Geomagnetic Disturbances Research Articles

Electrical Safety Considerations of Neutral Blocker Placements for Mitigating DC

The dc in a power network might be caused by geomagnetic disturbances that result from either a geomagnetic storm or a high-altitude nuclear detonation. The augmenting trend of inverter-based resources is also acting as a source of small dc injection into the power systems. As the resultant, dc could lead toward a possible power system failure, a myriad of neutral blocking devices (NBDs) have been proposed, where, these devices are installed between the neutral and ground of wye-grounded transformers. However, the electrical safety assessment of these devices is critical prior to adding them to the grid as they might raise serious concerns both for the power equipment and the power system maintenance staff. This work is the first effort toward hazard identification and quantitative risk assessment associated with NBDs. It proposes a risk management framework for augmented electrical safety pertinent to these devices. Later, it analyzes the proposed neutral blocking strategies and highlights the associated risks to the operational safety of these installations, particularly concerning electromagnetic pulse (EMP) attacks, cyber threats, and equipment malfunction. Finally, an ideal NBD operational design is proposed incorporating a variety of risk reduction measure to avoid any hazardous situation arising from such installations. This work could provide a guideline for the electric utilities and academic researchers to consider these safety implications prior to proposing or installing these devices.

Longitudinal Variation of the Ionospheric Response to the 26 August 2018 Geomagnetic Storm at Equatorial/Low Latitudes

We have studied the ionospheric response at near-equator latitudes during the geomagnetic storm of 26 August 2018, which was the strongest geomagnetic disturbance that year (minimum Dst value: −174 nT). For the analysis, we considered the F2-layer critical frequency (foF2) and peak height (hmF2), as well as total electron content (TEC) data for Jicamarca (geographic coordinates: 12° S, 283.2° E; geomagnetic coordinates: 2.26° S, 4.09° W), Saoluis (geographic coordinates: 2.6° S, 315.8° E; geomagnetic coordinates: 5.94° N, 28.5° E), Guam (geographic coordinates: 13.4° N, 144.8° E; geomagnetic coordinates: 5.73° N, 143.2° W) and Libreville (geographic coordinates: 0.39° N, 9.45° E; geomagnetic coordinates: 1.64° N, 82.6° W). First, we observed pre-storm improvements, which could be due to previous moderate geomagnetic activity. Second, only one station (Jicamarca) clearly revealed a prompt penetration electric field (PPEF) effect when Bz turned strongly negative during the initial phase of the storm. Over the stations Saoluis and Guam, a PPEF effect was not evident. These stations presented pre-storm enhancements in foF2. In this case study, disturbed dynamo electric fields appear not to have played a crucial role in increasing electron density near equatorial regions during the recovery phase because the observed disturbances did not correspond with those produced by these electric fields, that is, negative (positive) storm effects on the dayside (night). Third, the increases in electron density observed during recovery are most likely caused by neutral composition changes.

Thermospheric gravity wave characteristics in the daytime over low-latitudes during geomagnetic quiet and disturbed conditions

The importance of gravity waves (GWs) in the redistribution of energy and momentum in the Earth's atmosphere is well known. It is extremely important to understand the nature of variation in the GW characteristics to address issues of coupling in the Earth's atmosphere. We have used digisonde measurements to investigate the variation in thermospheric wave dynamics in the daytime over low-latitudes (Ahmedabad, India) during geomagnetic quiet and disturbed times. Vertical phase speeds and wavelengths of GWs are calculated by monitoring the phase offsets in the digisonde derived height variations of constant electron densities throughout the day. During geomagnetic quiet times, the magnitudes of vertical propagation speeds of GWs and their vertical wavelengths show seasonal variation and vary in the range of 10–70 ms−1 and 70–520 km, respectively. The distributions of vertical propagation parameters of GWs for geomagnetic quiet days show two peaks annually and are anti-correlated with the thermospheric horizontal winds. As these winds over a given location flow in different directions in different seasons, this information can be used to infer the season dependent preferential direction of propagation of GWs. Changes in the vertical propagation characteristics of GWs during geomagnetic disturbed days as compared to their average quiet time values show good semblance with the integrated values of the AE index. A linear relation has been obtained between the changes in vertical phase speeds of GWs and the integrated values of AE index during geomagnetic disturbed days. This linear relation, in combination with empirical formulation arrived at for averaged values of vertical propagation speeds during geomagnetic quiet times, yields comprehensive information on propagation characteristics of GWs as a function of day of the year that includes geomagnetic disturbance conditions as well. Such systematic information on the GW characteristics in the daytime thermosphere and their quantification during geomagnetic quiet times and their changes due to enhancement in energy input at high-latitudes (as characterized by the AE index) also provides a strong and direct information on high-to low-latitude coupling.

