PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
Dynamics of magnetospheric activity (Ap_M) has features which are not present in dynamics of
solar activity (SSN M) (see Fig. 1b). Dynamics Ар_M contains an 11-year component of dynamics of solar
activity, but has essential differences. They are visible in details with characteristic time scale in some years.
Namely: a local minimum of Ар when SSN has maximum or a maximum of Ар on a SSN declining phase
are observed. So dynamics of SSN amplitude does not define dynamics of amplitude of magnetospheric
activity, at least, with time scales in solar cycle duration.
In this paper we wish to answer the question – whether the solar activity contains the information on
dynamics of magnetospheric activity? If “yes”, what parameter of dynamics SSN defines dynamics of Ар,
what parameter SSN is geoeffective? The magnetosphere is a dynamic system in which the external force is
generated by the sun. This force consists of quasi-periodic and chaotic components. Can exactly the solar
activity chaotic component define the features of the Earth magnetospheric activity?
Chaotic component SSN_Ch (see Fig. 1c) will be analysed. Note that dynamics of average amplitude
of chaotic component SSN_Ch_M is also not define Ap_M, as SSN_Ch_M correlates with SSN_M (see Fig.
1c).
We have developed the approach considering the Earth’s magnetosphere as a nonlinear system with
own noise, being under action of external force which is the Solar activity chaotic component. Even a weak
external noise influencing nonlinear system can change effectively its condition. If there exists an optimum
amplitude of chaotic influences on the nonlinear system, when a required signal-to-noise ratio has a
maximum, it can be attributed to a stochastic resonance effect - SR. In the experiment, when there is no
opportunity to operate the amplitude of chaotic influences, for search of the effect SR it is possible to use the
concept which has the name of not dynamic threshold effect. [Anishchenko at all, 1999]. When analyzing
chaotic components of solar activity for search of the parameter correlating with dynamics of the Ap-index,
we have applied the SR method modified by us.
Daily values of a chaotic component of the solar activity SSN_Сh have been analyzed. At each level
of the comparison we get a signal which contains the basic features of a chaotic signal, namely a level of
amplitude and an “average frequency” of dynamics SSN_Ch corresponding to this level. The concept of
nondynamic threshold scanning was used in the authors modification. The signal SSN_Ch was transformed
for the given level of comparison S so that signal SR SSN_Ch = 1 if SSN_Ch is transition through S and SR
SSN_Ch = 0 if SSN_Ch is not transition through S. Further, we scanned the level S and for each level of a
comparison S we calculated the correlation coefficient between average series SR SSN_Ch_M and the
Ap_M.
The result of analysis of chaotic component SSN_Ch by the method SR – curve SR SSN_Ch_M and
its comparison with Ap_M at Ccor = maximum = 0.75 is presented at Fig. 2. SR SSN_Ch_M has a features
of magnetospheric activity AP_M which are not present in dynamics of solar activity SSN_M.
Fig. 2. Dynamics of geoeffective parameter SSN (SR SSN_Ch_M) and magnetospheric activity Ap_M at
maximum Ccor.
The magnetosphere can be viewed as the system which is in a metastable state. The influence of an
external noise on such systems will lead to occurrence of casual switching between attractors of the system.
As a result the geomagnetic activity will be defined by properties of the external noise.
At the Fig. 3 we can see that there is an optimum of chaotic amplitude influences on nonlinear
system (magnetosphere) when the required signal-to-noise ratio has a maximum. It is an essential attribute of
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