 |
| Titel |
Long-term biases in geomagnetic K and aa indices |
| VerfasserIn |
J. J. Love |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 29, no. 8 ; Nr. 29, no. 8 (2011-08-19), S.1365-1375 |
| Datensatznummer |
250017071
|
| Publikation (Nr.) |
 copernicus.org/angeo-29-1365-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| Analysis is made of the geomagnetic-activity aa index and its source
K-index data from groups of ground-based observatories in Britain, and
Australia, 1868.0–2009.0, solar cycles 11–23. The K data show persistent
biases, especially for high (low) K-activity levels at British (Australian)
observatories. From examination of multiple subsets of the K data we infer
that the biases are not predominantly the result of changes in observatory
location, localized induced magnetotelluric currents, changes in magnetometer
technology, or the modernization of K-value estimation methods. Instead,
the biases appear to be artifacts of the latitude-dependent scaling used to
assign K values to particular local levels of geomagnetic activity. The
biases are not effectively removed by weighting factors used to estimate
aa. We show that long-term averages of the aa index, such
as annual averages, are dominated by medium-level geomagnetic activity levels
having K values of 3 and 4. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|