Statistical analysis of magnetotail fast flows and related magnetic disturbances

Dennis Frühauff, Karl-Heinz Glassmeier
2016 Annales Geophysicae  
<p><strong>Abstract.</strong> This study presents an investigation on the occurrence of fast flows in the magnetotail using the complete available data set of the THEMIS spacecraft for the years 2007 to 2015. The fast flow events (times of enhanced ion velocity) are detected through the use of a velocity criterion, therefore making the resulting database as large as almost 16<span class="thinspace"></span>000 events. First, basic statistical findings concerning velocity distributions,
more » ... ibutions, occurrence rates, group structures are presented. Second, Superposed Epoch Analysis is utilized to account for average profiles of selected plasma quantities. The data reveal representative time series in near and far tail of the Earth with typical timescales of the order of 1–2<span class="thinspace"></span>min, corresponding to scale sizes of 3<span class="thinspace"></span><i>R</i><sub>E</sub>. Last, related magnetic field disturbances are analyzed. It is found that the minimum variance direction is essentially confined to a plane almost perpendicular to the main flow direction while, at the same time, the maximum variance direction is aligned with flow and background field directions. The presentation of the database and first statistical findings will prove useful both as input for magneto-hydrodynamical simulations and theoretical considerations of fast flows.</p>
doi:10.5194/angeo-34-399-2016 fatcat:vqyaofbu4bhbvekhzt6jdcm2em