A critical note on the IAGA-endorsed Polar Cap index procedure: effects of solar wind sector structure and reverse polar convection
Open Access
- 30 November 2015
- journal article
- Published by Copernicus GmbH in Annales Geophysicae
- Vol. 33 (11), 1443-1455
- https://doi.org/10.5194/angeo-33-1443-2015
Abstract
The International Association of Geomagnetism and Aeronomy (IAGA) has recently endorsed a new Polar Cap (PC) index version to supersede the previous seven different versions of the PCN (North) index and the five different PCS (South) index versions. However, the new PC index has some adverse features which should be known and taken into account by users of the index. It uses in its derivation procedure an "effective" quiet day level (QDC) composed of a "basic" QDC and an added solar wind sector term related to the azimuthal component (By) of the interplanetary magnetic field (IMF). The added IMF By-related terms may introduce unjustified contributions to the PC index of more than 2 index units (mV m−1). Furthermore, cases of reverse convection during strong northward IMF Bz (NBZ) conditions included in the database for calculation of index coefficients can cause unjustified index enhancements of 0.5–1 mV m−1 during calm conditions, reduction of index values by more than 20 % during disturbed conditions, and inconsistencies between index coefficients and index values for the northern and southern polar caps. The aim here is to specify these adverse features and quantify their effects, and to suggest alternative steps for future modifications of the index procedure.Keywords
This publication has 30 references indexed in Scilit:
- Utilizing the polar cap index to explore strong driving of polar cap dynamicsJournal of Geophysical Research, 2012
- Identification of the IMF sector structure in near-real time by ground magnetic dataAnnales Geophysicae, 2011
- PCN magnetic index and average convection velocity in the polar cap inferred from SuperDARN radar measurementsJournal of Geophysical Research, 2009
- Determination of the running quiet daily geomagnetic variationJournal of Atmospheric and Solar-Terrestrial Physics, 2008
- Unified PC indices: Relation to isolated magnetic substormsJournal of Geophysical Research, 2007
- Variations of polar cap index in response to solar wind changes and magnetospheric substormsJournal of Geophysical Research, 2005
- Correlation of auroral power with the polar cap indexJournal of Geophysical Research, 2003
- Joule heating patterns as a function of polar cap indexJournal of Geophysical Research, 2002
- Polar cap index as a proxy for hemispheric Joule heatingGeophysical Research Letters, 1999
- Energy coupling function and solar wind‐magnetosphere dynamoGeophysical Research Letters, 1979