## Session 2 - Geomagnetic Storms - Ground and near-Earth Space Weather Impacts

Craig Rodger (University of Otago), Mark Clilverd (British Antarctic Survey)
Monday 5/11, 13:30-15:00 & 15:45-17:15
MTC 00.15, Small lecture room

Large geomagnetic storms pose a significant Space Weather impact through ground and near-Earth impacts. Coupling via processes in the ionosphere, space weather drives changes throughout the ionosphere and also in structures on the Earth’s surface. One example is the hazard to electrical transmission networks as a consequence of geomagnetically induced currents (GIC). The GIC-hazard is one of the better recognised examples of Space Weather, appearing in many national risk registers. Instances of damage to power network transformers have been reported at high, mid and even comparatively low geomagnetic latitudes - recent studies have even suggested there may be a risk around the geomagnetic equator due to intensification from the equatorial electrojet. However, understanding the origin of the hazard, and providing alerts to power grid operators is challenging, due to the complexity of the physical linkages involved. Understanding the coupling between the solar wind and near-Earth/ground impacts may well require large scale dynamic models of the magnetosphere, for example using MHD approaches. The measurement, modelling, prediction and mitigation of the effects of Space Weather on the ground, such as unwanted geomagnetically induced currents in power systems, pipelines, and railway networks are required by the industries affected. In near-Earth space the same current systems lead to atmospheric expansion and increased drag on LEO spacecraft.

In this session we particularly encourage submissions from those involved in developing early warning of ground-level geomagnetic disturbances from solar wind measurements, members of industry, and from those involved in the modelling of the magnetosphere during geomagnetic storms with a regard to understanding the processes involved in the generation of ground-level and near-Earth disturbances.

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### Talks : Time schedule

Monday November 5, 13:30 - 15:00, MTC 00.15, Small lecture room
 13:30 On the little-known consequences of the August 1972 ultra-fast coronal mass ejecta Knipp, D et al. Invited Oral Delores Knipp[1], Brian Fraser[2], Margaret Shea[3], Don Smart[4] [1] University of Colorado, [2] University of Newcastle, [3] Retired, [4] Retired The extreme space weather events of early August 1972 are still discussed as benchmarks for Sun-Earth transit times of solar ejecta and for fluxes of solar energetic particles. We will address storm effects, some of which have been buried in the Vietnam War archives. One important effect, a nearly instantaneous, unintended detonation of dozens of sea mines south of Hai Phong, North Vietnam on 4 August 1972, occurred under the veil of war. The dramatic event was attributed to ‘magnetic perturbations of solar storms.’ We provide insight into the solar, geophysical and military circumstances of this extraordinary situation. We further argue that this storm deserves a scientific revisit as a predictive grand challenge for ultra-fast coronal mass ejections. 13:50 Investigating the relationship between low frequency variations in the surface geomagnetic field and maximum rates of change Meredith, N et al. Oral Nigel Meredith [1],, Mervyn P. Freeman[1], Alan W. P. Thomson[2] [1]Space Weather and Atmopshere, British Antarctic Survey, Cambridge, UK, [2]Geomagnetism, British Geological Survey, Edinburgh, UK Space weather causes rapid changes in the magnetic field at the Earth’s surface. These induce an electric field that causes unwanted currents to flow in grounded electrical infrastructure such as electricity supply networks, pipelines, and railways. It is therefore desirable to reproduce and forecast the surface magnetic field variations but space weather models can at best only capture the low-frequency behaviour. To overcome this limitation, we explore the statistical relationship between low frequency variations in the horizontal surface magnetic field H in a given interval and the maximum rate of change dH/dt. Using surface geomagnetic field measurements from the INTERMAGNET magnetometers located at Eskdalemuir, Hartland, and Lerwick in the UK, we find a power law relationship between the variance of H and maximum dH/dt. We argue that the relationship arises from the statistical stability of the fluctuation power spectrum over any given interval and consider factors affecting the details of the relationship. 14:05 Forecasting & Analysis of dB/dt with the Space Weather Modeling Framework Welling, D et al. Invited Oral Daniel Welling[1], Gabor Toth[1], Yuxi Chen[1], Agnit Mukhopadhyay[1], Michael Henderson[2], Howard Singer[3], Michele Cash[3] [1]University of Michigan [2] Los Alamos National Laboratory [3] NOAA Space Weather Prediction Center Predicting ground-based magnetic perturbations is a critical step towards specifying and predicting geomagnetically induced currents (GICs) in high voltage transmission lines. Particularly important is dB/dt, as it is directly related to the surface geoelectric field that drives GICs. This talk reviews the current and developing dB/dt forecast capabilities of the Space Weather Modeling Framework (SWMF). The SWMF couples multiple physics-based models of the space environment together to create a comprehensive and self-consistent simulation. The SWMF is currently in operations at NOAA’s Space Weather Prediction Center, where it produces short term forecasts of surface dB/dt as a function of observed upstream drivers. Advances in the underlying physics are being made to the SWMF as part of multiple projects; these new changes and their implications for GIC & dB/dt forecast capability are explored. The new changes are placed in the context of the recent September 2017 storm event. 14:25 Active Experiments for Space Weather Applications Reeves, G et al. Oral Geoffrey Reeves[1] and the CONNEX Team [1] Los Alamos National Laboratory Long-standing challenges in space weather applications often stem from our inability to make fundamentally new measurements. Active experiments hold the potential to overcome some of those challenges. In the 1960s and 1970s the ionosphere was often described as a 'TV Screen' where magnetospheric processes could be visualized as they were projected down along magnetic field lines the way that electrons were magnetically steered and projected in CRT monitors. A major problem arises from the fact that for the geospace system the magnetic field is both poorly known and highly dynamic. The result has been decades of controversy over exactly which magnetospheric processes are connected to which features in the ionosphere as well as how the ionosphere determines where, when, and how specific magnetospheric processes manifest. Our ability to connect (physically and unambiguously) ground-based ionospheric measurements to the conditions and processes in the magnetosphere could enable fundamental breakthroughs in space weather forecasting both because of the relatively low cost of ground-based systems compared to satellites and because of the incredible density of observations possible. The basic impediment we currently face is to determine the magnetic connectivity between the two coupled parts of the system - particularly during active space weather conditions. We will describe a new mission designed to resolve the long-standing controversies surrounding magnetic connectivity: the Magnetosphere Ionosphere Connections Explorer. CONNEX is a co-designed magnetospheric constellation and ground-based array. It uses an advanced linear accelerator on spacecraft in an approximately 5 x 8 Re near-equatorial orbit which is the tricky transition region between the dipole magnetosphere and the magnetotail. The MeV electron beam is powerful enough to produce an artificial auroral 'spot' that can be detected by ground-based imaging arrays and incoherent scatter radars to unambiguously determine the magnetic footpoint of the satellite. A constellation of smaller satellites provides spatial-temporal gradients of key quantities in the vicinity of the main satellite and ground-based observations provide regional-scale context of the auroral ionospheric processes. By employing this active magnetic mapping technique CONNEX will both make fundamental discoveries in magnetosphere-ionosphere coupling but also enable transformational space weather capabilities. 