Geomagnetic Phenomena Research Articles

Solar physics and space weather research at the Institute of Astronomy and NAO - BAS: Solar cycle trends of space weather drivers

Abstract This report summarizes the available space weather catalogs hosted at https://catalogs.astro.bas.bg/, supported by the Institute of Astronomy and National Astronomical Observatory – Bulgarian Academy of Sciences. Namely solar flares, solar energetic protons, electron associated radio bursts and geomagnetic storms are considered. All these comprehensive records of analysed events are provided with an open access with the aim to be supported in the future. The lists cover solar cycles 23 and 24 (1996–2019) and contain the relevant parameters and their associated solar and/or interplanetary origin. The focus of this report is the solar cycle trend of solar and geomagnetic phenomena, indicating reduced productivity of either type of events in the last solar cycle and offsets with respect to the sunspot numbers.

Evolution and disappearance of the paleo-West Pacific Anomaly: Implications to the future of South Atlantic Anomaly

Palaeomagnetic and modern geomagnetic measurements indicate that the South Atlantic Anomaly (SAA) has undergone rapid changes over the past few hundred years. Its minimum intensity decreased at an average rate of 26 not yr−1, accompanied by a continuous westward drift and spatial expansion. Recently, a secondary minimum of SAA emerged near southern Africa, leading to speculation that expansion of the SAA could indicate an impending geomagnetic reversal. Here, we focus on the evolution and disappearance of the paleo-West Pacific Anomaly (WPA), as another SAA-like structure, which may have implications for the future of SAA evolution. We regard the WPA as SAA-like due to its feature and its association with a reversal flux patch on the core-mantle boundary. Consequently, we suggest that the observed evolutionary pattern in the WPA can serve as a reference for other negative anomalies, such as the SAA. By analysing models that combine datasets of archaeomagnetic and historical records, such as gufm1 and HistKalmag, it is found that the WPA occurred between 1600 and 1820 CE. Over its duration, the WPA experienced phases of rapid expansion, drift, and division. Eventually, its primary component faded away, giving rise to a new segment that continued to expand. The initial two evolutionary phases of the WPA are similar to the evolution of the SAA over the past century. According to the WPA's evolution, it suggests that the current state of the SAA may correspond to an early stage of splitting. Forecasts based on the evolution of the WPA indicate a rapid expansion of the anomalous region in the short term, followed by a gradual reduction in its primary component and continued expansion of a new local minimum. This study provides valuable insight into the evolution of the SAA and highlights the potential utility of the WPA as an evolutionary reference for such geomagnetic phenomena.

Study on the Transition to True North in Air Navigation

The paper is an introductory study on the possible transition from Magnetic North reference to True North reference in air navigation, as envisaged by the International Association of Institutes of Navigation’s AHRTAG Group. The use of the Magnetic Field of the Earth as a direction reference in aviation is explained briefly. Magnetic North is an unstable and irregular directional reference that aviation manages well, but with significant costs. The unpredictability and uncertainties of the Magnetic Field of the Earth might be critical in the future, especially in the case of reversal of the magnetic poles, or incipient reversal. The paper puts forward the case for calculating the probability of such a catastrophic event, with a view to engaging further expert research in the geomagnetic phenomena. The purpose of such a probability estimate would be for the aviation decision makers to determine whether contingency planning might be required or not. Furthermore, the paper analyses the adoption of True North in maritime navigation as a possible model.

