Featured Science Paper
A Statistical Study of the Open Magnetic Flux Content of the Magnetosphere at the time of Substorm Onset
Can we predict quakes in space?
The Aurora Borealis, along with its southern counterpart the Aurora Australis, is one of the seven natural wonders of the world. Despite forty years of study, the trigger mechanism that leads to a global activation of the aurora, known as the substorm, is one of the great outstanding problems of solar terrestrial physics. In this paper scientists from the British Antarctic Survey and University of Leicester use over 12,000 images of the Aurora Borealis taken by the IMAGE spacecraft to address this issue.
Substorms can be compared to earthquakes with a slow storage of energy which is suddenly explosively released. In both cases this release of energy is seemingly unpredictable. In the case of substorms the energy is stored by increasing the amount of the Earth’s magnetic field which is connected to outer space (open magnetic flux). There are many models suggesting different scenarios of substorm development that are hotly contested within the space physics community. One such model predicts that substorms occur when the amount of open magnetic flux reaches some fixed threshold.
The large data set used in this study allowed the probability of substorm onset as a function of open magnetic flux to be determined for the first time. It was shown that although a significant amount of open magnetic flux needed to be present at substorm onset, there was no evidence for a fixed threshold. Furthermore, the results of this study place important constraints on future substorm models.
Boakes, P. D. (BAS, Univ. of Leicester), S. E. Milan (Univ. of Leicester), G. A. Abel, M. P. Freeman, G. Chisham (BAS) and B. Hubert (Univ. of Liege, Belguim), 2009.
Geophysical Research Letters, 36, L04105, doi:10.1029/2008GL037059