Implementing a toroidal flux rope model in EUHFORIA and assessing its performance in predicting CME magnetic-field at 1 AU

<p>One of the major challenges in space weather forecasting is to reliably predict the magnetic structure of interplanetary coronal mass ejections (ICMEs) in the near-Earth space<span data-contrast="auto">. </span><span data-contrast="auto">In the framework of global MHD modelling, several efforts have been made to model the CME magnetic field from Sun to Earth. However, it remains challenging to deduce a flux-rope solution that can reliably model the magnetic structure of a CME. Spheromaks are one of the models that are widely used to characterize the internal magnetic structure of a CME. However, recent studies show that spheromaks are prone to </span><span data-contrast="auto">experience</span><span data-contrast="auto"> a </span>large rotation <span data-contrast="auto">when injected </span><span data-contrast="auto">in the heliospheric domain which may affect the prediction efficacy of CME magnetic field at 1 AU. Moreover, the fully inserted spheromaks do not have any legs attached to the Sun</span><span data-contrast="auto">. </span><span data-contrast="auto">In addition, d</span><span data-contrast="auto">ue to the inherent topology of the </span><span data-contrast="auto">spheromak</span><span data-contrast="auto">,</span><span data-contrast="auto"> the in-situ signature may exhibit a double flux-rope</span><span data-contrast="auto">-like</span> <span data-contrast="auto">profile </span><span data-contrast="auto">n</span><span data-contrast="auto">ot reproduced by standard locally cylindrical flux rope models</span><span data-contrast="auto">. Aiming to study the </span><span data-contrast="auto">dynamics of </span><span data-contrast="auto">CMEs exhibiting different magnetic topologies</span><span data-contrast="auto">, we implement a new flux-rope model in &#8220;European heliospheric forecasting information asset&#8221; (EUHFORIA). Our flux-rope model includes a</span><span data-contrast="none">n initially</span><span data-contrast="none"> force free toroidal flux-rope that is embedded in the low-coronal magnetic field. The dynamics of the flux rope in the low and middle corona is solved by a non-uniform advection constrained by the observed kinematics of the event. This results in a global non-toroidal loop-like magnetic structure that locally manifests as a cylindrical structure. At heliospheric distances, the evolution is modeled as a MHD process using EUHFORIA. We track the evolution of the flux-rope up to 1 AU and assess the model results with the observed in situ profile of the associated CME. &#160;This work is an important step forward in developing a realistic CME model that can be used for reliable space weather forecasting. </span></p>