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In this study, we used GPS-TEC measurements from six stations in East Africa located in low/equatorial latitudes to investigate medium-term ionospheric response to solar and geomagnetic circumstances during 2014-2016. Daily mean solar proxies (F10.7 and SSN) and geomagnetic activity indices (Kp and Dst) were used to determine solar and geomagnetic activity effects on ionospheric vertical Total-Electron-Content (vTEC). We have applied statistical analysis and quadratic fits with solar indices to find the type of trends, forecast vTEC, and describe the daily fluctuations of vTEC. Asab and Debark had the highest vTEC values among the six stations during the months of equinoxes in which they are located at 13.06 0 and 13 0 geographic latitudes, respectively. The highest vTEC values were 86, 80, and 75 TECU in March, October, and April 2014, respectively; 72 TECU in March and April 2015, and 70 TECU in February 2015. Within 24 hours, the magnitudes of vTEC were greater in February, March, and April 2014, 2015, and 2016 than in the remaining months. The changes in vTEC have demonstrated good agreement with the trend of solar parameters, and F10.7 has a stronger correlation with vTEC than SSN by 20%. The effects of solar activity on GPS-vTEC were positive, whereas the vTEC was disturbed during the storm's main and recovery phases, which led to positive and negative ionospheric effects, respectively. We found both linear and non-linear trends. Nevertheless, when we approximated (F10.7) 2 and (SSN) 2 coefficients, linear trends in vTEC were dominant. The anticipated and observed vTEC measurements are in moderately good agreement.

In this study, a TEC variation window value was selected based on the wavelet power spectrum method to analyze the seismic–ionospheric coupling relationship. In the full-time domain, a 27-day periodicity of the wavelet power spectrum was obtained that passed the 95% significance test. The sliding interquartile range method was used to analyze earthquakes above Mw6.5 in Japan from 2011 to 2022, excluding the hybrid effects between earthquakes close to one another. The sunspot number (SSN), 10.7 cm radio flux (F10.7), total solar irradiance (TSI), solar wind velocity (Vsw), geomagnetic activity index in the equatorial region (DST), and global geomagnetic activity index (KP) were used as indices representing solar and geomagnetic activity. After removing solar and geomagnetic interference from ionospheric anomaly changes using the sliding interquartile range method, the TEC anomaly changes before the earthquake were verified as being caused by the earthquake and analyzed. The statistical analysis of ionospheric total electron content (TEC) anomalies showed that earthquake magnitude was positively correlated with the amplitude of TEC anomalies but not linearly. The occurrence time of ionospheric anomalies lagged behind to some extent with the increase in earthquake magnitude. Additionally, abnormal changes on the 29th day (15 February 2022) before the 20th earthquake did not conform to previous research rules. According to the lithosphere–atmosphere–ionospheric coupling (LAIC) mechanism and global ionospheric map (GIM) studies, the TEC anomaly was consistent with the vertical projection of the epicenter with obvious regularity. The results show that these TEC anomalies may be related to earthquakes.

This paper presents a comparison of the vertical total electron content (vTEC) estimated over Italy using two different approaches: the GPS Global Ionosphere Maps (GIMs) and the so-called “calibration technique” developed by Ciraolo in 2007. The study has been carried out at a regional level by considering three Italian dual-frequency stations of the GPS permanent network “Rete Integrata Nazionale GPS (RING)”. The GPS receivers are permanently installed at Madesimo (geographical coordinates: 46.5 N, 9.4 E), Rome (geographical coordinates: 41.8 N, 12.5 E) and Resuttano (geographical coordinates: 37.7 N, 14.1 E), respectively in the north, center and south of Italy. Time windows selected for the analysis include periods of both low (July 2008 to June 2009) and high (September 2013 to August 2014) solar activity. The two datasets have also been studied considering both quiet and disturbed geomagnetic activity conditions. Moreover, the effects of an extreme geomagnetic storm have been investigated in March 2015 when the well-known St. Patrick storm occurred. Overall, GIM estimated values are always higher than those calibrated by the Ciraolo procedure for all the considered datasets. The differences between the two methods increase as the latitude decreases, and they increase as the solar activity intensifies. The outcomes of this study shall be helpful when applying GlMs at a regional level.

The effects of sharp variations in geomagnetic and solar activity at high latitudes on human brain bioelectrical activity were studied using a multichannel EEG structural function. Studies were performed on 10 healthy men aged 19–37 years. EEG recordings were made daily for 25 days. Solar flares of classes C and M occurred during the study period, as did geomagnetic storms of levels G2–G3. A first-order temporal structural function (SF) in eight-dimensional space was calculated from the EEG. The time scales of internal correlations in the multichannel EEG were assessed using the radius of the correlation of the SF, while the spatial correlational structure of the EEG was assessed in terms of the SF asymptote. Variations in geomagnetic activity were found to be reflected more in changes in the correlation radius than the level of the SF asymptote. Perturbing and modulating effects of geomagnetic and solar activity on SF parameters and the SF spectrum were identified. Thus, the SF of the multichannel EEG can be used to evaluate the integral reaction of the brain as a unified system to the actions of heliogeophysical factors and can be used in studies of the effects of the environment on humans.

