The scientific objective of this investigation is to evaluate the contribution of lower atmospheric dynamics to the variability of ionospheric electrodynamics and electron densities. The investigation addresses the two scientific questions:
1. How well can winds generated internally in a whole-atmosphere model explain observed quiet-day ionospheric electric fields and currents? What information can model-observation discrepancies give us about atmospheric processes?
2. How much of the observed quiet-day variability of ionospheric electric fields, currents, and electron densities can be attributed to variable winds from the lower atmosphere?
The Whole Atmosphere Community Climate Model (WACCM), a numerical simulation model of atmospheric dynamics, chemistry, energetics, and electrodynamics from the ground to about 500 km altitude, will be upgraded to simulate ionospheric dynamics and electrodynamics realistically, and to calculate geomagnetic perturbations produced by ionospheric electric currents. Comparisons between simulated and observed ionospheric electric fields and electron densities, as well as geomagnetic perturbations on the ground and at low-Earth-orbit satellite altitudes, will indicate how well WACCM can simulate winds in the ionospheric dynamo region. Additional simulations using adjustments to uncertain WACCM parameterizations, to achieve improved model-data agreement, will provide information about the parameterized processes, especially the effects of momentum transport by gravity waves. The WACCM results will then be analyzed to evaluate the variability of electric fields, currents, and ionospheric densities associated with variability in atmospheric tides and planetary waves produced in the lower and middle atmosphere. This variability will be assessed in relation to that caused by magnetospheric electrodynamic effects on the ionosphere, through additional simulations that vary the magnetospheric electric potential imposed at high latitudes.
The investigation will contribute to the development of WACCM, a community model for exploring and understanding effects of coupling between the lower and upper atmosphere. The WACCM documentation will be expanded to include the new model developments, and the enhanced version of WACCM will be made available to the scientific community for use in other studies. The developments of WACCM components in this investigation will also be used to improve other upper-atmosphere models on which the research team are collaborating.
The scientific objective of the proposed investigation was to evaluate the contribution of lower-atmospheric dynamics to the variability of ionospheric electrodynamics and electron densities. To support this objective, we added more-realistic ionospheric physics to the NCAR Thermosphere-Ionosphere-Electrodynamics General-Circulation Model (TIE-GCM) and to the Whole Atmosphere Community Climate Model (WACCM), and we analyzed the variability of winds, electric fields, currents, and ionospheric densities associated with variability in atmospheric tides, planetary waves, and gravity waves produced in the lower and middle atmosphere. This variability was assessed in relation to that caused by magnetospheric electrodynamic and particle inputs to the upper atmosphere. The WACCM documentation has been expanded to include the new model developments, and the enhanced version of WACCM has been made available to the scientific community for use in other studies as part of the Community Earth System Model. This work has involved the participation of two postdoctoral researchers, two graduate students, and two summer undergraduate students (both from underrepresented groups), thereby contributing to their training in research methods. The grant contributed to 22 journal publications and 3 monograph chapters. A few of the findings are summarized here. Model simulations using the TIE-GCM coupled with the Global Ionosphere-Plasmasphere (GIP) model, showed that the vertically integrated total electron content (TEC) observed with the six-satellite Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) can be reasonably well reproduced. Especially noteworthy is an agreement between observations and data of a strong seasonal variation of plasmaspheric TEC that is dominant at American longitudes. The addition of lunar tidal forcing to WACCM and the use of the calculated upper-atmosphere winds to drive the GIP model demonstrated that the lunar tide changes during stratospheric sudden warmings in a way that significantly modulates the low-latitude ionosphere. WACCM simulations that use El Nino/La Nina variations of sea-surface temperatures are found to cause variations of atmospheric tidal winds in the upper atmosphere capable of causing measurable changes in the ionosphere. This discovery points to the need to consider sea-surface temperature variations as a contributor to space weather.
