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Geomagnetically induced currents (GICs) constitute an integral part of space weather research and are a subject of ever‐growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. Here, we exploit data from the HellENIc GeoMagnetic Array, which is deployed in Greece, complemented by magnetic observatories in the Mediterranean region (Italy, France, Spain, Algeria, and Turkey), to calculate values of the GIC index, that is, a proxy of the geoelectric field calculated entirely from geomagnetic field variations. We perform our analysis for the most intense magnetic storms (Dst < −150 nT) of solar cycle 24. Our results show that GIC index increases are well correlated with storm sudden commencements. However, the GIC indices do not exceed “low” activity levels despite the increases in their values, at all magnetic stations/observatories under study during the selected storm events.

Radial diffusion is one of the dominant physical mechanisms driving acceleration and loss of electrons in the outer radiation belt. Therefore, the accurate estimation of radial diffusion coefficients (DLL) is crucial for detailed radiation belt modeling. In recent years several semi‐empirical (SE) models have been developed for the estimation of radial diffusion coefficients which predominantly rely on parameterizations of the Kp index. However, several studies have suggested that the estimations derived from such models can have large deviations from actual (measurement derived) DLL values. In this work we have used the extensive DLL database created in the framework of the Horizon 2020 SafeSpace project which spans 9 years of hourly DLL calculations to develop a model which uses solely solar wind parameters for the derivation of DLL values. The Electric and MagnEtic RAdiaL Diffusion (EMERALD) model is able to derive simultaneously the magnetic and electric components (DLLB ${\\mathrm{D}}_{LL}^{B}$ and DLLE ${\\mathrm{D}}_{LL}^{E}$, respectively) of the radial diffusion coefficient, and furthermore, provide realistic confidence levels on their estimation, which allows the transition from a deterministic paradigm to a robust probabilistic one. Evaluations on the performance of the EMERALD model are shown by comparing its outputs to the DLL data, and examining the reproduction of various DLL characteristics. Finally, comparisons with widely used SE models are shown and discussed.

The urban heat island (UHI) effect is one prominent form of localized anthropogenic climate modification. It represents a significant urban climate problem since it occurs in the layer of the atmosphere where almost all daily human activities take place. This paper presents the development of a high-resolution modeling system that could be used for simulating the UHI effect in the context of operational weather forecasting activities. The modeling system is built around a state-of-the-art numerical weather prediction model, properly modified to allow for the better representation of the urban climate. The model performance in terms of simulating the near-surface air temperature and thermal comfort conditions over the complex urban area of Athens, Greece, is evaluated during a 1.5-month operational implementation in the summer of 2010. Results from this case study reveal an overall satisfactory performance of the modeling system. The discussion of the results highlights the important role that, given the necessary modifications, a meteorological model can play as a supporting tool for developing successful heat island mitigation strategies. This is further underlined through the operational character of the presented modeling system.

In this paper I am reviewing recent advances and open disputes in the study of the terrestrial ring current, with emphasis on its storm-time dynamics. The ring current is carried by energetic charged particles flowing toroidally around the Earth, and creating a ring of westward electric current, centered at the equatorial plane and extending from geocentric distances of about 2 R^sub E^ to roughly 9 R^sub E^. This current has a permanent existence due to the natural properties of charged particles in the geospace environment, yet its intensity is variable. It becomes more intense during global electromagnetic disturbances in the near-Earth space, which are known as space (or magnetic or geomagnetic) storms. Changes in this current are responsible for global decreases in the Earth's surface magnetic field, which is the defining feature of geomagnetic storms. The ring current is a critical element in understanding the onset and development of space weather disturbances in geospace. Ring current physics has long been driven by several paradigms, similarly to other disciplines of space physics: the solar origin paradigm, the substorm-driver paradigm, the large-scale symmetry paradigm, the charge-exchange decay paradigm. The paper addresses these paradigms through older and recent important investigations.[PUBLICATION ABSTRACT]