H-Component Variations Induced by Geomagnetic Storms during Solar Cycle 24: Insights from TAM Observatory

Large geomagnetic storms of extreme solar event periods in solar cycle 23

Coronal mass ejections: a driver of severe space weather

We present a statistical analysis of the geomagnetic storm (GMSs) with the solar activity features (Sunspot number (SN), H-α flare and coronal mass ejection (CME)) during solar cycle 23 and 24. Sunspot number (SN) shows good correlation with peak values of GMSs indices (correlations coefficient R= 0.76) while CME(R=0.59) and H-α (R=0.55) show moderate correlation. So we conclude that GMSs have good correlation with solar activity features during major geomagnetic storms of solar cycle 23 and 24. These parameters may act as reliable indicators for predicting GMSs and their strength. We have also correlated peak values of various geomagnetic indices among themselves with the highest correlations between Dst-ap (R=0.80) and A.E-ap (R=0.71). We have analyzed the GMSs data during different phases of the solar cycle 23 and 24 and concluded that CMEs are more important drivers of GMSs during the maximum phase of solar cycle while CIR are more significant drivers of GMSs during the decay phase. Keywords: GMSs, Solar Cycle, GI indices Cite this Article Bimal Pande, Mahesh Chandra Mathpal, Seema Pande. Statistical Analysis of Geomagnetic Activity and Solar Activity Features during Solar Cycle 23 & 24. Research & Reviews: Journal of Physics . 2017, 6(2): 14–20p.

Approaching the peak year of the 25th solar activity cycle, the frequency of strong geomagnetic storms is gradually increasing, which seriously affects the navigation and positioning performance of GNSS. Based on the globally distributed GNSS station data and FORMOSAT-7/COSMIC-2 occultation data, this paper explores for the first time the effects of the G4-class geomagnetic storm that occurred on 23–24 April 2023 on the global ionosphere, especially the ionospheric equatorial anomalies and F-layer perturbations. It reveals the precise point positioning (PPP) accuracy degradation during a geomagnetic storm. The results show that the ionospheric rate of total electron content index (ROTI) and near high latitude GNSS phase scintillations index have varying levels of perturbation during geomagnetic storms, with the maximum ROTI and phase scintillations index exceeding 0.5 TECU/min and 0.8, respectively. The equatorial ionization anomaly (EIA) shows an enhanced state (positive ionospheric storms) during geomagnetic storms, and the cause of this phenomenon is most likely the equatorward neutral wind. The variation of the S4 index of the FORMOSAT-7/COSMIC-2 satellite reveals the uplift of the F-layer during geomagnetic storms. During geomagnetic storms, the PPP accuracy degrades most seriously at high latitudes, the maximum MAE exceeds 2.3 m, and the RMS in the three-dimensional (3D) direction exceeds 2.0 m. These investigations can provide case support for space weather and GNSS studies of the impact of geomagnetic storms during peak solar activity years.

It was in the mid-1800s that extraordinary, worldwide disturbances in the Earth's magnetic field were coined “geomagnetic storms.” It would not be too much of an exaggeration to state that space weather predictions originated in early studies of geomagnetic storms. The effects of geomagnetic storms in space surrounding Earth result from a chain of processes involving flow/transformation of solar wind energy, and electrodynamic coupling among the interplanetary medium, magnetosphere, ionosphere, and upper atmosphere. The importance of predicting geomagnetic storms lies not only in its “academic” purposes in understanding physical processes in the solarterrestrial environment, but also in its practical aspects, influencing societal problems such as the effects on communications and satellite anomalies. This chapter discusses the characteristic signatures of geomagnetic storms, obtained from a number of statistical studies, and addresses recent major issues which impact directly our fundamental understanding of solar wind effects on magnetospheric and ionospheric processes, i.e., solar wind control of geomagnetic storms, storm/substorm relationships, ring current constituents, and solar cycle and seasonal dependence of geomagnetic storms. The following are the main points of the discussion: (1) Most of the Dst variance during intense geomagnetic storms can be reproduced by knowledge about changes in large-scale electric fields in the solar wind. A continuing controversy exists, however, as to whether the successive occurrence of substorms plays a direct role in the energization of storm-time ring current particles. (2) The increase in the ring current of about 50% of the largest geomagnetic storms goes through two steps at the main phase. The solar wind causes of this double enhancement in the ring current must be identified. (3) CMEs (coronal mass ejections) and CIRs (corotating interaction regions) appear to be the primary sources leading to major geomagnetic storms. These are dominant near the maximum phase and during the declining phase of the solar cycle, respectively. The 22-year solar cycle dependence of geomagnetic activity must also be quantitatively evaluated in terms of CMEs and CIRs. (4) Recent satellite observations in the inner magnetosphere have shown that the abundance of ionospheric origin ions is high and is correlated well with substorm activity during the main phase of geomagnetic storms. The relative importance of solar wind-origin and ionosphere-origin ions in constituting ring current particles is currently a critical unsolved question.

