4:00pm - 4:20pm
Keynote: GNSS-Based Studies of the Ionosphere and the Role of Swarm and Complementary Missions
University of Calgary, Canada
Global Navigation Satellite System (GNSS) technologies are rapidly developing with new constellations emerging from Europe, Russia and China in addition to the original U.S. GPS. By the end of this decade there will be more than 150 navigation satellites transmitting more than 400 multi‐frequency signals. Positioning accuracies are approaching the threshold of sub-centimetre globally with a multitude of new services supporting everything from precision timing to autonomous platforms and drones. GNSS signals experience propagation delays and attenuation in the Earth's ionosphere and these effects must be quantified with high levels of accuracy and mitigated for precise positioning.
GNSS signals also provide opportunity for ionospheric remote sensing. The ubiquity of GNSS observations available from ground-based and space-borne receivers allows direct calibration of ionospheric parameters, modeling of signal propagation errors, and monitoring of regional and global space weather events. Phenomena of interest include storm-enhanced density, polar patches and aurora. Observations from Swarm instruments and those from complementary missions allow resolution of such events for GNSS integrity studies and GNSS-based models of ionospheric electron density. This presentation describes opportunities for exploiting new capabilities in the context of current GNSS-based initiatives and needs for future GNSS services.
4:20pm - 4:35pm
The Canadian Ionosphere and Atmosphere Model and Its Application in Support of Satellite Missions
1York University, Canada; 2University of Calgary, Canada; 3University of New Brunswick, Canada; 4University of Saskatchewan, Canada; 5Beijing Aerospace Control Center, China; 6GFZ German Research Centre for Geosciences, Germany
The C-IAM is a first principles global three-dimensional model extending from the Earth's surface to the inner magnetosphere, which incorporates all known major physical and chemical processes of importance within its domain. The model is able to calculate in a self-consistent manner the atmospheric composition (including neutral species, ions and electrons), temperature (neutral, ion, electron), motion (wind and electromagnetic drift of charged components) and the electric field of both magnetospheric and dynamo origin. A two-way coupling between the ionosphere and neutral atmosphere is implemented that allows for the reproduction of both the impact of the lower atmosphere on the ionospheric plasma and the impact of the ionosphere on the neutral atmosphere (including the impact of geomagnetic storms on the thermosphere). The presentation will describe the model and obtained results including first comparisons of the modeling results with direct in situ satellite observations.
4:35pm - 4:50pm
Atmospheric Signatures in the EEJ During Stratospheric Warming Events and Comparison Between Ground and Space Based Magnetic Observations
1GFZ Potsdam, Germany; 2NOAA/NGDC, Boulder, USA
Vertical coupling between atmospheric layers is detectable in modulations of ionospheric currents. Due to its high conductivity, the equatorial E region is especially sensitive. Based on suitable ground magnetic observations, we investigate modulations of the Equatorial Electrojet (EEJ) that show enhanced wave activity in lunitidal periods during northern winter months, e.g. during those with weakening of the stratospheric polar vortex (Stratospheric Warming) events. Timing and amplitude of EEJ modulations correlates significantly with respective stratospheric observations. From observatories at different longitude sectors, it was found that the effect in the ionosphere/lower thermosphere is longitudinal dependent. The longitudinal variation is confirmed by EEJ observations from LEO satellites like CHAMP, when separated into longitudinal sectors. This is new since previous studies only considered global averages of satellite data.
We also show a direct comparison between space observations of the EEJ from the Swarm satellites with ground magnetometer data from equatorial stations at Huancayo (-75.3°lon), Tatuoca (-48.5°lon), and Tirunelveli (77.8°lon).
