Testing predictors of eruptivity using parametric flux emergence simulations

Abstract

Solar flares and coronal mass ejections (CMEs) are among the most energetic events in the solar system, impacting the near-Earth environment. Flare productivity is empirically known to be correlated with the size and complexity of active regions. Several indicators, based on magnetic field data from active regions, have been tested for flare forecasting in recent years. None of these indicators, or combinations thereof, have yet demonstrated an unambiguous eruption or flare criterion. Furthermore, numerical simulations have been only barely used to test the predictability of these parameters. In this context, we used the 3D parametric magnetohydrodynamic (MHD) numerical simulations of the self-consistent formation of the flux emergence of a twisted flux tube, inducing the formation of stable and unstable magnetic flux ropes of Leake et al. (2013Leake et al. ( , 2014. We use these numerical simulations to investigate the eruptive signatures observable in various magnetic scalar parameters and provide highlights on data analysis processing. Time series of 2D photospheric-like magnetograms are used from parametric simulations of stable and unstable flux emergence, to compute a list of about 100 different indicators. This list includes parameters previously used for operational forecasting, physical parameters used for the first time, as well as new quantities specifically developed for this purpose. Our results indicate that only parameters measuring the total non-potentiality of active regions associated with magnetic inversion line properties, such as the Falconer parameters L ss , WL ss , L sg , and WL sg , as well as the new current integral WL sc and length L sc parameters, present a significant ability to distinguish the eruptive cases of the model from the non-eruptive cases, possibly indicating that they are promising flare and eruption predictors. A preliminary study about the effect of noise on the detection of the eruptive signatures is also proposed.

A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

“…These parameters (e.g., mean gradient of the horizontal magnetic field, mean current helicity, mean twist parameter, etc) are intensive (i.e., do not depend on the AR size but are spatial averages) and not extensive (i.e., dependent on the AR size and corresponding to spatial sums). Guennou et al (2017) by means of MHD analyzed a set of eruptive and non-eruptive MHD simulations and found, in agreement with Bobra and Ilonidis (2016), that intensive parameters are more relevant to eruptivity.…”

Relative magnetic helicity as a diagnostic of solar eruptivity

“…Along with Guennou et al (2017), the present study is dedicated to the analysis of the eruptivity properties of the simulations of Leake et al (2013Leake et al ( , 2014. Our goal is to determine whether or not a unique scalar quantity, computable at a given instant, is able to properly describe the eruptive potential of the system.…”

Which Photospheric Characteristics Are Most Relevant to Active-Region Coronal Mass Ejections?

“…related more to active-region complexity than size) physical parameters have been found to be better suited for CME prediction (Bobra and Ilonidis, 2016). Recent simulations appear to corroborate these results: for example, Guennou et al (2017) show that naturally intensive parameters related to MPILs are the most promising predictors of CMEs. Earlier studies have also shown that there may be a correlation between the CME speed and some measure of magnetic energy (Venkatakrishnan and Ravindra, 2003), reconnection flux (Qiu and Yurchyshyn, 2005), or effective connected magnetic-field strength (Georgoulis, 2008).…”