The effect of solar features on geospheric conditions leading to geomagnetic storms (GMSs) with planetary index,A P ≥ 20 and the range of horizontal component of the Earth’s magnetic fieldH such that 250γ <H < 400γ has been investigated using interplanetary magnetic field (IMF), solar wind plasma (SWP) and solar geophysical data (SGD) during the period 1978–99. Statistically, it is observed that maximum number of GMSs have occurred during the maximum solar activity years of 21st and 22nd solar cycles. A peculiar result has been observed during the years 1982, 1994 when sunspot numbers (SSNs) decrease very rapidly while numbers of GMSs increase. No distinct association between yearly occurrence of disturbed days and SSNs is observed. Maximum number of disturbed days have occurred during spring and rainy seasons showing a seasonal variation of disturbed days. No significant correlation between magnitude (intensity) of GMSs and importance ofH α , X-ray solar flares has been observed. Maximum number of GMSs is associated with solar flares of lower importance, i.e., SF during the period 1978-93.H α , X-ray solar flares occurred within lower helio-latitudes, i.e., (0–30)°N to (0–30)°S are associated with GMSs. NoH α , X-ray solar flares have occurred beyond 40°N or 40°S in association with GMSs. In helio-latitude range (10–40)°N to (10–40)°S, the 89.5% concentration of active prominences and disappearing filaments (APDFs) are associated with GMSs. Maximum number of GMSs are associated with solar flares. Coronal mass ejections (CMEs) are related with eruptive prominences, solar flares, type IV radio burst and they occur at low helio-latitude. It is observed that CMEs related GMS events are not always associated with high speed solar wind streams (HSSWSs). In many individual events, the travel time between the explosion on the Sun and maximum activity lies between 58 and 118 h causing GMSs at the Earth.

The abrupt decrease in cosmic ray intensity and disturbances in geomagnetic field are known as Forbush decreases (FDs) and Geomagnetic storms (GSs) respectively. We have selected the number of FDs and GSs during solar cycles 20–23. It is found that the occurrence of FDs follows the sunspot cycle 23, whereas the occurrence of GSs does not follow the sunspot cycle during the descending phase of solar cycle 23. The event of FDs has been observed to occur more in odd solar cycles in comparison to even solar cycles which show the even–odd asymmetry, whereas the occurrence of GSs increases with the progress of solar cycles from cycle 20–23. Similarly the grouped solar flare (GSF), solar flare index (SFI), bright solar flare and type II solar radio emission are positively correlated with sunspot cycles 20–23 whereas, the halo coronal mass ejections and type IV SREs show their peculiar behaviour in the descending phase of sunspot cycle 23. The occurrence of type IV SREs shows the even–odd asymmetry, whereas type II SREs increases with the progress of solar cycles. The sunspot number, GSF, SFI decreases as the solar cycle progresses from 20 to 23. In the present paper, the contradictory behaviour of FDs and GSs during cycle 23 has been presented in relation to solar parameters.

