Abstract
Abstract. Magnetic reconnection has long been believed to be an efficient engine for energetic electrons production. Four different structures have been proposed for electrons being energized: flux pileup region, density cavity located around the separatrix, magnetic island and thin current sheet. In this paper, we compare the electron acceleration efficiency among these structures based on 12 magnetotail reconnection events observed by the Cluster spacecraft in 2001–2006. We used the flux ratio between the energetic electrons (> 50 keV) and lower energy electrons (< 26 keV) to quantify the electron acceleration efficiency. We do not find any specific sequence in which electrons are accelerated within these structures, though the flux pileup region, magnetic island and thin current sheet have higher probabilities to reach the maximum efficiency among the four structures than the density cavity. However, the most efficient electron energization usually occurs outside these structures. We suggest that other structures may also play important roles in energizing electrons. Our results could provide important constraints for the further modeling of electron acceleration during magnetic reconnection.
Highlights
Electron energization is an outstanding issue in plasma physics and astrophysics
Their study raises some interesting questions: does any specific sequence exist in which electrons are accelerated through these structures (Hoshino et al, 2001; Huang et al, 2012a; Imada et al, 2007)? At which structure is the electron acceleration the most efficient? In this paper we extend their study by comparing the energetic electron acceleration efficiency among these different structures during multiple reconnection events in the Earth’s magnetotail
Multiple instruments of Cluster spacecraft were used in this study, including the fluxgate magnetometer (FGM) (Balogh et al, 2001), the electric fields and waves (EFW) (Gustafsson et al, 2001), the Cluster ion spectrometry (CIS) (Rème et al, 2001), the plasma electron and current experiment (PEACE) (Johnstone et al, 1997), and the research with adaptive particle imaging detectors (RAPID) (Wilken et al, 2001)
Summary
Electron energization is an outstanding issue in plasma physics and astrophysics. Magnetic reconnection is able to produce a large number of energetic electrons (Sonnerup, 1979). A secondary acceleration at the magnetic flux pileup region downstream of X-line was proposed by Hoshino et al (2001) They suggested that electrons can be energized by inductive electric field at the flux pileup region due to their gradient-B or curvature-B drift against the electric field. Thin current sheet, magnetic island, density cavity around the separatrix and flux pileup region are four different structures which are frequently involved in electron energization during reconnection. Their study raises some interesting questions: does any specific sequence exist in which electrons are accelerated through these structures (Hoshino et al, 2001; Huang et al, 2012a; Imada et al, 2007)? At which structure is the electron acceleration the most efficient? In this paper we extend their study by comparing the energetic electron acceleration efficiency among these different structures during multiple reconnection events in the Earth’s magnetotail
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