Space Weather and GOCE Measurements

Abstract:

The latest gravity field mission GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) has mapped the Earth's static gravity field with an unrivalled precision. The satellite completed its mission in November 2013 and the most recent gravity field models (e.g., GOCE 5th generation gravity field models) have already been released. However, there are still unanswered questions in the data processing which leak into GOCE Level 1b and 2 products. It is found that there are signals of non-gravitational origin present in the cross-track gravity gradients that are about three to five times larger than the expected noise level of the gravity field components derived from GOCE gradiometer. These disturbances are observed around the magnetic poles during particular time periods that correspond to geomagnetically active days. In this study, we investigate the unexpected disturbances present in GOCE gradiometer gravity tensor's diagonal components along the satellite track and analyze possible causes. External datasets, interplanetary magnetic, and electric field observations from the solar wind monitoring spacecraft ACE- (Advanced Composition Explorer) and WIND, geomagnetic activity observed at CARISMA (Canadian Array for Real-time Investigations of Magnetic Activity) stations and Ionospheric Equivalent Currents (EICS) and Elementary Current Amplitudes (SECS) derived from terrestrial geomagnetic field disturbances observed over North America and Greenland are used to understand the effect of the space weather variations and ionospheric dynamics on the GOCE Gradiometer measurements. We have shown that the variation in the amplitude of the equivalent currents and changes in the current directions show high correlation with the disturbances observed in GOCE measurements along the satellite track which hints the interaction between the two.