An Assessment of Solar Cycle 25 progress through observation of SRBs and associated Geomagnetic Storms

Relationship between interplanetary field/plasma parameters with geomagnetic indices and their behavior during intense geomagnetic storms

The distribution properties of great geomagnetic storms (Dst≤−200 nT) and super geomagnetic storms (Dst≤−300 nT) across the solar cycles (19–23) are investigated. The results show that 73.2% of the great geomagnetic storms took place in the descending phase of the solar cycles. 72.7% of super geomagnetic storms occurred in the descending phase of the solar cycles. About 83% of the great geomagnetic storms appeared during the period from the two years before solar cycle peak and the three years after solar cycle peak time. 90.9% of the super geomagnetic storms appeared between the two years before solar cycle peak and the three years after solar cycle peak. When a solar cycle is very strong, the phenomenon that great geomagnetic storms concentrated during the period from the two years before the solar cycle peak time to the three years after the solar cycle peak time is very prominent. The launch time of space science satellite is suggested according to the distribution properties of great geomagnetic storms and super geomagnetic storms in solar cycles.

A geomagnetic storm is a global disturbance of Earth's magnetosphere, occurring as a result of the interaction with magnetic plasma ejected from the Sun. Despite considerable research, a comprehensive classification of storms for a complete solar cycle has not yet been fully developed, as most previous studies have been limited to specific storm types. This study, therefore, attempted to present complete statistics for solar cycle 24, detailing the occurrence of geomagnetic storm events and classifying them by type of intensity (moderate, intense, and severe), type of complete interval (normal or complex), duration of the recovery phase (rapid or long), and the number of steps in the storm's development. The analysis was applied to data from ground-based magnetometers, which measured the Dst index as provided by the World Data Center for Geomagnetism, Kyoto, Japan. This study identified 211 storm events, comprising moderate (177 events), intense (33 events), and severe (1 event) types. About 36% of ICMEs and 23% of CIRs are found to be geoeffective, which caused geomagnetic storms. Up to four-step development of geomagnetic storms was exhibited during the main phase for this solar cycle. Analysis showed the geomagnetic storms developed one or more steps in the main phase, which were probably related to the driver that triggered the geomagnetic storms. A case study was additionally conducted to observe the variations of the ionospheric disturbance dynamo (Ddyn) phenomenon that resulted from the geomagnetic storm event of 2015 July 13. The attenuation of the Ddyn in the equatorial region was analyzed using the H component of geomagnetic field data from stations in the Asian sector (Malaysia and India). The variations in the Ddyn signatures were observed at both stations, with the TIR station (India) showing higher intensity than the LKW station (Malaysia).

The aim of this paper is to study the effect of solar wind parameters (solar wind speed \(V\), plasma flow pressure, and plasma density) on cosmic ray intensity and on geomagnetic storms for the period 1998–2005 (solar cycle 23). A Chree analysis by the superposed epoch method has been done for the study. From the present study we have found that the solar wind speed is a highly effective parameter in producing cosmic ray intensity decreases and geomagnetic storms. No time lag is found between cosmic ray intensity decreases, geomagnetic storms, and peak value of solar wind speed. Further, we have found that the plasma flow pressure is effectively correlated with geomagnetic storms but it is weakly correlated with cosmic ray intensity. The cosmic ray intensity and geomagnetic storms are found to be weakly correlated with plasma density. The decrease in cosmic ray intensity and geomagnetic storms takes place one day after the peak values of plasma flow pressure and plasma density. There is a time lag of one day between solar wind parameters (plasma flow pressure and plasma density) and cosmic ray intensity decrease, geomagnetic storms. Also, we have found a high correlation of cosmic ray intensity and geomagnetic storms with the product of interplanetary magnetic field \(B\) and solar wind speed \(V\) i.e. \(B\cdot V\). This study may be useful in predicting the space-weather phenomena.

