Active ionospheric experiments, where perturbations to the ionosphere are created via addition of energy and/or injected constituents, have great potential for aiding understanding of the processes that occur in the ionospheric plasma and upper atmospheric gas, especially for conditions outside the range typical of day-to-day natural variability. However, to fully realize this potential, diagnostics and modeling capable of reconstructing and reproducing the phenomena and processes in the perturbed region are essential. RF, optical, in-situ, and other diagnostics techniques to better specify the composition and densities in the region as a function of time, as well as models capable of ingesting these measurements and recreating the observed effects are all areas where further work is needed. In particular, many of the assumptions employed in studies of the natural background ionosphere and upper atmosphere, such as large scale sizes compared to the wavelength of the probing waves, or prevalence of ground states over excited states, break down when applied to localized discrete perturbations, especially at early times when the affected area can be very small. Additional features of interest include stability of gradients and development of irregularities, as well as motion and evolution of the perturbed regions in response to plasma and neutral motions in the background. Models of these processes have been developed, but are poorly constrained by the observational data, especially at early times when the perturbation is too intense and too small for standard measurement techniques to succeed. This topic focuses on development of better observation and modeling techniques to fill these gaps and improve our understanding of processes in the ionosphere and upper atmosphere. Our group maintains a large data set of measurements of active experiments, to include RF heating experiments and a variety of chemical releases, as well as close collaborations with a number of theorists and modelers.
References:
Ober, D. M., Crawford, T. S., Eccles, J.V., & Holmes, J. M. (2021). 3D multi-fluid MHD simulation of the early time behavior of an artificial plasma cloud in the bottom side ionosphere. Journal of Geophysical Research: Space Physics, 126, e2020JA029036. https://doi.org/10.1029/2020JA029036
Haerendel, Gerhard et al. (2019), Experiments With Plasmas Artificially Injected Into Near-Earth Space, Frontiers in Astronomy and Space Sciences, Vol. 6. DOI=10.3389/fspas.2019.00029 https://www.frontiersin.org/article/10.3389/fspas.2019.00029
Pedersen, T. R., Caton, R. G., Miller, D., Holmes, J. M., Groves, K. M., and Sutton, E. (2017), Empirical modeling of plasma clouds produced by the Metal Oxide Space Clouds experiment, Radio Sci., 52, 578– 596, doi:10.1002/2016RS006079.
Pedersen, T., Gustavsson, B., Mishin, E., Kendall, E., Mills, T., Carlson, H. C., and Snyder, A. L. (2010), Creation of artificial ionospheric layers using high-power HF waves, Geophys. Res. Lett., 37, L02106, doi:10.1029/2009GL041895.
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