Investigations of the sensitivity of a coronal mass ejection model (ENLIL) to solar input parameters : PARAMETER SPACE OF ENLIL

Understanding space weather is not only important for satellite operations and human exploration of the solar system but also to phenomena here on Earth that may potentially disturb and disrupt electrical signals. Some of the most violent space weather effects are caused by coronal mass ejections (CMEs), but in order to predict the caused effects, we need to be able to model their propagation from their origin in the solar corona to the point of interest, e.g., Earth.

Many such models exist, but to understand the models in detail we must understand the primary input parameters. Here we investigate the parameter space of the ENLILv2.5b model using the CME event of 25 July 2004. ENLIL is a time‐dependent 3‐D MHD model that can simulate the propagation of cone‐shaped interplanetary coronal mass ejections (ICMEs) through the solar system.

Excepting the cone parameters (radius, position, and initial velocity), all remaining parameters are varied, resulting in more than 20 runs investigated here. The output parameters considered are velocity, density, magnetic field strength, and temperature. We find that the largest effects on the model output are the input parameters of upper limit for ambient solar wind velocity, CME density, and elongation factor, regardless of whether one's main interest is arrival time, signal shape, or signal amplitude of the ICME.

We find that though ENLILv2.5b currently does not include the magnetic cloud of the ICME, it replicates the signal at L1 well in the studied event. The arrival time difference between satellite data and the ENLILv2.5b baseline run of this study is less than 30 min.