Speaker: Jean Carlos Perez, Florida Institute of Technology
Abstract: Understanding the Eulerian space-time correlation of magnetohydrodynamic (MHD) turbulence, as well as its possible universal properties, is of critical importance in the analysis and interpretation of solar wind measurements when the Taylor hypothesis is not valid. This so-called frozen-in-flow hypothesis posits that the temporal variation of spacecraft signals is solely due to the spatial variation of a frozen structure passing by the observation point, in which case the turbulence dynamics can essentially be considered to be frozen in the plasma frame. The Parker Solar Probe (PSP) mission, launched in 2018, is presently probing the near-Sun solar wind with an orbit that will reach its point of closest approach next year at a heliospheric radius of approximately 0.045 au, which is seven times closer than any previous mission. During each close encounter with the Sun, the assumptions supporting TH are expected to break down. In this talk, I will discuss a recent semi-phenomenological model of the Eulerian two-time two-point (space-time) correlation for incompressible MHD turbulence and its impact on the interpretation of PSP data. Using this model we introduce a methodology that allows one to reconstruct the reduced energy spectrum of magnetic fluctuations vs spatial wavenumber from the frequency spectrum of fluctuations measured by PSP near the Alfven critical point, where TH is expected to break down.