CEDAR: Atmosphere-Ionosphere Coupling as Revealed in Global Magnetic Field Perturbations

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The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) program, a broad-based, community-guided, upper atmospheric research program, is aimed at understanding the behavior of atmospheric regions from the lower atmosphere upward through the ionized upper layers of the atmosphere. Of particular interest is the coupling of the lower atmosphere to the ionized layer near 100-150 km that is called the "dynamo region". Large-scale wave variations of winds and temperatures in the lower atmosphere that are called thermal tides are generated by the heating caused by the daily passage of the Sun overhead or by the absorption of solar radiation by water vapor or stratospheric ozone at tropical latitudes. Other large-scale waves called planetary waves (PW) may also be caused by weather activity within the lower atmosphere. These large-scale waves may have periodicities as long as 16 days and very large horizontal wavelengths (thousands of km). These waves will propagate to higher altitudes where the winds, ionized gas content, and Earth?s magnetic field interact to generate electric fields and currents. These, in turn, will induce magnetic field perturbations that may be measured by the global network of magnetometers (141 sites). The production of PW and tidal waves within the lower atmosphere is highly variable, and consequently, the winds and temperature profiles associated with these wave structures will exhibit significant variability from day-to-day that can be detected through the application of sophisticated analysis procedures to the global magnetometer data. Part of the research motivation for this approach is that the electric fields generated within the dynamo region will map upward into the ionosphere above 250 km and generate variability of electron density at high altitudes that need to be understood for successful space weather forecasting, which has been given national priority. The research supported by this award would determine the ionospheric variability using the magnetometer data to measure the meridional and zonal components of magnetic field variations relative to a steady state baseline. The origins of this variability can then be considered in regard to possible factors to identify causal relationships. The award represents a strong potential for exciting and transformative science because the global analysis of ground magnetometer data will provide new insights into atmosphere-ionosphere coupling by tides and PW in a way that cannot be achieved by any satellite-based series of observations that is limited by the nature of local time sampling of the ionospheric variability. The broader impact of this award is that a woman Egyptian graduate student would be supported in her PhD work in this award thus enhancing the cultural diversity of the aeronomy community.The science motivation for this award is summarized by the following list of physical processes that need to be fully understood to understand space weather variability: (1) The dynamo region (ca.100-150 km) of Earth?s atmosphere is where electric fields are mainly generated through the dynamo action of neutral winds during daytime; (2) These electric fields have profound influences on the variability of the whole ionosphere; (3) Dynamo region variability is thought to originate from solar flux influences on electrical conductivity, and from the variability imposed by tidal and PW neutral winds, and disturbance winds associated with geomagnetic activity; (4) This variability has never been observationally quantified globally in a systematic way; (5) Knowledge concerning the variability of the dynamo region provides insight into the sources of variability for the overlying ionosphere; and (6) A global array of ground magnetometers exists that can provide the above knowledge. Examination of the global magnetometer data through application of standard time-series analysis tools would seek to understand the cause-effect factors underlying the ionospheric variability with the focus being that a major fraction of this ionospheric variability is likely to be caused by the large-scale waves reaching into this region from below. These results would be compared with variations of the standard solar and magnetic field indices to search for evidence of causal relationships between the tides and PW excited in the lower atmosphere and whose influences extend into the 100-150 km dynamo region generate electric fields that then map along magnetic field lines into the F region ionosphere. The F-region plasma redistributions that they produce carry with them the spatial and temporal signatures of these tides and PW, and of the processes that produced or modified them at lower altitudes.