Simulations of Ionospheric Turbulence near the Upper Hybrid Layer A. Najmi – University of Maryland B. Eliasson – University of StrathClyde X. Shao, G. Milikh, S. Sharma, K. Papadopoulos – University of Maryland

Introduction Observation of DAILs (Descending Artificial Ionized Layers) (Pedersen et al 2009, 2011) Model formation Langmuir turbulence accelerates fast electrons Suprathermal electrons ionize neutral gas at lower altitudes Plasma becomes dense enough to absorb HF wave Entire interaction region descends Requires initial bulk of 4000K for effective Langmuir turbulence (Eliasson et al 2012) Our Results: UH Turbulence can produce bulk heating up to 6000K Can also produce tail accelerations with average kinetic energy 10-12000K Mechanism: Bulk heating due to electron Bernstein waves, tail heating due to UH waves near gyroharmonic.

Objectives What is the mechanism for pre-heating LT? How do these simulations compare with other experiments? Stimulated Electromagnetic Emission (SEE) Ground-based measurements of electromagnetic radiation Broad Upshifted Maximum (BUM) – associated with heating above 𝑁 𝜔 𝐶𝐸 Downshifted Maximum (DM) – associated with UH turbulence and 3-wave decay (UH -> UH + LH) Pedersen et al. – GRL 2010 doi:10.1029/2009GL041895

Methods Vlasov Simulation Test Particle follow-up Simulate distribution functions Low noise Keep wave modes as well Shift background w/ pump to maintain UH resonance Test Particle follow-up Manipulate Wave Modes Beeman Explicit Predictor-Corrector Algorithm Test convergence with 10 3 − 10 6 particles

Wave Modes

Temperature

Test Particle Simulations - I

Test Particle Simulations - II

Test Particle Simulations - II Pump DM-01

SEE Features - I Simulation Results Courtesy NRL: Bernhardt, Briczinski, Siefring. BRIOCHE Campaign 2013 Simulation Results Ground-Based SEE Receiver Measurements

SEE Features - II BUM Pump DM Simulation Results Courtesy NRL: Bernhardt, Briczinski, Siefring. BRIOCHE Campaign 2013 BUM Pump DM Simulation Results Ground-Based SEE Receiver Measurements

Conclusions Observations: Mechanism: Below the cyclotron resonance, heating at the UH layer can heat bulk electrons in striation to 4-6000K At and above resonance, the heating changes to a supra thermal acceleration, average kinetic energy up to 10000K, distribution function is long-tailed. Both are potentially useful for pre-heating Langmuir Turbulence Mechanism: Bulk heating driven by high-frequency, small-wavenumber components of the first electron Bernstein wave. Supra thermal acceleration driven UH waves near 4 𝜔 𝐶𝐸