14:40 Geomagnetic storm forecasting service StormFocus and performance evaluation over 5 years of real-time operation Podladchikova, T et al. Oral Tatiana Podladchikova[1], Anatoly Petrukovich[2], Yuri Yermolaev[2] [1] Skolkovo Institute of Science and Technology, Moscow, Russia, [2] Space Research Institute, Moscow, Russia Operational forecasting of geomagnetic storms is of great importance for many space weather applications. An online geomagnetic storm forecasting service StormFocus was implemented in 2011 at SpaceWeather.Ru. StormFocus provides the warnings on the expected geomagnetic storm magnitude (negative peak Dst index) for the next several hours on an hourly basis using L1 solar wind and IMF measurements from ACE and DSCOVR satellites. The prediction algorithm of the Dst peak is based on the relation of the solar wind parameters at the beginning of the storm development with the ultimate storm strength reached at the saturation point. A lower limit of the storm strength is estimated on basis of steady-state solution of the differential equation of the Dst index evolution (introduced by Burton et al, 1975). An upper limit estimate is made on basis of choice of the intermediate point between the current state and saturation point on the storm saturation trajectory. We evaluate the performance analysis of StormFocus over more than 5 years of real-time operation. We also analyze the sources of prediction errors and identify the errors that can be fixed by improving the prediction algorithm and those that cannot be removed in real-time. This source of error is related with the missing data and the calibration-related differences between the real-time and the final data. These latter errors are often not recognized, but actually account for a significant part of the forecast uncertainty. StormFocus provided a successful real-time forecast of 87% storms, while the reanalysis running on final OMNI data successfully predicted 97% of storms. The prediction of the actual final peak Dst using the real-time input was successful for 90% of storms, that proves the practical usefulness of the real-time forecast. These results confirm the general reliability of StormFocus service to provide advance warnings of geomagnetic storm strength and space weather conditions in the near-Earth environment in real-time.

Monday November 5, 15:45 - 17:15, MTC 00.15, Small lecture room
 15:45 The intense geomagnetic storms of solar cycle 24 and the associated surface electric field over Europe Dobrica, V et al. Oral Venera Dobrica, Crisan Demetrescu, Razvan Greculeasa, Cristiana Stefan Institute of Geodynamics, Romanian Academy The largest geomagnetic storms in solar cycle 24 (March 2015 and September 2017) are studied from the perspective of (1) solar source – solar wind – geomagnetic storm chain and (2) the hazardous induced response as shown by the surface electric field, the geophysical input in assessing ground space weather impact constituted by geomagnetically induced currents (GICs). The evolution of the solar wind parameters, of the corresponding geomagnetic indices as means of characterizing the sources of the disturbed geomagnetic field, and the evolution of the recorded one-minute geomagnetic field data from the INTERMAGNET network of European geomagnetic observatories, in certain time intervals that include the disturbance one, will be addressed. The surface electric field over Europe produced by the variable magnetic field of geomagnetic storms will be determined, based on the above-mentioned data and on information regarding the underground electric conductivity. 16:00 Validating modelled transformer-level GIC flow in New Zealand’s South Island with extensive observations Divett, T et al. Oral Tim Divett[1], Craig J Rodger[1], Daniel Mac Manus[1], Malcolm Ingham[2], Michael Dalzell[3], Ciaran Beggan[4], Gemma Richardson[4], Ellen Clarke[4], Yuki Obana[5], and Alan W P Thomson[4] [1] Department of Physics, University of Otago, Dunedin, New Zealand, [2] School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, [3] Transpower New Zealand Limited, New Zealand, [4] British Geological Survey, Edinburgh, United Kingdom, [5] Osaka Electro-Communication University, Osaka, Japan Transformers in Transpower New Zealand Ltd.'s South Island electrical transmission network have been impacted by geomagnetically induced currents (GICs) during geomagnetic events in the past. For example, during the St. Patrick’s Day Storm of 2015 and the September 2017 storms up to 50A of GIC were measured. We aim to advance our understanding of these impacts and the potential severity of GIC on this network during extreme events. We have developed geophysical and network models to calculate transformer-level GICs in the South Island’s electrical transmission network. We now seek to validate our modelling. We have taken advantage of New Zealand’s similarities with the UK and Ireland to build on previous modelling approaches successfully applied there in the past; the island nature and geomagnetic latitude. We extended their approach to calculate the geoelectric field as a function of ground level magnetic field variations (interpolated from New Zealand’s sparse observations), and a ground conductance model that we developed from magnetotelluric studies, geology, and bathymetry. In many previous studies, the network model has assumed that each substation can be represented by a single resistor to calculate substation-level GICs. However, in New Zealand Transpower NZ Ltd. have measured and archived GICs flowing through up to 58 individual transformers since 2001. Hence, we have extended the network model to account for every transformer in a single phase of the South Island’s network. This extension is necessary to compare our modelled GICs with these measured GICs. We will present validation of our modelled GICs through individual transformers against Transpower’s extensive observations at substations where the highest GICs were recorded. Further, we will present predictions of sites that Transpower may wish to monitor in the future, based on high modelled GICs. Although initially applied to the South Island of New Zealand, our network modelling technique can be applied to any electrical transmission network where the resistance of each transformer, transmission line, and earth connection is available. By validating our model against Transpower’s observations our approach should also confirm the geophysical and network GIC modelling approaches used by many in the wider international community. 