The Evershed effect observed with 0.2 arsec angular resolution

Abstract

We present an analysis of the Evershed effect observed with a resolution of 0.2 arcsec. Using the new Swedish 1-m Solar Telescope and its Littrow spectrograph, we scan a significant part of a sunspot penumbra. Spectra of the non-magnetic line Fe I 7090.4 A allows us to measure Doppler shifts without magnetic contamination. The observed line profiles are asymmetric. The Doppler shift depends on the part of the line used for measuring, indicating that the velocity structure of penumbrae remains unresolved even with our angular resolution. The observed line profiles are properly reproduced if two components with velocities between zero and several km/s co-exist in the resolution elements. Using Doppler shifts at fixed line depths, we find a local correlation between upflows and bright structures, and downflows and dark structures. This association is not specific of the outer penumbra but it also occurs in the inner penumbra. The existence of such correlation was originally reported by Beckers & Schroter (1969), and it is suggestive of energy transport by convection in penumbrae.

To appear in ApJ. 14 pages and 17 figures

References in corpus (5)

• Fine structure, magnetic field and heating of sunspot penumbrae
• Quiet Sun magnetic fields from simultaneous inversions of visible and infrared spectropolarimetric observations
• Simultaneous visible and infrared spectro-polarimetry of a solar internetwork region
• Physical properties of the solar magnetic photosphere under the MISMA hypothesis III: sunspot at disk center
• High-resolution proper motions in a sunspot penumbra

Cited by in corpus (13)

• Penumbral structure and outflows in simulated sunspots
• Numerical sunspot models: Robustness of photospheric velocity and magnetic field structure
• Structure of sunspot penumbral filaments: a remarkable uniformity of properties
• Depth-dependent global properties of a sunspot observed by Hinode using the Solar Optical Telescope/Spectropolarimeter
• Lateral downflows in sunspot penumbral filaments and their temporal evolution
• SST/CRISP Observations of Convective Flows in a Sunspot Penumbra
• Evidence for convection in Sunspot penumbrae
• Penumbral models in the light of Hinode spectropolarimetric observations
• Searching for overturning convection in penumbral filaments: slit spectroscopy at 0.2 arcsec resolution
• Convective motions and net circular polarization in sunspot penumbrae
• Can overturning motions in penumbral filaments be detected?
• Waves as the source of apparent twisting motions in sunspot penumbrae
• A Topology for the Penumbral Magnetic Fields