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SUMMARY:MHD waves in the solar corona - Dr. Giuseppe Nistico (University o
 f Warwick)
DTSTART:20140211T130000Z
DTEND:20140211T140000Z
UID:TALK50420@talks.cam.ac.uk
CONTACT:Dr. Jaroslav Dudik
DESCRIPTION:Observations of the Sun at Extreme Ultra-Violet or X-Ray wavel
 engths from space-borne instruments show that the solar corona is a highly
  dynamic region. The coupling between the coronal magnetic field and the l
 ow density fully-ionized plasma\, makes the corona an "elastic" medium\, a
 ble to sustain the formations and propagation of waves\, interpreted in te
 rm of magnetohydrodynamics theory. Moreover\, the advent of high spatial a
 nd temporal resolution instruments (e.g.\, COMP\, Hinode\, STEREO\, SDO)\,
  have shown that waves are truly ubiquitous in the atmosphere.\n\nA large 
 variety of modes are triggered in standing and propagating form\, includin
 g transverse oscillations of coronal loops\, more properly defined as "kin
 k" waves. Excited by a flare or an eruption nearby\, kink oscillations are
  usually observed to damp in about 3--4 periods. The physical mechanism re
 sponsible for the rapid damping has been subject to a number of theoretica
 l studies\, and the general accepted interpretation is the phenomenon of r
 esonant absorption: linear coupling of the kink mode to unresolved torsion
 al motions at a very narrow resonant layer.\n\nHere\, we provide the state
 -of-art in the observations of wave phenomena in the solar corona\, focusi
 ng on kink oscillations of coronal loops observed by the Solar Dynamics Ob
 servatory (SDO). The presence of almost persistent low-amplitude (close to
  the spatial resolution of the telescopes) transverse motions\, in additio
 n to the well-known large-amplitude and decaying mode is shown. The behavi
 our is consistent with the empirical model of a damped linear oscillator e
 xcited by a continuous low-amplitude harmonic driver and/or by an impulsiv
 e high-amplitude driver. The properties of this type of transverse oscilla
 tions make them interesting object of study in the framework of coronal he
 ating.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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