Geomagnetism and Aeronomy最新文献

A comparative analysis of various model representations of seismogenic quasi-stationary electric fields/currents from large-scale sources on the Earth’s surface was carried out. It has been established that previously proposed analytical models of seismogenic quasi-stationary sources of electric field/current with field/current amplitudes continuously decreasing to zero at infinity are consistent with extreme values of electric field/current experimentally observed in epicentral zones before earthquakes. It is also shown that sharply spatially limited models of seismogenic sources of quasi-stationary electric fields/currents in the epicentral zones of future earthquakes on the Earth’s surface lead to their values being an order of magnitude or more greater than those actually observed.

The well-known problem of nonlinear wave–ionosphere interaction under conditions of threshold nonlinearity is considered. It is believed that nonlinear effects arise only for high-power radiation, when the wave amplitude exceeds a certain threshold value. The possibility of the existence of concentrated wave fields under these conditions is shown. It is revealed that a certain ratio of nonlinearity parameters leads to an increase in the radio emission intensity, since the interaction of individual solitons can lead to their merging into a higher-power solitary wave. The presence of threshold nonlinearity can lead to the formation of an ordered structure of solitary waves.

Earthquake indicators provide a huge advantage in the preparation for the calamity and its aftermaths. Total electron content (TEC) is an ionospheric measurement that varies before the possible happenstance of an earthquake. In this research paper, ordinary kriging based surrogate model (OKSM) which is used for forecasting ionospheric TEC variation is adapted as an earthquake indicators in low-latitude and mid-latitude regions. Seven International GNSS Service (IGS) stations from the mid-latitude and low-latitude region are chosen for observation. The stations are from different countries such as Indonesia (BAKO), Ecuador (RIOP), Greece (ORID), Cyprus (NICO), Hawaii (HNLC) and Italy (MATE & MAT1). The OKSM prediction program is performed with previous 2 months of TEC data from the observed date and its accompanying solar parameters such as Planetary K and A index (Kp & Ap), Radio Flux at 10.7 cm (F10.7) and disturbance storm time (DST) index acquired from OMNIWEB data servers. The performance of the model is evaluated using statistical metrics such as root mean square error (RMSE), normalized – RMSE (NRMSE), mean absolute error (MAE), Pearson’s correlation coefficient (PCC) and chi-squared goodness of fit test. The evaluation of the prediction model on the same date shows that the performance deviation of OKSM is in the range of 2–5 TECU and also establishes the fact that the prediction capability of the OKSM is accurate. Application of the OKSM constructed with previous days data collected from high earthquake prone areas by omitting effects of solar storms and solar activities will act as a highly economical and simple early warning indicator of an earthquake.

The GPS-based total electron content (TEC) data observed at four low-latitude TEC stations—Lucknow (LCK3), Bangalore (IISC), Hyderabad (HYDE), and Lhasa (LHAZ) are subjected to Quartile-based statistical analysis to study the effect of six major shallow earthquakes (M > 6.0, depth < 30 km) that occurred in and around India in 2017. The results show anomalous enhancements in the TEC data 2–14 days before and 3–15 days after the onset of the earthquakes considered. These pre- and postseismic TEC enhancements are between 1.2–8.7 and 0.7–25.6 TECU, respectively, and percentage TEC enhancements before and after these earthquakes range from 3.82–69.04 and 4.40–95.53%, respectively. The influence of solar activity and magnetic storms on GPS-TEC data have also been examined, and it has been noted that the recorded anomalous TEC enhancements are not associated with these spurious sources except for correlation of TEC enhancements for three with magnetic storms. To confirm the association of observed precursory TEC enhancements occasions with the earthquakes considered in the present analysis probabilities for the pairs of TEC enhancements with the focal depths and precursory times with the distances of epicenters of the earthquakes from the observing stations are computed using t-test. The probabilities for the said pairs were 99.7 and, 70.5% for Lucknow; 47.5 and 98.9% for Bangalore; 95.7 and, 98.5% for Hyderabad; and 71.7 and 99.9% for Lhasa which are fairly large except for the Bangalore TEC observing station for the pair of precursoy time and epicentral distances, confirming the relationship between the TEC enhancements and considered earthquakes. In addition, possible mechanisms for perturbation in the TEC data due to seismic events are also discussed.

