Abstract
As a test of the action of MHD turbulence in the solar wind, the compression of the heliospheric magnetic structure at 1AU by 109 interplanetary shocks is examined. In the magnetic structure the orientations of solar-wind strong current sheets are statistically examined versus time in the downstream plasmas after shock compression. If the current sheets of the solar wind are features of an active MHD turbulence, they should be destroyed and remade with isotropic orientations on the timescale of an eddy-turnover time. If the current-sheet orientations remain anisotropic after the shock compression, it is an indication that the current sheets of the solar wind are not created by MHD turbulence. This statistical analysis finds no evolution of the current-sheet orientations after the solar wind is compressed by the shocks, implying a non-turbulent origin of the current sheets. A possibility is that the heliospheric magnetic structure at 1 AU is fossil structure from the solar corona.
Highlights
The magnetic structure of the solar wind in the inner heliosphere is dominated by strong current sheets (e.g., Burlaga and Ness, 1969; Vasquez et al, 2007; Li, 2008; D’Amicis et al, 2012)
Statistical examinations of the spacings and orientations of the solar-wind current sheets lead to a picture of a spaghetti-like network of flux tubes forming the magnetic structure of the heliosphere (Mariani et al, 1973, 1983; Borovsky, 2008a, 2010; Greco et al, 2009; Arnold et al, 2013; Ruffolo et al, 2013)
An outstanding question concerns the origin of the heliospheric magnetic structure (Neugebauer and Giacalone, 2010, 2015; Li and Qin, 2011; Owens et al, 2011; Tu et al, 2016; Borovsky, 2020a; Viall and Borovsky, 2020): Is the observed magnetic structure created in situ in the heliosphere or is it fossil structure from the solar coronal? A strong argument for the in situ creation of the heliospheric magnetic structure focuses on MHD turbulence: simulations of Compression of Heliospheric Magnetic Structure
Summary
The magnetic structure of the solar wind in the inner heliosphere is dominated by strong current sheets (directional discontinuities) (e.g., Burlaga and Ness, 1969; Vasquez et al, 2007; Li, 2008; D’Amicis et al, 2012). If the current-sheet orientations isotropize with time (distance) downstream from the shock, they are likely created in situ: if they do no isotropize they are likely fossil from the Sun. The existence of “planar magnetic structures” downstream from coronal-mass-ejection-driven interplanetary shocks is well known (Neugebauer et al, 1993; Jones et al, 1999; Kataoka et al, 2005; Savani et al, 2011; Palmiero et al, 2016; Shaikh et al, 2018, 2019). Borovsky and Denton (2016) have used the observed statistical orientations of the noodle (flux-tube) walls as a measure of the amount of solar-wind compression in corotating interaction regions and as FIGURE 1 | The shocking of one flux tube in the spaghetti structure of the heliosphere is sketched, with the variable shock normal angle resulting in different amounts of magnetic compression. A measure of the amount of solar-wind rarefaction in the trailing edges of high-speed streams
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
