Naslov
On minimizing the external field contributions in annual means of the European geomagnetic observatories

Autori
Verbanac, Giuliana ; Korte, Monika ; Mandea, Mioara.

Izvornik
Geofizika (0352-3659) 25 (2008), 1; 27-39

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
observatory annual means ; external field ; ring current

Sažetak
The aim of this study is to provide a method for minimizing the external field contri- butions in the observatory annual means and try to separate, interpret and explain all the different external field signals present in these data. Investigating the European geomag- netic observatory biases over 42 years, considered as contributions of the crustal field, and generally assumed to be constant in time, we noticed the link to the solar cycle, with short period variations in the order of ± 10 nT. Developing an empirical method for minimizing the external fields presented in the observatory annual means, we were able to reduce them better than the used of the external field description included in the global Comprehen- sive Model, CM4 (Sabaka et al., 2004) was. The external field module provided by the POtsdam Magnetic model of the Earth, POMME-2.5, (Maus et al., 2005) was considered for investigating the sources and characteristics of various external field contributions. We have been able to separate magnetospheric and ionospheric fields, as well as to remove a still significant variation with a function properly scaled by Ap and Dst indices. With this procedure the external field contributions in the annual means are minimized to an uncertainty level of ± 2 nT. Our study shows a way to obtain corrected observatory annual means, in order to be used for different studies of the internal geomagnetic field.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA