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The space hurricane is a newly discovered large-scale three-dimensional magnetic vortex structure that spans the polar ionosphere and magnetosphere. It has been suggested to open a fast energy transport channel for the solar wind to invade Earth's magnetosphere under northward interplanetary magnetic field (IMF) conditions. It is, therefore, an important phenomenon to understand the solar wind–magnetosphere–ionosphere coupling process under northward IMF conditions. In this study, we report the three-dimensional ionospheric plasma properties of a space hurricane event in the Northern Hemisphere observed by multiple instruments. Based on the convection velocity observations from ground-based radars and polar satellites, we confirm that the major modulation to the polar cap convection called a space hurricane rotates clockwise at the altitude of the ionosphere. Ground-based incoherent scatter radar and polar satellite observations reveal four features associated with the space hurricane: 1) strong plasma flow shears and being embedded in a clockwise lobe convection cell; 2) a major addition to the total energy deposition in the ionosphere–thermosphere system by Joule heating; 3) downward ionospheric electron transport; and 4) multiple ion-temperature enhancements in the sunward velocity region, likely from the spiral arms of the space hurricane. These results present, first, the impact of space hurricane on the low-altitude ionosphere and provide additional insights on the magnetospheric impact on structuring in the polar ionosphere. [ABSTRACT FROM AUTHOR]

The space hurricane is a newly discovered large-scale three-dimensional magnetic vortex structure that spans the polar ionosphere and magnetosphere. At the height of the ionosphere, it has a strong circular horizontal plasma flow with a nearly zero-flow center and a coincident cyclone-shaped aurora caused by strong electron precipitation associated with intense upward magnetic field-aligned currents. By analyzing the long-term optical observation onboard the Defense Meteorological Satellite Program (DMSP) F16 satellite from 2005 to 2016, we found that space hurricanes in the Northern Hemisphere occur in summer and have a maximum occurrence rate in the afternoon sector around solar maximum. In particular, space hurricanes are more likely to occur in the dayside polar cap at magnetic latitudes greater than 80°, and their MLT (magnetic local time) dependence shows a positive relationship with the IMF (interplanetary magnetic field) clock angle. We also found that space hurricanes occur mainly under dominant positive IMF By and Bz and negative Bx conditions. It is suggested that the stable high-latitude lobe reconnection, which occurs under the conditions of a large Earth’s dipole tilt angle and high ionosphere conductivity in summer, should be the formation mechanism of space hurricanes. The result will give a better understanding of the solar wind–magnetosphere–ionosphere coupling process under northward IMF conditions.