Analysis of Tec Variations over Nepal Obtained from GPS Data on Geo-Magnetically Quiet and Disturbed Days of the Year 2015

Dual frequency Global Positioning System (GPS) receiver in two nearby stations i.e. BESI (28.228 °N, 84.739 °E) and GHER (28.375 °N, 84.739 °E) located at almost same latitude and longitude are used to measure ionospheric total electron content (TEC) for the year 2015. Since Year of 2014- 2016 have been known as most active years in terms of geomagnetic events, the year 2015 shows some abnormal results. Diurnal, monthly and seasonal variations of GPS TEC have been studied. The difference in the value of TEC is observed between quiet and disturbed days. Moreover, the correlation between GPS-data of each month with solar activities parameters such as Kp index, disturbance storm time (Dst) index, and Solar Flux index (F10.7 cm) have been studied, separately for quiet and disturbed days for each station. In case of diurnal variation, mean TEC varies from 0100 UT (LT= UT+5:45) to maximum from 0900 UT to 1100UT. The value of TEC is observed higher on quiet days than disturbed days. For seasonal variation, local seasons i.e. autumn, Spring, Summer and Winter is taken and, the value of TEC is found to be higher in Spring (March, April and May) in both stations in quiet and disturbed days. The difference in value of quiet and disturbed days of GPS-TEC explained the geomagnetic phenomena difference in these days in ionosphere. This study can be useful to calculate the water vapor concentration in the atmosphere which is useful for weather prediction and meteorological department.

Shock Induced Strong Substorms and Super Substorms: Preconditions and Associated Oxygen Ion Dynamics

It is well known that the interaction between interplanetary (IP) shocks and the Earth’s magnetosphere would generate/excite various types of geomagnetic phenomena. Progresses have been made on the Earth’s magnetospheric response to solar wind forcing in recent years in the aspects associated with magnetospheric substorms. Strong substorms and super substorms could be triggered externally by sudden changes of solar wind dynamic pressures. When a strong substorms (AE > 1000 nT) or super substorms (AE > 2000 nT) occurs, singly charged oxygen ions escaped from the Earth’s ionosphere are found to be a dominated ion population in the magnetotail and in the inner magnetosphere—ring current region. The products of a strong substorms or super substorms- plasmoid, burst bulk flows are also found to contain significant oxygen ions, even substorm injections can be dominated by oxygen ions. Thus, the magnetospheric dynamic must consider the contributions from the heavy oxygen ions. Also, the IP shock induced super substorms associated electromagnetic pulses (dB/dt) would shift the energetic particle (injections) inward and accelerate existing population significantly. Extensive attempts have also been made to understand how the solar wind energy couples with the magnetosphere to excite magnetospheric substorms. The statistical analysis shows that strong substorms (AE > 1000 nT) and super substorms (AE > 2000 nT) triggered by interplanetary shocks are most likely to occur under the southward interplanetary magnetic field (IMF) and fast solar wind pre-conditions. In addition, strong substorms after the IP shock arrival are more likely to occur when IMF points toward (away from) the Sun around spring (autumn) equinox, which can be ascribed to the Russell-McPherron effect. Thus, the southward IMF precondition of an interplanetary shock and the Russell-McPherron effect can be considered as precursors of a strong substorm and/or super substorm triggered by IP shocks. Moreover, the average duration of CME sheath region which is just behind the interplanetary shock are found to be about 7 hours. This indicates that southward IMF compressed by shock could last at least 7 hours long in the downstream of the interplanetary shock (sheath region) if a southward IMF pre-condition is present, which explains why the largest substorm often occur in the CME sheath.

Землетрясения и геомагнитные возмущения

The article addresses the problem of the connection of earthquakes with geomagnetic phenomena. We have carried out an experimental study using a method based, firstly, on the separation of periods of geomagnetic activity into extremely quiet and disturbed, and, secondly, on the description of seismic activity with an index called the global daily magnitude (GDM). By analyzing the NEIC earthquake catalog of the US Geological Survey over a 20-year period from 1980 to 1999, we have shown that the planetary activity of earthquakes under extremely quiet geomagnetic conditions is noticeably higher than under disturbed conditions. The detected tendency for seismic activity to increase in extremely quiet periods of geomagnetic activity has indirectly been confirmed by the analysis of 35 earthquakes with magnitude 8 and higher, which occurred on Earth from 1980 to 2019. We have found that in extremely quiet geomagnetic conditions, the probability of the occurrence of strong earthquakes is noticeably higher. The result qualitatively confirms the assumption of a change in the regime of seismic activity due to the influence of alternating magnetic fields on the ductility of rocks.

