Models for coronal mass ejections

Abstract

a b s t r a c tCoronal mass ejections (CMEs) play a key role in space weather. The mathematical modelling of these violent solar phenomena can contribute to a better understanding of their origin and evolution and as such improve space weather predictions. We review the state-of-the-art in CME simulations, including a brief overview of current models for the background solar wind as it has been shown that the background solar wind affects the onset and initial evolution of CMEs quite substantially. We mainly focus on the attempt to retrieve the initiation and propagation of CMEs in the framework of computational magnetofluid dynamics (CMFD). Advanced numerical techniques and large computer resources are indispensable when attempting to reconstruct an event from Sun to Earth. Especially the simulations developed in dedicated event studies yield very realistic results, comparable with the observations. However, there are still a lot of free parameters in these models and ad hoc source terms are often added to the equations, mimicking the physics that is not really understood yet in detail.

Nanodust dynamics during a coronal mass ejection

“…Despite the wealth of observational data that have been accumulated and the modeling effort invested by the space-weather community, key questions about their origin and the physical mechanisms that govern their eruption and propagation remain unanswered to this day. Details on CME modeling may be found in reviews by Jacobs and Poedts (2011) and Kleimann (2012) and the references given therein, while observational aspects have been summarized by, e.g., Webb and Howard (2012) and Howard (2015).…”

The birth of a solar eruption

“…This model contains more physics than previous models and, as a result, brings important new insights and understanding of the reorganization of the surrounding solar corona in response to the emergence of the new flux, the role of the neutral points and magnetic field connectivity in the formation and dynamics of the plasmoid and the nature of the hot X-ray 'double-J' sigmoid. 3 He might be cooled simply by squeezing it was based on a striking, if straightforward, observation: Pomeranchuk saw that the entropy of solid 3 He exceeded that of liquid 3 He at very low temperatures, and inferred that compressing a mixture of the two would result in cooling, as the liquid was converted into solid 2 . Writing in Nature Physics, Shintaro Taie and colleagues have made use of this idea to achieve a Mott-insulating state in 173 Yb -revealing an important distinction between the symmetry classes of ultracoldatomic ensembles 3 .…”

CMEs' Speed, Travel Time, and Temperature: A Thermodynamic Approach

“…Mainly, for this reason, CMEs have been widely studied in order to predict their speed and arrival time at the orbit of the Earth (Borgazzi et al, ; Cantó et al, ; Gopalswamy et al, ; Howard, ; Jacobs. C. & Poedts, ; Lara et al, ).…”

“…So far, most of the solutions to this equation are numerical approximations (Jacobs. C. & Poedts, ), though some have succeeded in obtaining analytical solutions (Borgazzi et al, ; Cantó et al, ; Lara et al, ; Niembro et al, ). Borgazzi et al () derive an analytical expression for the CME speed while studying the dynamics of CMEs from near the Sun to the orbit of the Earth considering both laminar and turbulent regimes.…”