Modeling of space plasma physics phenomena on large KROT plasma device

Large KROT device is developed in IAP RAS for modeling of space plasma physics phenomena. The core of the facility is pulsed RF plasma source with MW power level. Well repeated and highly uniform plasma, magnetized or not, can be produced in a volume of several tens of cubic meters. An overview of the facility operational parameters is presented along with the results of recent experiments. 1. KROT device description KROT plasma facility was constructed in the beginning of 1980s for model studies of space phenomena and interaction of superstrong microwaves with plasmas. Device represents a stainless steel vacuum chamber with the volume 180 m, which is evacuated down to the base air pressure p = 3 × 10 torr. Working gas (Ar, Ne, He, H2) pressure is p = 5 × 10... 5 × 10 torr. Plasma is produced via pulsed inductive RF discharge. Four paraphase vacuum tube RF generators are used for gas ionization and plasma heating (power 1 MW, operating frequency 5 MHz, pulse duration 0.2 ... 2 ms). Loop antennas for plasma production are installed within a chamber. The discharge is pulsed ones per five, ten, or twenty seconds. At a low pressure (p < 5 × 10 torr) the dimensions of nonmagnetized plasma are determined by the length and the diameter of the chamber working section, which are 10 m × 3m. Nonmagnetized plasma with density ne = 8 × 10 cm and electron temperature Te ~ 10 eV can be produced in a volume of about 80 m. To magnetize the plasma, the solenoid is installed within a vacuum chamber, which generates the magnetic field of mirror configuration with trap ratio R = 2.4. To form a current pulse in the solenoid, the capacitor storage is used (5 kV, 86 mF) which stores energy of about 1 MJ. Magnetic field pulse duration is 20 ms, magnetic field strength in minimum is up to B0 = 1500 G. The magnetized plasma of maximum density ne = 2 × 10 cm is produced mainly within the solenoid (4 m in length, 1.5 m in diameter) in a volume of about 10 m. 2. Experimental results The paper contains a brief review of the recent experimental results. Large plasma column of the KROT device is ideally suited for studies of propagation of the waves in “boundary-free” conditions, similar to those in near-Earth plasma environment. We focus on whistler mode waves, which play an important role in many magnetospheric and ionospheric processes, including the transfer of the electromagnetic energy in ELF and VLF bands, generation of natural emissions, precipitation of energetic electrons from radiation belts. First, model studies are performed on whistler waves’ propagation in elongated irregularities (ducts), generated in quasiuniform background magnetoplasma. In magnetosphere, sporadic ducts are responsible for guided field-aligned propagation of natural and man-made whistlers. In ionosphere, artificial density ducts can occur due to the operation of heating facilities. Since the refractive index of whistler mode waves depends both on plasma density and ambient magnetic field strength, the density and magnetic field “duct-like” irregularities can strongly affect the propagation of whistlers. Detailed laboratory results on whistler wave trapping and propagation in ducts can be find in [1], [2], [3]. Second, the experiments are performed, in which the parametric modulation of whistlers in plasma with time-varying parameters is studied. The modulation of the amplitude and the spectrum of whistlers by low-frequency plasma disturbances represents an effect, which is observed in near-Earth plasmas both for noise-like and discrete natural emissions. One of the possible modulation mechanisms is adiabatic (non-resonant) conversion of the amplitude and EPSC Abstracts Vol. 5, EPSC2010-159, 2010 European Planetary Science Congress 2010