EARTHQUAKES AND GEOMAGNETIC DISTURBANCES

The article addresses the problem of the connection of earthquakes with geomagnetic phenomena. We have carried out an experimental study using a method based, firstly, on the separation of periods of geomagnetic activity into extremely quiet and disturbed, and, secondly, on the description of seismic activity with an index called the global daily magnitude (GDM). By analyzing the NEIC earthquake catalog of the US Geological Survey over a 20-year period from 1980 to 1999, we have shown that the planetary activity of earthquakes under extremely quiet geomagnetic conditions is noticeably higher than under disturbed conditions. The detected tendency for seismic activity to increase in extremely quiet periods of geomagnetic activity has indirectly been confirmed by the analysis of 35 earthquakes with magnitude 8 and higher, which occurred on Earth from 1980 to 2019. We have found that in extremely quiet geomagnetic conditions, the probability of the occurrence of strong earthquakes is noticeably higher. The result qualitatively confirms the assumption of a change in the regime of seismic activity due to the influence of alternating magnetic fields on the ductility of rocks.

Spatial distribution of historical geomagnetic measurements in Mexico

The spatial analysis of the geomagnetic field through time allows obtaining some crucial information about the evolution of the Earth's deep interiors and outer core-mantle conditions. Apart from discrete palaeomagnetic and archaeomagnetic records, the direct magnetic measurements of declination, inclination and intensity may largely contribute to unearthing historical geomagnetic distribution maps. The available historical data in Mexico (https://doi.org/10.1016/j.pepi.2020.106433, Physics of the Earth and Planetary Interiors 300, 2020, 106433) may be divided into two large groups: Data from the different observatories in Mexico between 1879 and 2018 (139 years); and the historical values of magnetic cartography accumulated in several documents between 1587 and 2018 (431 years). Part of the specific objectives of magnetic mapping in Mexico is the estimation and analysis of the local and global behavior of the geomagnetic phenomena. The historical geomagnetic record gathers data on the declination, inclination and total geomagnetic intensity obtained initially by sailors that represent a unique scientific heritage in Latin America.

The Intense Substorm Incidence in Response to Interplanetary Shock Impacts and Influence on Energetic Electron Fluxes at Geosynchronous Orbit

AbstractThe interaction between interplanetary (IP) shocks and the Earth's magnetosphere would generate/excite various types of geomagnetic phenomena. In order to analyze what kind of IP shock is more likely to trigger intense substorms (SME/AE > 1,000 nT) and how the energetic electrons response to intense substorms at geosynchronous orbit, we perform a systematic survey of 246 IP shock events using SuperMag and LANL observations between 2001 and 2013. The statistical analysis shows that intense substorms (SME > 1,000 nT) triggered by IP shocks are most likely to occur under the southward interplanetary magnetic field (IMF) and fast solar wind preconditions. Besides, intense substorms after the IP shock arrival are much more likely to occur when IMF points toward (away from) the Sun around spring (autumn) equinox, which can be ascribed to the Russell‐McPherron effect. Thus, the IMF Bs precondition of an IP shock and the Russell‐McPherron effect can be considered as precursors of an intense substorm. Furthermore, after the shock arrival associated with intense substorms, low‐energy (<200 keV) electron fluxes increase significantly at geosynchronous orbit, and high‐energy (>200 keV) electron fluxes decrease. The spectral index becomes softer with intense substorms and remains almost unchanged with moderate substorms no matter whether the IMF precondition is southward or northward.