4:50pm - 5:05pm
Observation and Modeling of Ionospheric Equinoctial Asymmetry
University of Calgary, Calgary, Alberta, Canada
Ionospheric Equinoctial Asymmetry (IEA) is a phenomenon that reveals itself by significantly larger F region ionospheric electron densities during the March equinox than during the September equinox irrespective of similar levels of solar energy input into the Earth’s upper atmosphere. The causes of the asymmetry are not fully understood and its modeling remains a challenge. In this work we investigate the IEA globally in the topside ionosphere by analyzing different ionospheric plasma parameters, such as electron and ions densities and temperatures, from various satellite missions (Swarm, CHAMP, COSMIC, ROCSAT). Our analysis reveals that plasma densities are considerably larger (often exceeding 100 %) around March than around September globally. The electron and ion temperatures show reversed asymmetry indicating hotter electron and ion gases during September. This difference is more pronounced for the electron temperatures at low and middle latitudes where it exceeds several hundreds of Kelvins. In order to understand possible causes of the observed equinoctial asymmetry, we employ physics-based ionospheric and coupled ionosphere-thermosphere models to simulate the observations. The model calculations are performed with default and modified ionospheric drivers. Specifically, we investigate the role of neutral composition, temperature, thermospheric winds and E×B drifts, and quantify their relative contribution to the asymmetry. We show observation and modeling results and also discuss limitations of ionosphere/thermosphere models used in this study.
5:05pm - 5:20pm
Observable Signatures of Swarm Field-Aligned Current (FAC) Data in Global Navigation Satellite System (GNSS) Ionospheric Total Electron Content (TEC) Data Using Network Analysis
1Dartmouth College, Hanover, NH 03577, USA; 2University Center for Atmospheric Research (UCAR), Boulder, CO 80301, USA; 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
System science has emerged as a promising approach to understanding, and ultimately predicting, the complex, coupled magnetosphere-ionosphere-thermosphere (MIT) environment. Fundamental to the success of system science in the MIT system is the ability to describe coupling phenomena, especially in the polar regions where the effects are most direct. This coupling is controlled by the system of field-aligned currents (FACs) that flow between the magnetosphere and ionosphere. FACs at high-latitudes are ubiquitous across the high-latitude regime and have unique characteristics depending on the magnetospheric or solar wind source mechanism, and, therefore, mapping location in the ionosphere (i.e. auroral zone, polar cap, cusp). Further complicating the picture, FACs also exhibit a large range of spatial and temporal scales. In order to create new understanding of FAC spatial and temporal scales, their cross-scale effects, and the impact on the polar region new data analysis approaches are required.
In this work we apply network analysis [Newman, 2003] to investigate relationships between Swarm FAC data and polar features. We develop our approach to answer the question of whether characteristic ionospheric scales of FACs drive observable signatures in ionospheric total electron content (TEC) from Global Navigation Satellite System (GNSS) signals. Swarm data are used to specify periods during which specific FAC characteristics exist, in terms of geomagnetic location and scale, and TEC data are analyzed for observable signatures and spatio-temporal relationships. Given the dense, global coverage of polar features provided by GNSS signals and that these data are critical for the future of space weather and geospace system science research, exploring Swarm-TEC synergies extends the future utilization of Swarm data.
We find significant new relationships between FACs and polar ionospheric TEC features, which can be exploited for future modeling and prediction of the geospace system.
Newman, M. E. J. “The structure and function of complex networks.” SIAM Review 45.2 (2003): 167-256.
5:20pm - 5:35pm
Ionospheric Long-term Cooling: Observation, Ionsophere-thermosphere Coupling Aspects, and Potential Impact on the Topside Ionosphere in situ Measurement
MIT Haystack Observatory, United States of America
Using mutliple incoherent scatter radar observations spanning from a few solar cycles up to 50+ years at middle (Millstone Hill), auroral (Poker Flat/Chatanika) and higher (Sondrestrom) latitudes, we estimate ionospheric climate (long-term) changes over the broad E and F region altitude range. Significant ionospheric cooling in ion temperature (Ti) is found which generally increase in height from the F2 peak region into the topside. The lower altitude Ti trend is an indicator of the neutral atmospheric long-term change which has been known from satellite drag measurements over multiple decades, however, the topside Ti trend involves additional forcing and possibly magnetosphere-ionosphere-thermosphere processes. Nevertherless, the topside ionosphere is expected to experience appreciable long-term decrease in electron density and should be detectable with the topside in situ measurements.