Electric current and magnetic field geometry in flapping magnetotail current sheets

By A. Runov, V. Sergeev, Wolfgang Baumjohann, R. Nakamura, S. Apatenkov, Y. Asano, M. Volwerk, Z. Vörös, T. Zhang, A. Petrukovich and 4 more. 2005

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Using four-point magnetic field measurements by the Cluster spacecraft, we statistically analyze the magnetic field and electric current configurations during rapid cross- ings of the current sheet observed in July-October 2001 at geocentric distances of 19 RE. The database includes 78 crossings, specially selected to apply multi-point data analy- sis techniques to calculate vector derivatives. Observed bipo- lar variations of jz, often with |jz|>jy , indicate that the elec- tric currents follow kinks of the current sheet. The current density varies between 5-25 nA/m 2 . The half-thickness of the current sheet during flapping varies over a wide range, from 1 to 20 ion thermal gyroradii (Lcp, calculated from av- erage temperature and lobe magnetic field for each crossing). We found no relationship between the tilt angle of the cur- rent sheet normal and the half-thickness. In 68 cases the magnetic field curvature vector has a positive (earthward) X-component. Ten cases with a negative (tailward) cur- vature, associated with reconnection, were detected within 0<YGSM<7RE. The minimum curvature radii vary mainly between 1 and 10Lcp, and the adiabaticity parameter 1 for 73% of the events. The electric current density during flapping is often off-central, i.e. the main current density is shifted from the neutral sheet (|Bx|<5 nT) to the Northern or Southern Hemisphere. This is most likely a temporal ef- fect related to the flapping. The analysis shows that the flap- ping motion of the current sheet is associated with kink-like waves on the sheet surface. The kink fronts, tilted in the Y Z plane, moved toward dawn in the morning half and to- ward dusk in the evening half of the magnetotail.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/4ef7f6ccbd735d40592af1cfd04c1cb2b8180f8c

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Citations in the corpus

Circulation of Heavy Ions and Their Dynamical Effects in the Magnetosphere: Recent Observations and Models (2014, background): “…long time periods from several minutes to 2 hours, but then may be spontaneously destroyed due to plasma instabilities (e.g. tearing perturbation) with the appearance of accelerated and thermalized plasma beams (Lui et al. 1992; Sergeev et al. 1993; Baker et al. 1996b; Runov et al. 2005).”
Survey of large-amplitude flapping motions in the midtail current sheet (2006, background): “Other average crossing characteristics evaluated in our study (typical crossing duration of the order of∼1 min, wave amplitudes of∼1 Re and CS half thickness about a fraction of 1 Re) are also similar to those found in Cluster-based surveys (Runov et al., 2005).”
Evolution of dipolarization in the near-Earth current sheet induced by Earthward rapid flux transport (2009, background): “6c is therefore due to the negative excursion in the Southern Hemisphere and positive excursion in the Northern Hemisphere, suggesting sausage mode, which have been seldom observed by Cluster for this time scale of oscillation (Sergeev et al., 2003; Runov et al., 2005b).”