Direct Observation of the Space Hurricane Disturbed Polar Thermosphere

The space hurricane is a three-dimensional magnetic vortex structure with strong flow shears and electron precipitation in the polar cap. This study investigates for the first time how a space hurricane disturbs the polar thermosphere. During the formation and development of the space hurricane, the directional reversal of the horizontal neutral wind and the plasma convection will both be relocated from the poleward auroral oval boundary to the edge of the space hurricane, but the neutral wind responds slower compared to the plasma convection. Strong flow shears in the space hurricane causes enhanced Joule heating in the polar cap, which heats the thermosphere and triggers Atmospheric Gravity Waves (AGWs). Statistical results reveal that significant AGWs mainly are located on the dawnside of the space hurricane, suggesting that the space hurricane plays a significant role in ion-neutral coupling and generation of polar cap AGWs. The space hurricane is a cyclonic aurora structure over the Earth's polar cap region under northward interplanetary magnetic field condition. It can transfer large amounts of energy and plasma into the polar ionosphere during otherwise extremely quiet geomagnetic times. Joule/Frictional heating due to ion-neutral collisions plays a key role for the energy budget, resulting in non-negligible atmospheric disturbances, which may impact the orbits of low-altitude satellites through enhanced frictional drag. Using in situ observations from the Defense Meteorological Satellite Program satellites and the Gravity Field and Steady-State Ocean Circulation Explorer satellite, we report the first evidence of a disturbed thermosphere triggered by a space hurricane. The neutral wind shows a slow variation in response to the space hurricane plasma convection. Significant wave-like thermospheric density and vertical wind disturbances are observed around the space hurricane. Enhanced Joule heating from flow shears inside the space hurricane may be the generator. These findings show that the space hurricane plays a significant role for ion-neutral coupling in the polar cap region. The space hurricane can relocate the reversal of the neutral wind from the auroral oval to the edge of the space hurricaneThe space hurricane can heat the thermosphere and generate Atmospheric gravity waves (AGWs) that disturb the neutral density and vertical windThe space hurricane can significantly enhance polar cap AGW activity in the dawn sector