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Title: An interpretation of flare-induced and decayless coronal-loop oscillations as interference patterns

We present an alternative model of coronal-loop oscillations, which considers that the waves are trapped in a two-dimensional waveguide formed by the entire arcade of field lines. This differs from the standard one-dimensional model which treats the waves as the resonant oscillations of just the visible bundle of field lines. Within the framework of our two-dimensional model, the two types of oscillations that have been observationally identified, flare-induced waves and 'decayless' oscillations, can both be attributed to MHD fast waves. The two components of the signal differ only because of the duration and spatial extent of the source that creates them. The flare-induced waves are generated by strong localized sources of short duration, while the decayless background can be excited by a continuous, stochastic source. Further, the oscillatory signal arising from a localized, short-duration source can be interpreted as a pattern of interference fringes produced by waves that have traveled diverse routes of various pathlengths through the waveguide. The resulting amplitude of the fringes slowly decays in time with an inverse square root dependence. The details of the interference pattern depend on the shape of the arcade and the spatial variation of the Alfvén speed. The rapid decay of thismore » wave component, which has previously been attributed to physical damping mechanisms that remove energy from resonant oscillations, occurs as a natural consequence of the interference process without the need for local dissipation.« less
Authors:
 [1] ;  [2]
  1. JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0440 (United States)
  2. School of Mathematics and Statistics, University of Sheffield, Sheffield S3 7RH (United Kingdom)
Publication Date:
OSTI Identifier:
22357280
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 784; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; AMPLITUDES; DECAY; INTERFERENCE; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; ONE-DIMENSIONAL CALCULATIONS; OSCILLATIONS; STOCHASTIC PROCESSES; SUN; TRAPPING; TWO-DIMENSIONAL CALCULATIONS; VELOCITY; WAVEGUIDES