Geoinformation system for analyzing the dynamics of extreme geomagnetic disturbances from observations of ground stations

The paper is concerned with an approach to developing a specialized web-GIS based on a microservice architecture that provides analytical control of the disturbed component of geomagnetic field variations, according to observation data from magnetic observatories and variational stations published on the SuperMAG portal <http://supermag.jhuapl.edu/>. A method of spatial interpolation of geomagnetic data implemented in the proposed web-GIS, together with the proposed scheme for ranking and interpreting them, as well as a visualization method in the form of isolines, allows a user to track the structure, observe the dynamics, identify probable regions, duration and time intervals of the occurrence of extreme geomagnetic disturbances.

An Ephemeral Red Arc Appeared at 68° MLat at a Pseudo Breakup During Geomagnetically Quiet Conditions

AbstractVarious subauroral optical features have been studied by analyzing data collected during periods of geomagnetic disturbances. Most events have been typically found at geomagnetic latitudes of 45–60°. In this study, however, we present a red arc event found at geomagnetic 68° north (L ≈ 7.1) in the Scandinavian sector during a period of geomagnetically quiet conditions within a short intermission between two high‐speed solar wind events. The red arc appeared to coincide with a pseudo breakup at geomagnetic 71–72°N and a rapid equatorward expansion of the polar cap. However, the red arc disappeared in approximately 7 min. Simultaneous measurements with the Swarm A/C satellites indicated the appearance of the red arc at the ionospheric trough minimum and a conspicuous enhancement of the electron temperature, suggesting the generation of the arc by heat flux. Since there are meaningful differences in the red arc features from already‐known subauroral optical features such as the stable auroral red (SAR) arc, we considered that the red arc is a new phenomenon. We suggest that the ephemeral red arc may represent the moment of SAR arc birth associated with substorm particle injection, which is generally masked by bright dynamic aurorae.

Identifying Flux Rope Signatures Using a Deep Neural Network

Among the current challenges in Space Weather, one of the main ones is to forecast the internal magnetic configuration within Interplanetary Coronal Mass Ejections (ICMEs). Currently, a monotonic and coherent magnetic configuration observed is associated with the result of a spacecraft crossing a large flux rope with helical magnetic field lines topology. The classification of such an arrangement is essential to predict geomagnetic disturbance. Thus, the classification relies on the assumption that the ICME's internal structure is a well organized magnetic flux rope. This paper applies machine learning and a current physical flux rope analytical model to identify and further understand the internal structures of ICMEs. We trained an image recognition artificial neural network with analytical flux rope data, generated from the range of many possible trajectories within a cylindrical (circular and elliptical cross-section) model. The trained network was then evaluated against the observed ICMEs from WIND during 1995-2015. The methodology developed in this paper can classify 84% of simple real cases correctly and has a 76% success rate when extended to a broader set with 5% noise applied, although it does exhibit a bias in favor of positive flux rope classification. As a first step towards a generalizable classification and parameterization tool, these results show promise. With further tuning and refinement, our model presents a strong potential to evolve into a robust tool for identifying flux rope configurations from in situ data.

Human health response to geomagnetic disturbances

Human health response to geomagnetic disturbances

Processing Magnetometer Signals for Accurate Wide-Area Geomagnetic Disturbance Monitoring and Resilience Analysis

Geomagnetic disturbances (GMDs) can disrupt the operation of power systems by inducing a quasi-dc voltage and generating geomagnetically induced currents (GICs) in a vast area of the power systems. This gives rise to the importance of wide-area monitoring of magnetic field on earth's surface. Assessment of power system resiliency against GMDs requires an accurate calculation of GIC flows, which is achieved by wide-area monitoring of the magnetic field B, and processing the B signals that are recorded by magnetometers on the earth's surface. In this paper, a method is proposed to denoise the B signal. Spikes in the signal are detected using a stationary wavelet transform and then replaced. Time derivative of B signal is taken by a continuous wavelet transform to prevent amplification of the noises. Furthermore, a quantitative analysis is performed to detect the optimum sampling frequency to overcome the practical limitations associated with transmitting the recorded B signal and to modify peaks of dB/dt signal negligibly. It is demonstrated that a sampling frequency of 1/15 Hz satisfies these conditions. Finally, GICs in a 118-bus benchmark power system are calculated with respect to a realistic geomagnetic storm to demonstrate the effectiveness of the proposed signal processing method.

