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The shape of the electron velocity distribution function plays an important role in the dynamics of the solar wind acceleration. Electrons are normally modelled with three components, the core, the halo, and the strahl. We investigate how well the fast strahl electrons in the inner heliosphere preserve the information about the coronal electron temperature at their origin. We analysed the data obtained by two missions, Helios spanning the distances between 65 and 215 R$_S$, and Parker Solar Probe (PSP) reaching down to 35 R$_S$ during its first two orbits around the Sun. The electron strahl was characterised with two parameters, pitch-angle width (PAW), and the strahl parallel temperature (T$_{sparallel}$). PSP observations confirm the already reported dependence of strahl PAW on core parallel plasma beta ($beta_{ecparallel}$)citep{Bercic2019}. Most of the strahl measured by PSP appear narrow with PAW reaching down to 30$^o$. The portion of the strahl velocity distribution function aligned with the magnetic field is for the measured energy range well described by a Maxwellian distribution function. T$_{sparallel}$ was found to be anti-correlated with the solar wind velocity, and independent of radial distance. These observations imply that T$_{sparallel}$ carries the information about the coronal electron temperature. The obtained values are in agreement with coronal temperatures measured using spectroscopy (David et al. 2998), and the inferred solar wind source regions during the first orbit of PSP agree with the predictions using a PFSS model (Bale et al. 2019, Badman et al. 2019).
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 d
We present a statistical analysis for the characteristics and spatial evolution of the interplanetary discontinuities (IDs) in the solar wind, from 0.13 to 0.9 au, by using the Parker Solar Probe measurements on Orbits 4 and 5. 3948 IDs have been col
We make use of the Parker Solar Probe (PSP) data to explore the nature of solar wind turbulence focusing on the Alfvenic character and power spectra of the fluctuations and their dependence on distance and context (i.e. large scale solar wind propert
The Solar Wind Electrons Alphas and Protons experiment on the Parker Solar Probe (PSP) mission measures the three-dimensional electron velocity distribution function. We derive the parameters of the core, halo, and strahl populations utilizing a comb
We report proton temperature anisotropy variations in the inner heliosphere with Parker Solar Probe (PSP) observations. Using a linear fitting method, we derive proton temperature anisotropy with temperatures measured by the Solar Probe Cup (SPC) fro