We studied the inter-annual distributions of the nightglow intensities of the thermosphere atomic oxygen red 630.0 nm and green 557.7 nm lines observed from Abastumani during cloudless nights, the planetary geomagnetic Ap index, solar F 10.7 , and galactic cosmic rays (GCRs) flux. It is demonstrated that: on magnetically weakly disturbed/ quiet conditions (Ap < 12) in equinoctial months the red line intensities are minimal, while those of the green line are maximal; the red line intensity increases in May-July and is comparatively low in June, where, unlike most mid-latitude regions, the green line intensity is maximal. The red and green line intensities increase with growing solar activity but their behaviors stay the same, which is considered as a possible regional manifestation of lower and upper atmosphere vertical coupling. It was also detected that, for cloudless nights in June, the number of magnetically disturbed day-nights is maximal and the decrease of the GCRs flux is the biggest during a year.

So far, many efforts have been made to provide a reliable and robust mechanism for the occurrence of large earthquakes. In recent years, different studies have been conducted on the possible correlation between solar-terrestrial interactions and the occurrence of earthquakes. In this paper, the hypothesis that there is a correlation between solar-geomagnetic activities and powerful earthquakes first is investigated in three case studies, and then it is discussed by studying the variations of indices, including F10.7, Kp, ap, and Dst, before 333 large earthquakes (Mw ≥ 7.0) that occurred between 1 January 2000 and 28 April 2022. As the time series of the solar index follows special cycles, in another scenario, after removing the non-linear variations with fitting a polynomial, the anomalous F10.7 variations above and below the median ± 1.25 × interquartile ranges were considered. Although anomalies in solar and magnetic indices are observed in 33% of earthquakes one day before the occurrence, by analyzing 100 simulated data sets, we find that analogous anomalies can be found. Therefore, it can be concluded that there is no significant correlation between solar and geomagnetic indices and the occurrence of strong earthquakes. These findings could be effective in better defining alternative robust mechanisms for the occurrence of earthquakes that are more of internal origin than external to the Earth system.

Changes in solar and geogmagnetic activity (S-GMA) have been correlated with health effects. Geophysical processes link these activities; the environmental factors that foster the physical and biological effects are unknown. Occupational, animal, and human studies which elucidate the relationships with blood pressure, melatonin, cancer, reproductive disease, cardiac disease, and neurologicl disorders are explored. The Schumann Resonance signal, a global ULF/ELF signal was examined as a biophysical factor for these effects. There is a very high correlation with S-GMA indices of sunspot number and the Kp index and the Schumann Resonance signal.

We present results of a classical global induction analysis of the geomagnetic variation data in the range of daily Sq variations, as well as for long period variations within the period range of about 8 to 400 days. The Sq data from 88 to 94 world observatories are processed in two ways, first by constructing and analyzing average monthly daily variations for the whole months of the International Quiet Sun Year (IQSY) 1995, and second by analyzing the individual, especially quiet Q* daily records from the same year. The electrical images of the Sq response functions obtained via the Schmucker’s ρ* — z* procedure show a good fit with results of other induction studies, though especially our global impedance phases show a larger scatter than two other published data sets used for comparison. The long period variations from three 3-years’ intervals with different solar and geomagnetic activities and for 44 to 57 world observatories have been processed by power spectral and Fourier analyses, as well as by a simplified GDS approach. The induction response functions show a good correspondence with other deep induction studies, the seasonal processing did not, however, allow us to detect any significant effects of the solar/geomagnetic activity on the transfer functions. The obtained global geomagnetic induction functions along with other two published data sets are analyzed by a bayesian Monte Carlo analysis for the mantle conductivity distribution. We use a modified version of the Monte Carlo method with Markov chains based on an effective, data adaptive Metropolis sampling approach, and simulate samples from the posterior probability distribution of the resistivities in the mantle. Stochastic sampling provides comprehensive maps of the parameter space based on fairly ranking the models according to their ability to explain the experimental data, as well as on respecting the prior information on the model parameters. From four generally formulated and tested priors for the mantle resistivities, the non-informative distribution on strictly increasing conductance is the most non-restricting prior that, at the same, avoids the non-likely high-resistivity tails in the marginal resistivity distributions. A prediction power of the Monte Carlo sampling approach is demonstrated by a comparison of published maximum likelihood bounds on average conductivities in specific mantle zones with those produced simply by computing the average conductivities from the Markov chain of models.

Cyclic outbreaks of accumulation of paralytic shellfish poisoning (PSP) toxins in mussels attributed to Gymnodinium catenatum blooms displayed several of the highest inter-annual maxima coincidental with the minima of the 11-year solar sunspot number (SSN) cycle. The monthly distribution of PSP was associated with low levels of the solar radio flux, a more quantitative approach than SSN for fluctuations in solar activity. Comparison between monthly distribution of PSP and other commons biotoxins (okadaic acid, dinophysistoxin-2, and amnesic shellfish poisoning toxins) demonstrated that only PSP was significantly associated with low levels of radio flux ( p < 0.01). PSP occurrence suggests a prior decline in solar activity to be required as a trigger, similarly to a photoperiodic signal. The seasonal frequency increased towards autumn during the study period, which might be related to the progressive atmospheric cutoff of deleterious radiation associated with the seasonal change in solar declination, and might play an additional role in seasonal signal-triggering. PSP distribution was also associated with low levels of the geomagnetic index A a. Comparison between monthly distributions of PSP and other common biotoxins also demonstrated that only PSP was significantly associated with low levels of the A a index ( p < 0.01). In some years of SSN minima, no significant PSP outbreaks in mussels were detected. This was attributed to a steady rise in geomagnetic activity that could disrupt the triggering signal. Global distribution patterns show that hotspots for G. catenatum blooms are regions with deficient crustal magnetic anomalies. In addition to the variable magnetic field mostly of solar origin, static fields related to magnetized rocks in the crust and upper mantle might play a role in restricting worldwide geographic distribution.