THE TEMPERATURE EFFECT IN SECONDARY COSMIC RAYS (MUONS) OBSERVED AT THE GROUND: ANALYSIS OF THE GLOBAL MUON DETECTOR NETWORK DATA

ABSTRACT The analysis of cosmic ray intensity variation seen by muon detectors at Earth's surface can help us to understand astrophysical, solar, interplanetary and geomagnetic phenomena. However, before comparing cosmic ray intensity variations with extraterrestrial phenomena, it is necessary to take into account atmospheric effects such as the temperature effect. In this work, we analyzed this effect on the Global Muon Detector Network (GMDN), which is composed of four ground-based detectors, two in the northern hemisphere and two in the southern hemisphere. In general, we found a higher temperature influence on detectors located in the northern hemisphere. Besides that, we noticed that the seasonal temperature variation observed at the ground and at the altitude of maximum muon production are in antiphase for all GMDN locations (low-latitude regions). In this way, contrary to what is expected in high-latitude regions, the ground muon intensity decrease occurring during summertime would be related to both parts of the temperature effect (the negative and the positive). We analyzed several methods to describe the temperature effect on cosmic ray intensity. We found that the mass weighted method is the one that best reproduces the seasonal cosmic ray variation observed by the GMDN detectors and allows the highest correlation with long-term variation of the cosmic ray intensity seen by neutron monitors.

Frequency distributions of magnetic storms and SI+SSC-derived records at Kakioka, Memambetsu, and Kanoya

The Japan Meteorological Agency keeps records of geomagnetic phenomena observed at Kakioka (magnetic latitude, 27.47°), Memambetsu (magnetic latitude, 35.44°), and Kanoya (magnetic latitude, 22.00°). We used these records to examine the cumulative frequency distribution of magnetic storms, sudden impulses, and storm sudden commencements. The distributions of magnetic storms resemble the Gutenberg–Richter relation between earthquake frequency and magnitude used in seismology. The coefficients determined with the maximum likelihood method show that when the H-range of a magnetic storm at Kakioka is doubled, the frequency of the magnetic storm is about one seventh, for example. Intense magnetic storms occur less frequently than calculated by the functions. This statistical analysis proves that there are no significant differences between slopes of the frequency distribution functions of the magnetic phenomena at Kakioka, Memambetsu, and Kanoya.

High paleointensities for the Canary Islands constrain the Levant geomagnetic high

Understanding the behavior of enigmatic geomagnetic traits such as the Levant intensity high is currently challenged by a lack of full vector records of regional variations in the geomagnetic field. Here we apply the recently proposed multi-method paleointensity approach to a suite of 19 lavas from the Canary Islands dating between ∼4000 BC and 1909 AD. Our new record reveals high paleointensities (VADMs >120 ZAm2) coinciding with and shortly after the peak in geomagnetic intensity in the Levant at ∼1000 BC. Furthermore our data suggests a westward movement of this geomagnetic phenomenon at a rate of 6.7–12° per century. In addition to IZZI-Thellier, microwave-Thellier and the multi-specimen method, the calibrated pseudo-Thellier method is an important part of the multi-method paleointensity approach. The calibration of this relative paleointensity method was derived from a suite of Hawaiian lavas; it is improved with the results of the Canarian cooling units. Pseudo-Thellier results from samples with very low Curie temperature (<150 °C), however, cannot be reliably converted to absolute paleointensity estimates. The multi-method paleointensity approach yielded a reliable estimate for ∼60% of the flows sampled – an unusually high success rate for a paleointensity study involving lavas.

Seasonal Variation of Worldwide Solar Quiet of the Horizontal Magnetic Field Intensity

Numerous investigations have been carried out on many geomagnetic phenomena with a view of understanding the ionosphere. Solar Quiet (Sq) is caused by electric currents induced in the Earth by the external source. We studied the variations of Sq over the various seasons Winter (November, December, January and February), Summer (May, June, July, August), Autumn (September, October) and Spring (March, April), using data from 64 geomagnetic stations for the year 1996 across the globe. The seasonal variations were studied across various latitudes and longitudes. Results show that Sq(H) exhibits transient variations with varying amplitude according to seasons of the year.

