scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Ground Magnetic Characteristics of the Solar Diurnal Variations: A Case Study Based
on Records from Vassouras Observatory (Brazil)
Klausner Virginia 1 , Papa Andres R. R. 1 , Mendes Jr Odim 2 , Domingues Margarete O.
1 Observatorio Nacional, 2 Instituto Nacional de Pesquisas Espaciais, 3
A recently developed method is used to perform a spectral analysis study of global quiet
geomagnetic field variations via a principal component analysis. It is well known that the
solar quiet variation measured on the Earth’s surface presents characteristic frequencies with
24, 12, 8 and 6-hour periods. Those typical kinds of oscillations are primarily due to the
global thermotidal wind systems which conduct currents flowing in the “dynamo region” of
the ionosphere, the E-region. In this study, the horizontal component amplitude observed by
ground-based observatories belonged to the INTERMAGNET network have been used to
analyze the global pattern variance of the Sq variation. The methodological approach is based
on Principal Component Analysis (PCA). The PCA is a mathematical tool useful to transform
a number of correlated variables into a number of uncorrelated variables called principal
components. The first principal component accounts for as much of the variability in the data
as possible, and each succeeding component accounts for as much of the remaining variability
as possible. By applying the PCA to datasets of geomagnetic quiet days, we determined the
global dominant patterns of the geomagnetic field variance. The purpose of this work is to
describe the global dominant patterns of variance in the time series of Vassouras (VSS) and
other magnetic stations reasonably well-distributed over the whole Earth’s surface.