16:15 Regional 3-D modelling and verification of geomagnetically induced currents in Sweden Rosenqvist, L et al. Oral Lisa Rosenqvist and Jan-Ove Hall [1] Swedish Defence Research Institute, 164 90 Stockholm, Sweden Geomagnetically induced currents (GIC) flowing in long conductors can pose a threat to critical infrastructure such as the power grid in cases of extreme geomagnetic activity. Geomagnetic activity is more pronounced at high latitudes, thus Nordic countries, such as Sweden, can potentially be vulnerable to problems caused by GICs. Previous studies have identified the southern region of Sweden as most vulnerable to extreme space weather but most studies have relied on 1D models of the ground conductivity. Sweden, however, has large variation in the ground conductivity structure across the country as well as lateral conductivity variations, e.g. in coastal regions. Thus, the understanding of the ground response to space weather events cannot be captured by 1D models. In this paper we utilize a 3D crustal conductivity map with surrounding oceans, sea basins and continental areas to derive the geoelectric ground response due to a uniform magnetic field. We show that the resulting electric fields are dominated by the ocean-land boundary in southern Sweden which is thus exposed to stronger electric fields due to a combined effect of a low crustal conductivity and the influence of the coast-land interface from both the east and west coast. The model can further be used to calculate GIC in the Swedish power grid and has been validated by GIC measurements from a site in northern Sweden. The measured and predicted GIC amplitudes are in excellent agreement. The model can be used to quantitatively asses the hazard from space weather in Sweden and if it can be validated at other sites the model can be used as a powerful predictive tool of the response to extreme space weather events in the Swedish power network. 16:30 Initial results of pipeline modelling in the United Kingdom Richardson, G et al. Oral Gemma Richardson[1], Alan Thomson[1], Ciaran Beggan[1] [1] British Geological Survey Large geomagnetic field variations during geomagnetic storms induce telluric currents in pipelines. These currents can lead to variations in the pipe-to-soil potentials (PSPs) which interfere with corrosion-prevention measures and may enhance corrosion, leading to localised damage and a reduced lifetime of the pipeline. Modelling PSP fluctuations is useful for mitigation measures in existing pipelines, as well as at the design stage to allow new pipelines to be built to withstand such impacts. We present a first attempt to build capability for modelling these currents in the high-pressure gas pipeline network of the United Kingdom. Our philosophy is similar to the approach used in the modelling of the UK high-voltage (HV) electrical network, as the pipeline network topology is somewhat similar to that of the HV network across much of Britain. We use the method of Boteler (GJI, 2013, doi: 10.1093/gji/ggs113) and modify our existing HV code to account for the continuous grounding of the pipelines, splitting each pipeline into straight-line segments and assuming a constant surface electric field within each section. We present some early results for simple pipeline models and simplified electric fields and we discuss the results. 16:45 Geomagnetically Induced Currents and Harmonic Distortion: Observations from New Zealand Rodger, C et al. Oral Craig J. Rodger[1], Mark A. Clilverd[2], Ian Martin[3], Michael Dalzell[3], James B. Brundell[1], Daniel H. Mac Manus[1], Tim Divett[1], Neil R. Thomson[1], Tanja Petersen[4], and Yuki Obana[5] [1] Department of Physics, University of Otago, Dunedin, New Zealand, [2] British Antarctic Survey (NERC), Cambridge, United Kingdom, [3] Transpower New Zealand Limited, New Zealand, [4] GNS Science, New Zealand, [5] Osaka Electro-Communication University, Neyagawa, Osaka, Japan. There are multiple routes by which Geomagnetically Induced Currents (GIC) can adversely affect electrical power infrastructure through physical damage or disruption to supply. One of the routes to disruption comes from the production of harmonic distortion to the AC waveform generated by saturated transformers. We believe this is one of the few ways to produce even order harmonics (rather than odd harmonics). Even-order harmonic distortion can cause unexpected tripping of protective relays, leading to power black-outs. GIC-produced-harmonic-distortion was the primary cause of both the significant space weather driven disruptions to electrical supply to date: Hydro Quebec in 1989 and the Swedish outage during the 2003 Halloween storm. Until now there have been limited simultaneous harmonic distortion experimental observations and GIC measurements presented in the literature. One reason for this may be that most countries have limited GIC measurements available to link to the harmonic distortion observations. New Zealand is unusually well positioned to investigate the occurrence of GIC in a mid-latitude country. Transpower New Zealand Ltd, the national electrical grid operator, makes transformer neutral DC measurements at ~60% of all earthed substations in the high voltage South Island network. In addition, Total Harmonic Distortion (THD) measurements are also available across the network in both the South Island, as well as for the more populous North Island. It has been suggested that New Zealand may be "perfect laboratory" to study GIC. Recently, we have investigated the occurrence of even order THD and GIC magnitude for a single New Zealand substation during intense geomagnetic storm activity on 7 8 September 2017 [Clilverd et al., 2018]. In this presentation we examine even order THD observations from the entire of New Zealand network during this storm period. These observations demonstrate how GIC effects can be seen in locations where no GIC measurements are present (for example, the majority of the North Island). We understand THD measurements are fairly common in electrical networks, much more so than DC measurements, and could allow a new approach for Space Weather researchers. Investigating the even order THD observations should allow a wider range of countries and regions to examine GIC during active space weather periods, allowing better hazard estimates. Clilverd, M. A., et al., Space Weather, 2018SW001822 (submitted). 17:00 Real-time forecast of GIC in power grids Trichtchenko, L et al. Oral Larisa Trichtchenko, Lidia Nikitina Natural Resources Canada Geomagnetic disturbances (GMD) can affect power systems producing transformer heating, relay misoperation, voltage sag and, in extreme cases, system collapse. Concern that an extreme geomagnetic storm could seriously affect power systems across North America has prompted the development of new standards that require power utilities to conduct a geomagnetic hazard assessment and take appropriate mitigation measures if necessary. The best way to be prepared for a GMD event is to have a real-time forecasting system, which will give the predictions of the GIC level in the system. Canadian Space Weather Forecast Centre/Geomagnetic Observatory operated by Natural Resources Canada is actively researching the possibility of providing a forecast of the GIC in power systems by utilising the currently operational forecast of ground geomagnetic activity indices on a regional scale. The presentation will discuss the up-to-date results of the ongoing investigations. Several possible approaches will be utilised to demonstrate a forecast of geoelectric indices. Validation of the forecast for existing geomagnetic and developed geoelectric indices will be demonstrated based on the statistics. The results of GIC forecasting for a generic “benchmark” power grid network will be shown and validated for a past large event (November 2004), used as an example. The final goal of these ongoing investigations are to supply the power grids with a realistic forecast of GIC values for each component of the network, which could be utilised in mitigation strategies and procedures.

