Geomagnetic Activity Parameters Research Articles

Machine learning approach for prediction of ionospheric irregularities on ROTI index over the Northern anomaly crest in Egypt during solar cycle 24

This paper reports the prediction results of the ionospheric irregularities represented by the ROTI index close to the equatorial ionization anomaly's Northern peak. A feedforward backpropagation Neural Network (NN) approach is implemented using a time series Nonlinear Autoregressive approach with Exogenous inputs (NARX). We used the data from a dual frequency GPS-SCINDA station located at Helwan (geographic coordinates of 29.86°N, 31.32°E, and MLAT of 29.94°N) in Egypt. To allow the model to be independently tested during varying levels of solar activities, we collected a 5-minute resolution of ROTI data for the solar cycle 24 from 2009 to 2017. The factors that influence the development of ionospheric irregularities are involved in the established model representing the diurnal and seasonal variations as well as solar and geomagnetic activity parameters. To support learning, we included IRI-foF2 and IRI-hmF2 parameters in the input layer neurons to improve the model learning about the behavior of the ionospheric F layer. The results show that the NN-ROTI values precisely match the GPS-ROTI values with an RMSE of 0.106 TECU/min and a prediction efficiency of 95%. The predicted values are highly correlated with the originals, with a regression of 0.89. Furthermore, the irregularities were more prevalent during the equinox months than during the solstice months. It is also observed that predicted NN-ROTI values in all seasons have RMSEs less than 0.03 and 0.05 TECU/min for the low and high solar activity, respectively. The results also showed a clear correlation between solar activity and the occurrence percentage of ionospheric irregularities indicating a solar cycle dependency. The prediction values of the NN-ROTI occurrence % demonstrated a remarkable correlation with the observed GPS-ROTI occurrence % across SC24.

Forbush decreases and geomagnetic disturbances: 2. Comparison of solar cycles 23–24 and events with sudden and gradual onset

Statistical relationships between the values of geomagnetic indices and the characteristics of cosmic rays and interplanetary disturbances are studied for Forbush decreases with sudden and gradual onset associated with different types of solar sources: a) coronal mass ejections from active regions accompanied by solar flares; b) filament eruptions outside active regions; c) high-speed streams from coronal holes; d) several sources. Using statistical methods, the dependence of geomagnetic indices on cosmic ray and solar wind parameters for Forbush decreases in solar cycles 23 and 24 is also compared. The results obtained showed: a) interplanetary disturbances associated with coronal mass ejections from active regions cause mainly magnetic storms with a sudden onset; b) interplanetary disturbances associated with high-speed streams from coronal holes cause mainly storms with a gradual onset; c) interplanetary disturbances associated with filament eruptions outside active regions cause equally probable storms with a sudden and gradual onset. For sporadic Forbush decreases the values of cosmic ray and geomagnetic activity parameters are, on average, higher for events with a sudden onset; for recurrent Forbush decreases, the nature of the event onset does not affect the value of these parameters. For all types of solar sources the parameters of the disturbed solar wind are, on average, higher in events with a sudden onset. The geoefficiency of interplanetary disturbances is much higher in the 23rd cycle for events associated with ejections from active regions; for other types of disturbances, the difference between the cycles is weak.

Analysis of ionospheric TEC response to solar and geomagnetic activities at different solar activity stages

Studying the relationship of total electron content (TEC) to solar or geomagnetic activities at different solar activity stages can provide a reference for ionospheric modeling and prediction. On the basis of solar activity indices, geomagnetic activity parameters, and ionospheric TEC data at different solar activity stages, this study analyzes the overall variation relationships of solar and geomagnetic activities with ionospheric TEC, the characteristics of the quasi-27-day periodic oscillations of the three variables at different stages, and the delayed TEC response of solar activity by conducting correlation analysis, Butterworth band-pass filtering, Fourier transform, and time lag analysis. The following results are obtained. (1) TEC exhibits a significant linear relationship with solar activity at different solar activity stages. The correlation coefficients |R| are arranged as follows: |R|EUV > |R|F10.7 > |R|sunspot number. No significant linear relationship exists between TEC and geomagnetic activity parameters (|R| < 0.35). (2) TEC, solar activity indices, and geomagnetic activity parameters have a period of 10.5 years. The maximum amplitudes of the Fourier spectrum for TEC and solar activity indices are nearly 27 days and those of geomagnetic activity parameters are nearly 27 and 13.5 days. (3) The deviations of the quasi-27-day significant periodic oscillation of TEC and solar activity indices are consistent. (4) No evident relationship exists between the quasi-27-day periodic oscillation of TEC and geomagnetic activity parameters. (5) The delay time of TEC for the 10.7 cm solar radio flux and extreme ultraviolet is always consistent, whereas that for sunspot number varies at each stage.

