Alfvén-character oscillations in ohmic plasmas observed on the COMPASS tokamak T. Markoviˇ c 1,2 , A. Melnikov 3,4 , J. Seidl 1 , L. Eliseev 3 , J. Havlicek 1 , A. Havránek 1,5 , M. Hron 1 , M. Imríšek 1,2 , K. Kovaˇ rík 1,2 , K. Mitošinková 1,2 , J. Mlynar 1 , R. Pánek 1 , J. Stockel 1 , J. Varju 1 , V. Weinzettl 1 , the COMPASS Team 1 1 Institute of Plasma Physics of the CAS, Prague, Czech Republic 2 Faculty of Mathematics and Physics, Charles Uni. in Prague, Prague, Czech Republic 3 National Research Centre ’Kurchatov Institute’, Moscow, Russian Federation 4 National Research Nuclear University MEPhi, Moscow, Russian Federation 5 Faculty of Electrical Engineering, Czech Tech. Uni. in Prague, Prague, Czech Republic Figure 1: High-frequency magnetic fluctuations. f AE curve from eq. (1). a) Quasi-coherent oscilla- tions observed on inboard-torus side. b) Chirping coherent oscillations observed close to separatrix on outboard-torus side. Energetic Particle (EP) driven plasma modes resulting from interaction of shear Alfvén waves with fast (i.e. comparable to plasma Alfvén velocity V A ) ions generated by fu- sion reactions, NBI or ICRH heating [1] are capable of causing fast particle losses, hence negatively affecting the plasma per- formance or having detrimental effects on plasma-facing components or vacuum vessel [2]. A number of comprehensive reviews has already been published, describing properties of EP modes, their appearance, excitation and damping mechanisms, etc. (e.g. [1, 2, 3]). The modes are not trivially expected to appear in ohmic plasmas, however, plasma oscillations bearing their typical signatures have been re- ported in plasmas without an apparent source of EP on a number of devices (such as TFTR [5], ASDEX-U [6], MAST [7], TUMAN-3M [8]). While impact of these specific phenom- ena on plasma performance does not seem to be as significant, their closer investigation will yield better understanding of the under- 44 th EPS Conference on Plasma Physics P5.140