• Two artificial neural network (ANN) models are built to forecast SYM-H index 1 hour ahead using interplanetary magnetic field measurements. • The developed models are based on two conceptually different neural networks: Long Short-Term Memory and Convolutional Neural Network (CNN). • CNN, used here for the first time for geomagnetic indices forecasting, has proved potentialities worth being further explored.

[1] One of the most interesting aspects of the global magnetospheric response to solar wind changes is the relationship between storms and substorms. Here we present new results on the relationship between these two different classes of magnetospheric phenomena by approaching the problem on the side of information theory. Using the Auroral Electrojet AL and SYM-H indices as representative proxies of magnetic substorms and storms, we investigate the transfer of information by means of transfer entropy analysis (Schreiber, 2000). The obtained results seem, on average, to indicate the presence of a net transfer of information from AL to SYM-H on time scales shorter than 10 h. On the basis of this result, geomagnetic substorms may act as a driver for the occurrence of geomagnetic storms. However, carrying out a more careful analysis which takes into account the global geomagnetic daily activity, we suggest that the direction of information flow between substorms and storms depends on the global activity level. Indeed, if it is true that a sequence of magnetospheric substorms may drive a moderate storm, it is also true that very large storms may dominate and drive the occurrence of magnetospheric substorms.Citation: De Michelis, P., G. Consolini, M. Materassi, and R. Tozzi (2011), An information theory approach to the stormsubstorm relationship,

Geomagnetically induced currents (GICs), occurring as a result of space weather events, represent a hazard for the secure and safe operation of electrical power grids and oil/gas pipelines. The most exposed countries are those at high latitudes where, in the past, the occurrence of intense GICs has seriously damaged part of their power networks. However, very powerful space weather events have resulted in intense GICs also at middle and low latitudes. The GIC index is a proxy of the geoelectric field, and it can be estimated straightforwardly from magnetic observatory data. In this work, the GIC index is computed to investigate the possible impact of space weather events on the Italian territory. We first calculate the GIC index using data from the magnetic observatories of Castello Tesino, Duronia, and Lampedusa, together covering the whole Italian latitudinal extension, and show its behavior during the 2015 St. Patrick's day storm. Then, we consider measurements from the two longest running Italian magnetic observatories, that is, Castello Tesino and L'Aquila, and estimate the GIC index over more than 20 years of observations. A preliminary characterization of the general risk to which the Italian power grid network is exposed is given. Results show that during periods of high magnetic activity, potentially detrimental GICs could flow through the power network, especially at the highest Italian latitudes that are characterized by a low conductivity lithosphere.

No abstract

Abstract. On 25 August 2018 the interplanetary counterpart of the 20 August 2018 coronal mass ejection (CME) hit Earth, giving rise to a strong G3 geomagnetic storm. We present a description of the whole sequence of events from the Sun to the ground as well as a detailed analysis of the observed effects on Earth's environment by using a multi-instrumental approach. We studied the ICME (interplanetary-CME) propagation in interplanetary space up to the analysis of its effects in the magnetosphere, ionosphere and at ground level. To accomplish this task, we used ground- and space-collected data, including data from CSES (China Seismo-Electric Satellite), launched on 11 February 2018. We found a direct connection between the ICME impact point on the magnetopause and the pattern of Earth's auroral electrojets. Using the Tsyganenko TS04 model prevision, we were able to correctly identify the principal magnetospheric current system activating during the different phases of the geomagnetic storm. Moreover, we analysed the space weather effects associated with the 25 August 2018 solar event in terms of the evaluation of geomagnetically induced currents (GICs) and identification of possible GPS (Global Positioning System) losses of lock. We found that, despite the strong geomagnetic storm, no loss of lock had been detected. On the contrary, the GIC hazard was found to be potentially more dangerous than other past, more powerful solar events, such as the 2015 St Patrick's Day geomagnetic storm, especially at latitudes higher than 60∘ in the European sector.

No abstract

The European Space Agency's Swarm mission provides a qualitatively new level of observational geomagnetic data, which allows us to study the spatial features of magnetic field fluctuations, capturing their essential characteristics and at the same time establishing a correlation with the dynamics of the systems responsible for the fluctuations. Our study aims to characterize changes in the scaling properties of the geomagnetic field's spatial fluctuations by evaluating the local Hurst exponent and to construct maps of this index at the Swarm's altitude (∼460 km). Since a signal with a larger Hurst exponent is more regular and less erratic than a signal with a smaller one, the maps permit us to localize spatial structures characterized by different scaling properties. This study is an example of the potential of Swarm data to give new insights into ionosphere‐magnetosphere coupling; at the same time, it develops new applications where changes in statistical parameters can be used as a local indicator of overall magnetospheric‐ionospheric coupling conditions.

Recent findings on the nature of magnetic field fluctuations in the high-latitude ionospheric regions have suggested the existence of scaling features, which are the signature of the occurrence of turbulence. These features mainly characterize the magnetic field fluctuations in those regions where the field-aligned currents flow. Here, we investigate the nature of the Earth's magnetic field fluctuations using the high-resolution (50 Hz) magnetic measurements from the European Space Agency Earth's observation mission Swarm. Our study indicates that spatiotemporal anomalous scaling features characterize low-frequency magnetic field fluctuations in the high-latitude ionospheric regions of field-aligned currents at spatial scales in the range 0.8-80 km (timescales in the range 0.1-10 s). The signature of a multifractal nature of these fluctuations suggests a highly complex structure of the field-aligned currents. Our results support the view of inhomogeneous (filamentary) field-aligned currents, which can have relevant implications in the comprehension of the physical processes responsible for the magnetospheric-ionospheric coupling and ionospheric heating.