GOCE Gradiometer Measurements Response to Ionospheric Dynamics

• Published in: Journal of geophysical research. Space physics Vol. 122; no. 10; pp. 10,712 - 10,726
• Main Authors: Ince, E. Sinem, Pagiatakis, Spiros D.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-10-2017
• Subjects: Accelerometers; Aerospace environments; Atmosphere; Atmospheric models; crosswind; Data processing; Disturbances; dynamic system; Dynamics; Earth atmosphere; Earth gravitation; Earth orbits; Energy consumption; Energy flow; Energy flux; equivalent ionospheric currents; Geomagnetism; Global positioning systems; GOCE (experiment); GOCE gradiometer; GPS; GRACE (experiment); Gradiometers; Gravitation; Gravitational fields; Gravity; Instrumentation; Ionospheric currents; Ionospheric dynamics; Magnetic measurement; Magnetic storms; Ocean circulation; Ocean currents; Physics; Plasma drift; Polar environments; Polar regions; Poynting flux; Satellites; Solar activity; Space missions; Spatial resolution; Storms; Studies; Thermospheric dynamics; Upper atmosphere; Water circulation; Wind
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2017JA023890

With the launch of dedicated satellite gravity missions, starting with CHAllenging Minisatellite Payload (CHAMP) in 2000, with Gravity Recovery and Climate Experiment (GRACE) in 2002, and Gravity field and steady‐state Ocean Circulation Explorer (GOCE) in 2009, the accuracy and spatial resolution of the Earth's global gravity field models have been improved. Highly sensitive accelerometer measurements have not only been useful for gravity field modeling but have also been contributing to the studies of thermospheric dynamics. While improving the sensitivity of the accelerometer measurements, the new instrumentation used on board GOCE brings different challenges in understanding the data and developing sophisticated data processing. Our analyses reveal that the GOCE gravitational gradient measurements were affected by highly variable ionospheric dynamics that did not only degrade the quality of the GOCE Electrostatic Gravity Gradiometer (EGG) measurements but also proved that some characteristics of ionospheric dynamics can be measured by GOCE accelerometers and other Low Earth Orbiters. In this paper, we show how GOCE‐retrieved neutral winds respond to main ionospheric currents and we develop the impulse‐response relation between intense ionospheric dynamics (plasma drift) represented by Poynting energy flux and the gravity gradiometer tensor trace disturbances observed over the north geomagnetic polar region.
Plain Language Summary
The European Space Agency's (ESA) GOCE satellite gravity mission was launched in 2009 to study the Earth's gravitational field with the help of a gradiometer and a GPS receiver mounted onboard. The gradiometer consisted of six accelerometers in a special configuration that measured gravitational and nongravitational accelerations in space. The quality of the GOCE accelerometer measurements was degraded over the Earth's polar regions during periods of increased solar activity that caused uncommon dynamics in the space environment, known as magnetic storms. This finding did not only require to reinvestigate the GOCE data processing but has also compelled scientists to use GOCE accelerometer measurements, in an inverse mode, to understand the Earth's upper atmosphere dynamics. In our recent contribution, we showed for the first time that there exists a direct relationship between GOCE gradient disturbances and magnetic storms over the Earth's polar regions. This contribution takes our previous findings a step further by developing a mathematical model that reduces the GOCE gradient disturbances up to 30% over North America and Greenland, using electromagnetic energy flow derived from terrestrial magnetic disturbance measurements. Our contribution paves the way for a combination of gravity and ESA's Swarm mission to study and understand the Earth's upper atmosphere physics.
Key Points
Equivalent ionospheric currents and GOCE‐retrieved neutral winds in east‐west direction are remarkably coherent
GOCE measurement errors are modeled using external data that are markers of ionospheric dynamics
Low Earth orbiter accelerometer measurements can be extensively used to investigate specific features over specific areas in space physics