Work

Regional Characteristics of Geomagnetic Activity: Comparative Analysis of Local K and Global Kp Indices

Year: 2025

Type: article

Abstract: Geomagnetic activity reflects the complex coupling between the solar wind, magneto-sphere and ionosphere. While the global Kp index serves as a standard proxy for geo-magnetic disturbances, it obscures regional variations linked to local current systems and ionospheric conductivity. This study investigates regional features of geomagnetic activity using the local K index from the Almaty (AAA) observatory and compares its temporal dynamics with Kp for 2007–2025. A combination of statistical, spectral, wavelet, and nonlinear methods was applied, including power spectral density, continuous and cross-wavelet transforms, multifractal detrended fluctuation analysis, and permutation entropy. These approaches capture both linear and nonlinear features of variability and reveal scale-dependent structures in geomagnetic fluctuations. The results show a high correlation (r ≈ 0.84) between K (AAA) and Kp, but with a consistent positive offset of the local index, indicating sensitivity to regional ionospheric processes. Wavelet coherence highlights strong coupling in the 13–27-day band associated with solar rotation. Multifractal spectra reveal broader, more heterogeneous scaling in Kp and narrower, more intermittent dynamics in K during disturbed periods. Local indices, like K (AAA), thus provide essential insight into mid-latitude electrodynamics, complementing global measures in characterizing the nonlinear spatio-temporal complexity of geomagnetic activity.

Source: Atmosphere

DOI: 10.3390/atmos16121319