### Posters

 1 The solar cycle 24 geomagnetic storms triggered by ICMEs and CIRs Dumitrache, C et al. p-Poster Cristiana Dumitrache, Nedelia A.Popescu Astronomical institute of Romanian Academy Based on an automatic detection of the events during solar cycle 24, developed on specific criteria in terms of the solar wind plasma parameters and magnetic field, we approach a statistical study of the geomagnetic storms produced by the interplanetary mass ejections (ICMEs) and by corotating interaction regions (CIRs). The presence and features of heliospheric current sheets (HCSs) through this solar cycle are also analysed. 2 Differential Magnetometer Measurements of Geomagnetically Induced Currents in the UK Power Grid Huebert, J et al. p-Poster Juliane Huebert[1], Ciaran Beggan[1], Thomas Martyn[1], Anthony Swan[1], Tim Taylor[1], Christopher Turbitt[1] and Alan Thomson[1] [1] British Geological Survey, Edinburgh, UK Extreme events of space weather can have severe effects on satellites and other technology in orbit, but also pose potential risk to ground-based infrastructure like power lines, railways and gas pipe lines through the induction of geomagnetically induced currents (GICs). Modelling GICs requires knowledge about the source magnetic field and the conductivity structure of the Earth to calculate electric fields during enhanced geomagnetic activity. The electric field in combination with detailed information about the network topology enable the derivation of GICs in power lines. Directly monitoring GICs in power grid substations is possible with a Hall probe, but scarcely realised. In the UK, data from only four such stations located in Scotland is available at the moment. Therefore we will deploy the differential magnetometer method (DMM) to measure GICs across the whole UK power grid, specifically in high voltage network segments that appear as hotspots during electric field calculations for historic geomagnetic storms due to their location within the network (mainly the distances between transformer substations) and the underlying conductivity and coastal effects in the British Isles. The setup of the DMM includes the installation of two fluxgate magnetometers, one directly under a power line affected by GICs, and one as a remote site further away. The difference in recordings of the magnetic field in both instruments allows for the calculation of GICs in the respective power line segment. The recorded data are transferred back in real-time to the geomagnetic data centre in Edinburgh and compared to the predicted GICs. The installation of DMM instrumentation at around 12 sites in the UK is anticipated to validate theoretical modelling of GICs and improve the understanding of effects and hazards on the power grid. 3 Periodicities and Singularities observed on IMF (Bz-component) and Auroral Electorjet (AE) Index during High Intensity Long Duration Continuous Auroral Activities Adhikari, B et al. p-Poster Binod Adhikari Department of Physics, St. Xavier’s College, Maitighar, Kathmandu, Nepal High Intensity Long Duration Continuous AE Activities (HILDCAAs) are form of geomagnetic disturbances caused by intermittent magnetic reconnection. They last for time period longer than 2 days and have AE values greater than 1000nT such that the value of AE never remains below 200nT for time greater than 2 hours at a time. In this work, we study the characteristics of HILDCAA events based on Solar wind parameters, magnetic fields and its components and geomagnetic indices. We found that during HILDCAAs, there is high fluctuation in IMF-Bz and the AE index during recovery phase of storms indicating the presence of the HILDCAA due to the presence of Alfven waves. The CWT analysis shows highest intensity power areas from 50 to 300 minutes on both AE and Bz. The DWT analysis observes the higher amplitudes of square wavelet coefficients to identity the common singularities present on both AE and IMF-Bz datasets. Moreover it was found that HILDCAA effects that we found dependent on the amount of energy that is injected into the ring current during intermittent magnetic reconnection. 4 Stream interaction regions impact on weather variables in mid-latitudes Kiznys, D et al. p-Poster Deivydas Kiznys[1], Jone Vencloviene[1] [1]Vytautas Magnus University, Faculty of Natural Sciences, Lithuania Space weather affects Earth’s atmosphere has been analyzed more than 40 years. Svensmark (1998) found that global cloud cover is correlated with the cosmic ray flux. Changes in cyclonic activity occurring in response to geomagnetic activity and high-speed solar wind. Also, after experiments, researchers found that ions can affect the formation of small aerosols (Svensmark et al., 2007; Kirkby et al., 2011). In this research, we analyzed how stream interaction regions (SIRs) affect the air temperature (T), atmospheric pressure (AP), and relative humidity (RH) in Kaunas city (geographic coordinates: 54°53′ N; 23°58′ E), Lithuania, during 2008-2017. Data were collected from open source websites and publications. Meteorological variables were collected from wunderground.com, Ap index used to identify geomagnetic storms (GS) – OMNIWeb database (omniweb.gsfc.nasa.gov). Stream interaction events were collected from L. Jian publication. The relationship between weather variables and SIR and geomagnetic storms (GS) was assessed by using linear regression, adjusting for years. We assessed the effects of days of SIR and GS with a lag of 0-3 days by including in the model these variables as binary. The analysis was performed separately during the 2011-2017 period of increased and high solar activity (HSA) and low solar activity (LSA) period (2008-2010). During years of HSA, on days of SIR and 1-3 days after, an increase in T by 1.69°C (p = 0.001) and in RH by 2.04% (p=0.007) was observed during winter and an increase in T by 1.01°C (p < 0.001), in AP by 1.58 hPa (p=0.001), and a decrease in RH by 2.14% (p=0.013) was observed in summer, as compared to other days. During years of LSA, the effect of SIR tended to be opposite and was insignificant. During autumn, SIR has associated a lower air temperature and a higher relative humidity both during years of HAS and LSA. GS with a lag of 0-3 was associated with a higher AP during winter (9.54 hPa, p=0.024), spring (5.41 hPa, p=0.003), and autumn (3.41 hPa, p=0.052) during years of HAS, meanwhile, during LSA, this impact was negative and insignificant. The days of SIR (lag 0-3) that coincident with GS (lag 0-3) were associated with a lower by 2.4 °C air temperature during winter and spring during years of HSA. SIR and GS have a different impact on weather variables during seasons and periods of HSA and LSA. SIR has a stronger effect on T and RH during autumn and GS a stronger effect has during winter and spring. Svensmark, H., 1998. Influence of Cosmic Rays on Earth’s Climate. Physical Review Letters 81, 5027–5030. https://doi.org/10.1103/physrevlett.81.5027 Svensmark, H., Pedersen, J.O.P., Marsh, N.D., Enghoff, M.B., Uggerhøj, U.I., 2006. Experimental evidence for the role of ions in particle nucleation under atmospheric conditions. