Perturbations in the wave parameters near active regions

Rabello-Soares M. Cristina, cristina@sun.stanford.edu, Stanford University, United States
Bogart Richard S., rick@sun.Stanford.EDU, Stanford University
Scherrer Philip H., phil@sun.Stanford.EDU, Stanford University

Abstract
The wave characteristics in magnetically quiet regions with a nearby active region are compared with those of quiet regions at the same solar disk positions, but with no nearby active regions. We search for perturbations in the wave characteristics as the solar acoustic oscillations are affected as they propagate inside the nearby sunspot. We also look for anisotropy in these perturbations in relation to the direction of the nearby sunspot. The wave parameters are derived from ring-diagram analysis of HMI/SDO data from the first 18 months of the mission. We find perturbations in all parameters (frequency, amplitude, and width) that are about five times smaller than those found in active regions, but with a different dependence on frequency. We also measure the variations in the amplitude as a function of the direction of the nearby sunspot. Evidence of small variations in the horizontal flows and some dependence on the direction of the nearby sunspot are observed.