Geomagnetic response to solar wind dynamic pressure impulse events at high‐latitude conjugate points

It is commonly assumed that geomagnetic activity is symmetrical between interhemispheric conjugate locations. However, in many cases, such an assumption proved to be wrong. Especially in high‐latitude regions where the magnetosphere and the ionosphere are coupled in a more complex and dynamic fashion, asymmetrical features in geomagnetic phenomena are often observed. This paper presents investigations of geomagnetic responses to sudden change in solar wind pressure to examine interhemispheric conjugate behavior of magnetic field variations, which have rarely been made mainly due to the difficulty of facilitating conjugate‐point measurements. In this study, using magnetometer data from three conjugate stations in Greenland and Antarctica, solar wind pressure impulse events (&gt;5 nPa in &lt;16 min) and their geomagnetic responses, typically seen as magnetic impulse events, have been examined. Our results suggest that asymmetry in ground response patterns between the conjugate locations often shows little correlation with interplanetary magnetic field orientation, season, and ionospheric conductivity, indicating that much more complex mechanism might be involved in creating interhemispheric conjugate behavior.

Comparison between the ring current energy injection and decay under southward and northward IMF Bz conditions during geomagnetic storms

The geomagnetic storm is one of the most important geomagnetic disturbance phenomena in the geospace. Many studies assume that input of solar wind energy into the Earth’s ring current only occurs when IMF Bz in GSM coordinates is southward; the ring current energy injection and decay under northward IMF Bz are not well understood and still need further investigation. In this paper, by using the large amount of data from the year 1964 to 2010, we use the empirical phase space analysis method to study the ring current energy injection and decay under northward IMF Bz and compare the results with those under southward IMF Bz condition. We have found that the largest injection Q under northward IMF Bz condition is only 7% of the largest injection under southward IMF Bz, implying that there is a very limit energy injected into the ring current region when IMF Bz is northward. The decay time τ decreases as VBz increases and shows a good linear trend for southward IMF Bz; while for the northward IMF Bz, there is not a clear relation between τ varies and VBz. Having taken τ as a function of injection Q instead of VBz, we have obtained the empirical relation of τ with Q for northward and southward IMF Bz conditions: the two categories are further combined together and the empirical relation τ=e(2.6+0.039-Q) is derived. Further, the pressure-corrected Dst formula \(Dst^* = Dst - b\sqrt P + c\) is derived for both southward and northward IMF Bz conditions, where the coefficients b and c are 6.9/10.4 and 10.0/15.2 when IMF Bz is southward and northward respectively. The statistical results on between the different geomagnetic indices (Dst, Kp, AE) and IMF Bz are also obtained.

Large-scale structure of solar wind and geomagnetic phenomena

In this work I propose a method for determining the solar wind parameters at distances from the Sun more than 1AU. The method is based on formulas for the scintillation indices and spectra for the interplanetary plasma with the large-scale flow structure. According to the results of observations of scintillations performed at the Ukrainian decameter radio telescope UTR-2, I analyzed the structure of the solar wind flows at different periods of the 23–24th solar cycles. The results of the work reveal that the speed of solar wind flows, which cause moderate geomagnetic storms with Ap≤66, was 590±40km/s. This is on average lower than that for the quasi-stationary fast solar wind, but higher than that for the slow solar wind. Solar wind disturbances which triggered geomagnetic storms showed a noticeable growth of solar wind velocity within a wider range of helio-latitudes comparing with disturbances which did not trigger geomagnetic storms. These results can be used to improve methods of forecasting magnetic storms on Earth.

Geomagnetic South Atlantic Anomaly and global sea level rise: A direct connection?

