Observational signatures of the interaction between acoustic waves and the solar magnetic canopy

¹ Istituto Tecnico Industriale Statale E. Fermi, via Trionfale 8737, Roma 00133, Italy e-mail: pierfrancesco.moretti@uniroma1.it
² Institute for Astronomy, University of Hawai'i, 4761 Lower Kula Road, Kula, Hawaii 96790, USA e-mail: stuartj@maile.ifa.hawaii.edu
³ Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 400, 80302 Boulder, CO, USA e-mail: mcintosh@boulder.swri.edu

Received: 6 February 2007
Accepted: 28 March 2007

Abstract

Aims.We show that the spatial distribution (and its variation with frequency) of the power spectra of the velocity and intensity signals, in and around solar active regions, is a manifestation of the interaction of acoustic waves at the magnetic canopy.

Methods.We analysed 6 h of simultaneous, full-disk, velocity and intensity images obtained using the MOTH instrument tuned in the Na D2 line at 589 nm and K D1 line at 770 nm, and full-disk velocity images from the SOHO/MDI experiment using the Ni line at 677 nm.

Results.We propose that more than one type of magneto-acoustic-gravity wave is required to explain the well-known phenomena of p-mode absorption and power halos.