A comparative study on geoeffective and non-geoeffective corotating interaction regions

A long database of corotating interaction regions (CIRs) is used to investigate their geoeffectiveness. Among 290 CIR events identified during Solar Cycle 24 (2008–2019), 88 (30%) are found to be geoeffective in causing geomagnetic storms with the symmetric ring current index [SYM-H] peak ⩽-50nT, and 202 (70%) are non-geoeffective with the minimum SYM-H >-50nT. Based on a comparative study of the geoeffective and non-geoeffective CIRs, following results are obtained. Geoeffective and non-geoeffective CIRs have comparable duration (28±15hours, 26±14hours, respectively) and radial extent (0.33±0.17AU, 0.30±0.17AU, respectively), on average. While the mean solar-wind plasma speed during the geoeffective (503±70km s−1) and non-geoeffective (491±63km s−1) CIRs exhibits no statistical difference, the geoeffective CIRs have ≈25% higher peak plasma density, ≈45% higher ram pressure, ≈42% higher temperature, ≈39% higher interplanetary magnetic field (IMF) magnitude, ≈57% stronger IMF southward component, and ≈61% stronger reconnection electric field than the non-geoeffective events, on average. The auroral electrojet index [AE] and SYM-H are found to be, respectively, ≈58% and ≈192% stronger during the geoeffective CIRs than the non-geoeffective events. The typical characteristic solar-wind and geomagnetic activity parameters given in this article can be useful for space weather modeling and prediction purposes.

The Role of Solar Activity in Endothelial Activation and Inflammation in the NAS Cohort

BACKGROUND AND AIM: Solar activity, which induces disturbances of the Earth’s magnetic field, periodically oscillates between minimum and maximum sunspot activity in cycles of approximately 11-years. Exposure to broad-spectrum electromagnetic solar activity can adversely affect human physiology, leading to adverse health outcomes. Recent epidemiological studies have shown that solar and geomagnetic activity are associated with chronic diseases, including cardiovascular diseases (CVD). However, the impact of solar activity on biomarkers for CVD, including biomarkers for endothelial function and inflammation in a large cohort, has not been previously studied. This study investigated the associations between solar and geomagnetic activity and circulating biomarkers of systemic inflammation and endothelial activation in the Normative Aging Study (NAS) cohort. METHODS: Mixed effects models with moving day averages from day 0 to day 28 were used to study the associations between solar activity [sunspot number (SSN) and interplanetary magnetic field (IMF)], geomagnetic activity [planetary K index (Kp index)] and various inflammatory and endothelial markers. Biomarkers included intracellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), C-reactive protein (CRP), and fibrinogen. RESULTS: After adjusting for demographic and meteorological variables, we observed significantly positive associations between sICAM-1 and sVCAM-1 concentrations and solar and geomagnetic activity parameters: IMF, SSN, and Kp index. Additionally, a negative association was observed between fibrinogen and Kp index and a positive association was observed for CRP and SSN. CONCLUSION: These results demonstrate that solar and geomagnetic activity might be upregulating endothelial activation and inflammation. KEYWORDS: Endothelial Activation, Inflammation, Solar Activity, Geomagnetic Activity, Geomagnetic Disturbance

The role of solar and geomagnetic activity in endothelial activation and inflammation in the NAS cohort.

