Rarely occurring solar superstorms generate X-rays and solar radio bursts, accelerate solar particles to relativistic velocities and cause major perturbations to the solar wind. These environmental changes can cause detrimental effects to the electricity grid, satellites, avionics, air passengers, signals from satellite navigation systems, mobile telephones and more. They have consequently been identified as a risk to the world economy and society. This paper will review their impact on a variety of engineered systems and will identify ways to prepare for these low-probability but randomly occurring events. The paper has an emphasis on the UK, but many of the conclusions also apply to other countries.

Explosive eruptions of energy from the Sun that cause minor solar storms on Earth are relatively common events. In contrast, extremely large events (superstorms) occur very occasionally - perhaps once every century or two. Most superstorms miss the Earth, travelling harmlessly into space. Of those that do travel towards the Earth, only half interact with the Earth's environment and cause damage. Since the start of the space age, there has been no true solar superstorm and consequently our understanding is limited. There have, however, been a number of near misses and these have caused major technological damage, for example the 1989 collapse of part of the Canadian electricity grid. A superstorm which occurred in 1859, now referred to as the 'Carrington event' is the largest for which we have measurements; and even in this case the measurements are limited to perturbations of the geomagnetic field.

An event in 1956 is the highest recorded for atmospheric radiation with August 1972, October 1989 and October 2003 the highest recorded radiation events measured on spacecraft. How often superstorms occur and whether the above are representative of the long term risk is not known and is the subject of important current research. The general consensus is that a solar superstorm is inevitable, a matter not of 'if' but 'when?'. One contemporary view is that a Carrington-level event will occur within a period of 250 years with a confidence of ~95% and within a period of 50 years with a confidence of ~50%, but these figures should be interpreted with considerable care.

Mitigation of solar superstorms necessitates a number of technology-specific approaches which boil down to engineering out as much risk as is reasonably possible, and then adopting operational strategies to deal with the residual risk. In order to achieve the latter, space and terrestrial sensors are required to monitor the storm progress from its early stages as enhanced activity on the Sun through to its impact on Earth. Forecasting a solar storm is a challenge, and contemporary techniques are unlikely to deliver actionable advice, but there are growing efforts to improve those techniques and test them against appropriate metrics. Irrespective of forecasting ability, space and terrestrial sensors of the Sun and the near space environment provide critical space situational awareness, an ability to undertake post-event analysis, and the infrastructure to improve our understanding of this environmnet.

The paper will explores a number of technologies and demonstrates that the UK is indeed vulnerable to a solar superstorm. In a 'perfect storm' a number of technologies will be simultaneously affected which will substantially exacerbate the risk. Mitigating and maintaining an awareness of the individual and linked risks over the long term is a challenge for government, for asset owners and for managers.

On 23 July 2012, NASA's Solar TErrestrial RElations Observatory - Ahead (STEREO-A) spacecraft observed in-situ an extremely fast coronal mass ejection (CME) that traveled one astronomical unit (1 AU) in about 17-hours. The July 23 event also had very strong interplanetary magnetic field components. In this case study, we use the Space Weather Modeling Framework (SWMF) to carry out simulations of this Extremely Rare (ER) type CME event. We consider STEREO-A in-situ observations to represent the upstream L1 solar wind boundary conditions. By varying various solar wind input parameters, we examine what would have happened if this ER-type CME were Earth-directed. We analyze the solar wind-magnetosphere-ionosphere coupling and the subsequent geomagnetic ground response. Our initial results of this ER-type CME show that the ground response would have been comparable, though slight higher, to the March 1989 storm event and the Halloween storm event of October 2003. This has important practical applications for hazard management of electrical power grids.

In an effort to understand the chain of events - at the Sun, in interplanetary space and at Earth - which lead to extreme geomagnetic storms, we have created a ranked list of the 100 largest geomagnetic storms in the period 1868-present. The selection and ranking is based on the aa-index and a set of single geomagnetic observatory data with long records. For these events, available historical data such as sunspot records, flare observations, neutron monitor data, in situ solar wind data and various geomagnetic measures, has been collected and analyzed. For a very large majority of the events, the erupting active region at the Sun has been identified, as well as the time of the major eruption associated with the storm.
The characteristics of geomagnetic records and solar wind in situ measurements have been compared statistically to less intense storms, and it is found that the extreme storms are in general more complex, displaying several storm peaks. The large majority (>90%) of the extreme storms are further associated with one or several shocks as indicated in the geomagnetic records by observed storm sudden commencements. Most of the events occur in spring or fall season. For all events in the time period where neutron monitor data is available they display Forbush decreases, mostly complex with several substructures. Ground Level Enhancements (GLEs) indicating intense Solar Energetic Particle (SEP) events are, on the other hand, only present in ~20% of the events. The presented work has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 263252 [COMESEP] .

