“Three-D MHD numerical simulations of coronal loop oscillations associated with flares” Miyagoshi et al., PASJ 56, 207, 2004

Issues of coronal seismology The dynamic spectrum of the coronal plasma structure has resonances (“normal modes”) Several lines of observation show these There is controversy with damping Their excitation is fundamentally interesting

Literature There is quite a bit of observational literature Analytic theory has been developed (especially by B. Roberts et al.) The problems presented by the oscillations seem ideally suited to ideal MHD theory But there are non-ideal effects observed

From Aschwanden et al (TRACE loop oscillations discovered!)

Case 2. Weird brown surface is density = 0.9.

Foregoing was for an empty loop (uniform hydrostatic potential-field medium. What about an overdense loop?

Conclusions Oscillations found, at P = 2L/V A Oscillations damp at  damp =  -1/2 Overdense loops oscillate more slowly, as expected Trapping effect is weak

Remaining questions How do these results compare with the analytic development of Roberts et al.? What modes are excited? How can this explanation of damping (the mere radiation of Alfven waves) be correct?

Periods Oscillations found, at P = 2L/V A Theory (Roberts, Edwin, Benz 1984) for “principal kink wave” gives P = 2L/C k, where C k = sqrt(2/(1+  e /  o ))V A

Possible causes of damping Unexpectedly high viscosity Phase mixing Wave leakage at footpoints Resonant absorption Direct Alfven-wave losses?

There is good review material in Erdelyi et al., NATO science series vol. 124 (book just received as a freeby from Markus, who is a co-editor)