THE ROLE OF ACTIVE REGION LOOP GEOMETRY. I. HOW CAN IT AFFECT CORONAL SEISMOLOGY?

Journal Article · Sat Jan 01 04:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/726/1/42· OSTI ID:21567694

Selwa, M; Ofman, L ^[1]

---

1. Department of Physics, Catholic University of America, 620 Michigan Avenue, NE, 200 Hannan Hall, Washington, DC 20064 (United States)

We present numerical results of coronal loop oscillation excitation using a three-dimensional (3D) MHD model of an idealized active region (AR) field. The AR is initialized as a potential dipole magnetic configuration with gravitationally stratified density and contains a loop with a higher density than its surroundings. We study different ways of excitation of vertical kink oscillations of this loop by velocity: as an initial condition, and as an impulsive excitation with a pulse of a given position, duration, and amplitude. We vary the geometry of the loop in the 3D MHD model and find that it affects both the period of oscillations and the synthetic observations (difference images) that we get from oscillations. Due to the overestimated effective length of the loop in the case of loops which have maximum separation between their legs above the footpoints (>50% of observed loops), the magnetic field obtained from coronal seismology can also be overestimated. The 3D MHD model shows how the accuracy of magnetic field strength determined from coronal seismology can be improved. We study the damping mechanism of the oscillations and find that vertical kink waves in 3D stratified geometry are damped mainly due to wave leakage in the horizontal direction.

• OSTI ID: 21567694
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 726; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ATMOSPHERES
DAMPING
DIPOLES
FLUID MECHANICS
HYDRODYNAMICS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MECHANICS
MULTIPOLES
OSCILLATIONS
SOLAR ATMOSPHERE
SOLAR CORONA
STELLAR ATMOSPHERES
STELLAR CORONAE
THREE-DIMENSIONAL CALCULATIONS