Abstract
It is important to study the ‘concentrated’ electrostatic solitary waves/structures (ESWs) associated with the magnetic reconnection. In the literature published as regards this topic, very few studies have reported the observation of such a large number of ESWs in a single magnetic reconnection event. In this work, we report our observation of a large number of ESWs around the magnetic null-pairs within the magnetic reconnection ion diffusion region of Earth's magnetosphere on 10 September 2001. With more than 9,600 cases of ESWs observed around magnetic null-pairs and more than 97,600 cases observed during the ion diffusion region crossing time span, the observation of such a large number of ESWs in the diffusion region has not been reported often in published works. We further perform single-event-based statistical analysis of the characteristics of the ESWs around magnetic null-pairs. Based on the statistical result, we speculate that the two-stream instability originating from the magnetic null and traveling outward along the plasma sheet boundary layer (PSBL) is the candidate mechanism of the large number of observed ESWs. Our observation and analysis in this work suggests that even with the presence of a complex magnetic structure around a magnetic null-pair in the three-dimensional regime, concentrated ESWs can be observed. This single-reconnection-event-based statistical result of ESWs around the magnetic null-pairs can aid in understanding the microdynamics associated with three-dimensional (3D) magnetic reconnection.
Highlights
We suggest that the spacecrafts skimmed the magnetic ion diffusion region along the boundary layer during the plasma flow reversal interval
As regards the electrostatic solitary waves (ESWs) amplitudes, our analysis shows that, during this magnetic reconnection process, the amplitudes of the observed ESWs in the vicinity of the X-line are mainly less than 1 mV/m, while for the whole data set of the ESWs within the ion diffusion region, the amplitude varies over a wider range from approximately 0.01 mV/m to approximately 2 mV/m
In the present work, by examining the 9.5-kHz bandwidth mode of the WBD data carefully, we determined that a large number ESWs was continuously observed along the trajectory of all the four spacecrafts around the magnetic null-pairs and within the ion diffusion region
Summary
The observation of electrostatic solitary waves (ESWs) and the study of their structure within the magnetic reconnection diffusion region of Earth's magnetosphere has attracted a surge of research interest recently (Matsumoto et al 2003; Deng et al 2004, 2009; Cattell et al 2005; Li et al 2009, 2010, 2012, 2013a, 2013b, 2014). ESWs were first observed in the plasma sheet boundary layer (PSBL) in the magnetotail by Matsumoto et al (1994). Magnetic reconnection is the most important mechanism for the energy transformation from magnetic energy to kinetic energy and its transportation from the source region to other regions of interest. Both the structure and the microphysics related to reconnection have been extensively studied. As a primary focus of these studies, the ESWs associated with magnetic reconnection have been investigated recently both through in situ observations (Deng et al 2004, 2009; Cattell et al 2005; Li et al 2009, 2010, 2013b) and simulations (Drake et al 2003; Cattell et al 2005). Fujimoto and Machida (2006) studied the generation mechanism of ESWs on the PSBL
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