ESTIMATED RELATIONS BETWEEN THE MAIN THERMOSPHERIC NEUTRAL COMPONENTS AT IONOSPHERIC F1-LAYER HEIGHTSABOVE IRKUTSK IN 2014–2017

We have estimated seasonal variations in the main thermospheric gas components [O]/[N₂] and [O₂]/[O] for the period 2014–2017. We have used the well-known authoring technique and electron density measurements made with the Irkutsk digisonde (52° N, 104° E) at ionospheric F1-layer heights under different geomagnetic activity conditions. We have found that at these heights during geomagnetic disturbances in all seasons the molecular component of the neutral composition of the thermosphere increases and the atomic component decreases. In comparison with 2014, [O₂]/[O] values increased by 2017 under quiet and disturbed geomagnetic conditions: up to 30 % and 20 % in summer and spring respectively; up to 10 % in winter and autumn. The [O]/[N₂] ratio decreased by an average of 15 % by 2017. The assumption has been confirmed that in summer under quiet geomagnetic conditions the relative molecular oxygen content [O₂]/[O] increases with decreasing solar activity.

Оценка отношений основных нейтральных составляющих термосферы в 2014–2017 гг. на высотах слоя F1 над Иркутском

We have estimated seasonal variations in the main thermospheric gas components [O]/[N₂] and [O₂]/[O] for the period 2014–2017. We have used the well-known authoring technique and electron density measurements made with the Irkutsk digisonde (52° N, 104° E) at ionospheric F1-layer heights under different geomagnetic activity conditions. We have found that at these heights during geomagnetic disturbances in all seasons the molecular component of the neutral composition of the thermosphere increases and the atomic component decreases. In comparison with 2014, [O₂]/[O] values increased by 2017 under quiet and disturbed geomagnetic conditions: up to 30 % and 20 % in summer and spring respectively; up to 10 % in winter and autumn. The [O]/[N₂] ratio decreased by an average of 15 % by 2017. The assumption has been confirmed that in summer under quiet geomagnetic conditions the relative molecular oxygen content [O₂]/[O] increases with decreasing solar activity.

HV Transformer Protection and Stabilization under Geomagnetically Induced Currents

This paper presents the results of research related to the issues arising from DC excitation of power transformers due to geomagnetically induced currents (GIC). First, the GIC phenomena and their influence on power system operation are discussed. Then, a recorded case of tripping of the transformer differential protection due to geomagnetic disturbances (GD), as well as simulation signals from a developed model of a transformer subjected to a GD are analyzed. Next, two algorithms for GIC detection utilizing the rate of change of transformer differential currents and the DC component in the neutral current are proposed, thoroughly tested, and recommended.

Estimation of the Ionospheric Effects of Geomagnetic Disturbances Based on Data from Wakkanai Station

Ionosonde measurements of the critical frequency of the ionospheric F2 layer (foF2) at Wakkanai station (Japan) are analyzed with the method of superposed epochs. The station is situated in a region of high seismicity. Winter periods with low sunspot and geomagnetic activity and high seismic activity are considered. The goals of this work were the quantitative characterization and comparison of ionospheric disturbances induced by the development of geomagnetic storms/geomagnetic disturbances. Geomagnetic disturbances refer to manifestations of geomagnetic activity with an intensity that is higher than “quiet” geomagnetic background but not higher than the threshold characteristic of weak geomagnetic storms. It is ascertained that weak geomagnetic storms and geomagnetic disturbances, from the time of the main trough in the Dst index after the onset of a geomagnetic storm/geomagnetic disturbance to the end of the third day, result in only positive foF2 deviations. The deviations exceed 6% of the background; the maximal relative deviations from the background (δfoF2max) are ~17% and ~14%, respectively. For geomagnetic disturbances, the most significant response of the ionosphere is observed ~7 h after the main trough in the Dst index. The resulting assessments can be used to filter out false ionospheric earthquake precursors with analysis of the ionospheric data from Wakkanai station.

