Preprints
https://doi.org/10.5194/angeo-2021-37
https://doi.org/10.5194/angeo-2021-37

  28 Jun 2021

28 Jun 2021

Review status: a revised version of this preprint is currently under review for the journal ANGEO.

Spatio-temporal development of large scale auroral electrojet currents relative to substorm onsets

Sebastian Käki1,2, Ari Viljanen1, Liisa Juusola1, and Kirsti Kauristie1 Sebastian Käki et al.
  • 1Finnish Meteorological Institute, Helsinki, Finland
  • 2University of Helsinki, Helsinki, Finland

Abstract. During auroral substorms the electric currents flowing in the ionosphere change rapidly and a large amount of energy is dissipated in the auroral ionosphere. An important part of the auroral current system are the auroral electrojets whose profiles can be estimated from magnetic field measurements from Low Earth Orbit satellites. In this paper we combine electrojet data derived from the Swarm satellite mission of ESA with the substorm database derived from the SuperMAG ground magnetometer network data. We organize the electrojet data in relation to the location and time of the onset and obtain statistics for the development of the integrated current and latitudinal location for the auroral electrojets relative to the onset. The major features of the behaviour of the westward electrojet are found to be in accordance with earlier studies of field aligned currents and ground magnetometer observations of substorm time statistics. In addition we show that after the onset the latitudinal location of the maximum of the westward electrojet determined from Swarm satellite data is mostly located close to the SuperMAG onset latitude in the local time sector of the onset regardless of where the onset happens. We also show that the SuperMAG onset corresponds to a strengthening of the order of 100 kA in the amplitude of the median of the westward integrated current in the Swarm data from 15 minutes before to 15 minutes after the onset.

Sebastian Käki et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on angeo-2021-37', Anonymous Referee #1, 21 Jul 2021
    • AC1: 'Reply on RC1', Sebastian Käki, 03 Sep 2021
  • RC2: 'Comment on angeo-2021-37', Anonymous Referee #2, 05 Aug 2021
    • AC2: 'Reply on RC2', Sebastian Käki, 03 Sep 2021

Sebastian Käki et al.

Sebastian Käki et al.

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Short summary
During auroral substorms the ionospheric electric currents change rapidly and a large amount of energy is dissipated. We combine ionospheric current data derived from the Swarm satellite mission with the substorm database from the SuperMAG ground magnetometer network. We obtain statistics of the strength and location of the currents relative to the substorm onset. Our results show that Low Earth Orbit satellites give a coherent picture of the main features in the substorm current system.