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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 2
Ann. Geophys., 36, 621-631, 2018
https://doi.org/10.5194/angeo-36-621-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Ann. Geophys., 36, 621-631, 2018
https://doi.org/10.5194/angeo-36-621-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 16 Apr 2018

Regular paper | 16 Apr 2018

A critical note on the IAGA-endorsed Polar Cap (PC) indices: excessive excursions in the real-time index values

Peter Stauning Peter Stauning
  • Danish Meteorological Institute, Copenhagen, Denmark

Abstract. The Polar Cap (PC) indices were approved by the International Association for Geomagnetism and Aeronomy (IAGA) in 2013 and made available at the web portal http://pcindex.org holding prompt (real-time) as well as archival index values. The present note provides the first reported examination of the validity of the IAGA-endorsed method to generate real-time PC index values. It is demonstrated that features of the derivation procedure defined by Janzhura and Troshichev (2011) may cause considerable excursions in the real-time PC index values compared to the final index values. In examples based on occasional downloads of index values, the differences between real-time and final values of PC indices were found to exceed 3mVm−1, which is a magnitude level that may indicate (or hide) strong magnetic storm activity.

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The Polar Cap (PC) indices, PCN (North) based on magnetic data from Qaanaaq (Thule) and PCS (South) based on Vostok data, reflect the transpolar convection of plasma and magnetic fields. The PC indices could be used, among others, to indicate the energy transfer from the solar wind to the magnetosphere–ionosphere–thermosphere system in space weather monitoring applications. The present IAGA-endorsed methods to derive PC indices in real time are found to generate inconsistent index values.
The Polar Cap (PC) indices, PCN (North) based on magnetic data from Qaanaaq (Thule) and PCS...
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