Can the Earth's electric fields be related to the Earth's weather and power grid? Why do solar activity and intense geomagnetic storms occur on Earth?

The solar influence on the Earth’s climate has been studied for a long time. The historic Maunder minimum (MM), between AD 1650 and 1715 [1] and the Medieval warm period, around 1000 AD [2] are well-known events at least in the space and atmospheric physics communities. During the space era, Earth-based and satellite measurements have shown that interplanetary coronal mass injections (ICMEs) affect the whole atmosphere up to low altitudes (~2000 m above sea level) [3]. The Sun is the principal energy source in the atmosphere and biosphere. The Sun affects the earth’s environment via electromagnetic radiation, solar energetic particle (SEP) events and solar wind plasma. The crucial question we address in relative science communities is whether solar activity may contribute to some extent to the increased number of dangerous extreme atmospheric events. In a previous case study, we considered for the first time, the possible solar influence on extreme events, by comparing space weather and atmospheric parameters during the March 2012 heatwave (M2012HW) in the northeast USA [4]. We found strong evidence that both the M2012HW and the historic March 1910 heatwave were most probably caused by solar activity-induced effects on the Earth’s magnetosphere and atmosphere. Global warming is considered to be a manifestation of the increased frequency of extreme events in our times [5,6]. A CarbonBrief report entitled “Attributing Extreme Weather to Climate Change” suggests that human activity has been raising the risk of some kind of extreme weather, in particular, heatwaves [7]. Many authors interpret this statement in the sense that climate change should not be considered the sole cause of each one of the extreme weather events. According to these authors, some natural variations can also trigger extreme events [8–10]. Ref. [7] claim that no reliable discernible influence owing to human activity has been found in ~10% of the extreme weather events and trends that they studied, while in a further 11% of the extreme weather events no reliable conclusion could be reached. Connolly et al., in a recent review paper entitled “How Much Has the Sun Influenced Northern Hemisphere Temperature Trends? An Ongoing Debate”, claimed that the debate on “anthropogenic versus solar influence” has not yet reached a consensus, and further data analysis and theoretical discussion is needed [11]. In this paper, we continued our previous studies on solar-terrestrial relationships by investigating the origin of the March 2012 heatwave in the northeast USA. We examine data from various remote sensing sources: the Sun (SDO satellite), the Interplanetary Space (ACE satellite), the Earth’s magnetosphere (Earth-based measurements, NOAA-19 satellite), the top of the clouds (Terra and Aqua satellites) and the near ground atmosphere. Ultimately, we check the possible relationship of solar activity with the early March 2012 bad weather in northeast Thrace, Greece. Our comparative data analysis suggests: (i) the winter-like weather in Thrace started on the same day as the heatwave started in the USA, (ii) during March 2012, the ACE satellite recorded enhanced flux of SEPs, while the high energy (>~2 MeV) proton flux showed an anti-correlation with the temperature in Thrace (Alexandroupoli), (iii) Thrace experienced particularly intense cyclonic circulation, with intensified events during two periods of magnetic storms (8–10 and 12–13 March), (iv) the winter-like period occurred after the detection of the main SEP event related with the main ICME, (v) the weather in Thrace was related with a deep drop of ~63 ◦C in the cloud top temperature measured by MODIS/Terra, (vi) SOHO and PAMELA recorded very high energy (>500 MeV) solar proton streams and large atmospheric electric field fluctuations recorded (with values reaching ~−2000 V/m) at the beginning of the two above mentioned magnetic storms. Finally, we present high-time resolution (within 1 s) data from Thrace’s power network (~41◦N). We discuss the winter-like March 2012 event in Thrace regarding the influence of solar cosmic rays on the low troposphere mediated by positive NAO. In the Discussion, we suggest that the novel methodology we used of continuous monitoring the geomagnetic effects on the electric power grid may open new opportunities for space weather applications research. Our data analysis provides good evidence of the influence of the unusual March 2012 solar and interplanetary space conditions on extreme events in Thrace, Greece at middle latitudes (~41◦N).One of the most important solar phenomena is coronal mass ejection (CME) [12]. Once a CME escapes from