This study investigated the associations between solar and geomagnetic activity and circulating biomarkers of systemic inflammation and endothelial activation in the Normative Aging Study (NAS) cohort. Mixed effects models with moving day averages from day 0 to day 28 were used to study the associations between solar activity (sunspot number (SSN), interplanetary magnetic field (IMF)), geomagnetic activity (planetary K index (Kp index), and various inflammatory and endothelial markers. Biomarkers included intracellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), C-reactive protein (CRP), and fibrinogen. After adjusting for demographic and meteorological variables, we observed significant positive associations between sICAM-1 and sVCAM-1 concentrations and solar and geomagnetic activity parameters: IMF, SSN, and Kp. Additionally, a negative association was observed between fibrinogen and Kp index and a positive association was observed for CRP and SSN. These results demonstrate that solar and geomagnetic activity might be upregulating endothelial activation and inflammation.

Regional Refined Long-Term Predictions Method of Usable Frequency for HF Communication Based on Machine Learning Over Asia

Due to the unique advantages of long-distance, non-relay, and flexible deployment, high frequency (HF) communication plays a vital role in military communication, disaster relief, and global broadcasting, etc. To satisfying the spectrum planning requirement for the next generation intelligent HF communication system, the machine learning method is introduced to develop the long-term prediction method of the usable working frequency for HF wireless communication. Especially, the refined mapping model of maximum usable frequency (MUF) propagation factor for one hop on the F2 layer is first reconstructed by using the statistical machine learning method. Then, the new mapping models of conversion factors of optimum working frequency (OWF) and the highest probable frequency (HPF) are proposed by using the fine-grained solar activity parameters and coupling with two geomagnetic activity parameters. This proposed model has higher prediction accuracy for the MUF, OWF, and HPF over Asia. Compared with the International Telecommunication Union (ITU) recommended model, the root-mean-square errors of MUF, OWF, and HPF are reduced by 1.18, 1.64, and 1.06 MHz, and the accuracies are improved by 10.89%, 15.47%, and 9.10%, respectively. The proposed model can achieve intelligent frequency planning for HF communication and has great potential in terms of improving HF communication quality, reliability, and efficiency.

Geomagnetic disturbances reduce heart rate variability in the Normative Aging Study

BackgroundSolar and geomagnetic activity (GA) have been linked to increased cardiovascular (CVD) events. We hypothesize that heart rate variability (HRV) may be the biological mechanism between increased CVD risk and intense geomagnetic disturbances (GMD). MethodsTo evaluate the impact of GA and intense GMD on HRV in 809 elderly men [age mean 74.5 (SD = 6.8)] enrolled in the Normative Aging Study (Greater Boston Area), we performed repeated-measures using mixed-effects regression models. We evaluated two HRV outcomes: the square root of the mean squared differences of successive normal-to-normal intervals (r-MSSD) and the standard deviation of normal-to-normal heartbeat intervals (SDNN) in milliseconds (ms). We also compared the associations between Kp and HRV in patients with and without comorbidities such as diabetes and coronary heart diseases (CHD). We used data on global planetary K-Index (Kp) from middle latitudes as a GA and GMD (>75th Kp) parameters from the National Oceanic and Atmospheric Agency's Space Weather Prediction Center. ResultsWe found a near immediate effect of continuous and higher Kp on reduced HRV for exposures up to 24 h prior to electrocardiogram recording. A 75th percentile increase in 15-hour Kp prior the examination was associated with a −14.7 ms change in r-MSSD (95 CI: −23.1, −6.3, p-value = 0.0007) and a −8.2 ms change in SDNN (95 CI: −13.9, −2.5, p-value = 0.006). The associations remained similar after adjusting the models for air pollutants over the exposure window prior to the event. In periods of intense GMD, the associations were stronger in patients with CHD and non-diabetes. ConclusionsThis is the first study to demonstrate the potential adverse effects of geomagnetic activity on reduced heart rate variability in a large epidemiologic cohort over an extended period, which may have important clinical implications among different populations.

