Interplanetary magnetic field control of polar ionospheric equivalent current system modes

Shore, Robert ORCID: https://orcid.org/0000-0002-8386-1425; Freeman, Mervyn ORCID: https://orcid.org/0000-0002-8653-8279; Gjerloev, Jesper. 2019 Interplanetary magnetic field control of polar ionospheric equivalent current system modes. Space Weather, 17 (7). 976-988. https://doi.org/10.1029/2019SW002161

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Text (Open Access) ©2019. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Shore_et_al-2019-Space_Weather.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (2MB) | Preview

Abstract/Summary

We analyse the response of different ionospheric equivalent current modes to variations in the interplanetary magnetic field (IMF) components By and Bz. Each mode comprises a fixed spatial pattern whose amplitude varies in time, identified by a month‐by‐month empirical orthogonal function separation of surface measured magnetic field variance. Here we focus on four sets of modes that have been previously identified as DPY, DP2, NBZ and DP1. We derive the cross‐correlation function of each mode set with either IMF By or Bz for lags ranging from ‐10 to +600 mins with respect to the IMF state at the bow shock nose. For all four sets of modes, the average correlation can be reproduced by a sum of up to three linear responses to the IMF component, each centered on a different lag. These are interpreted as the statistical ionospheric responses to magnetopause merging (15‐20 mins lag) and magnetotail reconnection (60 mins lag), and to IMF persistence. Of the mode sets, NBZ and DPY are the most predictable from a given IMF component, with DP1 (the substorm component) the least predictable. The proportion of mode variability explained by the IMF increases for the longer lags, thought to indicate conductivity feedbacks from substorms. In summary, we confirm the postulated physical basis of these modes and quantify their multiple reconfiguration timescales.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1029/2019SW002161
Additional Keywords:	solar wind driving, geomagnetic response, ionospheric reconfiguration timescale, equivalent current systems
Date made live:	29 May 2019 12:04 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/523561

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