A laboratory produced extremely large beta plasma

Abstract

This paper discusses laboratory production of an extremely large-beta (β∼103) plasma, termed ELB plasma, over an extended volume of 0.5m3. The plasma β can be varied from <1 to values as large as 103, thereby allowing us to study physical processes through a large range of β. Desired β values are achieved by tailoring the ambient magnetic field by compensating fields over time scales far less than the plasma confinement time. We observe that during this compensation, the magnetic field penetration from the wall to the plasma occurs at Whistler speed. The Whistler mode is accompanied by excitation of electrostatic ion wave. We have shown that the diamagnetism of the ELB plasma is considerably modified essentially through the effect of finiteness of electron Larmor radius (rLe) in the force equilibrium. Application of these results to the space plasma is pointed out.

Electron magneto-hydrodynamic waves bounded by magnetic bubble

“…The value of B 0 in this case is B applied À B dia À B comp . As discussed in our earlier report, 16 during this period, the magnitude and profile of the density (shown in Fig. 2(b)).…”

“…The operation of this B z compensation coil, installed inside the device, is in pulsed mode. Depending on the experiment, the field can be partially or fully compensated by varying the pulsed current applied to the B z compensation coil to produce different values of compensating field (B comp ) in the range 0-4 G. For complete field compensation, the current through the B z compensation coil has a peak $380 A with typical rise time $250 ls and a decay of $5 ms. 16 The magnetic field produced by this pulsed current has a rise time of $500 ls, followed by a plateau sustained for 200 ls. A typical radial vacuum field profile of the bubble configuration obtained when the applied magnetic field of 4 G is nearly compensated by switching the compensating field on is shown in Fig.…”

“…16 The B x ; B y compensation coils marked (b) and (a), respectively, in Fig. 1, installed outside the device and used to cancel the corresponding components of the Earths field, are fed with DC currents.…”

“…1, is discussed in detail in earlier reports. 13,15,16 For experiments in the uniform field condition, a set of 10 external magnet coils have been appropriately charged to produce a uniform magnetic field in the range 4-20 G, in the z direction (device axis).…”

Unusual dynamics and nonlinear thermal self‐focusing of initially focused magnetoacoustic beams in a plasma

“…There are reports of laboratory production of an extremely large plasma beta, termed ELB plasma. [ 18 ] Hence, in physically meaningful cases, the plasma beta can be varied from $$$ {10}^{-3} $$$ to values as large as $$$ {10}^3 $$$. The case $$$ {c}_0={C}_A $$$ is special and not paid attention in this study.…”