Deep Learning for Global Ionospheric TEC Forecasting: Different Approaches and Validation

AbstractThe application of deep learning technology to ionospheric prediction has become a new research hotspot. However, there are still some gaps, such as the prediction effect with different input solar and geomagnetic activity parameters, and the forecast accuracy with different prediction methods as well as the validation of long period data results, to be filled. We developed an ionospheric long short‐term memory network (Ion‐LSTM) with multiple input parameters to predict the global ionospheric total electron content (TEC). Two solutions with different ionospheric data based on Ion‐LSTM were assessed, namely spherical harmonic coefficients (SHC) and vertical TEC (VTEC) prediction solution. The results show two solutions, both perform well in accuracy and stability. The input of the geomagnetic activity index improves the prediction effect of the model in the storm period. For the 1‐ and 2‐day‐predicted global ionospheric maps (GIMs) from 2015 to 2020, the root mean square error (RMSE) of SHC prediction solution is 1.69 TECU and 1.84 TECU while that of the VTEC prediction solution is 1.70 TECU and 1.84 TECU, respectively. Over 70% of the absolute residuals are within 3 TECU in high solar activity and over 96% in low solar activity. Further, by comparing the predicted results between Ion‐LSTM and conventional methods (e.g., Center for Orbit Determination in Europe (CODE) predicted GIMs), the evaluation results show that the RMSE of Ion‐LSTM is 0.7 TECU lower than that of CODE predicted GIMs under different solar and geomagnetic activities. Additionally, the accuracy of the Ion‐LSTM prediction results decreases slightly as the input time span increases.

Prediction and Understanding of Soft-proton Contamination in XMM-Newton: A Machine Learning Approach

Abstract One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes are few tens to hundreds of keV (soft) protons concentrated by the mirrors. One such telescope is the European Space Agency’s (ESA) X-ray Multi-Mirror Mission (XMM-Newton). Its observing time lost due to background contamination is about 40%. This loss of observing time affects all the major broad science goals of this observatory, ranging from cosmology to astrophysics of neutron stars and black holes. The soft-proton background could dramatically impact future large X-ray missions such as the ESA planned Athena mission (http://www.the-athena-x-ray-observatory.eu/). Physical processes that trigger this background are still poorly understood. We use a machine learning (ML) approach to delineate related important parameters and to develop a model to predict the background contamination using 12 yr of XMM-Newton observations. As predictors we use the location of the satellite and solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in the southern direction, Z (XMM-Newton observations were in the southern hemisphere), the solar wind radial velocity, and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the first two individual predictors and an ML model that utilizes an ensemble of the predictors (Extra-Trees Regressor) and gives better performance. Based on our analysis, future missions should minimize observations during times associated with high solar wind speed and avoid closed magnetic field lines, especially at the dusk flank region in the southern hemisphere.

Correlation of the Cosmic-Ray Cutoff Rigidity with Heliospheric and Geomagnetic-Activity Parameters at Different Phases of a Magnetic Storm in November 2004

The correlation of the variations in geomagnetic cutoff rigidity of cosmic rays ΔR with the interplanetary medium parameters and geomagnetic activity indices Dst and Kp was calculated for different phases of the superstorm on November 7–8, 2004. The strongest correlation was observed between the cutoff rigidity and Dst at all stages of storm development (correlation coefficients k ≈ 0.70–0.98); some stable influence of the solar wind (SW) density N (k ≈ 0.50–0.80) should also be noted. The dependence of the cutoff-rigidity variation on all of the dynamic parameters of the SW is observed in the main storm phase and is especially strong for the density N and pressure P. The correlation between ΔR and V is negative in all phases, while the correlation of ΔR with N and P is positive during the main phase and negative in the recovery phase. The cutoff-rigidity variations showed no sensitivity to the Bz component of the interplanetary magnetic field (IMF), the azimuthal component By, or the IMF absolute value B before the storm or in its main phase. A significant correlation or anticorrelation of ΔR with B and all the IMF components is observed only in the recovery period. The specific response of the geomagnetic cutoff rigidity to the heliospheric and magnetospheric parameters at different phases of the magnetic storm is apparently determined by the different relative contributions of the magnetospheric global current systems during these periods.

