Decoding the Pre-Eruptive Magnetic Field Configurations of Coronal Mass Ejections

Abstract

A clear understanding of the nature of the pre-eruptive magnetic field configurations of Coronal Mass Ejections (CMEs) is required for understanding and eventually predicting solar eruptions. Only two, but seemingly disparate, magnetic configurations are considered viable; namely, sheared magnetic arcades (SMA) and magnetic flux ropes (MFR). They can form via three physical mechanisms (flux emergence, flux cancellation, helicity condensation). Whether the CME culprit is an SMA or an MFR, however, has been strongly debated for thirty years. We formed an International Space Science Institute (ISSI) team to address and resolve this issue and report the outcome here. We review the status of the field across modeling and observations, identify the open and closed issues, compile lists of SMA and MFR observables to be tested against observations and outline research activities to close the gaps in our current understanding. We propose that the combination of multi-viewpoint multi-thermal coronal observations and multiheight vector magnetic field measurements is the optimal approach for resolving

Improving the Medium-Term Forecasting of Space Weather: A Big Picture Review From a Solar Observer's Perspective

“…This turns out to be a rather simplistic, and potentially misleading, approach as the high quality and rapid cadence EUV imaging observations have demonstrated. The discovery of EUV waves (Thompson et al, 1999) and post-CME rays (Ciaravella et al, 2002) and their singular connection to eruptive flares (e.g., Long et al, 2017, and references therein) indicated a closer spatial and temporal relation between magnetic energy release and both flare and CME development that previously realized (Longcope and Beveridge, 2007;Qiu et al, 2007); see also Patsourakos et al (2020), and references therein. In my opinion, a paradigm-shifting advance was the identification of the EUV wave driver with a "super-expansion" phase in the very first stages of CME formation .…”

“…Thus, we cannot observe/measure many of the quantities important to coronal energy storage and release, such as magnetic free energy, helicity, or currents. Patsourakos et al (2020) reviewed the subject in detail and put forth a range of ideas for moving forward. • Formation Phase: As discussed earlier, most CMEs undergo their formation and acceleration phases in the inner corona (below 4 Rs).…”

“…Multi-height vector magnetic field measurements, from photosphere to (at least) the upper chromosphere, in active regions (because they host the most energetic eruptions), can provide the required information on energy and helicity flow and coronal currents. They will also provide strong constraints for coronal field extrapolations leading to robust 3D reconstructions of the magnetic morphology of the pre-eruptive structures thus removing the need for the much more difficult direct coronal field measurements (for more information and ideas see Patsourakos et al 2020).…”

Modeling a Coronal Mass Ejection from an Extended Filament Channel. I. Eruption and Early Evolution

“…Large-scale filament eruptions that drive coronal mass ejections (CMEs) are some of the most spectacular energetic and dynamic transients in the solar corona. A well-known property of CME source regions is that the magnetic free energy required to power a solar eruption is concentrated above radial magnetic field polarity inversion lines (PILs) in the form of stressed, sheared, and/or twisted magnetic field structures (e.g., see Patsourakos et al 2020 and references therein). Pevtsov et al (2012) examined several large-scale filament channels, i.e., long PILs in the underlying photospheric magnetic field distribution with highly sheared coronal magnetic fields, including those without any discernible filament or prominence material, and showed that these types of coronal structures were responsible for slow-to moderatespeed CME events.…”

Optimization of Magnetic Flux Ropes Modeled with the RBSL Method

“…Therefore, the accuracy of PEC reconstructions appears to be a crucial factor for a correct modeling of CMEs. An accurate reconstruction of PECs for observed cases, however, is particularly challenging (Patsourakos et al 2020), since the constraints required for the reconstruction can be inferred only indirectly from, e.g., observed filament shapes or the location of flare arcades or dimmings (e.g., Palmerio et al 2017).…”