Applicability of Taylor’s hypothesis during Parker Solar Probe perihelia

We investigate the validity of Taylor's Hypothesis (TH) in analysis Alfv\'enic fluctuations velocity and magnetic fields solar wind streams measured by Parker Solar Probe (PSP)~during first four encounters. use PSP field measurements from 24 h intervals selected each The applicability TH is investigated measuring parameter $\epsilon=\delta u_0/\sqrt{2}V_\perp$, which quantifies ratio between typical speed large-scale fluctuations, $\delta u_0$, local perpendicular frame, $V_\perp$. expected to be applicable for $\epsilon\lesssim0.5$ when moving nearly plasma irrespective Alfv\'en Mach number $M_{\rm A}=V_{\rm SW}/V_{\rm A}$, where $V_{\rm SW}$ A}$ are speed, respectively. For we find that 10% 60% time $\epsilon$ below 0.2 sampling angle (between spacecraft frame field) greater than $30^\circ$. angles above $30^\circ$, direction sufficiently oblique allow one reconstruct reduced energy spectrum $E(k_\perp)$ its frequency spectra. spectral indices determined power-law fits accurately represent associated with underlying spatial turbulent frame. Aside a broadening due sweeping requires careful consideration, can recovered obtain distribution fluctuation's among scales