We analyse the magnetic results of four Russian observatories in 1850-1862 located at geomagnetic latitudes of 46-56 N. During this period, the recordings were performed on a regular basis saving a 1-min spot reading once per hour. The data set contains the Carrington storm in Sep 1859 with nearly a complete temporal coverage. To quantify the activity level indicated by the old sparsely saved values, we reduce modern continuous 1-min magnetometer recordings at corresponding geomagnetic latitudes to the same format as the old Russian ones. By varying the hourly saving time of the 1-min spot value in the modern data, we can especially assess how accurately the old recordings reveal information of the extreme Carrington event.

The recovery phase of the largest storms ever recorded has been studied. These events provide an extraordinary opportunity for two goals: (1) to validate the hyperbolic model by Aguado et al. [2010] for the recovery phase after disturbances as severe as the Carrington event, or that related to the Hydro-Quebec blackout in March 1989, and (2) to check whether the linear relationship between the recovery time and the intensity of the storm still complies. Our results reveal the high accuracy of the hyperbolic decay function to reproduce the recovery phase of the magnetosphere after an extreme storm. Moreover, the characteristic time that takes the magnetosphere to recover depends in an exponential way on the intensity of the storm, as indicated by the relationship between the two parameters involved in the hyperbolic decay. This exponential function can be approached by a linear function when the severity of the storm diminishes.
This work analyzes also the severity of the 1989 storm responsible for the Hydro-Quebec power blackout, providing an estimation of the peak value for this storm. The comparison of this value with historical records indicates that, although the Carrington storm is the most intense geomagnetic storm ever recorded, it is not as extreme as usually is stated.

The potential effects of extreme solar weather on technology are widely understood within the scientific community. However there is a gap of knowledge on the potential societal and economic consequences (directly and indirectly) of such an event occurring. To highlight this gap in an Irish context, a breakdown of the direct and indirect costs to the Irish economy comparable to recent research conducted on extreme solar weather effects impacting on the US, UK and EU economies. These figures will further strengthen the argument for robust emergency planning and preparedness in Ireland at industry and government levels to mitigate potential impacts.

The Norwegian high-voltage power grid is the northernmost one in the world. Consequently, it is regularly affected by large geomagnetic variations. We have modelled geoelectric fields and geomagnetically induced currents (GIC) in Norway using 10-s magnetic recordings of 1994-2011. Based on this 18-years period, we have estimated the strength of an extreme 10-s value of the electric field occurring once in 100 years. We found that this value is approximately twice the modelled maximum in 1994-2011. On the other hand, the large geomagnetic storm on 13-14 July 1982 produced such extreme values in a large area in North Europe, and caused some disturbances in the Swedish grid. We also found that the 13-14 March 1989 and 24-25 Mar 1991 storms were equally large to the Halloween event in Oct 2003.

We present research on Sun-Earth connections in the context of the most extreme space weather events of the last 150 years. To identify the key-factors leading to these extreme events, we have selected the 100 most important geomagnetic storms in this time period based on the well-known aa index. Here we focus on characterizing the active regions most probably responsible for these major geomagnetic storms.

We use detailed sunspot catalogs as well as solar images and drawings. For the most recent geomagnetic events, vast amounts of detailed solar data is promptly available and thus solar terrestrial connections easy to access through numerous detailed studies. Events posterior to the creation of the H-alpha flare patrol in 1938 are still relatively easy to study, and numerous solar drawings span this period. However, back to the beginning of the aa index in 1868, solar data from catalogs become scarce as well as detailed sunspot drawings. For this study, we have systematically gathered the most interesting sunspot parameters back to 1868, hunting solar drawings from the old Greenwich archives, and extracting sunspot parameters ourselves.

We present a detailed statistical analysis of the active region parameters relative to the flare/geomagnetic parameters, which leads us to clues on how to characterize future storms from these specific sunspot parameters.

The presented work has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 263252 [COMESEP].

In September 1859, scientists observed what has gone down in history as the first ever Space Weather event, and what is also thought to be the greatest magnetic storm on record. At this time the development of magnetic observatory networks was in its infancy with few in existence and methods to continuously record the magnetic field variations were rare. Two competing London observatories, Greenwich and Kew were an exception and both recorded the Carrington storm on photographic paper. These magnetograms provide near-continuous measurements, from one or other of these two London observatories, for the entire Carrington storm. Over the past year, we have been running a project to glean time-series data from digital traces of these plots, as well as of fourteen other of the most powerful geomagnetic storms prior to the digital recording era. This has resulted in a new trove of data for studying these events.

