Complex systems methods characterizing nonlinear processes in the near-Earth electromagnetic environment: recent advances and open challenges

Learning from successful applications of methods originating in statistical mechanics, complex systems science, or information theory in one scientific field (e.g., atmospheric physics or climatology) can provide important insights or conceptual ideas for other areas (e.g., space sciences) or even stimulate new research questions and approaches. For instance, quantification and attribution of dynamical complexity in output time series of nonlinear dynamical systems is a key challenge across scientific disciplines. Especially in the field of space physics, an early and accurate detection of characteristic dissimilarity between normal and abnormal states (e.g., pre-storm activity vs. magnetic storms) has the potential to vastly improve space weather diagnosis and, consequently, the mitigation of space weather hazards. This review provides a systematic overview on existing nonlinear dynamical systems-based methodologies along with key results of their previous applications in a space physics context, which particularly illustrates how complementary modern complex systems approaches have recently shaped our understanding of nonlinear magnetospheric variability. The rising number of corresponding studies demonstrates that the multiplicity of nonlinear time series analysis methods developed during the last decades offers great potentials for uncovering relevant yet complex processes interlinking different geospace subsystems, variables and spatiotemporal scales

Ionospheric response to solar and interplanetary disturbances: A Swarm perspective

The ionospheric response to solar and interplanetary disturbances has been the subject of intense study for several decades. For 5 years now, the European Space Agency's Swarm fleet of satellites surveys the Earth's topside ionosphere, measuring magnetic and electric fields at low-Earth orbit with unprecedented detail. Herein, we study in situ the ionospheric response in terms of the occurrence of plasma instabilities based on 2 years of Swarm observations. Plasma instabilities are an important element of space weather because they include irregularities like the equatorial spread F events, which are responsible for the disruption of radio communications. Moreover, we focus on three out of the four most intense geospace magnetic storms of solar cycle 24 that occurred in 2015, including the St Patrick's Day event, which is the strongest magnetic storm of the present solar cycle. We examine the associated ionospheric response at Swarm altitudes through the estimation of a Swarm Dst-like index. The newly proposed Swarm derived Dst index may be suitable for space weather applications. This article is part of the theme issue 'Solar eruptions and their space weather impact'. © 2019 The Author(s) Published by the Royal Society. All rights reserved

Dynamical complexity in Swarm electron density time series using Block entropy

Our goal in this study is to investigate the dynamical complexity of the electron density profiles in the topside ionosphere as measured by the Swarm mission, employing the use of symbolic information-theoretic techniques. We perform a Block entropy analysis for a time interval associated with the most intense magnetic storm of solar cycle 24, which occurred on 17 March 2015. We produce entropy maps for varying degrees of magnetospheric disturbance, resolving the different effects that the various geomagnetic activity levels have in the dynamics of the complex magnetosphere-ionosphere coupling system. Understanding the impact of these effects on the ionospheric plasma constitutes a crucial factor for the functionality of the modern technological infrastructure operating around the Earth and, thus, human welfare. Copyright © 2020 EPLA