Influence of the Solar Wind and Geomagnetic Activity Parameters on Variations in the Cosmic Ray Cutoff Rigidity during Strong Magnetic Storms

The correlation between the variations of geomagnetic cutoff rigidity ΔR and interplanetary parameters and the Dst index of geomagnetic activity during one moderate and six strong storms of solar cycles 23 and 24 has been calculated. The ΔR values have been obtained with two methods: (1) the spectrographic global survey method (SGS), in which the determination of the cutoff rigidity RSGS is based on observational data from the neutron monitor network, and (2) a method in which the particle trajectories are calculated numerically in a model magnetic field of the magnetosphere to determine the cutoff rigidity Reff. In general, the results obtained by the two methods are in close agreement. The Dst index of geomagnetic activity has the greatest effect on ΔR, and the correlation increases with storm intensity. The sensitivity of ΔR to interplanetary parameters vary greatly for different storms. The most geoeffective interplanetary parameter is the solar-wind speed V. A significant anticorrelation of ΔR and V can be traced for almost all storms. The correlation of ΔRSGS with the Bz component of the interplanetary magnetic field is observed only for two storms, on November 7–14, 2003, and November 7–8, 2004, for which the absolute Bz value was very high (≈−50 nT). At the same time, there is a rather high correlation of ΔReff with Bz for most storms. The azimuthal component of the interplanetary field By and the solar-wind dynamic pressure P show almost no connection with ΔR.

Analysis of sea level changes in the Caspian Sea related to Cosmo-geophysical processes based on satellite and terrestrial data

Analysis results of the average annual sea levels in the Caspian Sea obtained from ground and satellite observations, corresponding to solar activity characteristics, magnetic field data, and length of day are presented. Spectra of the indicated processes were investigated and their approximation models were also built. Previously assumed statistical relationships between space-geophysical processes and Caspian Sea level (CSL) changes were confirmed. A close connection was revealed between the low-frequency models of the solar and geomagnetic activity parameters and the CSL changes. Predictions extending into the next decades showed a high probability of an increase in the CSL and a decrease of the compared space-geophysical parameters.

RESPONSE OF BIOLOGICAL SYSTEMS TO GEOMAGNETIC STORMS

At present, influence of weak magnetic fields associated with solar and geomagnetic activity on biological systems is gaining more interest. Taking into account the accumulated data on the influence of geomagnetic storms on different biological levels, it is obvious that the mechanism of influence is universal. One of the approaches in this search may be the study of patterns and differences in the response to geomagnetic storms of various biological objects. As a research material served: data on the number of ambulance calls in the city of Irkutsk for acute myocardial infarction, cerebral infarction; results of retrospective analysis of the number of spontaneous parturition of the city of Irkutsk; data on the motion activity of fruit fly Drosophyla melanogaster, obtained by automated monitoring. The investigated indicators were compared with the parameters of geomagnetic activity at different time scales. As indicators of geomagnetic storms, three-hour (ap) and daily (Ap) equal to the average amplitude of variation of the geomagnetic field of the Earth. In the case of comparing the motion activity of fruit flies with magnetic storms, the local companions of the Earth’s magnetic field were additionally considered according to the data of the Irkutsk magnetic observatory. As a result of the conducted studies it was established that the detected response of biological systems depends on the characteristics of the state of the Earth’s magnetic field, which falls on the period of passage of magnetic storms. The obtained data also indicate possible gender differences in the response to the effects of the geomagnetic factor by organisms of different levels.

