Assessing the Relationship Between the Quasi-Biennial Oscillation and D-Region Electron Density
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Abstract
High frequency (HF) communication is a vital aspect of military communication and is highly reliant upon ionospheric conditions. The variation in electron density within the lowest echelon of the ionosphere, the D-region, can significantly impact HF signals, making communication inconsistent and unreliable for these wavelengths. Despite the D-region’s important, research in this area mainly focuses on understanding the impact of space weather anomalies on the upper ionosphere, particularly its higher layers, with relatively little exploration of the D-region. This region, situated closest to the troposphere and stratosphere, has been definitively linked to solar weather events like solar flares and geomagnetic storms, as well as to terrestrial weather patterns. However, despite these established connections, there remains a notable gap in the scientific literature concerning the relationship between the lower ionosphere and meteorological phenomena. Within this study, Fast Fourier Transforms (FFT), Continuous Wavelet Transforms (CWT), and Cross Wavelet Transforms (XWT) are calculated to identify the relationship between stratospheric Quasi-Biennial Oscillation (QBO) and the ionosphere D-Region electron density. The FFT analysis of the averaged electron density revealed a notable association with the significant frequencies of both QBO pressure levels, particularly the frequency .33 yr−1 (period of approximately 3 years), which appeared prominently across latitude bins. The QBO’s impact on electron density, particularly during the day and at lower latitudes, produced statistical significance. The consistent phase relationship of approximately -.61 months for the QBO frequency .33 yr−1, suggested a significant and accurate relationship, possibly indicating QBO propagation from the upper stratosphere to the lower ionosphere with a time lag of about 18 days. This discovered time relationship could inform strategic planning and operational adjustments for HF communications reliant upon D-region conditions.