Abstract
The aim of this work is to study the properties of the magnetic field’s fluctuations produced by ionospheric and magnetospheric electric currents during the St. Patrick’s Day geomagnetic storm (17 March 2015). We analyse the scaling features of the external contribution to the horizontal geomagnetic field recorded simultaneously by the three satellites of the Swarm constellation during a period of 13 days (13–25 March 2015). We examine the different latitudinal structure of the geomagnetic field fluctuations and analyse the dynamical changes in the magnetic field scaling features during the development of the geomagnetic storm. Analysis reveals consistent patterns in the scaling properties of magnetic fluctuations and striking changes between the situation before the storm, during the main phase and recovery phase. We discuss these dynamical changes in relation to those of the overall ionospheric polar convection and potential structures as reconstructed using SuperDARN data. Our findings suggest that distinct turbulent regimes characterised the mesoscale magnetic field’s fluctuations and that some factors, which are known to influence large-scale fluctuations, have also an influence on mesoscale fluctuations. The obtained results are an example of the capability of geomagnetic field fluctuations data to provide new insights about ionospheric dynamics and ionosphere–magnetosphere coupling. At the same time, these results could open doors for development of new applications where the dynamical changes in the scaling features of the magnetic fluctuations are used as local indicators of magnetospheric conditions.
Highlights
The Swarm mission (Olsen 2013) is set up to study the Earth’s magnetic field and its temporal variations, as well as a variety of near-Earth environmental parameters
At very high latitudes (>80◦N altitude-adjusted corrected geomagnetic (AACGM) Lat), the correlations in the magnetic field fluctuations have an anti-persistent character and the size of this region changes with the geomagnetic activity level
We find a well defined region of anti-persistent character around 80◦N AACGM Lat during the whole recovery phase of the geomagnetic storm, while the width of this anti-persistent region becomes larger during both the main phase of the geomagnetic storm (17 March) and the day before (16 March 2015)
Summary
The Swarm mission (Olsen 2013) is set up to study the Earth’s magnetic field and its temporal variations, as well as a variety of near-Earth environmental parameters. The St. Patrick’s Day storm was characterised by a minimum value of the geomagnetic index Sym-H of −234 nT, realised on 17 March at 22:47 UT, and it produced a worldwide disturbance quantified by a value equal to 8 of the mid-latitude magnetic activity index Kp, which persisted for some hours during the main phase of the geomagnetic storm. Patrick’s Day storm was characterised by a minimum value of the geomagnetic index Sym-H of −234 nT, realised on 17 March at 22:47 UT, and it produced a worldwide disturbance quantified by a value equal to 8 of the mid-latitude magnetic activity index Kp, which persisted for some hours during the main phase of the geomagnetic storm As it is typical for a severe storm, during this event geomagnetic activity was intense at high latitudes and auroral phenomena were observed even at surprisingly low latitudes around the globe. As reported by Cherniak and Zakharenkova (2015) and Nishitani et al (2015) during the 17 March 2015 storm, auroral phenomena were observed even at very low magnetic latitudes in Europe, Japan and the USA
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