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World Data Center for Geomagnetism, Copenhagen

Unified Northern Polar Cap Magnetic Activity Index - PCNU

The above "PCN today" display of 2 days on-line updating (every 5 min) PCN index (current and preceding day) is based on 1-min values and the updating (every 1 hour) monthly summary plot "PCN this month" of preliminary PNC index values is based on 5-min averages.

Definitive PCN time series are available since 1975 in a resolution of either 1-min or 5-min values. Note that the current years PC index is still "preliminary" until the end of the year. The indices are given with an accuracy of 0.01 decimal units. The FTP directory contains yearly files PCNUyyyy.1m or .5m with the definitive 1-min and 5-min PCN indices in a new ASCII, "spreadsheet-friendly" format. The same FTP directory shall also (at a later time) contain monthly summary plots of the preliminary PCN index for the current year.

The Polar Cap Magnetic Activity Index (PC) was introduced about 20 years ago and since that time extensively used in many scientific studies [e.g., Troshichev et al., 1988; Vennerstrøm et al., 1994; Papitashvili et al., 2001; and references therein]. The two near-pole magnetic observatories are selected for derivation of this dimensionless index: PCN from Thule (now Qaanaaq) in Greenland at 85.4° corrected geomagnetic CGM latitude, and PCS from Vostok in Antarctica at -83.4°.

The northern PC index (PCN) and the southern PC index (PCS) are now both derived from using a "unified" procedure. The concept is published in the paper O. Troshichev et al., JGR, 2006 . Further details on the procedure, tables of all involved parameters, and validation analysis are available in the P. Stauning et al., DMI Scientific Report SR06-04, 2006.

Both indices are planned to become available on-line via the World Wide Web:

WDC for Geomagnetism, Solar-Terrestrial Physics Division, Danish Meteorological Institute, Lyngbyvej 100, DK-2100, Copenhagen, Denmark; Phone: +45 39 15 74 73; Fax: +45 39 15 74 60; Web: http://www.dmi.dk/projects/wdcc1/

If any questions arise about the unified PCN-index, please contact: Peter Stauning at DMI

Last update: 2006-07-27 (vop)