Electrostatic and Electromagnetic Fluctuation in the Boundary Layer of Laboratory-Created Ionospheric Depletion

 Ionospheric depletions have been frequently artificially-created in the past decades from releasing attachment chemicals[Mendillo and Forbes, 1978]. In the early phase of the ionospheric depletion, a boundary layer of width of electric scale length emerged and separated the ionosphere into two regions, the ambient plasmas and the negative ion plasmas. In the localized boundary layer, there exists sharp electron gradients and strong sheared flows, which have a pronounced effect on the nonlinear evolution of many plasma systems. Therefore, it reflects essential research significance to study the boundary layer processes in an ionospheric depletion. However, until now, few experiments have specially designed and conducted to characterize and study those boundary layer processes[ Liu et al., 2014].

In the work, We studied the evolution of boundary layer in laboratory-created ionospheric depletions. These experiments were performed in plasma conditions with key dimensionless parameters scaled to those of the ionosphere. These electrons depletions were produced by releasing attachment chemicals into pre-existing plasmas. These plasmas were separated into two regions by a boundary layer of width of electric scale length. In the modeling ionospheric hole, localized boundary layer, those fluctuations of the electron density , floating potential, and magnetic field were investigated varying with the plasma pressure and the partial pressure of released chemicals. These fluctuations were recorded by Langmuir probes and magnetic probes. We analyzed the fluctuation using digital spectral analysis techniques, and electrostatic and electromagnetic fluctuations in the lower hybrid range were observed. These modes may be electron-ion hybrid(EIH) and whistler mode, respectively. The possibility will be discussed in more detail during the presentation.

Reference

Liu, Y., J. Cao, L. Xu, X. Zhang, P. Wang, J. Wang, Y. Du, and Z. Zheng (2014a), Coherent structure generated in the boundary layer of a laboratory-created ionospheric depletion, Geophysical Research Letters, 41(5), 1413-1419, doi:10.1002/2014GL059211.

Mendillo, M., and J. Forbes (1978), Artificially created holes in the ionosphere, Journal
of Geophysical Research, 83 (A1), 151–163.