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463, 385–396. https://doi.org/10.1098/rspa.2006.1773 Kirkby, J., Curtius, J., Almeida, J., Dunne, E., Duplissy, J. Et al, 2011. Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation. Nature 476, 429–433. https://doi.org/10.1038/nature10343 5 Ground level enhancement event on September 10, 2017 Balabin, Y et al. p-Poster Yury Balabin, Boris Gvozdevsky, Eugenia Mikhalko, Aleksey Germanenko, Eugeny Maurchev Polar Geophysical Institute , Apatity, Russia Ground level enhancement (GLE) was detected by the worldwide network of neutron monitors. This is the second GLE event in the 24th solar cycle. The active "Beta-Gamma-Delta" region А2673 produced it. During September 2017 the region produced a series of strong flares (up to X class). The flare which produced the GLE was of X8.2 magnitude with coordinates S08W83 and started at 15:35 UT. GLE amplitude on neutron monitors did not exceed 6\% for 5-min data reduced to the sea level, a lot of stations registered it. Fort Smith (Canada) was the first station detected the solar cosmic rays in 16:10 UT. At the nearest station Inuvik the increase began about half hour later. This is an evidence of a strong anisotropy on the first phase. We have analyzed the GLE event: energy spectra and pitch-angle distribution were derived using a methodics developed by our group. It includes calculation of asymptotic cone for each station using a modern magnetosphere model and solution of the inverse problem. This methodics was already used to calculate many GLE events. Differential energy spectra during the event are derived with a 5-min step. The spectra are not purely power-law forms, but average slope is about $\gamma$ = -4. This is hard (rigid) spectrum of solar cosmic rays. The results were compared with GOES spacecraft measurements on adjacent energy range. There is an acceptable agreement. 6 Impact of large geomagnetic storms on space weather at the ground and earth environment during September 2017 Mishev, A et al. p-Poster Y.K. Tassev[1], P.I.Y. Velinov[1],A. Mishev[2,3],L. Mateev[1] [1]Institute for Space Research and Technology, Bulgarian Academy of Sciences, Soﬁa, Bulgaria, [2]Space Climate Research Unit, University of Oulu, Finland,[3] Sodankyl\"a Geophysical Observatory, Finland The outstanding solar activity in early September 2017 at minimum of solar cycle 24 is analized. The beginning of the intensive solar-terrestrial disturbances was the Active Region AR2673, which produced four powerful eruptions class X, including the strongest flareX9.3 of Solar Cycle 24 on September 6, 2017, after which began G4 – Severe geomagnetic storm on 07-08.09.2017 with Ap =106, Kp,max = 8 and also the second strongest flare Х8.2 of Solar Cycle 24 on September 10, 2017, which generated a Ground Level Enhancement (GLE) of cosmic rays. This GLE 72 with increase of solar cosmic ray flux of 6% in Oulu Station (Finland) (effective vertical geomagnetic cutoff rigidity: 0.8 GV), accordingly 9% in DOMC Antartica and 14% in DOMB Antartica (the latter a lead free neutron monitor with effective vertical cutoff rigidity <0.01 GV). Тhе GLE72 develops under the conditions of a deep Forbush decrease (around 15%) in South Pole cusp caused by September 7th Coronal Mass Ejection.The Forbush effect ends on September 11th( http://cosmicrays.oulu.fi ). But cosmic ray measurements by flying balloons to the stratosphere over California (T. Phillips, 2017) show that after solar eruptions in September 2017 the radiation levels in stratosphere took more than 2 months to fully rebound to the conditions of minimal solar activity. This is very interesting fact, which deserves to be explored in detail. It is precisely the study and interpretation of this process that is concerned with this work. This phenomena would be important not only for understanding the space weather and space climate, but also for the meteorological weather and climate. In fact, several G2 and G3 geomagnetic storms occurred on September 12-16 (Ap = 34, Kp, max = 6) and September 27-28 (Ap = 51, Kp, max = 7) causing additional Forbush decreases, and hence reduced ionization in the atmosphere. 7 Geomagnetic cut- off rigidity calculations for long term magnetic conditions forecasting Gerontidou, M et al. p-Poster M. Gerontidou[1], N. Katzourakis[1], H. Mavromichalaki[1], V. Yanke[2], E. Eroshenko[2] [1] Faculty of Physics, National and Kapodistrian University of Athens, Athens, Greece, [2]Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Troitsk, Moscow Region, Russia Calculations of a worldwide grid of cosmic ray cut-off rigidities in every five degrees in latitude and in longitude at the altitude of 20km have been performed. This study has been applied to a long time period extending from the year 1950 up today with a prediction for the next years. The values of the geomagnetic cut-off rigidity have been obtained from the method of particle trajectory calculations resulted from the theory of the particle motion in the in the Earth's magnetic field. This method is developed by IZMIRAN group and it is based on the International Geomagnetic Reference Field (IGRF 12) and the Tsyganenko models (T89,T96,T01) as well. An estimation of the variations of the vertical cut-off rigidity of cosmic ray particles arriving at Earth and measured by the ground based neutron monitor network has been also performed. The majority of neutron monitor stations present a decrease of their vertical geomagnetic rigidity relatively to the quiet reference year 1950 with a percentage of about 4.7%, while there are few stations presented a decrease of 26%. Beyond the use of the calculated cut-off rigidity values as a basic reference of charged particle access to different geographical locations during quiet and/or more intense geomagnetic periods, these results can be used for a long-term forecasting of the geomagnetic conditions’ variations. 