Mounting evidence has demonstrated that terrestrial weather greatly impacts the dynamics and mean state of the thermosphere via small-scale gravity waves and global-scale solar tidal propagation and dissipation effects. Much of this coupling is carried by waves that are excited by deep convection in the tropical troposphere and that propagate vertically into the thermosphere. While observations have shown significant intra-seasonal variability in the upper mesospheric mean winds, relatively little is known about this variability at satellite altitudes (~250-400 km). Using satellite observations (e.g., CHAMP, GOCE, TIMED/SABER), numerical models (TIME-GCM, WACCM-X 2.0), reanalysis data (e.g., MERRA-2), and Outgoing Longwave Radiation (OLR) data, we present evidence of a prominent and global-scale 90 day oscillation in the thermospheric zonal mean winds and in tropical tropospheric waves (e.g., DE3, UFKW) during 2009-2010 and present evidence of its connection to variability in tropospheric convective activity. We further elucidate the vertical evolution of this 90-day oscillation from the lower to the upper atmosphere and investigate potential connections to the Madden-Julian Oscillation (MJO). This study demonstrates that strong coupling between the troposphere and the thermosphere is occurring on intra-seasonal timescales, raising important questions including implications for the whole atmosphere system.

Magnetosphere-ionosphere coupling (MIC) provides an interface for space weather to influence the upper regions of the Earth’s atmosphere, responsible for transferring energy and momentum in this highly-coupled system. The European Space Agency Swarm mission, consisting of multiple satellites supporting high-resolution simultaneous electric and magnetic field measurements, makes it possible to analyse the electromagnetic energy transfer and dynamics from the perspective in low-Earth orbit. Utilising the extensive statistical data coverage over five years of Swarm operations, this study reports an unexpected preference for electromagnetic energy input into the northern hemisphere, even when averaged over season. This northern preference is repeated at multiple scales, and across local times, with significant energy transport being present at the small and meso-scales which are often ignored in global modelling of MIC processes. Some deviations from a power law at particular scales suggest preferential scale-dependent energy loss above the orbital altitude of the Swarm satellite, possibly due to energy transfer at higher altitudes associated with electron acceleration in the auroral acceleration region responsible for the discrete aurora. Collectively, our results support the theory of an active ionosphere where diurnal changes in the Pedersen conductance modulate incoming Poynting flux at multiple scales. Within this theoretical framework, the inter-hemispheric asymmetry in electromagnetic energy input could be explained by differential conductance, and hence differential Alfvén wave reflection, in the northern and southern hemispheres. Such is expected to be created by the differential solar illumination arising from different offsets between the magnetic poles with respect to the Earth’s rotation axis in each hemisphere.

Field line resonances (FLRs) are a unique phenomenon linking magnetohydrodynamic waves in the magnetosphere to signatures on the Earth's surface. The generation mechanisms of the optical signature of this phenomenon, seen as periodic auroral arcs, has been extensively studied and modelled. However, lack of simultaneous ground-based optical and in situ data has made rigorous validation of these theories problematic. Using the Redline Emission Geospace Observatory (REGO) imagers in conjunction with the electric and magnetic field instruments on board the Swarm constellation of satellites we can compare observational parameters with theoretical predictions. In this study, we analyze four swarm/REGO conjunctions of optical field-line resonance arcs. We present results analyzing the current and electrodynamic system associated with this particular arc morphology and compare to accepted theory. In addition we examine the role of the integrated Pedersen conductivity in the production of optical field line resonance arcs.

The ongoing Swarm mission of the European Space Agency provides an opportunity for a better knowledge of the near-Earth electromagnetic environment, including investigations of ultra-low frequency (ULF) and extremely-low frequency (ELF) wave events. In a recent study, we derived a Swarm orbit-by-orbit Pc3 (20–100 mHz) wave index for the topside ionosphere based on two years of low-resolution (LR) 1 Hz vector field magnetometer (VFM) data and compared its values to the corresponding variations of solar wind variables and geomagnetic activity indices. This was the first attempt, to our knowledge, to derive a ULF wave index from low-Earth orbit (LEO) satellite data. The technique developed for that study could now be used to define a new Level 2 product from the Swarm mission, the Pc3 wave index, which is suitable for space weather applications. In the context of a new ESA Swarm DISC (Data, Innovation, and Science Cluster) pre-study, an open community effort has, thus, been initiated aiming at the recommendation of new Swarm data products, services or tools focusing on the Pc1 (0.2–5 Hz) and Pc3 wave indices using the high-resolution (HR) 50 Hz VFM data and absolute scalar magnetometer (ASM) 250 Hz Burst mode data. This presentation reports on progress achieved within the context of this initiative, also discussing the possibility of providing a new ELF whistler dispersion index that could be used to improve ionospheric models such as the International Reference Ionosphere (IRI) model.

In 1999, the first sprites, spectacular lightning-related processes in the upper atmosphere, were observed above European thunderstorms using low-light sensitive cameras. Since then, Eurosprite campaigns have been conducted to observe sprites and other transient luminous events (TLE’s), expanding into a network covering large parts of Europe and coastal areas. The number of European optical observations of TLEs gradually reached over 1000 per year (mostly sprites), leading to a first climatology of TLEs observed above about 1000 thunderstorms, and study for the first time their distribution and seasonal cycle above Europe and parts of the Mediterranean sea.

The climatology shows that TLE activity in Europe is intense during summer over continental areas, and in late autumn over coastal areas and sea. The two seasons peak respectively in August and November, whereas almost no TLEs are recorded in March and April. The observed TLE activity, i.e. mostly sprites, is shown to be consistent with the seasonal distribution of lightning activity from ground-based lightning detection networks. The consistency among individual years makes the observed seasonal cycle a robust general feature of TLE activity above Europe.

Because of the inhomogeneous spatial distribution of the adopted ground-based observing systems, observations were treated in terms of anomalies about the yearly mean. In order to obtain absolute values, infer occurrence rates and adopt this climatology e.g. for simulations of their impact onto the atmosphere, we here present preliminary results of a re-scaling of the TLE distribution using ground-based lightning detection over reference areas. The results are discussed in view of applying the same technique to lower detection rate but spatially homogenous TLE observations from the Atmosphere-Space Interactions Monitor (ASIM) flying on the International Space Station, and to future lightning observations from the Meteosat Third Generation Lightning Imager in order to produce a joint space- and ground-based climatology of these processes above Europe.

Measurements of the plasma density and electron temperature can be used to estimate magnetic field disturbances that are associated with so-called diamagnetic currents, a manifestation of force balance between particle pressure gradients and magnetic stresses. We use plasma measurements from the Swarm satellites to calculate the diamagnetic disturbances and compare with magnetic field measurements to determine when and where the two quantities match. We show that diamagnetic currents explain much of the small-scale variations in the scalar magnetic field in the polar cap, where other magnetic disturbances are small. We also present a climatological analysis to reveal the dependence on seasons, solar wind conditions, and geomagnetic activity.