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Saturn's magnetic field periodicities at high latitudes and the effects of spacecraft motion and position
Author(s) -
Carbary J. F.,
Provan G.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023611
Subject(s) - spacecraft , physics , magnetic field , amplitude , astrophysics , saturn , latitude , longitude , position (finance) , field (mathematics) , computational physics , geodesy , astronomy , geology , optics , planet , mathematics , finance , quantum mechanics , pure mathematics , economics
Lomb periodogram analyses have been applied to magnetic field observations made by the Cassini spacecraft during its high‐latitude orbits from 2006 to 2009. Only data from open‐field regions (OFRs), identified by absence of thermal electrons, were used to separate pure north and south periodic signals. In agreement with previous investigations, the periodograms reveal signals at 10.6 h in the northern OFR and at 10.8 h in the southern OFR but only for the B θ and B ϕ components. The B r component exhibited essentially no periodicity in either the north or south, or at least its periodicity amplitude was too small for detection. In addition, the B θ and B ϕ components displayed signals at ~10.0 h and ~11.2 h in the north and ~10.2 h and ~11.5 h and possibly ~9.6 h in the south. These periods can be reproduced by a simulation by using a rotating “searchlight” model with different north and south periods and an r −3 dependence. This investigation employs a Lomb‐Scargle method to analyze magnetic field periodicities and confirms that the magnetic fields have “pure” north and south periods in the respective hemispheres. The results also imply that a radial dependence in these fields exists, which is expected if the fields are produced by field‐aligned currents. Using this model, the effects of spacecraft motion and position can be readily detected in the Lomb analyses.