The ultimate goal of petroleum industry is to perform their routine operations with minimal risks. Nevertheless, the possibilities of jeopardies for instance; blowout of a well always remains in the offering. This event normally occurs when all the well control barriers are failed in their functionality. Therefore, a contingency plan in the form of Relief well should always exist to tackle this acute risk associated event. In this study, two modeled well trajectories were designed in two different zones having different chorography. These regions are Pakistan and Norwegian Sea that are situated in lower and higher latitude regions respectively. The primary goal of this article is to study the influence of magnetic declination on wellbore positioning. During the initial phase of analysis, it was investigated from IGRF model that the internal geomagnetic field and the secular variations in Norwegian Sea are different than those in Pakistan. Upon further investigation, it was observed that in Norwegian Sea, the lower value of horizontal component of magnetic field of the Earth and higher values of dip angle results in increasing azimuthal uncertainty. Both of these components are part of weighting function of measurement while drilling, declination error source. This measurement while drilling model error source was then transformed in ellipses of uncertainty (EOUs). In Norwegian Sea almost 92% contribution in EOU size is from declination, whereas, in Pakistan this influence significantly drops to 35%. Furthermore, as EOUs size increases, the chance of premature collision also intensifies. This was experience in Norwegian Sea well, where the Relief well demonstrates separation factor less than 30 m before the desired depth, thus indicating an early intersection. Quite a reverse behavior was observed in Pakistan where the probability of premature collision with the Targeted well and the separation factor between the two wells before the desired depth are all in the desired range. Thus, it can be concluded that in Norwegian Sea, magnetic declination will have some serious consequences if not properly taken into consideration.

Based on the double probe method, we investigated the ionospheric preseismic electric effects for the strong Chile earthquake of magnitude M = 8.8 that occurred on February 27, 2010, at 06:3414 universal time (UT). To correlate the electrical disturbance to natural geophysical activities in the ionosphere associated with the earthquake, we used a new approach to analyze these disturbances a few days before the event, based on DEMETER spacecraft collected data in the ultra low frequency (ULF) band. The double probes method and the calculated preseismic ionospheric electric field resulting from the potential difference between two electrical probes of ICE (Instrument Champ Electrique) onboard the DEMETER satellite are investigated. Once the effect of the satellite motion is canceled, it is found that the disturbance is caused only by the telluric activity. Moreover, the investigation of the collected data illustrates a clear correlation between preseismic electrical disturbances and ionospheric plasma parameters recorded near the future epicenter. The strongest ionospheric electrical disturbances are located near the future epicenter and close to the geomagnetic conjugate points.

An analysis of a large array of observation data (over ~50–80 years) for 456 meteorological stations in Russia revealed a distinct difference in the monthly amount of precipitation (DP) during years of maximum and minimum solar activity depending on months and seasons of the year and on latitudes and longitudes. Particularly large DP values are observed in the latitude belt of U = 40°–55° N in the longitude range D = 20°–40° E in October, DP being 13.6 ± 2.2 mm, as well as in the longitude range D = 110°–130° E in June, DP being −8.5 ± 1.0 mm. In the zone of maximum influence of solar activity on the amount of precipitation, a study was conducted on the presence of a correlation between Wolf numbers and the amount of precipitation. As a result, a strong increase in the correlation was discovered in the case of a backward shift in the Wolf numbers, which argued in favor of the influence of solar activity on weather. The author is convinced of the physical significance of the correlation, because it is obtained from data from several geographical points. It is concluded that solar and geomagnetic activity can govern the development of internal instabilities of the atmosphere and thereby influence climate.

Based on the results of measurements near the equatorial plane a fluxes and energy spectra of H⁺ and O⁺ ions of the magnetosphere’s ring current by the OGO-3, Explorer 45, AMPTE/CCE, and Van Allen Probes (A and B) satellites, a systematic analysis of spatial distributions of the energy density for these ions on the main phase of magnetic storms was carried out. Twelve storms of different strength were considered, with max|Dst| from 64 to 307 nT. The radial profile of the ring current ions energy density is characterized by the maximum (L_m) and by the ratio of the energy densities of the ions and the magnetic field at this maximum (β_m), and at L > L_m this profile is approximated by the function w(L) = w₀ exp(–L/L₀). Quantitative dependences of the parameter L_m on the Dst index and MLT, and also the dependences of the parameters β_m, w₀ and L₀ on the Dst, MLT and L_m, are obtained. These dependences are different for H⁺ and O⁺ ions, as well as for ions of low (E < 60 keV) and higher energies. It has been established that in a narrow inner region of the ring current near its maximum in the nighttime hemisphere of the magnetosphere, the RC asymmetry is much smaller (especially for O⁺ ions) than at L > L_m. It was found that with increasing L, the asymmetry of the ring current by MLT increases significantly, with H⁺ ions concentrated at near 18 MLT, and O⁺ ions at near 24 MLT. It is shown that for O⁺ ions with E ∼ 1–300 keV, β_m ∝ (L_{m}^{{ - 9}}); this result shows that a deeper penetration of hot plasma into a geomagnetic trap, during strong storms, requires not only a stronger electric field of convection, but also a significant preliminary accumulation and acceleration of ions (especially O⁺ ions) in the sources of the ring current.

