A statistical study of space hurricanes in the Northern Hemisphere

Abstract

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.

A Statistical Study of Space Hurricanes in the Southern Hemisphere

“…These space hurricanes were found to have the following characteristics: (a) persistent existence in the polar cap near the magnetic pole for tens of minutes to several hours; (b) occurrence mainly in summer months under dominant negative IMF By and northward Bz in the SH; and (c) no clear dependence on solar wind parameters. These results are in good agreement with the NH results (S. Lu et al., 2022). Space hurricanes mainly occur in the summer hemisphere, near the magnetic poles on the dayside, and under By dominant northward IMF.…”

“…To examine the spatial distribution of space hurricanes, we manually selected the center positions of these space hurricane events from SSUSI images. The space hurricane center is considered as the geometric center of the bright spot‐like structure in the polar cap (S. Lu et al., 2022). In Figure 5a, we can see that the space hurricanes mainly occur in the afternoon sector around 13 MLT and at magnetic latitudes poleward of −80° MLAT.…”

“…A previous statistical study identified that the space hurricane occurred on average 12 times a year in the NH (S. Lu et al., 2022). The space hurricane has been confirmed to occur mainly in summer with maximum occurrence rate in the afternoon sector under northward IMF and a dominant positive By component in the NH.…”

Direct Observation of the Space Hurricane Disturbed Polar Thermosphere

“…Furthermore, we conduct a statistics study in Northern Hemisphere from January 2010 to October 2013, to prove the AGWs around space hurricane is not occasional. Lu et al (2022) provide the criteria to select space hurricanes from SSUSI data and a list of events. The space hurricane events during the statistics periods are selected from their list.…”

“…Lu et al. (2022) provide the criteria to select space hurricanes from SSUSI data and a list of events. The space hurricane events during the statistics periods are selected from their list.…”