Evolution of High-Latitude Geomagnetic Disturbances during the Magnetic Storm of July 22, 2009

The behavior of geomagnetic disturbances during a moderate CIR storm, the most intense magnetic storm of 2009 in the solar activity minimum are considered. It is found that the substorm activity during the main phase of the storm was observed not in the nighttime but in the morning sector (0700–0900 MLT) of auroral geomagnetic latitudes (65°–67°) and was accompanied by extremely large (up to 1000 nT) geomagnetic pulsations of the Рс5 range, evidently of a non-resonant nature; the amplitude of the Y component of waves considerably exceeded that of the Х component. In the recovery phase of the magnetic storm, the tangential discontinuity in the IMF caused a substorm observed near the polar boundary of the auroral oval in the global scale in the longitude, from the evening sector to midday hours. In the daytime sector, the magnetic bay was observed several minutes later than in the nighttime sector and rapidly moved to the pole, which can be interpreted as the motion to the pole of the boundary between closed and open geomagnetic field lines and contraction of the auroral oval.

Modeling Geoelectric Fields Induced by Geomagnetic Disturbances in 3D Subsurface Geology, an Example From Southeastern Australia

AbstractGeomagnetic storms can cause power grid instabilities and blackouts due to excessive geomagnetically induced currents (GICs) flowing in electric transmission systems. In this study, we assess regional vulnerability to GICs by modeling the geoelectric fields induced by significant historic geomagnetic disturbance events in the presence of 3D subsurface geology using data from the Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) magnetotelluric array, Australia‐Wide Array of Geomagnetic Stations (AWAGS) magnetometer array, and Geoscience Australia geomagnetic observatory network. We analyze the vertical component of the magnetic field with respect to the horizontal magnetic‐field polarization for two magnetic storms and gain insight into the inductive effects associated with field polarization orientations in the 3D case. We also analyze the telluric field intensity and polarization for a unit geomagnetic field polarized in northerly and easterly directions at AusLAMP sites and find that in the presence of 3D geology the induced field has a very polarization‐sensitive anomaly. We model the geoelectric fields in southeastern Australia for the 1989 “Québec storm.” The induced ground electric fields are typically in the range 1,000–2,000 mV/km with a few sites within 2,000–5,000 mV/km on highly resistive regions and in coastal areas, and below 300 mV/km on inland sedimentary basins. The current study focuses on magnetic‐field variations with periods between 120 and ~20,000 s due to bandwidth limits in our magnetotelluric tensor data and the Nyquist limit for the 60 s sampling of our geomagnetic‐field data. Hence, our modeled maximum values should be considered lower estimates of potential real values.

Algorithms for mitigating the effect of uncertain geomagnetic disturbances in electric grids

Geomagnetic disturbances (GMDs), a result of space weather, pose a severe risk to electric grids. When GMDs occur, they can cause geomagnetically-induced currents (GICs), which saturate transformers, induce hot-spot heating, and increase reactive power losses in the transmission grid. Furthermore, uncertainty in the magnitude and orientation of the geo-electric field, and insufficient historical data make the problem of mitigating the effects of uncertain GMDs challenging. In this paper, we propose a novel distributionally robust optimization (DRO) approach that models uncertain GMDs and mitigates the effects of GICs on electric grids. This is achieved via a set of mitigation actions (e.g., line switching, locating blocking devices, generator re-dispatch and load shedding), prior to the GMD event, such that the worst-case expectation of the system cost is minimized. To this end, we develop a column-and-constraint generation algorithm that solves a sequence of mixed-integer second-order conic programs to handle the underlying convex support set of the uncertain GMDs. Also, we present a monolithic exact reformulation of our DRO model when the underlying support set can be approximated by a polytope with three extreme points. Numerical experiments on ‘epri-21’ system show the efficacy of the proposed algorithms and the exact reformulation of our DRO model.

Climatology Characteristics of Ionospheric Irregularities Described with GNSS ROTI