This paper investigates the diurnal variations of modelled and observed vertical total electron content (VTEC) over the African region (40° N to +40° S, 25° W to 65° E) obtained from ground-based global navigation satellite system (GNSS) receivers. The investigations on ionospheric response during the super geomagnetic storm time (March 17 2015) are crucial, especially over African low latitudes. Hence, the performance of ionospheric models has been evaluated in this paper. The VTEC predictability by regional/global ionospheric models (AfriTEC, IRI-2016, IRI-Plas 2017, GIM-CODE, and Nequick-G) is assessed by using root mean square error (RMSE) method and percentage deviation by comparing the GPS/GNSS-VTEC obtained from 10 IGS (International GNSS Service) stations with the modelled-VTEC values over the African region. The peculiarity in VTEC values is evident during the superstorm’s sudden commencement compared to the pre- and post-storm periods. Northern hemisphere GPS station TEC data showed a twin peak in the daily VTEC patterns. The enhanced VTEC values were observed over all the selected 10 IGS stations on the storm day than on other quiet days. Moreover, during the post-storm days (March 18–20, 2015), these VTEC values decreased more than on quiet days over the IGS stations in the southern hemisphere (MBAR, MAYG, HARB, SBOK). On the other hand, during the post-storm days (March 18–20, 2015), the VTEC values remained high over the geomagnetic northern hemisphere (NOT1, SFER, MAS1, CPVG, NKLG). It is worth mentioning that three northern IGS stations (NOT1, SFER, and MAS1) displayed a VTEC increase record of approximately 75–90% due to the extension of equatorial ionization anomaly (EIA) during the geomagnetic storm. In contrast, the other northern stations at the EIA trough region (CPVG, BJCO, NKLG) registered a VTEC increment of 7, 26, and 25%, respectively. Southern IGS stations registered an enhancement in VTEC of about 5%. The VTEC maps from AfriTEC, IRI-2016, and Nequick-G were able to predict the feature of EIA at around 20° N/15° S. The GPS-VTEC values at IGS stations located on the geomagnetic EIA crests (in both northern and southern hemispheres) and in the trough (equatorial stations) are higher than those of the IGS stations situated at mid-latitudes. AfriTEC, a regional model, recorded the lowest RMSE values over all the stations. The prediction results show that the regional model performance is better than the global ionospheric models (IRI-2016 and Nequick-G models), especially over EIA latitudes of the African region.

This study delved into the response of the equatorial ionosphere in the South American region to the geomagnetic storm in September 2017. Six global positioning system (GPS) receivers, positioned along 45° W and 70° W, were utilized to estimate the daily variation of total electron content (TEC). A pair of magnetometers measured the strength of the equatorial electrojet (EEJ) (inferred E × B drift), and the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite revealed changes in the thermospheric neutral composition before, during, and after the geomagnetic storm on September 8, 2017. The pre-storm effect and occurrence of solar flares, accompanied by solar bursts are responsible for the significant enhancement in TEC magnitudes days prior to geomagnetic storm event. However, the significant enhancement observed in the TEC magnitude during the main phase of the geomagnetic storm was primarily driven by DP2 (disturbance polar number 2), created by the daytime prompt penetration of electric field (PPEF) signature. Other mechanisms responsible for this enhancement included the increase in thermospheric neutral composition, O/N₂ ratio, and more ionization of electrons due to the increase in solar flux. Furthermore, the drastic increase in the amplitude of the morning-afternoon magnetometer-inferred upward-directed E × B drift during the main phase of the storm, compared to the quiet periods, was attributed to the magnetic signature (DP2) due to PPEF. Additionally, the inhibition of ionospheric irregularities at the equatorial ionosphere during the main phase of the geomagnetic storm may be associated with the storm-time occurrence.