Modeling the Early Evolution of a Slow Coronal Mass Ejection Imaged by the Parker Solar Probe

Abstract

During its first solar encounter, the Parker Solar Probe (PSP) acquired unprecedented up-close imaging of a small Coronal Mass Ejection (CME) propagating in the forming slow solar wind. The CME originated as a cavity imaged in extreme ultraviolet that moved very slowly ($<50$ km/s) to the 3-5 solar radii (R${}_{\odot }$) where it then accelerated to supersonic speeds. We present a new model of an erupting Flux Rope (FR) that computes the forces acting on its expansion with a computation of its internal magnetic field in three dimensions. The latter is accomplished by solving the Grad-Shafranov equation inside two-dimensional cross sections of the FR. We use this model to interpret the kinematic evolution and morphology of the CME imaged by PSP. We investigate the relative role of toroidal forces, momentum coupling, and buoyancy for different assumptions on the initial properties of the CME. The best agreement between the dynamic evolution of the observed and simulated FR is obtained by modeling the two-phase eruption process as the result of two episodes of poloidal flux injection. Each episode, possibly induced by magnetic reconnection, boosted the toroidal forces accelerating the FR out of the corona. We also find that the drag induced by the accelerating solar wind could account for about half of the acceleration experienced by the FR. We use the model to interpret the presence of a small dark cavity, clearly imaged by PSP deep inside the CME, as a low-density region dominated by its strong axial magnetic fields.

19 pages, 10 figures, to appear in ApJS, 2 animations of Figure 2 available at https://nuage.irap.omp.eu/index.php/s/8ynNotNVWU6PrtN and https://nuage.irap.omp.eu/index.php/s/dflQ94DKuMbiaTv

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• Overview of the remote sensing observations from PSP solar encounter 10 with perihelion at 13.3 Rsun
• WISPR Imaging of a Pristine CME
• Analysis of coronal mass ejection flux rope signatures using 3DCORE and approximate Bayesian Computation
• Observations of Energetic-Particle Population Enhancements along Intermittent Structures near the Sun from Parker Solar Probe
• Cross Helicity of the November 2018 Magnetic Cloud Observed by the Parker Solar Probe
• Variability of the slow solar wind: New insights from modelling and PSP-WISPR observations
• Internal Structure of the 2019 April 2 CME
• Sequential Small Coronal Mass Ejections Observed In~situ and in White-Light Images by Parker Solar Probe
• Constraints on the variable nature of the slow solar wind with the Wide-Field Imager on board the Parker Solar Probe
• Energetic Ion Composition as a Means of Investigating the Physical Origins of Alpha Particle Heavy Magnetic Switchbacks
• Tracking solar wind flows from rapidly varying viewpoints by the Wide-field Imager for Parker Solar Probe