Abstract
The magnetic, thermal and velocity structure of a sunspot at the solar disk centre () is investigated by inverting the full Stokes profiles of three infrared lines. A single magnetic component atmosphere is assumed with height gradients of the physical quantities. Since the line-of-sight (LOS) is perpendicular to the solar surface, differential optical or projection effects do not interfere, as often is the case for the usual observations at oblique LOS. We find a symmetric configuration of the field and flow and the downward motion that increases with radial distance by up to 3 km s-1 near the outer penumbral border. The magnetic field is found to be highly axially symmetric without any indication of azimuthal vortices. A tight relation between field strength and inclination is obtained with a gradient of /1000 G independent of height. The penumbra shows “spines” hosting a pronounced negative correlation between field strength and inclination in the sense that steeper and stronger magnetic fields are related to brightenings in the line cores but not in the continuum. We discuss the dependence of the obtained results on different assumptions of parasitic light, and present indications of its overestimation by the inversion code.
Highlights
Due to their occurrence at latitudes of the solar activity belts, sunspots are mostly seen under a line-of-sight (LOS) not perpendicular to the solar surface
This code returns for each pixel the depth stratification of temperature (T ), magnetic field strength (B), field inclination (γ), field azimuth (φ), LOS velocity (v) and single values for micro- and macro-turbulence, both assumed to be constant with depth
We find that the canopy is pierced by more vertical “plage” magnetic fields associated with down-flows which might be identified as the foot-points of magnetic arches hosting a flow
Summary
Due to their occurrence at latitudes of the solar activity belts, sunspots are mostly seen under a line-of-sight (LOS) not perpendicular to the solar surface This produces projection effects which can only be considered under certain assumptions about the spot geometry being important when trying to disentangle structures of individual inclination. The mean magnetic field has a larger inclination to the solar surface than the Evershed flow (see Stellmacher & Wiehr 1971, and references therein), which is found to be largely horizontal (Wiehr et al 1984; Balthasar et al 1996; Westendorp Plaza et al 2001b). Several properties of the magnetic, the thermal and the flow configuration of sunspots can be optimally studied if the LOS is perpendicular to the solar surface
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
