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<...
Main Author: | |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2011-08-01
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Series: | Annales Geophysicae |
Online Access: | https://www.ann-geophys.net/29/1331/2011/angeo-29-1331-2011.pdf |
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. |
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ISSN: | 0992-7689 1432-0576 |