[IGPP Everyone] Reminder - Friday - EPSS Space Physics seminar announcement - Friday November 5, 2021 - 03:30 PM Pacific Time (US and Canada)

[Sowmendran, Margie (IGPP)]

R E M I N D E R
SPACE PHYSICS SEMINAR

DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES
DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES
UNIVERSITY OF CALIFORNIA, LOS ANGELES

ZOOM LINK PROVIDED BELOW

 https://ucla.zoom.us/j/92101918782?pwd=Z2o5RmI4OEpBWW4zcG1DZStIUWgrZz09


Laboratory Realization of an Ion-ion Hybrid Alfvén Wave Resonator

Stephen Vincena
UCLA Department of Physics and Astronomy

In a magnetized plasma with two ion species, shear Alfvén waves (or guided electromagnetic ion cyclotron [EMIC] waves) have zero parallel group velocity and experience a cut-off near the ion-ion hybrid frequency $\omega_{ii}$ [1]. Since the ion-ion hybrid frequency is proportional to the magnetic field, it is possible, in principle, for a magnetic well configuration to behave as an Alfvén wave resonator in a two-ion plasma. The important role
played by the wave cut-off at $\omega=\omega_{ii}$ in determining the structure of low frequency wave spectra has long been recognized in space plasma studies. For instance, Temerin and Lysak [2] identified that the narrow-banded ELF waves seen in the S3-3 satellite were generated by the auroral electron beam in a limited spatial region determined by the local value of $\omega_{ii}$ for a mix of H+-He+ ions. In addition to playing a key role in magnetospheric resonators, EMIC waves and the existence of multiple ion species are also important in the
scattering of high-energy electrons in the earth's inner magnetosphere [3].

The present study demonstrates [4] such a resonator in a controlled laboratory experiment (in the Large Plasma Device at UCLA) using a H+-He+ mixture. The resonator response is investigated by launching monochromatic waves and sharp tone-bursts from a magnetic loop antenna. The topic is also investigated theoretically, and the observed frequency spectra are found to agree with predictions of a theoretical model of trapped eigenmodes. Results of the experiment and theory will also be discussed in their relation to the ion-ion resonator feature proposed for planetary magnetospheres [5-6] and to magnetic confinement devices containing multiple ion species [7].

1. Vincena, S.T., Farmer, W.A., Maggs, J.E.,  and Morales G.J., Phys. Plasmas, 20, 012111 (2013); 2. Temerin, M, and  R. L. Lysak, JGR, 89, 2849 (1984); 3. Meredith, N. P., R. M. Thorne, R. B. Horne, D. Summers, B. J. Fraser, and R. R. Anderson JGR 108(A6) (2003); 4. Vincena, S.T., Farmer, W.A., Maggs, J.E., and Morales, G.J., RL, 38, L11101 (2011); 5. Guglielmi, V. A., A. S. Potapov, and C. T. Russell, JETP Lett., 72, 298 (2000); 6. Mithaiwala, M., L. Rudakov, and G. Ganguli, JGR, 112, A09218 (2007); 7. Intrator, T.,  M. Vukovic, A. Elfimov, P. H. Probert, and G. Winz, Phys. Plasmas 3 (1996)

Friday, November 5,  2021
3:30 - 5:00 PM

In-Charge:  Marco Velli

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