Modelling the outer radiation belt as a complex system in a self-organised critical state
1University College London, Mullard Space Science Laboratory, Holmbury St.\ Mary, Dorking, Surrey, RH5 6NT, UK
*now at: Belgian Institute for Space Aeronomy, Ringlaan-3-Avenue Circulaire, 1180 Brussels, Belgium
**now at: British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge, CB3 0ET, UK
Abstract. The dynamic behaviour of the outer electron radiation belt makes this area of geo-space a candidate for the concept of self-organized criticality. It is shown here that frequency distributions of measured outer electron radiation belt data are well-represented by power-laws over two decades. Applying the concept of self-organized criticality to interpret the shape of the distributions suggests another approach to complement existing methods in the interpretation of how this complicated environment works. Furthermore sub-grouping the radiation belt count rate data as a function of spatial location or temporal interval (e.g. L-shell, magnetic local time, solar cycle, ...) shows systematic trends in the value of the slope of the power-laws. It is shown that the inner part of the outer radiation belt is influenced in a similar manner to the outer part, but in a less profound way. Our results suggest that the entire outer radiation belt appears to be affected as the sum of its individual parts. This type of study also gives the probability of exceeding a given threshold value over a given time; limiting the size of "an event". The average values could then be compared with models used in spacecraft design.
Citation: Crosby, N. B., Meredith, N. P., Coates, A. J., and Iles, R. H. A.: Modelling the outer radiation belt as a complex system in a self-organised critical state, Nonlin. Processes Geophys., 12, 993-1001, doi:10.5194/npg-12-993-2005, 2005.