The dependence of geomagnetic activity on solar features and interplanetary (IP) parameters is investigated. Sixty-seven intense (−200 nT ≤ Dst < −100 nT) and seventeen superintense (Dst < −200 nT) geomagnetic storms (GMSs) have been studied from January 1996 to April 2006. The number of intense and superintense GMSs show three distinct peaks during the 11-year period of 23rd solar cycle. The largest number of high strength GMSs are observed during maximum phase of solar cycle. Halo and partial halo CMEs are likely to be the major cause for these GMSs of high intensity. No relationship is observed between storm duration and the number of CMEs involved in its occurrence. The intensity of the GMS is also independent of the number of CMEs causing the occurrence of storm. These geoeffective CMEs show western and northern bias. Majority of the geoeffective CMEs are associated with X-ray solar flares (SFs). Solar and IP parameters, e.g., VCME, VSW, B, Bz (GSE and GSM coordinates) and their products, e.g., VSW · B and VSW · Bz are observed and correlated to predict the occurrence of intense GMSs. VCME does not seem to be the appropriate parameter with the correlation coefficient, r = −0.2 with Dst index, whereas the correlation coefficient, r = −0.57, −0.65, 0.75, −0.68 and 0.77 of the parameters VSW, B, Bz, VSW · B and VSW · Bz respectively, with Dst indicating that VSW · Bz and Bz may be treated as the significant contributors in determining the strength of GMSs.

Background/aim Recent research shows that not only geomagnetic storms (GS), but also other space weather events affect human health. The main goal of this research is to evaluate GS, solar wind (SW) velocity, and flow of stream interaction regions (SIR) in the formation of influence patients for acute coronary syndromes. Methods In research we used daily heliophysical data from 2001 till 2003 (maximum of 23 Solar cycle). The data of 1391 patients, who were hospitalised at the Hospital of Lithuanian University of Health Sciences, were used. Patient health variables were classified using binary state variables. The univariate associations between patients’ characteristics and space weather variables were analysed by using χ2 test and the logistic regression. The space weather variables were used as categorical: days of the events, 1–2 days before and after event. For the assessment of the impact of environmental variables on unfavourable cardiovascular characteristics, we used the percentage increase and odds ratio with 95% confidence interval, and p-values of coefficients in the logistic regression analysis. Results On days of fast solar wind (SW≥600 km/s), more than 50% increased risk of acute coronary syndrome (ACS) in patients with hypertension, diabetes and kidney disease. SIR events increase risk of arrhythmias more than two times. In patients, hospitalised during GS or 1–2 days after their increased the risk of hyperglycemia over 1.5-fold. GS lasted more than one day at SW≥600 km/s over 2.5 times increased of myocardial infarction with ST elevation. In patients with the metabolic syndrome the risk of ACS increased over 1.5 times during GS and on 1–2 days before and after. Conclusion The results obtained suggest that the 1–2 days prior to GS, GS, 1–2 days after GS, the faster solar wind velocity (≥600 km/s), and SIR can be identified as independent risk factors in humans.

The intense Geomagnetic Storms (GMSs) with Dst < −100 nT have been investigated for the period from Jan 1996 to Dec 2006. Seven GMSs of doublet and four of triplet nature are observed. Firstly, each GMS has been studied separately as if they are associated with independent Coronal Mass Ejections (CMEs). Secondly, for each doublet and triplet, the accumulated effect on GMS has been investigated and correlated with Dst index so as to understand the geoeffectiveness of Successive Intense GMSs. Majority of the successive intense GMSs have occurred during maximum phase of Solar cycle. During the occurrence of overlapping successive storms Dst falls abruptly. For non-overlapping successive storms, the Dst value falls gradually to minimum, showing a trend of recovery before the geosphere is hit by another storm. It is observed that the combined effect on GMSs is due to the Solar Wind (SW) being complex, having a very high value of SW velocity (Vsw) continuously for a very long period of 2 to 6 days. Further, Bz falls to a much lower value and B rises to a pretty high value for accumulated effect than for isolated GMS. When the GMSs are considered as separate entity, the correlation coefficient of Interplanetary Magnetic Field (IMF) parameters B and Bz and further, their products Vsw.B and Vsw.Bz correlated with Dst index are found to be −0.65, 0.72, −0.66 and 0.77 respectively; whereas, the coefficients are much better with the respective values of −0.7, 0.87, −0.78 and 0.90, for the accumulated effect of GMSs. Thus, it is preferable to investigate the accumulated effect of CMEs causing successive GMSs as compared to their isolated effects.