8 The 06-09 September 2017 "Mega" event of solar cycle 24 Bouya, Z et al. p-Poster Z. Bouya1, R. Marshall1, M. Terkildsen1, G. Steward1, M. Parkinson1, V. Lobzin1, D. Neudegg1, B. Carter2, P. Maher1, V. Kumar1, J. Young1, A. Kelly1 1-Space Weather Services, Australian Bureau of Meteorology, Sydney, Australia. 2- SPACE Research Centre, RMIT University, Melbourne, Australia Over the period 06-09 September 2017 occurred one of the most significant space weather events of Solar Cycle 24. The source of the event was an active region (NOAA Region 12673) located in the Sun's south-west quadrant that, on 06 September, produced an X9.3 magnitude solar flare. It was the strongest solar flare in more than a decade, despite the solar cycle 24 nearing solar minimum when the sun tends to have fewer sunspots. X-ray and UV radiation from the blast ionized the top of Earth's atmosphere, causing a strong shortwave radio blackout over Europe, Africa and the Atlantic Ocean. At 06/1202 UT the SOHO/LASCO coronagraph recorded a full halo Coronal Mass Ejection (CME), which was associated with Type II/IV radio sweeps. The initial propagation speed of this CME was estimated to be 1500 km/s. The CME arrived much earlier than predicted by all space weather agencies, including the Bureau of Meteorology's Space Weather Services which had predicted an arrival time 12 hours later based on the WSA-Enlil solar wind model. The Bureau of Meteorology (BoM) closely monitored the storm’s development and its impact on the solar terrestrial environment, in particular potential disruptions to power grids, telecommunications, positioning services and other space weather sensitive technologies, services and infrastructure. In this paper we discuss the whole chain of events extending from the Sun to the Earth’s surface including detailed observations and prediction tools introduced and developed at BoM Space Weather Services. 9 Local time variations in mid-latitude magnetic field perturbations and geomagnetically induced currents during the 07-08 September 2017 geomagnetic storm Clilverd, M et al. p-Poster Mark A. Clilverd[1], Craig J. Rodger[2], James B. Brundell[2], Michael Dalzell[3], Ian Martin[3], Daniel H. Mac Manus[2], Neil R. Thomson[2], Tanja Petersen[4], Yuki Obana[5], Ellen Clarke[6], Alan Thomson[6], Gemma Richardson[6], Rachel-Louise.Bailey[7], and Mervyn Freeman[1] [1] British Antarctic Survey (NERC), Cambridge, United Kingdom, [2] Department of Physics, University of Otago, Dunedin, New Zealand, [3] Transpower New Zealand Limited, New Zealand, [4] GNS Science, New Zealand, [5] Osaka Electro-Communication University, Neyagawa, Osaka, Japan, [6] British Geological Survey (NERC), Edinburgh, United Kingdom, [7] Zentralanstalt für Meteorologie und Geodynamik, Vienna, Austria. Several periods of Geomagnetically Induced Currents (GIC) were detected in the Halfway Bush substation in Dunedin, South Island, New Zealand, as a result of intense geomagnetic storm activity during 07-08 September 2017. One of the GIC events was associated with the arrival of a strong solar wind shock which generated large but short-lived GIC effects at this geomagnetically mid-latitude site. However, a subsequent longer-lasting, larger, GIC period of up to 30 minutes in duration was detected about 12 hours after the shock arrival. Nearby and more distant magnetometers showed differences in their measurements of the magnetic field perturbations during these two times, suggesting the influence of small-scale ionospheric current structures close to the mid-latitude Dunedin substation. In this study we analyse magnetic field data from mid-latitude sites around the world to better understand the large-scale and smaller scale current structures that were developed during the storm interval, and compare GIC observations from the same regions. We address the question of whether the immediate impact of solar wind shock events, or more delayed magnetospheric storming events, are more significant for electrical power systems at mid-latitudes. This also contributes to our understanding of how a global GIC-event might occur - would the global event strike all longitudes simultaneously, our would it impact regionally over subsequent hours? 10 The geoelectric and geomagnetic response over Fennoscandia to the 7-8 September 2017 storm Dimmock, A et al. p-Poster A. P. Dimmock[1], L. Rosenqvist[2], J-O. Hall[2], A. Viljanen[3], E. Yordanova[1], K. Kauristie[3], M. André[1], E. Carlsson[4] (1) Swedish Institute of Space Physics, Uppsala, Sweden (2) Swedish Defence Research Agency, Stockholm, Sweden (3) Finnish Meteorological Institute, Helsinki, Finland (4) Swedish Institute of Space Physics, Kiruna, Sweden Geomagnetically Induced Currents (GIC) are a well-known hazard of space weather which affect numerous ground infrastructures such as railways, pipelines, telecommunication lines, and power networks. They are one end-link of the space weather chain in which rapid variations in the geomagnetic field induce currents in the conductive ground, creating a geoelectric field. GIC are particularly difficult to predict, as they can manifest locally as a result of localized ionospheric current enhancements and/or complex ground conductivity gradients (e.g. from mineral deposits, or coastal effects) resulting in regional geoelectric peak enhancements. Fennoscandian countries may be susceptible to such effects due to their high-latitudes; as they experience the effects from intense Auroral electrojet currents during intervals of high geomagnetic activity. In some regions such as Sweden, very