Using data assimilation to reconstruct convection patterns below an active region of solar corona from observed magnetograms

Details Using data assimilation to reconstruct convection patterns below an active region of solar corona from observed magnetograms Using data assimilation to reconstruct convection patterns below an active region of solar corona from observed magnetograms

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsh54a..07p&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #SH54A-07

Astronomy and Astrophysics

Astrophysics

[7524] Solar Physics, Astrophysics, And Astronomy / Magnetic Fields, [7529] Solar Physics, Astrophysics, And Astronomy / Photosphere

Scientific paper

Solar magnetic field originates deep inside the convection zone and rises through it to produce active regions. Detailled simulations of solar convection including granulation and radiation that have been performed in the past are important both to understand the physics of magnetic flux tube evolution as well as the algorithms used for simulations. A challenging problem is the reconstruction of the effective patterns of convection below an observed active region as given by magnetograms and temperature maps at photospheric levels. Since convection in the sun is strongly stratified in density it can be regarded as being anelastic, therefore we used ANMHD software. Here we chosed AR9077-20000714 also known to have produced the ''Bastille day'' flare a region of area 175 Mm2.
To this purpose we used an anelastic convection model that we modified to include the Nudging Back and Forth, a Newtonian relaxation technique for the data assimilation of SOHO/MDI temperature and magnetograms. Vector magnetograms are first choice for the upper boundary condition to be data assimilated. However they have been computed from SOHO line of sight magnetograms using the force free hypothesis as if we would be just above photosphere. We found that velocity shears between slow diverging upflows and fast turbulent downflows produce Ω and U-shaped magnetic field loops. The coronal arcade system of AR9077-20000714 (the ``slinky'') is here understood as the emerging part of the magneto convective pattern below.

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