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K. D. Leka (Colorado Research Associates/NWRA), O. Steiner, U. Grossmann-Doerth (Kiepenheuer-Institut fur Sonnenphysik)
We perform direct comparisons of high-resolution spectropolarimetric observations with a full MHD model of the magnetized solar atmosphere. In this manner we investigate the evolution and dynamics of small magnetic elements by fully utilizing the diagnostics available with Stokes spectropolarimetry, both computed and observed.
The model is a 2-D time-dependent numerical simulation of a small (\approx 600 km diameter) magnetic feature embedded in a non-magnetized atmosphere (Steiner et al., 1998). At select time-steps, synthetic emergent Stokes I and V profiles are computed using a polarized radiation transfer code. The data consist of Stokes I and V spectra from the Advanced Stokes Polarimeter for seventeen small magnetic elements located near disk-center.
For both the observed and computed Stokes spectra, diagnostics are computed including the emergent continuum intensity, V-crossing shift, and amplitude and area asymmetries of the V-profile. We find that it is possible to differentiate between salient processes occurring in the magnetic atmosphere (strong flows, gradients, etc.) by their spectropolarimetric signature; from this, we determine the dominant processes present in the observed magnetic structures.
The results are extremely encouraging. We find good qualitative agreement between the amplitude and area asymmetries and their spatial variation. Quantitatively, the agreement is surprisingly good in many cases. While limitations exist for both the model and observations, this stringent test allows us to comment on the dynamics and possible evolutionary differences present in the observed magnetic features.
This work is funded in part by NSF grant ATM-9710782.
Reference: - Steiner, O., Grossmann-Doerth, U., Knölker, M., Schüssler, M.: 1998, ApJ 495, 468
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