In this poster, we briefly describe the process of digitally-tracing, scaling and interpolation used to derive this data supply. We then go on to compare the results with other available data or the Carrington storm, including samples in observatory yearbooks. The results are also discussed in relation to the Dst results of Tsurutani et al (2003). Comparisons with other digitised storms are also made. Finally, we describe our efforts to derive dB/dt values, which are relevant for estimating Space Weather effects on technology, from the analogue records.

The GPS-derived Global Ionospheric Maps of Total Electron Content (GIM-TEC) provide an opportunity to identify the extreme ionosphere - plasmasphere storm events characterized by the ionospheric W-index at each cell of a map. Two extreme events are identified for a period from January 1999 to May 2013 in the present study: (1) 20-21 May, 2001, with the peak occurrence of storm W-index (W = -3, -4, 3, 4) observed at 73% of the global ionosphere map; and (2) 07-11 November, 2004, with 64% of the global map with TEC storm occurrence. The 1st event was the autonomous ionosphere storm under quiet solar and geomagnetic conditions, and the 2nd event was typical solar - magnetosphere - ionosphere storm well identified in space weather studies. The characteristics of the both events are discussed in the paper.

This study is supported by the joint grant from TUBITAK 112E568 and RFBR 13-02-91370-CT_a.

Only a few solar and geomagnetic events exist that have caused electrical power blackouts. However, many more events exist that have caused less severe but manageable effects. In this work geomagnetic data since 1996, during which good solar and solar wind data are available, have been analysed in terms of time derivative of the local ground geomagnetic field (dB/dt). Criteria to define large dB/dt events are derived from the distribution of dB/dt and associated power grid effects. Only large events are studied, considering the analysed time period, leading to approximately 15 individual events. The events are related to the conditions in the solar wind, the associated coronal mass ejection(s), and the solar active regions. The minimum solar conditions causing large dB/dt events are derived and are discussed in terms of their occurrence rate and their use in warnings and alerts with lead time of days.

The Nagycenk observatory now has more than 50 years of geoelectric (or telluric) field data. In this poster we apply the technique of extreme value statistics to these data to determine the 1 in 100 and 1 in 200 year peak values of the surface electric field. In 2012, geoelectric monitoring sites were installed at each of the three UK geomagnetic observatories. The data now being recorded at these sites is also analysed in comparison with the Nagycenk data, to provide an initial look at the wider European scale view of surface geoelectric fields.

Highly elliptical orbit is used for the communication and surveillance satellites. The analyses of radiation data on HEO orbit were undertaken to provide an impact of space weather events on radiation hazard for spacecrafts on these orbits. HEO data were provided online by the Aerospace Corporation at http://virbo.org/HEO . These data cover 1998-2006 and include years with high and low solar activity as well as data for extreme space weather events like the Bastille Day Event in July 2000 and Halloween events in October-November 2003.

The radiation data for highly elliptical orbit was analyzed using methods of robust and non-robust statistics. It was shown that the robust statistics give the better description of the impact of strong space weather events on the radiation environment. The results of the analyses provide distribution of radiation environment on highly elliptical orbit and its dynamics during space weather events. The influence of severe space weather events on the dynamics of the radiation environment is discussed.

Many modern technological infrastructures on the ground and in space are vulnerable to the effects of severe space weather. Of particular concern is the long-distance high-voltage power grid, which is vulnerable to the effects of geomagnetic storms through the induction of GICs that can damage or destroy equipment and lead to grid collapse due to cascading effects. While there is some awareness and knowledge among European power-grid operators and regulators of the space-weather hazard, levels of awareness, as well as vulnerabilities differ from country to country.

In order to launch a dialogue on the topic and invite European countries to learn from each other, the European Commission's Joint Research Centre (JRC), the Swedish Civil Contingencies Agency, and NOAA will organize a 2-day workshop on the impact of extreme space weather on the power grid to be held on 29-30 October 2013 at the JRC's Ispra site. The event aims at attracting power-grid operators and regulators, as well as representatives of policy making and academia. The primary goal of the workshop is to raise awareness of the hazard and to encourage vulnerability and risk analyses including scenario development which is lacking to date. Topics for discussion will be space-weather phenomena and the dynamics of their potential impact on the grid including modeling, experiences with prediction and now-casting in the US and in Europe, risk assessment and preparedness, and policy implications.

This talk will present the main conclusions and recommendations from the JRC-MSB-NOAA event.