Letter to the Editor

Brightness and size of small-scale solar magnetic flux concentrations

¹ Universitäts-Sternwarte, Geismarlandstraße 11, 37083 Göttingen, Germany e-mail: ewiehr@uni-sw.gwdg.de
² Institut für Geophysik, Astrophysik und Meteorologie, Universitätsplatz 5, 8010 Graz, Austria

Received: 13 April 2004
Accepted: 22 June 2004

Abstract

The new 1 m Swedish Solar Telescope SST on La Palma allows to observe inter-granular G-band bright points (igBP) in solar active regions at an unprecedented spatial resolution. The igBP are reasonably assumed to be small-scale magnetic flux-concentrations. A sample of more than 1500 igBP shows tight relations of diameter and brightness in the G-band and in the continuum; it covers a diameter range of 100 km to 300 km, with a most frequent value near 160 km. Features larger than 300 km formerly reported, evidently result from insufficient spatial resolution; that upper diameter limit is close to the typical width of inter-granular lanes, and suggests a “gap” to small pores. The lack of igBP with sizes below 130 km is discussed not to arise from the finite spatial resolution of the 1 m telescope.