Aims: We investigate the solar wind energy flux in the inner heliosphere using 12-day observations around each perihelion of Encounter One (E01), Two (E02), Four (E04), and Five (E05) of Parker Solar Probe (PSP), respectively, with a minimum heliocentric distance of 27.8 solar radii (R⊙). Methods: Energy flux was calculated based on electron parameters (density ne, core electron temperature Tc, and suprathermal electron temperature Th) obtained from the simplified analysis of the plasma quasi-thermal noise (QTN) spectrum measured by RFS/FIELDS and the bulk proton parameters (bulk speed Vp and temperature Tp) measured by the Faraday Cup onboard PSP, SPC/SWEAP. Results: Combining observations from E01, E02, E04, and E05, the averaged energy flux value normalized to 1 R⊙ plus the energy necessary to overcome the solar gravitation (WR⊙) is about 70 ± 14 W m−2, which is similar to the average value (79 ± 18 W m−2) derived by Le Chat, G., Issautier, K., & Meyer-Vernet, N. (2012, Sol. Phys., 279, 197) from 24-yr observations by Helios, Ulysses, and Wind at various distances and heliolatitudes. It is remarkable that the distributions of WR⊙ are nearly symmetrical and well fitted by Gaussians, much more so than at 1 AU, which may imply that the small heliocentric distance limits the interactions with transient plasma structures.