the Sun, it propagates in interplanetary space and reaches the Earth’s orbit at velocities ranging from ~350 km/s to ~2000 km/s. The time it takes a CME to arrive from the Sun to the Earth is about two days, although there are significant variations as far as the duration time is concerned [13]. A CME expanding in the interplanetary space can create a shock wave (SW) accelerating particles to high (GeV) energies, which are observed as large particle fluxes around the SW, and are known as solar energetic particle (SEP) events. Whenever a CME erupts on the side of the Sun facing Earth, and the Earth’s orbit intersects the path of the CME cloud, spectacular and sometimes hazardous effects are observed [5,6]. An ICME reaching the Earth’s magnetosphere induces geomagnetic disturbance, a magnetic storm, due to solar wind plasma pressure and southward interplanetary magnetic field (IMF) interactions with the magnetosphere/bow shock. The most spectacular effect of ICMEs is the aurorae, which appear as curtains, rays and spirals in dynamic variations in the sky, predominantly seen in high-latitude regions. The corotating interaction regions (CIR) consist a second type of solar activity that influences the Earth’s enviroement. In this case, the fast solar wind catches up with upstream slow solar wind and a compressive region is formed at the interface of the fast and the slow streams. These structures reappear with the solar rotation period (∼27 days). When these coronal hole-associated fast solar wind streams are long lasting, they lead to the formation of CIRs. Both ICMEs and CIRs are drivers of geomagnetic storms. Furthermore, Solar activity (ICMEs and CIRs) causes various types of physical processes in Earth’s magnetosphere [13–16], ionosphere [17,18], atmosphere [4,19,20], lithosphere [21–23], biosphere [24–27] and technosphere [28–30]. 1.3. Solar Energetic Particles and Tropospheric Variations The research on solar–terrestrial relationships has emphasized solar cycle (≈11-year periodicity) climate trends so far and has concentrated on stratospheric changes, polar variations, cloudy and sea/surface temperatures [19,31]. Furthermore, it is accepted that solar activity affects both long-term (climate) and short-term (weather) variation [3,11,31–37]. Short-term meteorological responses to solar variable activity have been reported since the beginning of the space era [33]. For instance, Schuurmans [33] reported changes at the tropopause within 12 h after strong solar flares and other tropospheric effects 2–4 days after the flares. Furthermore, Pudovkin and Raspopov [38] and Pudovkin and Babushkina [39],provided significant evidence that the leading cause of weather variations in the lower atmosphere are solar and galactic cosmic ray radiation. Avakyan et al. [3] studied the meteorological variations at low heights during the Halloween October 2003 solar events and they observed a temperature increase after large magnetic storms (Kp > 5) in 84% of the cases studied at an altitude of 2100 m (at the mountain meteorological observatory near Kislovodsk). Moreover, strong electric field fluctuations were reported after the 2003 Halloween events in Kamchatka and many other researchers reported various other atmospheric reflections following the October 2003 solar events [40,41]. In addition galactic cosmic rays appear to play a significant part in climate and weather [42–45]. In conclusion, various studies indicate that after a solar flare, tropospheric variations can occur with in 2–4 days, i.e., the time required for a CME released into interplanetary space to reach our planet.During an ICME-induced magnetic storm the geomagnetic field changes. The induced electric field also creates currents in man-made conductor systems, such as telecommunication cables, electric power networks, oil and gas pipelines, and railway equipment; these currents have been called “geomagnetically induced currents” or GIC [28,46]. GICs are related with surface voltages with values between ~1 V/km and ~5 V/km, with maximum values of ~20 V/km [47]. The GICs are generally of the order of tens to hundreds of amperes. These quasi-DC currents are small compared to the normal AC flowing in the network, but they can induce an enormous impact on the operation of transformers. GIC levels of only 1–10 A can initiate magnetic core saturation in a transformer. The geomagnetic variations are slow (#mHz) compared to the frequency used in electric power transmission (50 or 60 Hz). Therefore when a GIC flows through a transformer, it acts as a DC current. Then, as a result, highly distorted transformer currents are injected into the electric power network [48]. Studies on the effects of solar eruptions on the Earth’s electric field and, consequently, in electric power grids, began