From solar sneezing to killer electrons: outer radiation belt response to solar eruptions

Application of Wavelet Methods in the Investigation of Geospace Disturbances: A Review and an Evaluation of the Approach for Quantifying Wavelet Power

Geospace disturbances refer collectively to the variations of the geomagnetic field and the trapped particle populations in the near-Earth space. These are the result of transient and recurrent solar activity, which consequently drives the variable solar wind. They may appear in multiple timescales, from sub-seconds to days, months and years. Wavelet analysis is one of the most popular, and powerful, methods in the study of these variations, as it allows for the local decomposition of non-stationary time series in frequency (or time-scale) and time simultaneously. This article is a review of the wavelet methods used in the investigation of geomagnetic field oscillations, which underlines their advantages as spectral analysis methods and demonstrates their utilization in the interdependence of multiple time-series. Lastly, the proper methodology for the accurate estimation of the power inferred from geophysical signals, applicable in quantitative studies, is included and is publicly available at the database of the University of Athens.

Introduction to the physics of solar eruptions and their space weather impact

The physical processes, which drive powerful solar eruptions, play an important role in our understanding of the Sun-Earth connection. In this Special Issue, we firstly discuss how magnetic fields emerge from the solar interior to the solar surface, to build up active regions, which commonly host large-scale coronal disturbances, such as coronal mass ejections (CMEs). Then, we discuss the physical processes associated with the driving and triggering of these eruptions, the propagation of the large-scale magnetic disturbances through interplanetary space and the interaction of CMEs with Earth's magnetic field. The acceleration mechanisms for the solar energetic particles related to explosive phenomena (e.g. flares and/or CMEs) in the solar corona are also discussed. The main aim of this Issue, therefore, is to encapsulate the present state-of-the-art in research related to the genesis of solar eruptions and their space-weather implications. This article is part of the theme issue 'Solar eruptions and their space weather impact'.