The Magnetosphere as a Complex Network: Dependence on Geomagnetic Activity

The magnetosphere is a distributed system with different features in different regions and can be viewed as a complex network, with its spatio-temporal dynamics represented by the magnetic field variations at ground magnetometer stations. In a typical complex network there are specific connections among the nodes and there is scale-free distribution of the connectivity. The connectivity among the magnetometer stations however is different because of the connections are characterized by a field, viz. the magnetic field. The time series data of magnetic field variations at 120 magneometer stations around the globe, covering the period 1995 - 2006, is used to analyze the network properties of the magnetospheric dynamics. The probability density function for different degrees of connectivity show distinct characteristics for different levels of geomagnetic activity. This result is in agreement with the earlier studies of magnetospheric activity and indicates multiscale nature of the complex network. Thus the scale-free behavior often represented by a single exponent in complex networks, could arise from the mixing of different levels of activity, e.g., the mixing of network behavior under normal and disturbed conditions. This underscores the necessity of studying the network behavior under different conditions, as it is expected to be more complicated than the scale-free case with a single exponent.