Temporal and spatial variations of the magnetic field vector in sunspots

¹ ESA Research and Scientific Support Department (RSSD), ESTEC, Keplerlaan 1, 2201 AZ, Noordwijk, The Netherlands
² National Solar Observatory/Sacramento Peak PO Box 62 Sunspot, NM 88349–0062, USA
³ Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, Germany e-mail: msig@kis.uni-freiburg.de
⁴ Astrophysikalisches Institut Potsdam, Telegrafenberg A27, 14473 Potsdam, Germany e-mail: kmuglach@aip.de

Corresponding author: A. Settele, asettele@rssd.esa.int

Received: 21 February 2002
Accepted: 28 May 2002

Abstract

In order to look for magnetic field vector oscillations in sunspots we used data measured with the Advanced Stokes Polarimeter at the Dunn Solar Telescope. We analyzed two time series of 65 and 110 min that were taken by scanning repeatedly a 62 field of view, while obtaining the full Stokes vector in the lines FeI 630.15 nm and 630.25 nm. An inversion was carried out and a Fast Fourier Transform (FFT) analysis was used to find oscillatory phenomena. We discuss possible unwanted effects that lead to apparent magnetic field oscillations and find an average amplitude of () 5.8 G/0.23° rms by excluding these effects, which also means that only 6% and 22% of the two sunspot umbrae respectively remained for analysis. If we smooth the power spectra over pixels, all significant power disappears.