The last year of the science mission and the deorbit phase of GOCE offer a unique opportunity to assess the results of models of the density and wind in the middle and lower thermosphere. After depletion of GOCE's xenon fuel on the morning of October 21, 2013, when the satellite's mean geodetic altitude was 239 km, it took 3 weeks before the satellite disintegrated during re-entry, shortly after UTC midnight on November 11. A continuous record of instrument and housekeeping data was received until about 7 hours before re-entry, at which point the satellite's minimum geodetic altitude was just 138 km. Although the along-track axes of the accelerometers on GOCE were saturated two days before the re-entry, accurate acceleration data could still be derived from the continuous GPS tracking up to the final day. The result is that a unique set of partially redundant, but largely complementary data on the aerodynamic interaction of the atmosphere with the spacecraft is available for this sparsely sampled altitude range. Density and wind data derived for the GOCE deorbit phase, as well as the science data from the period of October 2012 to October 2013, have been compared with both empirical models (NRLMSISE-00, JB-2008, DTM-2013, HASDM, HWM07, HWM14) and general circulation models (WACCM-X, TIE-GCM, GITM, UAM-P), exposing the relative strengths and weaknesses of these models. @en

The most severe geomagnetic storm in solar cycle 24 started with a sudden storm commencement (SSC) at 04:45 UT on St. Patrick's day March 17, 2015. It occurred without any significant precursor X- or M-type solar flares and appeared as a two-stage geomagnetic storm with a minimum SYM-H value of -233 nT. In the response to the storm commencement in the first activation, a short-term positive effect in the ionospheric vertical electron content (VTEC) occurred at low- and mid-latitudes on the dayside. The second phase commencing around 12:30 UT lasted longer and caused significant and complex storm-time changes around the globe with hemispherical different ionospheric storm reactions in different longitudinal ranges. Swarm-C observations of the neutral mass density variation along the orbital path as well as Langmuir probe plasma measurements of all three Swarm satellites and global TEC records during the storm interval are used for physical interpretations and modelling of the positive/negative storm scenario. At mid-latitudes, positive storm signatures were observed in the Northern Hemisphere (NH) of the European sector, whereas a large positive storm occurred in the Southern Hemisphere (SH) of the American sector. The negative storm phase was found to be strongest in the Asian sector, in particular in the NH, but developed globally on March 18 at the beginning of the recovery phase. These observations pose a challenge for the global numerical modelling of thermosphere-ionosphere storm processes as the storm, which occurred around spring equinox, obviously signify the existence of other impact factors than seasonal dependence for hemispheric asymmetries to occur. First numerical simulation trials using the Potsdam version of the Upper Atmosphere Model (UAM-P) are presented to explain these peculiar ionospheric storm processes. @en

The interaction between the solar wind with its inherent interplanetary magnetic field (IMF) and the geomagnetic field sets up a large-scale plasma circulation in the Earth's magnetosphere and the magnetically tightly connected ionosphere. The ionospheric ion drift at polar latitudes accelerates the neutral gas as a nondivergent momentum source primarily in force balance with pressure gradients, which are mainly directed from afternoon to midnight. The high-latitude neutral wind circulation is essentially modified by apparent forces due to Earth's rotation (Coriolis and centrifugal forces), while advection and viscous forces can significantly contribute. The apparent forces affect the dawn and dusk side asymmetrically, favoring a large dusk-side neutral wind vortex that dominates over the dawn-side vorticity cell. The IMF By component induces additional dawn-dusk differences in both ion drift and neutral wind patterns. Nonuniformities and steep gradients of the ionospheric conductivity can further modify locally the ionospheric convection and neutral wind circulation. Feedback effects of the neutral wind dynamics and its embedded ionosphere modify to a certain degree the large-scale magnetospheric convection, which includes dawn-dusk asymmetries of their behavior.@en