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Paper: Asymmetric Stokes--V Profiles at the Penumbral Boundary of a Sunspot
Volume: 325, The Solar-B Mission and the Forefront of Solar Physics
Page: 137
Authors: Choudhary, D.P.; Balasubramaniam, K.S.; Suematsu, Y.
Abstract: We present the spectropolarimetric measurements of a sunspot situated near central meridian disk passage. The sunspot was of positive polarity with several opposite polarity magnetic elements at and beyond the penumbral boundary. The Hα images of the sunspot show bright emission regions near the penumbral boundary towards the sun-center, which was of opposite polarity to the main spot. Doppler velocities determined by measuring the center-of-gravity (COG) of the Stokes-I profile, in general, agree with Evershed flow. In addition, it shows strong flows in the penumbra. The velocities derived from zero-crossing wavelengths of Stokes-V profiles show strong downflows at the penumbral boundary. Double-lobed Stokes-V profiles are observed at locations where penumbral fibrils terminate coinciding with Hα plages. Double lobed profiles have an unshifted component similar to the Stokes-V profiles of the sunspot penumbra and a shifted component with a velocity of about 5 kms−1. The amplitude of the second component increases along the penumbral fibril as a function of the distance from the center of the sunspot. In this paper we present the preliminary results and propose to observe with the Solar-B Solar Optical Telescope (SOT) for understanding the nature of emerging flux near the sunspots.
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