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Extrapolation vs. MHD modeling

Extrapolation vs. MHD modeling. Hardi Peter Kiepenheuer-Institut Freiburg, Germany. Contribution to the discussions at the SDO workshop / Monterey Feb 2006. 3D MHD coronal modeling. “emission” @ 10 6 K. 20. histogram of currents. mean B 2. vertical Z [Mm].

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Extrapolation vs. MHD modeling

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  1. Extrapolation vs. MHD modeling Hardi Peter Kiepenheuer-Institut Freiburg, Germany Contribution to the discussions at the SDO workshop / Monterey Feb 2006

  2. 3D MHD coronal modeling “emission” @ 106 K 20 histogram of currents mean B2 vertical Z [Mm] Bingert et al. (2005) 10 current log10J2 Gudiksen & Nordlund (2002) ApJ 572, L113 MDI magnetogram mean J2 20 0 10 30 40 horizontal X [Mm] horizontal y [ Mm] vertical z [ Mm] horizontal x [ Mm] • 3D MHD model for the corona: • 50 x 50 x 30 Mm Box (1503) • – fully compressible; high order • – non-uniform mesh • full energy equation (heat conduction, rad. losses) • starting with scaled-down MDI magnetogram – no emerging flux • photospheric driver: foot-point shuffled by convection • braiding of magnetic fields (Galsgaard, Nordlund 1995; JGR 101, 13445) â heating: DC current dissipation (Parker 1972; ApJ 174, 499) â heating rate h j2 ~ exp(- z/H ) â loop-structured 106K corona Gudiksen & Nordlund (2002) ApJ 572, L113 (2005) ApJ 618, 1020 & 1031 Bingert, Peter, Gudiksen & Nordlund (2005)

  3. Coronal emission and plasma–b Peter, Gudiksen & Nordlund (2006) ApJ 638 • atmosphere is mostly in low–b state, • numerous b >1 regions even at high T(but mostly at low density) • source region of coronal emission: 90% of emission from log I/áIñ > 0 Êthere ~5% of volume at b >1 • corona is not in a pure low–b state: plasma able to distort magnetic field to some extent

  4. Coronal emission and magnetic field lines I The "usual" paradigm: The coronal emission is aligned with the magnetic field Peter, Gudiksen & Nordlund (2004) ApJ 618 emission synthesized from a 3D coronal model side view / at the limb

  5. Coronal emission and magnetic field lines II synthesized emission top view / at the limb potential field extrapolation Peter, Gudiksen & Nordlund (2004) ApJ 618 Not all emission we see in EUV / X-rays outlines field lines !!! Gudiksen & Nordlund (2002)

  6. Conclusions • field extrapolations (NLFF): – possible to match photospheric B boundary conditions very well – time evolution through sequence of equilibria – do we really "see" field lines in EUV ? • MHD coronal models – proper time evolution – not easy to match observed B at photosphere (all 3 components) – proper interaction of B and plasma – emission properties through forward modeling • One needs both: MHD models and field extrapolations !

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