Electron Flux Enhancements at L = 4.2 Observed by Global Positioning System Satellites: Relationship With Solar Wind and Geomagnetic Activity

AbstractDetermining solar wind and geomagnetic activity parameters most favorable to strong electron flux enhancements is an important step toward forecasting radiation belt dynamics. Using electron flux measurements from Global Positioning System satellites at L = 4.2 in 2009–2016, we seek statistical relationships between flux enhancements at different energies and solar wind dynamic pressure Pdyn, AE, and Kp, from hundreds of events inside and outside the plasmasphere. Most ≥1‐MeV electron flux enhancements occur during nonstorm (or weak storm) times. Flux enhancements of 4‐MeV electrons outside the plasmasphere occur during periods of low Pdyn and high AE. We perform superposed epoch analyses of Global Positioning System electron fluxes, along with solar wind and geomagnetic indices, 40‐keV electron flux, ultralow frequency (ULF) wave index from Geostationary Operational Environmental Satellite, and chorus wave intensity from the Van Allen Probes and Time History of Events and Macroscale Interactions during Substorms mission. We demonstrate that 4‐MeV electron flux enhancements outside the plasmasphere start when the interplanetary magnetic field (Bz) reaches a minimum and develop during periods of low Pdyn, high AE, low but increasing Dst, moderate ULF wave index, and intense chorus waves. Flux enhancements at 100 keV occur under conditions with higher Pdyn, higher ULF wave index, and elevated 40‐keV electron flux at L = 6.6. Moreover, electron flux enhancements take much more time to develop at higher energies. This suggests that 100‐keV flux enhancements are dominated by injections, while MeV electron energization is predominantly induced by chorus waves with further amplification by inward transport.

Role of the solar wind parameters in changing orbital motion of the Earth’s satellites

The investigation of the solar wind and geomagnetic activity parameters' effect on variations of the orbital motion periods of artificial satellites has been continued. The periods of orbital motion of uncontrolled satellites from the database of the Ukrainian network of optical stations (UNOS) for 2012–2014 was used. The data have been compared with the values of geomagnetic planetary index K and the energy spectra of protons and electrons obtained by the GEOS satellites in events during which the orbital periods have changed. It is shown that, in the energy spectra of the proton and electron fluxes, there is no effect of softening the spectrum with time at the time of the flare appearance. This indicates the possibility of particle accumulation above the active region (AR), which entails further continuous energy emission of the solar flare from AR. Dependences have been obtained between the geomagnetic activity and the solar wind speed at a given interplanetary magnetic field strength during the periods under study for the changes in the orbital motion periods of satellites. The corresponding correlation coefficients are 0.93–0.96.

Geomagnetic Effects of Corotating Interaction Regions

We present an analysis of the geoeffectiveness of corotating interaction regions (CIRs), employing the data recorded from 25 January to 5 May 2005 and throughout 2008. These two intervals in the declining phase of Solar Cycle 23 are characterised by a particularly low number of interplanetary coronal mass ejections (ICMEs). We study in detail how four geomagnetic-activity parameters (the Dst, Ap, and AE indices, as well as the Dst time derivative, $\mathrm{dDst}/\mathrm{d}t$ ) are related to three CIR-related solar wind parameters (flow speed, $V$ , magnetic field, $B$ , and the convective electric field based on the southward Geocentric solar magnetospheric (GSM) magnetic field component, $\mathit{VB}_{s}$ ) on a three-hour time resolution. In addition, we quantify statistical relationships between the mentioned geomagnetic indices. It is found that Dst is correlated best to $V$ , with a correlation coefficient of $\mathrm{cc}\approx0.6$ , whereas there is no correlation between $\mathrm{dDst}/\mathrm{d}t$ and $V$ . The Ap and AE indices attain peaks about half a day before the maximum of $V$ , with correlation coefficients ranging from $\mathrm{cc}\approx0.6$ to $\mathrm{cc}\approx0.7$ , depending on the sample used. The best correlations of Ap and AE are found with $\mathit{VB}_{s}$ with a delay of 3 h, being characterised by $\mathrm{cc}\gtrsim 0.6$ . The Dst derivative $\mathrm{dDst}/\mathrm{d}t$ is also correlated with $\mathit{VB}_{s}$ , but the correlation is significantly weaker $\mathrm{cc}\approx 0.4$ – 0.5, with a delay of 0 – 3 h, depending on the employed sample. Such low values of correlation coefficients indicate that there are other significant effects that influence the relationship between the considered parameters. The correlation of all studied geomagnetic parameters with $B$ are characterised by considerably lower correlation coefficients, ranging from $\mathrm{cc}=0.3$ in the case of $\mathrm{dDst}/\mathrm{d}t$ up to $\mathrm{cc}=0.56$ in the case of Ap. It is also shown that peak values of geomagnetic indices depend on the duration of the CIR-related structures. The Dst is closely correlated with Ap and AE ( $\mathrm{cc}=0.7$ ), Dst being delayed for about 3 h. On the other hand, $\mathrm{dDst}/\mathrm{d}t$ peaks simultaneously with Ap and AE, with correlation coefficients of 0.48 and 0.56, respectively. The highest correlation ( $\mathrm{cc}=0.81$ ) is found for the relationship between Ap and AE.

