Scales of the magnetic fields in the quiet Sun

¹ THEMIS – CNRS UPS 853, C/ Vía Láctea s/n, 38200 La Laguna, Spain
e-mail: Arturo.Lopez@themis.iac.es
² Stanford-Lockheed Institute for Space Research, HEPL, Stanford University, Cypress Hall, 466 Via Ortega, Stanford, CA 94305, USA

Received: 30 September 2011
Accepted: 6 February 2012

Abstract

Context. The presence of a turbulent magnetic field in the quiet Sun has been unveiled observationally using different techniques. The magnetic field is quasi-isotropic and has field strengths weaker than 100 G. It is pervasive and may host a local dynamo.

Aims. We aim to determine the length scale of the turbulent magnetic field in the quiet Sun.

Methods. The Stokes V area asymmetry is sensitive to minute variations in the magnetic topology along the line of sight. Using data provided by Hinode-SOT/SP instrument, we performed a statistical study of this quantity. We classified the different magnetic regimes and infer properties of the turbulent magnetic regime. In particular we measured the correlation length associated to these fields for the first time.

Results. The histograms of Stokes V area asymmetries reveal three different regimes: one organized, quasi-vertical and strong field (flux tubes or other structures of the like); a strongly asymmetric group of profiles found around field concentrations; and a turbulent isotropic field. For the last, we confirm its isotropy and measure correlation lengths from hundreds of kilometers down to 10 km, at which point we lost sensitivity. A crude attempt to measure the power spectra of these turbulent fields is made.

Conclusions. In addition to confirming the existence of a turbulent field in the quiet Sun, we give further prove of its isotropy. We also measure correlation lengths down to 10 km. The combined results show magnetic fields with a large span of length scales, as expected from a turbulent cascade.