Understanding Magnetic Eruptions on the Sun and their Interplanetary Consequences

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Understanding Magnetic Eruptions on the Sun and
their Interplanetary Consequences

• A Solar and Heliospheric Research grant funded by
  the DoD MURI program
• George H. Fisher, PI
• Space Sciences Laboratory
• University of California, Berkeley

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Institutions of Solar Multidisciplinary
University Research Initiative Team

• UC Berkeley
• Big Bear Solar Observatory (NJIT)
• Drexel University
• Montana State University
• Stanford University
• UC San Diego
• University of Colorado
• University of Hawaii
• University of New Hampshire

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Goal

• Develop a state-of-the-art, observationally
  tested 3-D numerical modeling system for
  predicting magnetic eruptions on the Sun and the
  propagation of Coronal Mass Ejections (CMEs).

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Approach

• Perform in-depth, coordinated space and ground
  based observations of magnetic eruptions and
  Coronal Mass Ejection (CME) propagation
• Understand the physics of how magnetic eruptions
  are triggered and powered
• Develop numerical models for the initiation and
  propagation of CMEs and the acceleration of Solar
  Energetic Particles (SEPs)
• Couple together the observationally tested models
  of the Sun and Heliosphere

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Overview of Solar MURI

• 1. Active Region Emergence Fisher Abbett
  (UCB), LaBonte, Jing Li, Mickey (UH), Canfield
  Regnier (MSU), Liu (Stanford), Gallagher,Moon,
  Wang Goode (BBSO)

2. Effects of Large Scale Field and Solar Cycle
Evolution Hoeksema, Scherrer, Zhao (Stanford),
Ledvina Luhmann (UCB), Martens (MSU), Goode,
Wang Gallagher (BBSO)
3. Inner Corona Forbes (UNH), MacNeice (Drexel),
Abbett, Ledvina, Luhmann Fisher (UCB), Kuhn
H. Lin (UH), Canfield Longcope (MSU), Hoeksema,
Scherrer Zhao (Stanford)
4. Outer Corona, Solar Wind, SEPs Odstrcil (CU),
Jackson, Dunn Hick (UCSD), MacNeice (Drexel),
Luhmann R. Lin (UCB), Lee (UNH)
5. Geoeffects Luhmann R. Lin (UCB), Odstrcil
(CU), Hoeksema Zhao (Stanford)
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MURI mini-workshops related to CME initiation

• Using vector magnetogram data in MHD simulation
  and other theoretical models (April 29, G.H.
  Fisher R.C. Canfield, Berkeley)
• Well defined numerical experiments for CME
  eruption mechanisms (May 14-16, T.J. Forbes,
  Durham NH)

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UNH MURI Workshop Planned Numerical
Experiments1. The emerged bipole

• 3-d Emerged Bipole Form flux-rope in simulated
  corona by converging footpoints of coronal
  fields.
• computational domain is 3-d non-periodic box with
  high b 10?) on bottom boundary,
  w/stratification such that b ltlt 1 within lower
  part of simulation volume.
• initial condition (IC) has volume-filling dipole
  field.
• impose incompressible converging flows on bottom
  boundary .

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3d emerged bipole (contd)

• initial magnetic field ought to be sheared, such
  that some component of the magnetic field is
  parallel to the magnetic neutral line at the
  bottom boundary or
• if initial magnetic field is unsheared
  (potential?), imposed flow should have non-zero
  vorticity, to ensure some component of magnetic
  field is tangential to the magnetic neutral line
  on the bottom boundary
• primary goal is to form flux rope subsequent
  efforts to erupt flux rope envisioned upon
  attainment of flux rope in corona
• this experiment involves some modification of
  existing codes.
• Critical issue 3-d necessary (no 2.5-d, or
  periodicity)

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2. The 3-d Emerging Bipole

• Flux rope in coronal volume via emergence of a
  pre-existing twisted flux tube from a region of
  high b to low b
• IC buoyantly unstable horizontal twisted flux
  tube immersed in high-b plasma at base of
  gravitationally stratified 3-d box.
• Follow rise of twisted flux tube from deep in
  convection zone through photosphere into corona.
  Critical issue initial position of tube cannot
  be too near surface, as flux tube curvature
  matters.
• Unspecified parameter degree of twist in
  emerging tube. Twist too high perhaps prevents
  mass drainage, hampering emergence twist too low
  does not give true flux rope in corona.

