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<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">SPACE PHYSICS SEMINAR</span><o:p></o:p></p>
<p class="MsoNormal" align="center" style="text-align:center"> <o:p></o:p></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES</span><o:p></o:p></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES</span><o:p></o:p></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">UNIVERSITY OF CALIFORNIA, LOS ANGELES</span><o:p></o:p></p>
<p class="MsoNormal" align="center" style="text-align:center"> <o:p></o:p></p>
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<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">ZOOM LINK PROVIDED BELOW</span><o:p></o:p></p>
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<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue"> </span><a href="https://ucla.zoom.us/j/92101918782?pwd=Z2o5RmI4OEpBWW4zcG1DZStIUWgrZz09" target="_blank">https://ucla.zoom.us/j/92101918782?pwd=Z2o5RmI4OEpBWW4zcG1DZStIUWgrZz09</a><o:p></o:p></p>
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<p class="MsoNormal" align="center" style="text-align:center"><o:p> </o:p></p>
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<p class="MsoNormal" align="center" style="text-align:center"><b><span style="color:blue">Laboratory Realization of an Ion-ion Hybrid Alfvén Wave Resonator<o:p></o:p></span></b></p>
<p class="MsoNormal" align="center" style="text-align:center"><b><span style="color:blue"><o:p> </o:p></span></b></p>
<p class="MsoNormal" align="center" style="text-align:center"><i><span style="color:blue">Stephen Vincena<o:p></o:p></span></i></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">UCLA Department of Physics and Astronomy<o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:blue">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<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:blue">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<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:blue">scattering of high-energy electrons in the earth's inner magnetosphere [3].<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:blue"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:blue">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].<o:p></o:p></span></p>
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<p class="MsoNormal"><i><span style="color:blue">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)<o:p></o:p></span></i></p>
<p class="MsoNormal"><span style="color:blue"> <o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">Friday, November 5, 2021<o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">3:30 - 5:00 PM<o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue"> <o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue">In-Charge: Marco Velli<o:p></o:p></span></p>
<p class="MsoNormal" align="center" style="text-align:center"><span style="color:blue"><o:p> </o:p></span></p>
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