relatively recently, after a CME in 1979 [30]. The most famous GIC-induced electric failure occurred in the Hydro-Quebec power system in 1989 [47–50]. Although GICs usually appear at high latitudes, a large ICME may cause GICs at middle and even low latitudes. During the famous 2003 Halloween events, the magnetic variations produced an intense electric field on the ground across the UK. After that event, the GICs raised significant concern within the power industry and government [51]. Liu et al. [14] attempted to identify the responses to space disturbances in low latitude China during a modest magnetic storm on 14 July 2012. They inferred that some transformers had more or less responses to moderate storms depending on the type of transformer and the grid, under similar geographical conditions (i.e., latitude, ground resistivity) [52]. As GICs increase, the level of saturation of an electric transformer core and its impact on the operation of the power network increases. For large storms, the spatial coverage of the magnetic disturbance is large and a large number of transformers can be simultaneously saturated, which can rapidly escalate into a network-wide voltage collapse. In addition, individual transformers may be damaged from overheating due to the unusual operational mode, resulting in long-term outages to critical transformers in the network. Damage to these assets can slow the complete restoration of power network operations [48]. Space scientists have strengthened their research in space weather prediction so that industry and states can avoid catastrophic effects in electric power systems. In this study we will present results from the electric grid in Thrace, northeast Greece, at ~40◦N, revealing voltage disturbances during the March 2012 series of magnetic storms. This is the first (case) study focusing only on high time resolution (1 s) sudden voltage changes (SVCs) in an electric power grid. The new methodology of studying a plethora of SVCs (28 events on March 2012) is considered as a direct manifestation of magnetic storm influencing a power system and hopefully could be used in space-related power network failure forecasting research, as an independent index, in parallel to the GICs. 1.5. Vertical Atmospheric Electric Field Ez near the Ground during Magnetic Storms The atmospheric electric field (AEF) Ez is the field exists in the atmosphere due to the ground and ionosphere, which are negatively and positively charged, respectively. The AEF is formed by the potential difference of 250 kV between the ionosphere and the Earth’s surface [53] and is directed vertically toward the ground, under fair weather conditions. Globally, the Ez value is approximately 100 V/m–200 V/m [54,55]. The variability in the atmospheric electric field is strongly dependent on a combination of conditions and it is divided into fair-weather AEF and disturbed-weather AEF. The vertically orientated AEF Ez can be affected by weather conditions, soil morphology and solar activities [56]. The AEF can also be affected by thunderstorms [57–59], cloudiness [60], geomagnetic activities [61], solar activities [62,63] and air pollution [64,65].Also, in some places the environmental and meteorological differences can affect the AEF [66–70]. Furthermore, the AEF is influenced by earthquakes [71–74]. Significant work has recently been based on disturbed AEF Ez’s relationship with space weather. Among others, Kleimenova et al. presented the effect of 14 magnetic storm main phases in daytime mid-latitude variations in the vertical component Ez of the atmospheric electric field, without local geomagnetic disturbances [75]. They reported, under conditions of fair weather, considerable (~100–300 V/ m) decreases in Ez values at Swidermidlatitude Poland observatory (47.8◦N), during the onset of a substorm in nighttime auroral latitudes (College observatory). They inferred that an increase in the precipitation of energetic electrons into the nighttime auroral ionosphere, can result in considerable disturbances in the midlatitude AEF. Strong electric field fluctuations were reported, among others, by Smirnov et al. after the 2003 Halloween events in Kamchatka [40]. Michnowski et al. compared measurements made at ground level in both the Arctic (S. Siedlecki Polish Polar Station Hornsund, Spitsbergen, Svalbard, Norway) and at mid-latitudes (Swider, S. Kalinowski Geophysical Observatory, Swider, Poland) [ ´ 76]. They inferred that the solar wind changes produce measurable effects on ground-level Ez and Jz at middle latitudes, dependent on the strength of the ICME-induced magnetic storms. These authors claimed that the almost-simultaneous detection of solar wind parameter changes, magnetic storms and variations in the Ez/Jz confirms their physical relationship.