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Data-Driven MHD Modeling of CME Events - Day 2 Session Summary

The Day 2 session on "Data-Driven MHD Modeling of CME Events" featured notable presentations by experts Yuhong Fan, George Fisher, Mark Linton, and Brian Welsch. Key discussions included structural analysis of coronal magnetic fields, dynamic flux emergence simulations, and innovative approaches to modeling CMEs. Topics covered encompassed the relation between quasi-separators and reconnection sites, driving coronal models with self-consistent boundary conditions, and the impact of magnetic field geometry on eruptive events, enhancing the understanding of the observational features associated with CMEs.

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Data-Driven MHD Modeling of CME Events - Day 2 Session Summary

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  1. Data-Driven MHD Modeling of CME Events Session Summary, day 2 Session Organizers: Yuhong Fan (HAO), George Fisher (SSL/UCB), Mark Linton (NRL-DC), Brian Welsch (SSL/UCB)

  2. SlavaTitov: "Structural Analysis of the Coronal Mag-netic Field: How Can It Be Used in Models of CMEs?" Start: review of separatrix surfaces, and quasi-separatrix layers (QSLs) as sites of reconnection; Q := "squashing factor" quantifies rate of change of field-line connectivity near a QSL Q enables: • localising preferred sites of reconnection, i.e., quasi-separators • identifying building blocks, e.g., erupting and non- strands of flux ropes (3) determine evolving fluxes for each blocks (4) relate observable structures to building blocks: • H-alpha flare ribbons, • EUV dimmings, • X-ray sigmoids

  3. Relation to observational features t=32 (≈ 38 min after the CME onset)

  4. Roussev:Use Dynamic Flux Emergence Simulations (w/Galsgaard& Archontis) to Drive Coronal Model • This enables driving with more self-consistent boundary conditions. - required rescaling β from photospheric to coronal values, and decreasing peak field strength. • Flux rope forms, and erupts; post-eruption field consists of two flux ropes, which form a “double J” structure • synthetic X-ray emission resembles observed sigmoids • Topology matters: nulls & QSLs play important roles (cf., Titov) • Footpoints of erupting rope do not remain stationary, but move across surface as eruption proceeds. • Flux rope does not remain intact: after eruption, two flux ropes are formed, linking “core" of emerged field to external field

  5. Magnetic Field Geometry at Later Times t = 68 min t = 3 h

  6. Several “data inspired” simulations of actual eruptions were presented: Zuccarello; Fan; Jin. Models had varying degrees of thermodynamic realism. Fan’s CME was slower than the observed CME: • Fan: Rescaling must preserve height profile of B. • Fisher: If you get a 1000 km/sec eruption, how do you change parameters to achieve a 2000 km/sec eruption? • Mikic: To increase eruption energy, confine the pre-eruption field more strongly. • Fisher: So, for instance, if you want to build a pipe bomb, you should not use a cardboard tube, you should instead use a metal tube. • Mikic: Yes, you want to prevent expansion for a while… Meng Jin studied a CME shock with one-T and two-T models: • 1T: 9 MK precursor far ahead of shock • 2T: 3 MK peak e- T, 100 MK peak proton T (Mach #’s near 4) • Heat flux saturation (not in model) was discussed

  7. Reinard: Charge-state predictions from MHD CME simulations can be used to interpret in situ observations. QFe derived from Breakout model QFe derived from Flux cancellation QFeobservations for the two May 19-21, 2007 MCs MC1 STA MC2 ACE STB

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