SA034-05
Coincident Lower-Hybrid and Modulated Upper-Hybrid Waves Observed with TRICE-2 Sounding Rockets in Earth's Cusp

Tuesday, 15 December 2020: 19:16
Virtual
Chrystal Moser1, James W Labelle1, John W Bonnell2, Roger Roglans2, Iver Hugh Cairns3, Craig Kletzing4, Scott R Bounds4, Stephen A Fuselier5 and Rhyan Sawyer6, (1)Dartmouth College, Department of Physics & Astronomy, Hanover, NH, United States, (2)University of California, Berkeley, Space Sciences Laboratory, Berkeley, CA, United States, (3)University of Sydney, School of Physics, Sydney, NSW, Australia, (4)University of Iowa, Iowa City, IA, United States, (5)Southwest Research Institute, San Antonio, TX, United States, (6)University of Texas at San Antonio, Physics and Astronomy, San Antonio, TX, United States
Recorded Presentation
Abstract:
The TRICE-2 dual sounding rockets launched two minutes apart on 8 December 2018 at UT 08:26 into active cusp aurora, reaching apogees of 756 (low-flyer) and 1042 km (high-flyer). During the high-flyer's passage through the cusp the High Frequency (HF) radio wave receiver observed three intervals of banded Upper-Hybrid (UH) waves ranging from 2--10 s. The bands begin at the UH frequency (~1.2-1.3 MHz), descending to as low as 1.1 MHz, with amplitudes in the 100's of mV/m. The spacing of the bands are ~4.5-6 kHz and the number of bands ranging from three to ten. Simultaneously, the Very-Low Frequency (VLF) radio wave receiver observed Lower-Hybrid (LH) waves with amplitudes ranging from 1-10 mV/m and frequencies of 4.5-6 kHz. Slight variations within the spacings of the bands in the UH waves were compared to peak variations in the LH frequencies. The results showed a close correlation between the two waves, suggesting a nonlinear wave-wave interaction is occurring. Two possible interactions are explored to explain this phenomena; first, decay of an UH pump wave into a lower frequency UH and a LH wave (i.e. UH --> UH' + LH), and, second, coalescence of independent UH and LH waves that spawn another UH wave, (i.e. UH + LH --> UH'), both processes having the LH frequency equal to the difference in frequency of the two UH waves. Using the Waves in Homogeneous Anisotropic, Multicomponent Plasma (WHAMP) dispersion relation calculator with a losscone distribution function similar to that which is typical of the cusp ionosphere and measured with the particle instruments onboard the high-flyer rocket shows that UH waves can be excited. Analysis of the kinematics for nonlinear wave-wave processes, performed by combining frequency and wavevector conservation with the UH and LH wave dispersion relations, show that nonlinear wave-wave decay and coalescence processes involving UH modes and LH waves are possible.
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