Frequency-modulated solar rotational periodicity of geomagnetic indices

Abstract Many attempts have been made to search for various timescales in the power spectrum of geomagnetic indices so that common periodicities in the solar activity and geomagnetic activity indices are identified. The spectral behavior of geomagnetic activity parameters may also provide invaluable information about physical processes involved. In this study we attempt to demonstrate that the frequency modulation associated with a long-term variation may cause extra sidelobes around the principal peak with a periodicity of ∼ 27 d in the observed power spectrum of geomagnetic activity indices, and/or may even split the peak into two adjacent peaks. We employ a straightforward model of an oscillation frequency-modulated by an arbitrary agent to consider the solar rotational periodicity of geomagnetic indices. As a result, we have found that the peak with the periodicity of ∼ 27 d in the observed power spectrum of geomagnetic indices seems likely frequency-modulated by the amount of 0.0026 d−1 which corresponds to a ∼ 1 yr period. We thus suggest that the fundamental period of the periodic perturbative agent is much longer than a year according to our analysis. Finally, we conclude by discussing the implications of what we have found.

A study on the various types of arrhythmias in relation to the polarity reversal of the solar magnetic field

Over the last few years, various researches have reached the conclusion that cosmic ray variations and geomagnetic disturbances are related to the condition of the human physiological state. In this study, medical data concerning the number of incidents of different types of cardiac arrhythmias for the time period 1983–1992, which refer to 1902 patients in Tbilisi, Georgia, were used. The smoothing method and the Pearson r-coefficients were used to examine the possible effect of different solar and geomagnetic activity parameters and cosmic ray intensity variations on the different types of arrhythmias. The time interval under examination was separated into two different time periods, which coincided with the polarity reversal of the solar magnetic field occurred in the years 1989–1990, and as a result, a different behavior of all the above-mentioned parameters as well as of the different types of arrhythmias was noticed during the two time intervals. In addition, changing of polarity sign of the solar magnetic field was found to affect the sign of correlation between the incidence of arrhythmias and the aforementioned parameters. The primary and secondary maxima observed in the solar parameters during the solar cycle 22, also appeared in several types of arrhythmias with a time lag of about 5 months.

Traffic accident in India in relation with solar and geomagnetic activity parameters and cosmic ray intensity (1989 to 2010)

We studied the relation between deaths due to traffic accident in India and geomagnetic activity indices: Kp, Ap, Dst and solar activity (SA) parameters, sun spot number, solar flare index (FI), coronal index (CI) and yearly average of cosmic ray intensity, observed during the period of 1989-2011. It is seen that rate of death by traffic accident are well correlated with these parameters. We have found large negative correlation with correlation coefficient of -0.84,-0.79 between rate of death by traffic accident and Kp and Ap indices; large positive correlation with correlation coefficient 0.79 rate of death by traffic accident and Dst index. Further good medium correlation with correlation coefficient of -0.56,-0.60.-0.56 has been found between rate of death by traffic accident and yearly average of sunspot number, solar flare index and coronal index respectively. A positive correlation with correlation coefficient of 0.69 between rate of death by traffic accident and yearly average of cosmic ray intensity was also obtained. Key words: Sunspot numbers, solar flare index, coronal index, cosmic ray intensity, Ap index, Kp index, Dst index, traffic accident death.