Calibrating the WSA velocity in EUHFORIA based on PSP observations

Abstract

<p>Coronal models, usually extending between the solar photosphere and ~30 Rs, are an integral part of many space weather forecasting tools. They reconstruct the magnetic field in the solar corona and provide the necessary plasma conditions for initiating heliospheric models such as EUHFORIA or Enlil. A big gap in literature is identified when it comes to the validation of such models because of lack of observations, especially in situ. Nevertheless, the launch of the Parker Solar Probe (PSP) has provided, for the first time, in situ observations very close to the Sun that can help with the evaluation of such models. In this work, we aim to calibrate the Wang-Sheeley-Arge (WSA) semi-empirical formula used in EUHFORIA for the reconstruction of plasma and magnetic parameters at 0.1 AU. We exploit PSP in situ measurements between 0.1 – 0.4 AU obtained from the first 8 perihelia. We show how a parametric study of the WSA formula influences the velocity and density distributions very close to the Sun, how the modeled distributions are compared to PSP observations and present the relevant forecasting results at PSP and Earth.</p>