Phase diversity restoration of sunspot images

Abstract

Abstract. Two time series, taken simultaneously in the G-band and in white-light, and corrected for telescope aberrations and turbulence perturbations using the method of phase diversity, are employed to study the motions of granules and G-band bright points (GBPs) in the moat of an old regular sunspot. Local correlation tracking and feature tracking have been utilized for this purpose. A large-scale radial outflow with a mean velocity of 0.51 km s −1 has been measured in the sunspot moat. Centres of diverging horizontal motions, identified with families of granules formed by repeatedly splitting granules, move away from the sunspot. Most of the GBPs in the moat also move outwards through radially orientated "channels" (confined between the borders of adjacent families) with velocities comparable to those of the adjacent granules. However, 6% of the GBPs move faster (>1.4 km s −1 ) than the neighbouring granules. GBPs in the moat are not regularly distributed but they are less frequent on its solar centre side.

Dynamics of the solar atmosphere above a pore with a light bridge

“…In the WL map we see a typical rosetta pattern of centres of diverging motions caused by repeated expansion and splitting of granules and commonly associated with mesogranules (e.g. Bonet et al 2005, and references therein). The velocity magnitudes range from zero to 1.4 km s −1 with a mean value of 0.4 km s −1 .…”

High‐Resolution Proper Motions in a Sunspot Penumbra

“…We have not been able to find any estimate in which the LCT window has a size to track individual granules, say, 0B7-0B8. 7 Then we carried out an add hoc estimate using the quiet region outside the sunspot studied by Bonet et al (2005). The vertical velocities are computed employing equation (7) when the FWHM of the LCT window equals 0B75.…”

“…The size of the window must be set according to the size of the structures selected as tracers. As a rule of thumb, the size of the window is half the size of the structure that is being tracked (see, e.g., Bonet et al 2005). We adopt a window of FWHM 5 pixels ( 0B2), tracking small features of about 10 pixels ( 0B4).…”

“…Via line fitting and with proper modeling, this indirect technique allows us to infer the physical properties of unresolved structures. Second, one gains spatial resolution by directly improving the image quality of the observations, which involves both the optical quality of the instrumentation and the application of image restoration techniques (e.g., Muller 1973aMuller , 1973bBonet et al 1982Bonet et al , 2004Bonet et al , 2005Stachnik et al 1983;Lites et al 1990;Title et al 1993;Sütterlin et al 2001;Scharmer et al 2002;Rimmele 2004). Eventually the two approaches have to be combined when the relevant length scales are comparable to the photon mean-free-path (see, e.g., Sánchez Almeida 2001).…”

Evidence of small-scale magnetic concentrations dragged by vortex motion of solar photospheric plasma

“…Horizontal velocity magnitudes are averaging-dependent values (Vargas Domínguez 2008), though the flow patterns yielded by the analysis of proper motions are commonly assumed to represent plasma motions thus enabling the detection of general trends, which is our main aim here (e.g., sinks or granulation downdrafts where the cold plasma returns to the solar interior). The map of horizontal displacements is dominated by flows coming from granular explosive events and commonly associated with mesogranulation (Roudier & Muller 2004;Bonet et al 2005). We identified only a pair of examples where strong sinks are present at intergranular lanes (coordinates [6.5, 3.5] and [8.5, 7.5] in Fig.…”