Technical Article

HelioCast: heliospheric forecasting based on white-light observations of the solar corona

¹ IRAP, Université Toulouse III – Paul Sabatier, CNRS, CNES, 9, Avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
² Rosseland Centre for Solar Physics, University of Oslo, Postboks 1029 Blindern, 0315 Oslo, Norway
³ Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029 Blindern, 0315 Oslo, Norway
⁴ The Johns Hopkins University Applied Physics Laboratory, 11101 Johns Hopkins Road, Laurel, MD 20723, USA
⁵ Département d’Astrophysique/AIM, CEA/IRFU, CNRS/INSU, Univ. Paris-Saclay & Univ. de Paris, 91191 Gif-sur-Yvette, France
⁶ The Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, United Kingdom

^* Corresponding author: victor.reville@irap.omp.eu

Received: 19 October 2022
Accepted: 16 March 2023

Abstract

We present a new 3D magnetohydrodynamic (MHD) heliospheric model for space-weather forecasting driven by boundary conditions defined from white-light observations of the solar corona. The model is based on the MHD code PLUTO, constrained by an empirical derivation of the solar wind background properties at 0.1 au. This empirical method uses white-light observations to estimate the position of the heliospheric current sheet (HCS). The boundary conditions necessary to run HelioCast are then defined from pre-defined relations between the necessary MHD properties (speed, density, and temperature) and the distance to the current sheet. We assess the accuracy of the model over six Carrington rotations during the first semester of 2018. Using point-by-point metrics and event-based analyses, we evaluate the performances of our model varying the angular width of the slow solar wind layer surrounding the HCS. We also compare our empirical technique with two well-tested models of the corona: Multi-VP and WindPredict-AW. We find that our method is well-suited to reproduce high-speed streams, and does – for well-chosen parameters – better than full MHD models. The model shows, nonetheless, limitations that could worsen for rising and maximum solar activity.