighbourhood of Earth can give rise to much stronger magnetic field components. This gives the option of adding a grid of virtual spacecrafts to give a range of values for the magnetic field components.

VLF-emissions observed at stations close to the auroral zone and at stations on lower latitudes

A close relation has been found between increases of chorus indices continuing for a few hours and geomagnetic pulsations at the auroral zone, using the chorus indices and rapid-run magnetograms at College, Alaska, during July, 1959 to December, 1960.During this period 79 increases of chorus indices occurred in relatively quiet geomagnetic-conditions after geomagnetic bay-like disturbances. Of 79 chorus increases, 52 were associated with geomagnetic pulsations with periods between 1 and 6 minutes and 11 were associated with pulsations having periods of about 30 seconds.The chorus increases may be generated by penetration of high speed charged particles into the exosphere, which may also be related to the geomagnetic pulsations.A possible mechanism of the generation of geomagnetic pulsation has been discussed.

The relation between solar activities and the geomagnetic field induced currents (GIC) have been well studied in the auroral region and it usually occurs most frequently at high latitudes. However, during major geomagnetic storms, the auroral zone can extend substantially towards lower latitudes. Disturbance caused by solar activities can disrupt power grids and also increase the corrosion rate of buried natural gas pipelines. GIC are driven by the geomagnetic field induced by a geomagnetic disturbance. In this paper, we investigated the correlation between solar activities using the interplanetary magnetic field (IMF) and geomagnetic disturbance storm time (DST) index data with the telluric currents (also referred to as geomagnetic induced currents GIC) level through the disturbance pattern of geomagnetic field. The research areas are from Lunas in Kedah to Perlis. The pattern of geomagnetic field disturbance had been identified and analyzed to investigate the harmful effect of geomagnetic storms towards the performance of complex power grid in Malaysia.

Prediction tests by using “ISF” method for the geomagnetic disturbances

Analysis of geomagnetic variations registered by the stations of the North-Caucasian geophysical observatory (the Elbrus volcanic area) has been fulfilled. Anomalous "quasi-harmonic" magnetic disturbances have been distinguished which were observed during all the stages of development of catastrophic tsunami-producing earthquakes in the area of Indonesia and morphologic effects in variation structure of geomagnetic field of the Earth have been described. Experimental results cited permit to obtain general idea on geomagnetic activity and some features of induced geomagnetic disturbances which we refer to tsunami-producing earthquakes. In all the observed cases seismic events occurred under the conditions of specific ratios between the components of magnetic field; it has been found that in the structure of magnetic variations we succeeded to distinguish ultra-low-frequency quasi-harmonic wave forms of geomagnetic disturbances reflecting the conditions of preparation and development of tsunami-producing earthquake in the studied region. We do not consider in the paper the forecast of tsunamiproducing earthquakes because even if we can distinguish in geomagnetic field some specific indications, in the source preceding the start of seismic event its coordinates and time in the source are left uncertain so far.

A component compensation method for magnetic interferential field

Effects of interplanetary magnetic field and magnetospheric substorm variations on the dayside aurora

Radio wave emissions in the v.l.f.-band observed near the auroral zone—I occurrence of emissions during disturbances

A Maxwell–Schrödinger solver for quantum optical few-level systems