Smolyakov A.I., Bashir M.F., Elfimov A.G., Yagi M., Miyato N. «On the dispersion of Geodesic Acoustic Modes» Физика плазмы, 42, № 5, с. 417-427 (2016)

The problem of dispersion of Geodesic Acoustic Modes is revisited with two different methods for the solution of the kinetic equation. The dispersive corrections to the mode frequency are calculated by including the poloidal harmonics. Our obtained results agree with some earlier results but differ in various ways with other previous works. Limitations and advantages of different approaches are discussed.

Itoh K., Itoh S.I., Kosuga Y., Lesur M., Ido T. «Onset condition of the subcritical geodesic acoustic mode instability in the presence of energetic-particle-driven Geodesic Acoustic Mode» Физика плазмы, 42, № 5, с. 428-433 (2016)

An analytic model is developed for understanding the abrupt onset of geodesic acoustic mode (GAM) in the presence of chirping energetic-particle-driven GAM (EGAM). This abrupt excitation phenomenon has been observed on LHD plasma. Threshold conditions for the onset of abrupt growth of GAM are derived, and the period doubling phenomenon is explained. The phase relation between the mother mode (EGAM) and the daughter mode (GAM) is also discussed. This result contributes to the understanding of ‘trigger problems’ of laboratory and nature plasmas.