Experimental Investigation of Non-MHD Fast Magnetic Reconnection in TS-3
Abstract
Cause and mechanism for fast magnetic reconnection event have been investigated using spheromak/tokamak merging experiment in the TS-3 device. We have reported that the effective resistivity of the current sheet increased significantly, when the sheet width δ is compressed shorter than ion gyroradius ρ_i. However, ρi is almost equal to ion collisionless skin depth c/ω_pi in the current-sheet with ion beta ≈ 1. We scanned the ion beta by varying field component BX parallel to the X-line from 0.5 B_// to 5 B_//, where B_// is the reconnecting field component. A new finding is that this anomalous increase in resistivity depended clearly on the relationship between current sheet width δ and ion gyroradius ρ_i, not on that between δ and ion collisionless skin depth c/ω_pi. Ion motion effect is concluded to cause the fast magnetic reconnection observed in low-BX discharge. Current-sheet ejection was also found as another fast magnetic reconnection mechanism in high-BX and low density discharge. The current sheet was ejected rapidly outside of the X-point region by large external compressing force and this global instability of the current sheet caused a significant increase in reconnection speed, while the high-BX tokamak reconnection is much slower than the low-BX spheromak reconnection.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1999
- Bibcode:
- 1999APS..DPP.CP105I