The Entropy Index (EI): an Auxiliary Tool to Identify the Occurrence of   Interplanetary Magnetic Clouds
  By the study of the dynamical processes related to entropy, this work aims to create a mathematical tool to identify magnetic clouds (MCs) in the interplanetary space using only interplanetary magnetic field (IMF) data. Used as basis for an analysis methodology, the spatio-temporal entropy (STE) measures the image (recurrence plots) "structuredness" in both space and time domains. Initially we worked with the Huttunen et al. 2005's dataset and studied the 41 MCs presenting a shock wave identified before the cloud. The STE values for each Bx, By, Bz IMF time series, with dimension and time delay equal to one, were respectively calculated. We found higher STE values in the sheaths and zero STE values in some of the three components in most of the MCs (30 among 41 events). In a physically consistent manner, data windows of 2500 magnetic records were selected as the calculation interval for the time series. As not all MCs have zero STE simultaneously, we created a standardization index (an entropy index, called as EI) to allow joining the result of the three components. With the use of EI three not known MCs were indeed identified and then the MVA method allowed calculating their boundaries. Thus the EI is proposed as an auxiliary tool to identify MC candidates based only on IMF analysis. In a promissor condition, this methodology implemented gives basis for an automatic MC identification procedure and surely useful for space weather purposes. 
G. A. Ojeda, O. Mendes, M. A. Calzadilla, M. O. Domingues
physics.space-ph