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Session 17 - Magnetic Fields II.
Oral session, Tuesday, July 01
Ballroom A, Chair: Paul Charbonneau
Using data from the Advanced Stokes Polarimeter, we follow the development of a rudimentary penumbra around a small pore. A sub-hourly cadence coupled with the full vector spectro-polarimetry and non-linear least-squares inversion algorithm allows us to determine not only the vector magnetic field around the pore, but also thermodynamic parameters and Doppler shifts.
We find that a penumbra forms not by a gradual ``tilting'' of the field lines, but by the initial appearance of weaker fields at all inclinations. The distribution of these fields is sparse, but grows with time to where a fully-populated range of field strengths and inclination angles is present (as is common for fully-developed sunspots). At the same time, the range of Doppler velocities increases in the lower-field-strength areas. This implies that any difference between the start of the Evershed flow and the appearance of more inclined fields is small (less than half-hour).
We will discuss these results and their relation to the flux history of this pore, comparing it to a nearby region in which a penumbra-less pore develops from apparent quiet-sun.
