1 / 14

Why are coronal magnetic fields important? Models for magnetic field reconstruction.

Coronal magnetic fields Thomas Wiegelmann, MPI for Solar-System Research, (Former: MPI f ü r Aeronomie) Katlenburg-Lindau. Why are coronal magnetic fields important? Models for magnetic field reconstruction. Potential magnetic fields Linear force-free fields Non-linear force-free fields

Download Presentation

Why are coronal magnetic fields important? Models for magnetic field reconstruction.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Coronal magnetic fieldsThomas Wiegelmann,MPI for Solar-System Research, (Former: MPI für Aeronomie)Katlenburg-Lindau • Why are coronal magnetic fields important? • Models for magnetic field reconstruction. • Potential magnetic fields • Linear force-free fields • Non-linear force-free fields • Magnetic fields and coronal tomography • Conclusions

  2. Why are coronal magnetic fields important? • Magnetic fields couples the solar interior, photosphere and atmosphere. • Magnetic field dominates in the solar corona. (Magnetic pressure >> Plasma pressure). • Knowledge of the coronal B-Field is essentialto understand dynamic phenomena likecoronal mass ejections and flares.

  3. How to obtain coronal B-Fields • Direct measurements are extremely difficult. • Measure B on the photosphere (line of sight Bor vector B) and extrapolate it into the corona. • We need assumptions regarding coronal currents:- No currents  Potential fields-  Linear Force Free Fields •  Non Linear Force Free Fields

  4. Coronal magnetic field models

  5. Global Potential Field reconstruction

  6. Linear Force-Free Fields

  7. Linear Force-Free Fields

  8. Linear Force-Free Fields

  9. Linear Force-Free Fields 3D magnetic field lines withKitt Peak magnetogram EIT-image and projected magnetic field lines. (α · L=2)

  10. Non-linear force-free fields • Why do we need non-linear force-free fields?- In general alpha changes in space.- Potential and linear force-free fields have no free energy to be released during an eruption. • The computation is much more difficult:- Mathematical difficulties due to non-linearity.- Vector magnetograms have ambiguities.- Transversal B-field is very noisy.- Limited field of view for current instruments. (Soon: Full disc vector magnetograph SOLIS.)

  11. Non-linear force-free fields Potential field and non-linear force free reconstruction of a model active region regarding the same line of sight photospheric magnetic field. Our optimization code reconstructs the original analytic solution within the discretisation error.

  12. Magnetic fields and coronal tomography • Coronal tomography uses line of sight integrals of the coronal density from different viewpoints. • Aim: 3D reconstruction of coronal density structure. • Density and magnetic field have to be reconstructedselfconsistently (MHS-equations + observational data).

  13. Magnetic fields and coronal tomography • Use only line of sight density integrals. • Use only magneticfield data. • Use both line of sightdensity integrals andmagnetic field as regularization operator.

  14. Conclusions • Potential magnetic fields and linear force free fields are popular due to their mathematic simplicity and available data. (e.g. from MDI on SOHO, Kitt Peak) • Nonlinear force free fields are necessary todescribe active regions exactly. More challenging both observational and mathematical. • A consistent 3D model of the solar corona requirestomographic inversion and magnetic reconstructionin one model.

More Related