At equatorial and high latitudes, the intense ionospheric irregularities and plasma density gradients can seriously affect the performances of radio communication and satellite-based navigation systems; that represents a challenging topic for the scientific and engineering communities and operational use of communication and navigation services. The GNSS-based ROTI (rate of TEC index) is one of the most widely used indices to monitor the occurrence and intensity of ionospheric irregularities. In this paper, we examined the long-term performance of the ROTI in terms of finding the climatological characteristics of TEC fluctuations. We considered the different scale temporal signatures and checked the general sensitivity to the solar and geomagnetic activity. We retrieved and analyzed long-term time-series of ROTI values for two chains of GNSS stations located in European and North-American regions. This analysis covers three full years of the 24th solar cycle, which represent different levels of solar activity and include periods of intense geomagnetic storms. The ionospheric irregularities’ geographical distribution, as derived from ROTI, shows a reasonable consistency to be found within the poleward/equatorward boundaries of the auroral oval specified by empirical models. During magnetic midnight and quiet-time conditions, the equatorward boundary of the ROTI-derived ionospheric irregularity zone was observed at 65–70° of north magnetic latitude, while for local noon conditions this boundary was more poleward at 75–85 magnetic latitude. The ionospheric irregularities of low-to-moderate intensity were found to occur within the auroral oval at all levels of geomagnetic activity and seasons. At moderate and high levels of solar activity, the intensities of ionospheric irregularities are larger during local winter conditions than for the local summer and polar day conditions. We found that ROTI displays a selective latitudinal sensitivity to the auroral electrojet activity—the strongest dependence (correlation R > 0.6–0.8) was observed within a narrow latitudinal range of 55–70°N magnetic latitude, which corresponded to a band of the largest ROTI values within the auroral oval zone expanded equatorward during geomagnetic disturbances.

The Effects of Solar Activity and Geomagnetic Disturbance on Human Health

The Effects of Solar Activity and Geomagnetic Disturbance on Human Health

The Effectiveness of E-CALLISTO System in Predicting Geomagnetic Disturbance

This study focuses on analyzation of solar radio burst (SRB) data obtained by e-CALLISTO system in order to predict the occurrence of geomagnetic storm. E-CALLISTO is a global network of solar spectrometer that continually generates the observed radio signals in a form of spectrographs. Previous studies have strongly proved that the source of geomagnetic disturbance turned out to be type IV SRB which can be detected by CALLISTO instrument. Therefore, we selected 4 stations located at different locations to study the effectiveness and consistency of this system in detecting type IV bursts associated to solar storm during solar maximum. The data chosen was on 10th September 2014 where type IV bursts were formed at 1727 UT until 1745 UT within a frequency range of 135MHz to 390MHz. Accompanying the bursts was a halo CME prior to the bursts’ formation and an X1.6 flare was registered. From the results obtained by all stations, the pattern of the bursts depicts the same characteristic as theory says, by which, they emit a broadband continuum in a zebra pattern with varying fine structures. The formation of the bursts is due to magnetic reconnection and disruption of magnetic loops during large flares on Sept. 10th. As a consequence to type IV bursts associated to a vigorous CME, a major G2 storm was reported by NOAA a couple of days later. The presented results have shown a parallel correlation between type IV bursts detected by those 4 stations and the commencement of geomagnetic disturbance which took place 2 days afterwards.

Effect of intense solar flares on TEC variation at low-latitude station Varanasi

The effect of intense solar flares on total electron content (TEC) variability during the declining phase of solar cycle-24 is studied at the low-latitude station at Varanasi, India (Geog. Lat. 25.31° N, Geog. Long. 82.97° E, Geomag. Lat. 16.54° N, Geomag. Long. 157.09° E). In the present paper, we have chosen the intense solar flares that occurred during 9–13 March 2015, 1–2 January 2016, 12–14 February 2016, 6–8 August 2016, and 6–8 September 2017 in the solar cycle-24 period for which the data is available. Our results showed significant enhancements in TEC up to the order of 15 TECU during and after the solar flare events. We have also given a brief account of solar flare effect in TEC with and without geomagnetic disturbances, local time effects (solar zenith angle effects) and changing the location of the solar active region. In a few cases, our results revealed a delay in TEC response during the flare peak time as well as recovery time.

Real‐time detection of vulnerable power system areas to geomagnetic disturbance

This study proposes an approach for the fast and accurate identification of the vulnerable areas of the power system to geomagnetic disturbance (GMD). The proposed method can be used for real-time situational awareness and preparedness in power system control rooms and proactive mitigation of the GMD threats. In addition, it can be employed as an off-line GMD vulnerability assessment tool for power system planning analysis. In this study, a generalised mathematical basis is presented to find the maximum geomagnetically induced current (GIC) flow in the multi-zone earth structure based on the orthogonal GIC components. Furthermore, a real-time frequency estimation method is developed based on wavelet transform to estimate the frequency of the geomagnetic waveform for the maximum GIC calculation. The proposed approach is applied to the Ontario 500 and 230 kV transmission systems to identify the vulnerable equipment. The results are also compared with the angle sweep results. The numerical results reveal that not only the proposed method is more accurate but also significantly faster than the angle sweep method. Such prominent features introduce the proposed approach as a preferable method for real-time applications and optimisation of power system operation during GMDs.