Strong Ion Heating in a Magnetic Neutral Point Discharge

Abstract

An experiment is performed to study the magnetic energy dissipation and ion heating in a magnetic neutral point discharge which is related to both an explosive energy dissipation in space plasma phenomena and the ion heating in thermonuclear fusion research.A plasma current sheet is created by exciting a plasma current along the magnetic neutral line of a two dimensional quadrupole magnetic field. A sudden anomalous increase of resistivity is observed which results in fast energy dissipation and strong plasma heating. The sudden increase of the plasma resistivity appears earlier and its magnitude increases as, i) the plasma density is decreased, ii) the discharge plasma current is increased or iii) the external quadrupole magnetic field is increased. When the sharp rise of the resistivity appears, the electron and ion temperatures rise abruptly up to several keV range Within 0.5μsec and about 10% of the initial energy Stored in the capacitor (for the plasma current excitation) is converted into ion thermal energy. This strong and efficient ion heating cannot be explained by a simple classical process and the role of turbulent waves should be important.