Detection of Current Sheets and Magnetic Reconnections at the Turbulent Leading Edge of an Interplanetary Coronal Mass Ejection

Abstract

The relation between current sheets, turbulence, and magnetic reconnections at the leading edge of an interplanetary coronal mass ejection detected by four Cluster spacecraft on 2005 January 21 is studied. We report the observational evidence of two magnetically reconnected current sheets in the vicinity of a front magnetic cloud boundary layer with the following characteristics: (1) a Kolmogorov power spectrum in the inertial subrange of the magnetic turbulence, (2) the scaling exponent of structure functions of magnetic fluctuations exhibiting multi-fractal scaling predicted by the She-Leveque magnetohydrodynamic model, and (3) bifurcated current sheets with the current density computed by both single-spacecraft and multi-spacecraft techniques.

Additional acceleration of solar-wind particles in current sheets of the heliosphere

“…The observations with the Cluster satellites of an ICME recorded on the 21 January 2005 as reported by Chian and Muñoz (2011) revealed the two reconnecting current sheets that occurred at the edge of the ICME, which had a multifractal scale of turbulence with a plateau in the magnetic field component in the middle of the current sheet. This plateau is related to the region of the reconnection jets predicted by Swisdak et al (2010) and propagating flows of Alfvén waves, similar to those reported by McComas et al (1995) and Gosling et al (2011).…”

“…There are numerous observations of reconnection events in the solar-wind current sheets made by the Advanced Composition Explorer (ACE) and Helios (Gosling et al, 2006;Gosling, 2007), WIND (Phan et al, 2010) and Cluster (Chian and Muñoz, 2011) spacecraft as well as by combined instruments (Gosling, 2009;Gosling and Phan, 2013, and references therein). Many current sheets occur in the heliosphere at the leading edges of interplanetary coronal mass ejections (ICMEs) (see, for example, Xu et al, 2011, and references therein), although, the trigger mechanism initiating these reconnection events is not fully understood.…”

“…Very often the leading edge of the ICME (the sheath) is also known to contain a current sheet (Chian and Muñoz, 2011) that most probably represents an inseparable feature of each ICME. During the past decades several authors claimed to have observed a magnetic reconnection at such pre-ICME current sheets (McComas et al, 1994;Gosling et al, 2006;Gosling, 2007;Phan et al, 2011).…”

“…4, obtained from the ACE and Cluster 1 measurements. This ICME event occurred on 21 January 2005 and was considered in detail for Cluster 1 by Chian and Muñoz (2011). We are mainly interested in examining the unusually wide leading ICME edge of the compressed plasma, indicated by the grey arrows in Fig.…”

“…4 that shows a comparison of the ACE and Cluster measurements of the total IMF. The event was previously discussed by Chian and Muñoz (2011) on the basis of the Cluster data only. This area of the ICME was full of multiscale current sheets, which look like sharp decreases followed by increases in the magnetic field B and form small-scale magnetic islands that demonstrate the full set of possible signatures of magnetic reconnection in the vicinity of the ICME.…”