We highlight the existence of an intriguing and to date unreported relationship between the surface area of the South Atlantic Anomaly (SAA) of the geomagnetic field and the current trend in global sea level rise. These two geophysical variables have been growing coherently during the last three centuries, thus strongly suggesting a causal relationship supported by some statistical tests. The monotonic increase of the SAA surface area since 1600 may have been associated with an increased inflow of radiation energy through the inner Van Allen belt with a consequent warming of the Earth's atmosphere and finally global sea level rise. An alternative suggestive and original explanation is also offered, in which pressure changes at the core–mantle boundary cause surface deformations and relative sea level variations. Although we cannot establish a clear connection between SAA dynamics and global warming, the strong correlation between the former and global sea level supports the idea that global warming may be at least partly controlled by deep Earth processes triggering geomagnetic phenomena, such as the South Atlantic Anomaly, on a century time scale.

Discreteness of spatial-temporal manifestations of solar activity and solar-terrestrial phenomena

The discreteness of the time series of the solar-related geophysical phenomena is justified. The balance of the formation and decomposition (neglecting diffusion) of fractal elements during the evolution of the equilibrium systems as applied to the heliophysical and geomagnetic phenomena is the original position in this case. The discreteness properties of the spatial-temporal characteristics of solar activity are simply justified based on a fractal analysis. The performed calculations in the solar wind medium in the near-Earth space make it possible to classify the fluxes depending on their fractal dimension. The possible mechanism by which high-speed solar wind streams are generated is also briefly discussed in the scope of the fractal paradigm.

Forbush effects and their connection with solar, interplanetary and geomagnetic phenomena

AbstractForbush decrease (or, in a broader sense, Forbush effect) - is a storm in cosmic rays, which is a part of heliospheric storm and very often observed simultaneously with a geomagnetic storm. Disturbances in the solar wind, magnetosphere and cosmic rays are closely interrelated and caused by the same active processes on the Sun. Thus, it is natural and useful to investigate them together. Such an investigation in the present work is based on the characteristics of cosmic rays with rigidity of 10 GV. The results are derived using data from the world wide neutron monitor network and are combined with relevant information into a data base on Forbush effects and large interplanetary disturbances.

Changes in the cosmic ray and heliomagnetic components of space climate, 1428–2005, including the variable occurrence of solar energetic particle events

The cosmic-ray record has been used to study the variations in the space climate, 1428–2005. Inversion of the data shows that the heliomagnetic field (HMF) near Earth increased steadily over the past 580 years, exhibiting the strongest fields during the last 50 years. The estimates indicate that the HMF at sunspot minimum has exhibited steadily increasing “floors” between the several Grand Minima, similar to the one evident in satellite data since 1965. The cosmogenic data for the past 10,000 years contain an ∼2300 year periodicity, and it is proposed that the increasing HMF strength since the 15th century represents the first quarter cycle of a ∼2300 year quasi-periodicity. It is concluded that the 11-year average total magnetic flux of the Sun has increased by a factor of ∼4.5 over the past 580 years. It is speculated that this could indicate a factor of ∼9 variation over the ∼2300 year cycle. The cosmic ray data and theoretical considerations show that the 22-year periodicity in the cosmic radiation flux at Earth was more dominant at times of low solar activity, compared to the present epoch. Comparison of the occurrence of solar energetic particle events, and the estimated HMF, shows that a substantial decrease in the size and frequency of occurrence of GLE (ground level enhancements) after 1958 coincides with a substantial increase in the HMF. This is consistent with the conclusion of [McCracken, K.G., Dreschhoff, G.A.M., Smart, D.F., et al. A study of the occurrence of large-fluence solar proton events and the strength of the interplanetary magnetic field. Solar Phys., 224, 359–372, 2004.] that lower values of the solar magnetic fields result in increased values of the Alfven Mach number, and thence to more efficient acceleration of solar cosmic rays prior to 1958. It is suggested that the variability of the solar and heliospheric magnetic fields may have introduced long term changes into the nature of geomagnetic phenomena; particle acceleration throughout the heliosphere and heliosheath; and possibly to the luminosity of the facular network of the Sun.