Whistler wave propagation in the antenna near and far fields in the Naval Research Laboratory Space Physics Simulation Chamber

Abstract

In previous papers, early whistler propagation measurements were presented [W. E. Amatucci et al., IEEE Trans. Plasma Sci. 33, 637 (2005)] as well as antenna impedance measurements [D. D. Blackwell et al., Phys. Plasmas 14, 092106 (2007)] performed in the Naval Research Laboratory Space Physics Simulation Chamber (SPSC). Since that time there have been major upgrades in the experimental capabilities of the laboratory in the form of improvement of both the plasma source and antennas. This has allowed access to plasma parameter space that was previously unattainable, and has resulted in measurements that provide a significantly clearer picture of whistler propagation in the laboratory environment. This paper presents some of the first whistler experimental results from the upgraded SPSC. Whereas previously measurements were limited to measuring the cyclotron resonance cutoff and elliptical polarization indicative of the whistler mode, now it is possible to experimentally plot the dispersion relation itself. The waves are driven and detected using balanced dipole and loop antennas connected to a network analyzer, which measures the amplitude and phase of the wave in two dimensions (r and z). In addition the frequency of the signals is also swept over a range of several hundreds of megahertz, providing a comprehensive picture of the near and far field antenna radiation patterns over a variety of plasma conditions. The magnetic field is varied from a few gauss to 200 G, with the density variable over at least 3 decades from 107 to 1010 cm−3. The waves are shown to lie on the dispersion surface for whistler waves, with observation of resonance cones in agreement with theoretical predictions. The waves are also observed to propagate without loss of amplitude at higher power, a result in agreement with previous experiments and the notion of ducted whistlers.

Advances in Impedance Probe Applications and Design in the NRL Space Physics Simulation Chamber

“…The experiments were performed in the Space Physics Simulation Chamber at NRL which has been previously described in [20] and [21]. The chamber is a 2-m-diameter, 5-m-long vacuum chamber surrounded by five large magnet coils.…”

Exploiting Laboratory and Heliophysics Plasma Synergies

“…Further, laboratory research enables reproducible investigation of key small-scale processes that can be of central significance. Examples of successes that span across laboratory and heliophysical plasma physics research include the development of accurate atomic physics databases [4]; shuttle reentry and aeronautical flight [18]; and, understanding whistler wave dynamics [19][20][21][22]. The NRL gathering participants, all of whom are co-authors of this report, identified the following areas that are ready for coupled research in space-based Sun-Earth system research and laboratory-based confined plasma research.…”

“…Typically argon plasmas are produced (other species have also been used) with a biased large area hot filament to generate a 0.75 m diameter magnetized plasma column with density range n e~1 0 [5][6][7][8][9][10][11] /cm 3 , electron temperature T e~0 .5-2 eV, and cold ions. These plasmas have been used for ionospheric plasma instability and ion energization experiments, space and laboratory diagnostic development, and most recently, for nonlinear whistler wave propagation studies [20][21][22]. The SPSC source chamber, attached to the main chamber but independently operable, adds an additional 2-m of length with a smaller diameter of 0.55-m. Its magnetic coils permit up to a 1 kG solenoidal field.…”

“…For the fast wind, electron microturbulence generated by ion cyclotron conditions also could be investigated. These experiments possibly could be performed in an existing device such as the NRL Space Physics Simulation Chamber [19][20][21][22] (see Section 4.3 following), or in other large linear devices such as LAPD [35] at the University of California, Los Angeles.…”

Whistler waves with angular momentum in space and laboratory plasmas and their counterparts in free space

“…Solid-state plasmas also relied on external wave excitation and detection. But over time large diameter discharge plasmas were developed [57][58][59][60] which nearly eliminated the boundary effects. Nevertheless, plane waves cannot be excited with simple dipole antennas so that a comparison with prevailing theories was not rigorously justified.…”