Dedicated satellite missions for measuring the geomagnetic field such as Swarm, Oersted and CHAMP have revolutionized our understanding of the field originating in Earth’s interior field as well as the near-Earth magnetic environment. But one of the biggest obstacles to further progress is the space-time ambiguity due to the limited local time data sampling of these high-precision satellites, despite the enormous improvement which is possible due to the Swarm satellite constellation trio.

However, almost every satellite carries a platform magnetometer for navigation purposes. After careful calibration their data can also be used for scientific purposes.

We report on recent activities to calibrate and validate platform magnetometer data from satellites including Cryosat, GOCE, Grace and DMSP and cubesat fleets like Spire and discuss their use for scientific investigations.

ESA’s Swarm constellation mission consisting of three identical satellites, successfully launched on 22 November 2013, provides the excellent opportunity of reliable electric current density estimates in the ionosphere based on multi-satellite magnetic field measurements. The final constellation with Swarm A/C orbiting the Earth at about 470 km (flying side-by-side) and Swarm B at about 520 km altitude was achieved on 17 April 2014. Swarm satellites need a period of about 130 days to cover all local times; therefore the coverage of all local times and local seasons can be achieved in 5 years from the final constellation when the dual-satellite current density estimations have been started. We present the climatology of field-aligned currents (FACs) at polar cap, cusp and auroral regions, radial, interhemispheric (IHFACs) and F region dynamo currents at mid-latitude and equatorial regions, using the single and dual satellite approaches for the current density estimations. Also, the higher-flying Swarm B satellite provides from time to time well-matched observations with the 50 km lower Swarm A/C pair that gives the possibility for zonal current estimates by using Ampère’s ring integral for determining the mean current density passing through the encircled area.

Reversed ionization diurnal cycle is one of the distinctive features of the Earth`s ionosphere F region, with the most known example of such behavior named as the Weddell Sea Anomaly (WSA). Numerous studies have confirmed that in the area of the Antarctic Peninsula and surrounding seas, the density of ionospheric plasma is higher during nighttime hours rather than around local noon when ionization rates reach maximum.
Thanks to growing number of satellite observations it confirmed that WSA-like ionospheric behavior is not only limited to the Southern Hemisphere and it is an intrinsic ionospheric feature which exhibits seasonal behavior.

While numerous studies have examined the impact of changing solar activity on the formation of the WSA-like features, very little attention is paid to the fact how long-term changes in the Earth`s magnetic field can affect the spatial distribution of this peculiar ionospheric behavior.
The occurrence of the WSA-like phenomena is attributed to the role of neutral winds, but magnetic declination and inclination determine the relative role of the thermospheric meridional and zonal wind components in the ionospheric dynamics.
The goal of the study is to quantify the impact of changing magnetic field on the formation of the WSA, and in particular how it affects spatial patterns of the anomaly. The study exploits in-situ electron density measurements obtained by the ESA Swarm constellation and the CHAMP satellite. To unify measurements from different data sources, we define so called normalized density difference index.
In-situ measurements are confronted with results from the numerical modeling utilizing the physics-based thermosphere - ionosphere - magnetosphere model, NCAR TIEGCM.
Additionally, using a simplified model of the Earth`s magnetic field, we show that for a specific configuration of the magnetic dipole, expressed by relevant Gauss coefficients, we are able to "place" the anomaly in different regions of the globe. Such experiment intends to underline the role the Earth`s magnetic field on the formation of the WSA-like phenomena.

Space-based Global Navigation Satellite System (GNSS) total electron content (TEC) observations from the Swarm and Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellites constitute an important dataset to investigate the dynamics and morphology of the global ionosphere and provide a unique opportunity for comparisons with specifications obtained from global ionospheric models. In particular will comparisons with GNSS TEC observations obtained from the GOCE satellite near 240 km altitude provide important inside into the ability of ionospheric models to specify TEC throughout much of the ionosphere whereas comparisons with the corresponding Swarm observations near 450-500 km altitude provide information about the capability to model the topside ionosphere/plasmasphere. Model specifications, on the other hand, can provide a global context in which the observations can be interpreted. We have compared GNSS TEC observations from the GOCE and Swarm satellites at low and middle latitudes with specifications obtained from the Global Assimilation of Ionospheric Measurements Full Physics-Based (GAIM-FP) model. The model uses a physics-based ionosphere-plasmasphere model (IPM) and an Ensemble Kalman filter to assimilate a variety of different data types, including ground-based GPS/TEC, occultation, bottomside electron density profiles from ionosondes, in-situ electron densities, and space-based UV radiance measurements. The primary GAIM-FP output is in the form of 3-dimensional electron density distributions from 90 km to near geosynchronous altitude but the model also provides auxiliary information about the global distribution of the self-consistent ionospheric drivers (neutral winds and densities, electric fields). Statistical comparisons as well as case-by-case comparisons will be shown that on the one hand elucidate the capabilities of the model and on the other hand provide context for the interpretation of the observations.

Ionospheric Equinoctial Asymmetry is one of the most interesting and intriguing features of the terrestrial Ionosphere. Despite the Earth’s upper atmosphere receiving similar levels of solar ionization energy at a given latitude during the March and September equinoxes for similar solar activity conditions, the ionospheric parameters appear significantly different. Past studies have been mainly focused on electron densities at the ionospheric F region peak and have shown that the densities are larger during the Vernal equinox than during the Autumnal equinox. The level of the asymmetry in the topside ionosphere and in other plasma parameters is not fully investigated. Furthermore, the drivers of the asymmetry are not well understood and quantified. Their better understanding however, is important to provide insights into the atmosphere-ionosphere coupling processes. In this work we investigate the topside ionospheric equinoctial asymmetry by analyzing in-situ electron density and temperature data from the Swarm satellites. Launched in November 2013 into high inclination circular orbits at about 460 and 530 km altitude, the Electric Field Instruments (EFI) on the three Swarm satellites have been providing information on plasma density, temperatures and drifts in the topside ionosphere globally. Currently available Swarm measurements provide a unique opportunity to study the asymmetry under different geophysical conditions. Our analysis of Swarm topside ionospheric data from the EFI Langmuir probes at equatorial, low and middle latitudes reveals several times larger electron densities during March equinox than during September over both hemispheres at middle latitudes. At low and equatorial latitudes the density difference is considerably smaller. The electron temperature at middle latitudes shows the reverse asymmetry - the electron gas appears significantly hotter during September than during March. Interestingly, at low and equatorial latitudes the electron temperature is higher during the March equinox. Finally, in order to simulate the equinoctial asymmetry and understand its possible causes, we use the physics-based ionospheric (SAMI3) and coupled thermosphere-ionosphere (TIE-GCM) models. We specifically focus on the role of neutral composition, neutral winds, and plasma drifts.

The diurnal migrating tide (DW1) is a global scale oscillation with a period of one solar day. In addition to being the dominant mode of variability in the mesosphere and thermosphere, DW1 also imprints tropospheric and stratospheric variability upon the ionosphere through modulation of gravity waves and planetary waves. Although DW1 has been well-documented up to 110 km, and near 250 km and 400 km, it has not been globally observed in the critical 110-300 km range. This presentation will focus on the diurnal tide between 90-250 km as revealed in the NASA's upper atmosphere wind imaging interferometer (WINDII). Preliminary investigations show that the migrating diurnal tide is well defined in low-latitude zonal and meridional winds. Amplitudes are about 30 m/s, and the vertical wavelength increases from 30 km in the lower thermosphere to about 100 km. The WINDII data provide a context for interpreting differences between GFZ’s GOCE dawn-dusk wind measurements.