complex ground conductivity features could enhance their space-weather susceptibility. We study the ground impact over Fennoscandia during the geomagnetic storm of 7-8 September 2017. During this period, we observed 30A peak GIC in the Finnish natural gas pipeline at the Mäntsälä compressor station, and prolonged GIC intervals exceeding 10A. Although the largest GIC of 30A were associated with westward electrojet current enhancements, we also measured GIC exceeding 15A corresponding to variations in the eastward electrojet. From ground magnetometer measurements provided by the IMAGE magnetometer chain, we report that the geomagnetic response revealed many spatially and temporally localised features. Similarly, maps of ionospheric equivalent currents demonstrate complex small spatiotemporal structures and local rapid variations. Combining the maps of ionospheric equivalent currents with a three-dimensional ground conductivity model, we reconstruct the geoelectric field over Fennoscandia, and make a comparison between the modelled and measured GIC. In this presentation, we report our findings. 11 Global simulations of the solar wind magnetosphere interaction Eastwood, J et al. p-Poster J. P. Eastwood[1], L. Mejnertsen[1], J. W. B. Eggington[1], R. T. Desai[1], J. C. Chittenden[2] [1] Space and Atmospheric Physics Group, The Blackett Laboratory, Imperial College London, London, UK [2] Plasma Physics Group, The Blackett Laboratory, Imperial College London, London, UK Global simulations of the interaction between the magnetised solar wind plasma and the Earth’s magnetosphere are crucial for placing satellite observations in the proper context and for providing a better understanding of magnetospheric structure and dynamics under all possible input conditions. Furthermore, magnetospheric simulations are a key component in efforts to predict space weather: fluid-based codes are commonly used to model magnetospheric dynamics as they offer sufficiently fast performance at reasonable computational cost. Here we describe recent work at Imperial College London developing global simulations of the solar wind – magnetosphere interaction. This work is based on the Gorgon MHD code developed in the Plasma Physics group at Imperial, which has been used to successfully model a variety of different laboratory plasma devices such as wire array Z-pinches and inertial confinement fusion experiments. The code uses a unique explicit formalism which enables efficient parallel scaling, and employs other numerical techniques and approaches that are different from other codes used to perform similar modelling, but which may provide important capability. We present work benchmarking the code, as well as example results from the simulation of historic geomagnetic storm events and how changes to the onset time may result in different magnetospheric responses. Other results concerning the effects of variable solar wind flow and the modelling of magnetosphere-ionosphere coupling will be highlighted in this context. This work is funded by UKRI/NERC through the SWIGS consortium. 12 Modelling and monitoring induced electric fields (IEFs) in Ireland and the UK for space weather applications Campanya, J et al. p-Poster Joan Campanyà[1], Peter Gallagher[1], Seán Blake[1], Mark Gibbs[2], David Jackson[2], Ciarán Beggan[3], Gemma S. Richardson[3], Colin Hogg[4] [1] School of Physics, Trinity College Dublin, Dublin, Ireland, [2] Met Office, Exeter, UK, [3] British Geological Survey, Edinburgh, UK, [4] Dublin Institute for Advanced Studies (DIAS) Induced electric fields (IEFs) at the Earth’s surface caused by geomagnetic storms have the potential to disrupt and damage ground-based infrastructures such as electrical power distribution networks, pipelines, and railways. In this study we evaluated the possibilities for modelling and monitoring IEFs in Ireland and the UK. Magnetic time series from the magnetic observatories and electromagnetic tensor relationships were used to model the IEFs at several locations in Ireland and the UK, including locations where no measurements were performed during the geomagnetic storms. Coherence values between 0.5 and 0.95, and signal-to-noise ratio between 1 dB and 15 dB were observed when modelling IEFs. Within these ranges of values, the accuracy at modelling IEFs was controlled by the influence of local geomagnetic sources, and by the distance of the site of interest to the closest magnetic observatory. The modelling approach for modelling IEFs was then used to create a database with IEFs over the last 20 years, including the largest geomagnetic storms. Magnetic field data measured at permanent magnetic observatories, IEFs measured at Eskdalemuir (ESK), Lerwick (LER), and Hartland (HAD) magnetic observatories since 2012, and modelled IEFs were used to train several machine learning techniques for monitoring IEFs in Ireland and the UK. Differences between measured and both modelled and monitored IEFs were quantified using the correlation coefficient, the performance parameter, and root-mean-square error. 13 Regional geomagnetic indexes for Mexico: Kmex & $\delta$Hmex Corona-romero, P et al. p-Poster P. Corona-Romero[1], M. Sergeeva[1], J.A. Gonzalez-Esparza[1], G. Cifuentes-Nava[2], E. Hernandez-Quintero[2], A. Caccavari[2], E. Aguilar-Rodriguez[1], J.C. Mejia-Ambriz[1], V. de la Luz[1], L. X. Gonzalez[1], E. Romero-Hernandez[3] [1]Space Weather National Laboratory, UNAM. [2]Magnetic Service, UNAM, [3]Space Weather National Laboratory, UANL. Space weather affects the Earth's magnetic field in multiple ways. A geomagnetic storm is probably the most intense effect of space weather over Earth’s magnetosphere. Geomagnetic storm effects threaten the distribution of energy (electricity, oil and gas) as well as systems of geopositioning and telecommunication, and compromise technology and facilities related with security of nations. For this reason, the magnetosphere of Earth is continuously monitored in order to detect the occurrence of geomagnetic storms. Possibly the main tools to detect a geomagnetic perturbations are the geomagnetic Kp and Dst indexes and their regional K and $\Delta$H counterparts, respectively. The $\Delta$H(K) index is a scale for assessing the effects associated with the 1-hourly-averaged (3-hourly maximum) variations of the geomagnetic field. In this work we present the regional geomagnetic K and $\Delta$H indexes for the central region of Mexico, Kmex and $\Delta$Hmex, respectively. We also present a geomagnetic storm recorded by our regional geomagnetic indexes and how it compares with the planetary ones. Mexican Geomagnetic indexes are a collaboration between the National Space Weather Laboratory (LANCE) and the Magnetic Service (MS) of the Geophysics Institute (UNAM). 