Authors: Katayoun Movassaghi Gargari (Florida Institute of Technology), Jean C. Perez (Florida Institute of Technology), Sofiane Bourouaine (Florida Institute of Technology)

Solar wind turbulence is typically studied using statistical quantities such as the power spectrum and structure functions associated with turbulent fluctuations. However, a challenge when using spacecraft measurements is that plasma properties are measured in the time domain, which translates to the space domain via Taylor’s hypothesis, while theoretical models make predictions in frequency domain in terms of the turbulence energy spectrum. Therefore, time signals must be converted into the frequency domain (interpreted as wavevectors) via the Fourier transform in order to obtain power spectral densities needed for comparisons with turbulence theories. This intermediate step may be eliminated with the introduction of an analytical closed-form expression for the 2-point correlation in real space based on MHD turbulence theories, which can be used directly in the analysis of anisotropic turbulence in the solar wind. This is especially useful in multi-spacecraft studies such as MMS and Helioswarm, where data can be obtained simultaneously at varying spatial distances. This expression for the correlation is obtained from a general model for the 3D power spectrum parametrized by the spectral index so that both Goldreich & Sridhar (−5/3) and Iroshnikov-Kraichnan (−3/2) predictions can be tested. The dependence of the correlation function on the parallel and perpendicular spatial differences are analyzed separately.