1 Introduction Internal kink mode driven by barely trapped suprakthermal electrons is reported on D Ⅲ-D tokama . This instability is most active when electron cyclotron current drive （ ECCD ） is applied on the high field side of the flux surface. It has a bursting behavior with poloidal/toroidal mode number m/n = 1/1. In positive magnetic shear plasma this mode becomes fishbone instability.
WANG ZhongtianLONG YongxingDONG JiaqiWANG LongZonca F.
The geodesic acoustic mode （GAM）, first predicted by Winsor, Johnson and Dawson in an attempt to explain some experimentally observed low frequency oscillations in stellarators, is a special electrostatic fluid mode with low mode number and coupled with the so-called geodesic curvature of a toroidally confined plasma. The recent on this mode are due to the close relevance of the stabi- lization of drift turbulence by both the zonal flow and the GAM. Previously, the GAM was illustrated in very simple geometries,
The effects of radial and poloidal E×B drifts in the scrape-off layer （SOL） of a limiter tokamak are studied with a one-dimensional fluid code. The transport equations are solved in the poloidal direction with the radial influxes as the source terms. The simulation results show that in the high recycling regime, the effect of the radial E×B drift on plasma density tends to be stronger than that of the poloidal E × B drift. In the sheath-limited regime, the effects of the radial E × B drift and poloidal E × B drift on plasma density are almost equally important. Considering the influence on the electron temperature, the poloidal E × B drift tends to be more important than the radial E × B drift in both the high recycling regime and sheath-limited regime. For the normal By, the poloidal E × B drift tends to raise the pressure at the low field side while the radial E × B drift favours the high field side. The simulation results also show that the E × B drift influences the asymmetries on the parameter distributions at the high field side and low field side, and the distributions are much more symmetric with the field reversal.