14 Local and global geomagnetic responses of extreme geomagnetic storms at mid latitude (pros and cons of being in the middle) Saiz, E et al. p-Poster Elena Saiz[1], Antonio Guerrero[1], Consuelo Cid[1] [1] Space Weather Group, Physics and Mathematics Department, University of Alcalá (UAH), Spain Geomagnetic signatures registered at mid latitude as a response of severe space weather events are the result of the coupling between magnetic disturbances that are more significant at low latitude (ring current) and at high latitude (auroral electrojets). This coupling results in strong asymmetries (respect to the longitudinal average or Dst response) in the mid latitude geomagnetic field during storm/substorm time. In this work we study these asymmetries at mid latitude for geomagnetic storms (criteria Dst < -150 nT and AL < -2000 nT) during 1998-2017. We have selected five ground geomagnetic observatories at mid-latitude (IAGA codes: SPT, SUA, IRT, MMB and FRN) widely spread in longitude and with good data coverage during that period. Local disturbances are obtained by LDi procedure (Local Disturbance index), patented by University of Alcala. Those local disturbances are also used to obtained a global index similar to Dst (average of the local responses). The global and local response components are distinguished and its origin understood, which nowadays has become a turning point to advance towards a better geomagnetic storm forecasting. 15 Improving nowcast capability through automatic processing of combined ground-based measurements Yamauchi, M et al. p-Poster M. Yamauchi[1], U. Brandstrom[1], D. van Dijk[2], S. Kosé[3], M. Nishi[4], P. Wintoft[1], T. Sergienko[1] [1]Swedish Institute of Space Physics, Sweden, [2]The Hague University of applied science, Nederland (bachelor thesis work), [3]Kyoto University, Japan (master student), [4]Hiroshima City University, Japan In addition to daily or hourly space weather forecast using solar and interplanetary data, the nowcast at the ground/ionospheric level is needed for short-term but high accuracy pinpoint-warning, such as 5-minutes prediction of the ground induced current (GIC). The nowcast (or last-minute prediction) will be improved by combining different types of data: DC and pulsation magnetometers, all-sky camera and riometer. While such a combination has been used to predict substorm onsets for many years by experienced auroral scientists, automatic forecast using a combined data is not yet established. To combine auroral image and magnetometer data, we propose to make "all-sky index" that characterizes different aurora and it strength as a simple index (a number or a set of numbers). The all-sky index must be very local depending on the camera city light, and latitude of the location. Here we show our attempt using Kiruna and Abisko all-sky cameras. For the magnetometer data, we try two different methods to estimate local GIC: one is gradient of peak-to-peak variation within a fixed window (dB/dt method), and the other is standard deviation (sd(B) method). Then we compared these methods to the substorm breakup or surge. When we surveyed the strongest auroras during 2017, the peak of sd(B) is few minutes before the peak of dB/dt, which matches with the peak of all-sky index. This is not surprizing because fluctuations often arrives before the large change in the magnetic field. If this is true, it opens up a possibility of few-minutes forecast. We present our algorithm and some examples. 16 Electrical grids’ failures in southern Poland in 2010 and 2014 in association to space weather effects Gil, A et al. p-Poster A. Gil[1], R. Modzelewska[1], Sz. Moskwa[2], A. Siluszyk[1], M. Siluszyk[1], A. Wawrzynczak[3], and S. Zakrzewska[4] [1] Siedlce University, Faculty of Sciences, Institute of Mathematics and Physics [2] AGH University of Science and Technology in Krakow, Department of Electrical and Power Engineering, Krakow, Poland [3] Siedlce University, Faculty of Sciences, Institute of Computer Sciences [4] Siedlce University, Faculty of Humanities, Social Science and Security Institute The influence of space weather events on energy infrastructure via geomagnetically induced currents is very well known and extensively studied, especially since the Quebec blackout on 13rd of March 1989. Those effects are not very widely studied in connection to Polish energy infrastructure. Pulkkinen and coauthors (2005), considering the Halloween Storm’s in 2003 repercussions revealed two episodes on SwePol Link cable (under the Baltic Sea connection between Polish and Swedish energy infrastructure, by the 450 kV DC). Taking into account the conductances map of Europe (Viljanen et al., 2014) we consider the detailed data of failures in electrical grids in the south part of Poland. We analyze two years during the solar activity cycle 24: 2010 (an early ascending phase of the cycle, near to solar minimum) and 2014 (solar maximum). We consider 4 525 breakdowns in 2010 and 10 656 in the first seven months of 2014, which might be associated with space weather effects. We investigate data of unexplained failures, which happened during the periods of an amplified geomagnetic activity. Based on the data from The Institute of Meteorology and Water Management -National Research Institute (IMGW-PIB) we eliminate from the consideration those breakdowns which had meteorological causes. REFERENCES: Pulkkinen A., S. Lindahl, A. Viljanen, R. Pirjola, Space Weather, 3, S08C03, 2005, doi:10.1029/2004SW000123 Viljanen A., R. Pirjola, E. Pracser, J. Katkalov, M. Wik, Journal of Space Weather and Space Climate, 4, A09, 2014, doi: 10.1051/swsc/2014006