1211.5776 (G. B. Scharmer et al.)

The connection between convective downflows and spines in a sunspot penumbra    [PDF]

G. B. Scharmer, J. de la Cruz Rodríguez, P. Sütterlin, V. M. J. Henriques

We discuss NICOLE inversions of Fe I 630.15 nm and 630.25 nm Stokes spectra from a sunspot penumbra, recorded with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope and a spatial resolution close to 0.15". Our emphasis is on narrow downflow lanes, which are cospatial with the relatively dark and cool parts of penumbral filaments. We find that these downflow lanes are located at the boundaries between areas of relatively horizontal magnetic field (the inter-spines) and much more vertical field (the spines). These locations agree with predictions from the convective gap model (the "gappy penumbra") proposed six years ago, and more recent 3D MHD simulations. We also find that in the deep photosphere, the downflow lanes are frequently, but not always, associated with opposite polarity magnetic field. This is also consistent with the simulations, predicting that many of the convective downflows pull down the magnetic field, rather than flow passively along it.

View original: http://arxiv.org/abs/1211.5776