On the terms of geomagnetic daily variation in Antarctica

Abstract

Abstract. The target of this work is to investigate the nature of magnetic perturbations produced by ionospheric and magnetospheric currents as recorded at high-latitude geomagnetic stations. In particular, we investigate the effects of these currents on geomagnetic data recorded in Antarctica. To this purpose we apply a mathematical method, known as Natural Orthogonal Composition, to analyze the magnetic field disturbances along the three geomagnetic field components (X, Y and Z) recorded at Mario Zucchelli Station (IAGA code TNB; geographic coordinates: 74.7 • S, 164.1 • E) from 1995 to 1998. Using this type of analysis, we characterize the dominant modes of the geomagnetic field daily variability through a set of empirical orthogonal functions (EOFs). While such mathematically independent EOFs do not necessarily represent physically independent modes of variability, we find that some of them are actually related to well known current patterns located at high latitudes.

Sq solar variation at Medea Observatory (Algeria), from 2008 to 2011

“…In the Southern hemisphere, it is the contrary as the current flows reverse compared to the northern hemisphere. We must recall here that the main pattern of Sq observed on data is roughly similar to this ideal pattern (Pham et al, 2011;De Michelis & al., 2009;Torta et al, 2010). Figure 2: Sq current system schema (after Mazaudier, 1983).…”

On the origin of intermittency in wave turbulence

“…However, the physical mechanism of intermittency is still an open question [3]. Intermittency has also been observed in granular systems [4], in magnetohydrodynamic turbulence in geophysics [5] or in the solar wind [6], and in systems involving transport by a turbulent flow [7]. A recent observation of intermittency has been reported in wave turbulence [8], a system that strongly differs from high Reynolds number hydrodynamic turbulence.…”

Principal Component Analysis As a Tool to Extract Sq Variation from the Geomagnetic Field Observations: Conditions of Applicability

“…Later, Xu and Kamide (2004) and Chen et al (2007) revived the interest of the geomagnetic community in PCA as a useful tool that allows not only to extract regular variations of the geomagnetic eld, as Sq and SD but also to analyze seasonal and geographic variations of the phase and amplitude of the Sq and SD elds and the dependence of their intensity on the level of the solar and geomagnetic activity. Works of Wu et al (2007), De Michelis et al, (2009Michelis et al, ( , 2010, Bhardwaj et al (2015Bhardwaj et al ( , 2016 and others (see also review by Yamazaki and Maute, 2017), generally con rmed the applicability of PCA to the extraction of the regular geomagnetic eld variations observed at different latitudes, and for the time intervals of different length and corresponding to different geomagnetic activity levels. However, the results obtained for different regions/time intervals were somewhat different.…”

“…Another way to extract regular variations as Sq is to apply a decomposition method to the geomagnetic eld data: e.g., the wavelet analysis (Maslova et al, 2010), the empirical mode decomposition (Piersanti et al, 2017) or the principal component analysis, PCA (Xu and Kamide, 2004;Chen et al, 2007;De Michelis et al, 2009. On the other hand, the shape and position of the vortex can be deduced from the observational data using the spherical harmonic analysis by calculating the equivalent electric eld (Takeda, 1982;Haines and Torta, 1994) or it can be reconstructed as equivalent electric current vectors (horizontal component) from the observed horizontal geomagnetic eld vector (Stening et al, 2005;Stening, 2008).…”