The effect of the spontaneous magnetic reconnection events, characterizing reversed-field pinch plasmas, on Alfvén eigenmodes (AE) is studied in the RFX-mod device by means of insertable edge magnetic probes. In particular, reconnection is observed to induce a sudden growth of the amplitude of the long wavelength (m/n=1/0), high frequency (around 1 MHz), Alfvénic activity (appearing as two peaks in the frequency power spectra), interpreted in terms of two coupled Global AE, being associated to the presence of a minimum in the Alfvén continuum. The dynamical behavior of the amplitude of such modes suggests some hints on a possible driving mechanism in ohmically heated plasmas, which should be linked to the formation of a high energy particles tail during reconnection. Moreover, the behavior of mode frequencies allows a radial localization at the edge of the plasma.
Magnetic reconnection and Alfvén eigenmodes in the RFX-mod reversed-field pinch plasmas
Silvia Spagnolo;Matteo Zuin;Emilio Martines;Monica Spolaore;Nicola Vianello
2011
Abstract
The effect of the spontaneous magnetic reconnection events, characterizing reversed-field pinch plasmas, on Alfvén eigenmodes (AE) is studied in the RFX-mod device by means of insertable edge magnetic probes. In particular, reconnection is observed to induce a sudden growth of the amplitude of the long wavelength (m/n=1/0), high frequency (around 1 MHz), Alfvénic activity (appearing as two peaks in the frequency power spectra), interpreted in terms of two coupled Global AE, being associated to the presence of a minimum in the Alfvén continuum. The dynamical behavior of the amplitude of such modes suggests some hints on a possible driving mechanism in ohmically heated plasmas, which should be linked to the formation of a high energy particles tail during reconnection. Moreover, the behavior of mode frequencies allows a radial localization at the edge of the plasma.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
