This project will investigate several research topics on the effects of plasma and neutral gas transport processes on the ionosphere and surrounding regions. The methodology is based on time-dependent, high-resolution, physics-based theoretical and assimilative models in addition to auxiliary data from ground-based radars and magnetometers, particularly the Poker Flat (PFISR) and Resolute Bay (RISR) incoherent scatter radars. The scientific problems under investigation pertain to the ionosphere, thermosphere, exosphere, plasmasphere, polar wind, and to coupling mechanisms relevant to these regions. A focused goal of the project is to better understand the effect of mesoscale plasma structures on global-scale flows using ensemble Kalman filtering of high-latitude ionospheric electrodynamical variables. Other specific topics include: the atmospheric response to the recent extreme solar cycle phase minimum and to sporadic space weather events; the generation and evolution of ionospheric disturbances; and the climatology of atmospheric waves.
The Earth’s lower atmosphere displays numerous weather features, including hurricanes, tornados, snowstorms, blizzards, and gusty winds. Likewise, the Earth’s upper atmosphere and embedded ionosphere also display ‘space weather’ features, including sharp ridges of ionization, supersonic neutral winds, propagating atmospheric holes and ionization patches, rapidly rising bubble depletions, sporadic ionization layers, turbulent flows, and enhanced aurora borealis displays. The space weather disturbances can occur over a wide range of spatial and temporal scales, and they can arise as a result of generation mechanisms on the Sun, in the solar wind, in the lower atmosphere, and by instability processes in the upper atmosphere - ionosphere system. Unfortunately, space weather can have a detrimental effect on numerous operations and systems, including High-Frequency communications, Over-The-Horizon radars, navigation systems, electric power grids, ocean drilling operations, and satellite lifetimes. Because of society’s ever increasing reliance on technology, there is a strong need for space weather specification, forecasting and mitigation. The primary goals of the research were to study the effects that various ionization and neutral gas transport processes have on the upper atmosphere – ionosphere system, and to study coupling mechanisms that are relevant to the near-Earth space environment. The research focused on both long-term (climate) and event (space weather) studies connected with how solar storms and lower atmospheric waves affect the upper atmosphere – ionosphere system. The research team was composed of four Ph.D. scientists and both graduate and undergraduate students. The research was conducted with global, time-dependent, high-resolution models of the Earth’s upper atmosphere - ionosphere system. The research also involved extensive use of data from NSF-funded radars, magnetometers, and optical instruments as well as data from the NASA satellite Solar Dynamics Observatory. Our modeling and measurement studies have led to several important research findings: 1. The cumulative effect of small-scale density structures (< 1000 km) in the upper atmosphere-ionosphere system can affect the global mean circulation of the system. 2. We discovered that there is a significant outflow of atomic oxygen and hydrogen atoms from the Earth’s upper atmosphere. The outflow is global and continuous. 3. It was known that waves propagate up from the lower atmosphere and into the upper atmosphere, but we have shown that the waves can break in the upper atmosphere and excite new global-scale waves. 4. We have shown that at high latitudes heat is transported from high altitudes down into the upper atmosphere-ionosphere system and that this heat can lead to a significant electron temperature enhancement in the ionosphere (increase of more than 1000 K). 5. The Sun’s has a 27-day rotation rate, and long-lived jets of solar wind that radiate from fixed locations on the Sun will hit the Earth every 27 days. Our model/measurement studies have shown that the interaction of the solar wind jets with the Earth’s upper atmosphere acts to heat the upper atmosphere-ionosphere system. 6. Numerous computer simulations were conducted with our global physics-based upper atmosphere-ionosphere model in order to determine the accuracy of global models of this nature. Our findings indicate that models of this nature contain several uncertain parameters and processes, and missing physics. There are also modeling coupling issues and error propagation from the upper atmosphere model to the ionosphere model. As a result, global physics-based upper atmosphere-ionosphere models cannot provide reliable space weather specifications and forecasts. Data assimilation models are needed. The research we conducted provides a better understanding of the dynamics and energetics of the upper atmosphere-ionosphere system and its coupling to adjacent regions of space, and therefore, is directly relevant to both climate and space weather applications, including communications, navigation and surveillance.
