Magnetohydrodynamic simulation of interplanetary propagation of multiple coronal mass ejections with internal magnetic flux rope (SUSANOO‐CME)

Abstract

Coronal mass ejections (CMEs) are the most important drivers of various types of space weather disturbance. Here we report a newly developed magnetohydrodynamic (MHD) simulation of the solar wind, including a series of multiple CMEs with internal spheromak‐type magnetic fields. First, the polarity of the spheromak magnetic field is set as determined automatically according to the Hale‐Nicholson law and the chirality law of Bothmer and Schwenn. The MHD simulation is therefore capable of predicting the time profile of the southward interplanetary magnetic field at the Earth, in relation to the passage of a magnetic cloud within a CME. This profile is the most important parameter for space weather forecasts of magnetic storms. In order to evaluate the current ability of our simulation, we demonstrate a test case: the propagation and interaction process of multiple CMEs associated with the highly complex active region NOAA 10486 in October to November 2003, and present the result of a simulation of the solar wind parameters at the Earth during the 2003 Halloween storms. We succeeded in reproducing the arrival at the Earth's position of a large amount of southward magnetic flux, which is capable of causing an intense magnetic storm. We find that the observed complex time profile of the solar wind parameters at the Earth could be reasonably well understood by the interaction of a few specific CMEs.

The Physical Processes of CME/ICME Evolution

“…Some simulations restrict the calculation to the evolution in the corona (e.g., Zuccarello et al 2012b;Amari et al 2014;Fan 2016), while others model the propagation of the ejecta to 1 AU but do not include the coronal evolution. Instead, the latter models start the simulation in the inner heliosphere (typically at around 20-30 R ) and use for the initial ICME some idealized model whose parameters are chosen guided by coronagraph observations (e.g., Shiota and Kataoka 2016). Some of these models, such as ENLIL , which is the only MHD model that is currently used for operational space weather predictions (see Green et al in this Volume), simplify even further by neglecting the magnetic field of the ICME and initiating its propagation by specifying a cone of constant velocity at the inner boundary of the model.…”

The Effects of Uncertainty in Initial CME Input Parameters on Deflection, Rotation, Bz, and Arrival Time Predictions

“…These analytic models are often one‐dimensional and the only parameter describing the CME is its velocity in the radial direction (e.g., Gopalswamy et al, ; Vršnak & Žic, ), though the CME position and width can be used in higher‐dimensional models (e.g., Žic et al, ). The alternative to these simple, efficient analytic models are full simulations where the CME is embedded in the outflowing solar wind at the start and the system evolves self‐consistentently according to the hydrodynamic (e.g., Odstrčil & Pizzo, , ) or magnetohydrodynamic equations (Poedts & Pomoell, ; Shiota & Kataoka, ). Both the higher‐dimensional analytic models and the hydrodynamic models tend to use the cone model (Xie et al, ) to describe the CME shape, which is axisymmetric about the radial direction.…”

A new technique for observationally derived boundary conditions for space weather

“…The cone model performs this key role in the WSA-ENLIL model and has improved its predictive capabilities (Dewey et al, 2015), however it injects only a density and velocity perturbation in the solar wind, neglecting the magnetic flux that is an essential part of the CME disturbance to space weather. As an alternative to this, Shiota and Kataoka (2016) introduced the use of a spheromak to model the perturbation from an ejecting magnetic flux rope. It considers the injection of an idealised structure described in terms of density and magnetic field.…”