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3d emerging bipole (contd)

• Unspecified parameter Magnetic field
  configuration in corona prior to flux rope
  emergence. Initial runs w/field-free corona
  envisioned.
• As above, primary goal is to get flux rope in
  corona subsequent efforts to attain eruption
  envisioned after attainment of primary.
• As above, some modification of existing codes
  necessary.

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3. Bipole emergence in 3d multi-polar field

• Emerge one flux tube into into background
  magnetic field sheared arcade/flux rope
  formation by reconnection between emerging flux
  and pre-existing flux.

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Bipole emergence in multi-polar field (contd)

• IC buoyantly unstable flux tube immersed in
  high-b plasma at base of gravitationally
  stratified 3-d box with background magnetic field
  configuration composed of a pre-emerged flux tube
  and large scale restraining field, and form
  sheared arcade/flux rope by reconnection between
  the two flux tubes.
• Critical issue without restraining field,
  reconnected flux expected to rise to top of
  computational volume in non-explosive manner.

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Bipole emergence in multi-polar field (contd)

• Primary goal is attainment of sheared arcade/flux
  rope in corona subsequent effort to attain
  eruption envisioned.
• In one effort to attain eruption, additional
  polarity will be added to restraining field to
  make it quadrupolar.
• Unspecified parameter twist in either
  pre-emerged or newly-emerging flux ropes.
  Presence of twist might either enhance or
  diminish storage of energy in the field, and
  hence likelihood of eruption.

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Solar MURI Vector Magnetogram Mini-Workshop

• Using Vector Magnetograms in Theoretical Models
• Plan of Action

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Overview of the plan

• Phase I
• Analyze available data for 1998 May 1 event
• Construct coronal magnetic equilibria
• Develop velocity inversion methods
• Test velocity inversion methods
• Study a second (simpler) event May 12, 1997
• Phase II
• Carry out MHD simulations
• Couple coronal and IP codes
• Phase III
• Validation of modelling using available solar and
  IP data

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Analyze available data for 1998 May 1 event

• Generate a sequence of IVM magnetograms for the
  1998 May 1 2340 UT halo CME event (AR 8210),
  time cadence 15 min (too slow ?), before,
  during, and after eruption. (Regnier)
• Estimate the magnetic field uncertainties.(Metcalf
  , Leka)
• Determine line of sight and transverse
  velocities. (Welsch, Metcalf)
• Analyze the global solar (Li, Liu) and IP (Li,
  Luhmann) context (spatial, temporal) of this
  event, time scale several days, including
  previous and following events.
• Make an instrument vs time array on WWW (Li)

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Construct coronal magnetic equilibria

• Build force-free magnetic field models for each
  magnetogram, combined with a potential
  extrapolation of MDI data. (Regnier)
• Build magnetostatic models from the same
  magnetograms (Heinemann).
• Compare force-free magnetic field models to
  available coronal imaging data (Canfield,
  Metcalf)
• Compare connectivity of force-free models to that
  of point charge models (Regnier, Longcope, Leka)

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Develop velocity inversion methods

• Use vertical component of induction equation to
  derive velocity fields (Longcope, Fisher, Welsch)
• Constrain the solutions by minimizing total
  kinetic energy (ditto)

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Test velocity inversion methods

• Generate fake magnetogram sequences from the MHD
  simulations (Abbett, Fisher)
• Use velocity inversion techniques to infer
  velocities from these sequences (ditto Welsch)
• Compare photospheric boundary velocities from the
  simulation to those inferred from the inversion
  (same as 2)
• Explore implications of magnetogram uncertainties
  through Monte Carlo methods (same as 2).
• Compare velocities from the inversion to IVM
  observations (Welsch, Metcalf, Abbett, Fisher)

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Study a second (simpler) event (Liu)

• Identify a simpler solar and IP event for
  analysis (1997 May 12 halo CME in AR8038 ?).
• Produce a vector magnetogram (Solar Flare
  Telescope / Mitaka ?) sequence for this event.
• Carry out an analysis parallel to that of the
  1998 May 1 event (no velocity observations
  available or use LCT methods for v_t, MDI for
  v_l?) (Liu Welsch)

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Carry out MHD simulations

• Do Zeus AMR simulations using real magnetic field
  data near time of CME using synoptic magnetic
  field solutions as boundary condition. (Berkeley
  team members)
• Couple coronal and interplanetary codes
• (Abbett, Ledvina, Odstrcil)