Electron burst driven by near electric field effects of lower‐hybrid launchers

• Published in: Contributions to plasma physics (1988) Vol. 58; no. 6-8; pp. 465 - 470
• Main Authors: Valade, L., Ekedahl, A., Ghendrih, P., Sarazin, Y., Asahi, Y., Bufferand, H., Caschera, E., Di Cintio, P., Ciraolo, G., Dif‐Pradalier, G., Donnel, P., Garbet, X., Giorgi, P.‐A., Grandgirard, V., Latu, G., Lepri, S., Livi, R., Nouri, A., Serre, E.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag GmbH & Co. KGaA 01.07.2018; Wiley Subscription Services, Inc; Wiley-VCH Verlag
• Subjects: Amplification; Amplitudes; Chemical and Process Engineering; Decay rate; Distribution functions; Electric fields; Engineering Sciences; hot electron plateau; hotspot generation; island overlap; kinetic; Launchers; lower hybrid; Parameter sensitivity; Phase velocity; Resonance; scrape‐off layer; Structure-function relationships; Velocity; lower hybrid; waves; hot electron plateau; hotspot generation; scrape-off layer; heat-flux; island overlap; kinetic; resonance
• ISSN: 0863-1042; 1521-3986
• DOI: 10.1002/ctpp.201700156

Hotspot generation by lower‐hybrid (LH) launchers is found to be governed by a resonance in the plasma electric field response to the external drive. The kinetic analysis in 1D‐1V in the parallel direction allows one to compute the amplification effect for small amplitude of the external drive. The resonant Lorentzian response distorts the distribution function. An island structure is formed in the suprathermal part at the phase velocity of the external electrostatic drive. The non‐linear features enhance the plasma response, driving overlap effects between multiple waves at rather low amplitude. The onset of a plateau in the distribution function, with extent reaching one thermal velocity, is already obtained when the standard overlap condition is achieved. The sensitivity of the resonance to plasma parameters and large variation of the amplification magnitude can compensate the fast radial decay of the small‐scale features generated by the LH launchers, which are responsible for the interaction with the cold electrons. This mechanism can trigger hotspot generation further in the scrape‐off layer than otherwise expected.