Electrostatic Solitary Waves in the Solar Wind: Evidence for Instability at Solar Wind Current Sheets

Abstract

A strong spatial association between bipolar electrostatic solitary waves (ESWs) and magnetic current sheets (CSs) in the solar wind is reported here for the first time. This association requires that the plasma instabilities (e.g., Buneman, electron two stream) which generate ESWs are preferentially localized to solar wind CSs. Distributions of CS properties (including shear angle, thickness, solar wind speed, and vector magnetic field change) are examined for differences between CSs associated with ESWs and randomly chosen CSs. Possible mechanisms for producing ESW‐generating instabilities at solar wind CSs are considered, including magnetic reconnection.

Electrostatic solitary waves and electrostatic waves at the magnetopause

“…Assuming that l pp ∕ D does not change significantly for ESWs at the magnetopause and magnetotail, then based on equation (10), E pp ∝ D or equivalently E pp ∝ √ T e ∕n e . For typical solar wind conditions we would expect small-amplitude ESWs, as was found in Malaspina et al [2013]. Based on equation (9), ∝ T e ∕n e , so larger are also allowed.…”

“…For example, ESWs have been reported at Earth's magnetopause [Cattell et al, 2002;Matsumoto et al, 2003], magnetotail Cattell et al, 2005;Khotyaintsev et al, 2010b], auroral regions [Ergun et al, 1998a[Ergun et al, , 1998bMozer et al, 2015], magnetosheath , near the foreshock [Behlke et al, 2004;Shin et al, 2008], and in the solar wind [Mangeney et al, 1999;Malaspina et al, 2013]. For example, ESWs have been reported at Earth's magnetopause [Cattell et al, 2002;Matsumoto et al, 2003], magnetotail Cattell et al, 2005;Khotyaintsev et al, 2010b], auroral regions [Ergun et al, 1998a[Ergun et al, , 1998bMozer et al, 2015], magnetosheath , near the foreshock [Behlke et al, 2004;Shin et al, 2008], and in the solar wind [Mangeney et al, 1999;Malaspina et al, 2013].…”

Multispacecraft Analysis of Electron Holes

“…Later, Matsumoto et al (1994) were able to resolve this noise in the time domain, revealing the source to be bipolar electrostatic structures. ESWs have since been found in most space plasmas, including the auroral region (Temerin et al, 1982), the inner magnetosphere (Mozer et al, 2015), the flow breaking region (Ergun et al, 2014), the magnetopause , the bow shock (Bale et al, 1998;Vasko et al, 2018), the solar wind (Malaspina et al, 2013), and near Saturn's magnetosphere (Williams et al, 2006). ESWs have since been found in most space plasmas, including the auroral region (Temerin et al, 1982), the inner magnetosphere (Mozer et al, 2015), the flow breaking region (Ergun et al, 2014), the magnetopause , the bow shock (Bale et al, 1998;Vasko et al, 2018), the solar wind (Malaspina et al, 2013), and near Saturn's magnetosphere (Williams et al, 2006).…”

Slow electron phase space holes: Magnetotail observations

“…Henceforth, observations have been made by a multitude of missions in many regions of space, for example, at the Earth's magnetopause [Matsumoto et al, 2003;Graham et al, 2015], magnetosheath [Pickett et al, 2008], auroral acceleration regions [Cattell et al, 1999], plasma sheet boundary layer [Cattell et al, 1999;Franz et al, 1998], and magnetotail [Khotyaintsev et al, 2010], during magnetic reconnection [Viberg et al, 2013] and sometimes having a magnetic component [Andersson et al, 2009;Tao et al, 2011]. They have also been observed and studied in the solar wind [Malaspina et al, 2013], at interplanetary shocks [Williams et al, 2005], and in laboratories in connection with magnetic reconnection [Fox et al, 2008] and beam injections [Lefebvre et al, 2010]. The latter clearly show a spatial thermalization of the injected beam which is unstable to electron hole generation.…”