The high-β spherical tokamaks (ST), such as NSTX and MAST, are attractive fusion devices for studying the physics of current drive by electron cyclotron (EC) waves. While ST plasmas are overdense to conventional EC waves, electron Bernstein waves (EBW) can be used to generate plasma currents. Besides providing better confinement, EBW driven current can also help suppress neoclassical tearing mo...

Abstract: Using observations from the FAST small explorer spacecraft we present fields and plasma observations above the dayside auroral oval showing the erosion of ionospheric plasmas from the topside ionosphere by the action of Alfvén waves. Using interferometric techniques the waves are shown to approximately obey the expected dispersion for Alfvén waves with transverse scales extending from...

Whistler emissions close to the magnetopause on the magnetospheric side are investigated using the four Cluster spacecraft. The waves are found to be generated in thin (electron-scale) sheets moving with the plasma drift velocity. A feature in the electron data coincides with the waves; hot magnetospheric electrons disappear for a few satellite spins. This produces or enhances a temperature ani...

During lower-hybrid current-driven (LHCD) tokamak discharges with thermal electron temperature Te ~~ 150 eV, a two-parallel-temperature tail is observed in the electron distribution function. The cold tail extends to parallel energy Ell ~ 4.5 keV with temperature Tthd ~ 1.5 keV, and the hot tail extends to El > 150 keV with Thj' > 40 keV. Fokker-Planck computer simulations suggest the cold tail...

We analytically study the generation of longitudinal plasma waves in an underdense plasma by two electromagnetic waves with frequency difference approximately equal to the plasma frequency, as envisioned in the plasma beat-wave accelerator concept of Tajima and Dawson. The relativistic electron fluid equations describing driven electron oscillations with phase velocities near the speed of light...

Observations from the WHISPER (Waves of High frequency and Sounder for Probing of Electron density by Relaxation) instrument on board Cluster, for the interval spanning 2001–2012, are utilized to determine an empirical model describing the total electron density along closed geomagnetic field lines. The model, representing field lines in the region of 4.5≤ L<9.5, includes dependences on L and m...

Generation of shear Alfvén waves by the Doppler-shifted ion-cyclotron-resonance (DICR) of a spiraling H(+) ion beam with magnetic fluctuations in a dual-species magnetized plasma with He(+) and H(+) ions has been investigated on the Large Plasma Device. The ambient plasma density and electron temperature were significantly enhanced by the beam. The Alfvén waves were left-handed polarized and tr...

Continuous plasma coherent emission is maintained by repetitive Langmuir collapse driven by the nonlinear evolution of a strong electron two-stream instability. The Langmuir waves are modulated by solitary waves in the linear stage and electrostatic whistler waves in the nonlinear stage. Modulational instability leads to Langmuir collapse and electron heating that fills in cavitons. The high pr...