TY - JOUR

T1 - Swarm field-aligned currents during a severe magnetic storm of September 2017

AU - Lukianova, Renata

N1 - Funding Information: Swarm data are available through the European Space Agency Online platform (ftp://swarm-diss.eo.esa.int, last access: 1 December 2019), after registration. We acknowledge the Swarm Science Team for providing the Level 2 data and the Swarm visualization tool (https://vires.services/, last access: 1 December 2019). The OMNI data on the solar wind, interplanetary magnetic field and geomagnetic indices are obtained from NASA/GSFC s Space Physics Data Facility s CDA web service (http://omniweb.gsfc.nasa.gov/, last access: 12 October 2019). Publisher Copyright: © 2020 BMJ Publishing Group. All rights reserved. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/2/7

Y1 - 2020/2/7

N2 - Swarm satellite observations are used to characterize the extreme behavior of large- and small-scale field-aligned currents (FACs) during the severe magnetic storm of September 2017. Evolutions of the current intensities and the equatorward displacement of FACs are analyzed while the satellites cross the pre-midnight, pre-noon, dusk and dawn sectors in both hemispheres. The equatorward boundaries of FACs mainly follow the dynamics of the ring current as monitored in terms of the SYM-H index. The minimum latitude of the FAC boundaries is limited to 50ĝ' magnetic latitude (MLat). The FAC densities are very variable and may increase dramatically, especially in the nightside ionosphere during the storm-time substorms. At the peak of substorms, the average FAC densities reach >3μAm-2. The dawn-dusk asymmetry is manifested in the enhanced dusk-side R2 FACs in both hemispheres. In the 1Hz data filamentary high-density structures are always observed. In the pre-noon sector, the bipolar structures (7.5km width FACs of opposite polarities adjacent to each other) dominate, while at the other local times the upward and downward FACs tend to be latitudinally separated. The most intense small-scale FACs, up to ĝ'1/480μAm-2, are observed just in the post-midnight sector. Simultaneous magnetic and plasma perturbations indicate that this structure is likely a current system of a mesoscale auroral arc.

AB - Swarm satellite observations are used to characterize the extreme behavior of large- and small-scale field-aligned currents (FACs) during the severe magnetic storm of September 2017. Evolutions of the current intensities and the equatorward displacement of FACs are analyzed while the satellites cross the pre-midnight, pre-noon, dusk and dawn sectors in both hemispheres. The equatorward boundaries of FACs mainly follow the dynamics of the ring current as monitored in terms of the SYM-H index. The minimum latitude of the FAC boundaries is limited to 50ĝ' magnetic latitude (MLat). The FAC densities are very variable and may increase dramatically, especially in the nightside ionosphere during the storm-time substorms. At the peak of substorms, the average FAC densities reach >3μAm-2. The dawn-dusk asymmetry is manifested in the enhanced dusk-side R2 FACs in both hemispheres. In the 1Hz data filamentary high-density structures are always observed. In the pre-noon sector, the bipolar structures (7.5km width FACs of opposite polarities adjacent to each other) dominate, while at the other local times the upward and downward FACs tend to be latitudinally separated. The most intense small-scale FACs, up to ĝ'1/480μAm-2, are observed just in the post-midnight sector. Simultaneous magnetic and plasma perturbations indicate that this structure is likely a current system of a mesoscale auroral arc.

UR - http://www.scopus.com/inward/record.url?scp=85079412770&partnerID=8YFLogxK

U2 - 10.5194/angeo-38-191-2020

DO - 10.5194/angeo-38-191-2020

M3 - Article

AN - SCOPUS:85079412770

VL - 38

SP - 191

EP - 206

JO - Annales Geophysicae

JF - Annales Geophysicae

SN - 0992-7689

IS - 1

ER -