Browsing by Author "Mbonteh Roland"

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    Solar Variability: the Connection Between Solar Surface Magnetic Flux Density and Solar UV Variability
    (Addis Ababa University, 2024-07-30) Mbonteh Roland; Negessa Tilahun
    The strength of Solar surface magnetic flux plays an important role in the variability of solar UV irradiance. Several proxies of magnetic activity such as MgII, CaII, and f10.7 have been introduced to correlate solar UV irradiance variability. Daily weak flux densities (WFDs) during solar minimum in 2010 and solar maximum in 2014 calculated from the Solar Dynamic Observatory/Helioseismic Magnetic Imager was used. SSI measurements are from the Solar Stellar Irradiance Comparison Experiment (SOLSTICE). The influence of the magnetic flux density variation on the SSI has been characterized using Spearman, Pearson, and wavelet analysis. The Pear- son’s correlation shows that the SSI has a significant positive correlation with weak flux density (WFD) in 2010 and less in 2014; Spearman shows the same. Wavelet analysis also supports the idea that the WFD and SSI have a moderate causality linkage (in both 2010 and 2014) and that the WFD influences solar UV variability on the rotational timescale. The CWT also shows a significant correlation in 2010 than in 2014, while correlogram analysis follows suit and shows more sensitivity between SSI and CaII K lines, indicating a potential shift in solar activity mechanisms and signifying that other external factors are affecting solar activity.