Source separation techniques for characterising cosmic ray transients   from neutron monitor networks
  The analysis of weak variations in the energetic particle flux, as detected by neutron or muon monitors, can often be considerably improved by analysing data from monitor networks and thereby exploiting the spatial coherence of the flux. We present a statistical framework for carrying out such an analysis and discuss its physical interpretation. Two other applications are also presented: filling data gaps and removing trends. This study focuses on the method and its various uses. 
T. Dudok de Wit, A. A. Chilingarian, G. G. Karapetyan