Three-Dimensional MHD Modeling of Propagating Disturbances in Fanlike AR Coronal Loops
Abstract
Quasi-periodic propagating intensity disturbances (PDs) have been observed in cool (about 1 MK) coronal loops in EUV images over a decade. They are widely accepted to be slow magnetosonic waves since their propagation velocity is close to the coronal sound speed. However, recent spectroscopic observations from Hinode/EIS revealed their association with persistent coronal upflows, making this interpretation debatable. Motivated by the scenario that the observed persistent upflows could be cumulative result of numerous individual flow pulses generated by sporadic heating events (nanoflares) at the loop base, we constructed a broadband velocity driver with repetative tiny pulses, whose energy frequency distribution follows the flare power-law scaling distribution. We then performed 3D MHD modeling of an idealized bipolar active region by applying this broadband velocity driver at the footpoints of coronal loops which appear open in the computational domain. Our model successfully reproduced the propagating disturbances with similar features as the observed. We find, based on our simulations, that upflow pulses unavoidably excites a slow magnetosonic wave fronts propagating along the loop with the phase speed which is much larger than the local flow speed as the flow velocity decreases with height. Our modeling results support that the observed PDs are mainly the signature of waves above the footpoints of the loops, and suggest that the observed PDs and associated persistent upflows may be driven by the same mechanism such as impulsive heating at the loop base.
- Publication:
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AAS/Solar Physics Division Abstracts #44
- Pub Date:
- July 2013
- Bibcode:
- 2013SPD....44...36W