The correlation between solar and geomagnetic activity – Part 1: Two-term decomposition of geomagnetic activity

By analyzing the logarithmic relationship between geomagnetic activity as represented by the annual <I>aa</I> index and solar magnetic field activity as represented by the annual sunspot number (<I>R</I><sub>z</sub>) during the period 1844–2010, <I>aa<...

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Bibliographic Details
Main Author: Z. L. Du
Format: Article
Language:English
Published: Copernicus Publications 2011-08-01
Series:Annales Geophysicae
Online Access:https://www.ann-geophys.net/29/1331/2011/angeo-29-1331-2011.pdf
Description
Summary:By analyzing the logarithmic relationship between geomagnetic activity as represented by the annual <I>aa</I> index and solar magnetic field activity as represented by the annual sunspot number (<I>R</I><sub>z</sub>) during the period 1844–2010, <I>aa</I> is shown to lie in between two lines defined solely by <I>R</I><sub>z</sub>. Two ways can be used to decompose the <I>aa</I> index into two components. One is decomposing <I>aa</I> into the sum of the baseline (<I>aa</I><sub>b</sub>) and the remainder (<I>aa</I><sub>u</sub>) with a null correlation. Another is dividing the top-line (<I>aa</I><sub>t</sub>) into the sum of <I>aa</I> and the remainder (<I>aa</I><sub>d</sub>) with a null correlation. The first decomposition is similar to the traditional one. The second decomposition implies a nonlinear relationship of <I>aa</I> with <I>R</I><sub>z</sub> (<I>aa</I><sub>t</sub>) and a decay process (<I>aa</I><sub>d</sub>). Therefore, <I>aa</I><sub>t</sub>=<I>aa</I>+<I>aa</I><sub>d</sub>=<I>aa</I><sub>b</sub>+<I>aa</I><sub>u</sub>+<I>aa</I><sub>d</sub>: (i) <I>aa</I><sub>t</sub> is related to the solar energy potential of generating geomagnetic activity (associated with <I>R</I><sub>z</sub>); (ii) <I>aa</I><sub>b</sub> is related to transient phenomena; (iii) <I>aa</I><sub>u</sub> is related to recurrent phenomena; and (iv) <I>aa</I><sub>d</sub> is related to the energy loss in the transmission from solar surface to the magnetosphere and ionosphere that failed to generate geomagnetic activity.
ISSN:0992-7689
1432-0576