In Earth’s low atmosphere, hurricanes are destructive due to their great size, strong spiral winds with shears, and intense rain/precipitation. However, disturbances resembling hurricanes have not been detected in Earth’s upper atmosphere. Here, we report a long-lasting space hurricane in the polar ionosphere and magnetosphere during low solar and otherwise low geomagnetic activity. This hurricane shows strong circular horizontal plasma flow with shears, a nearly zero-flow center, and a coincident cyclone-shaped aurora caused by strong electron precipitation associated with intense upward magnetic field-aligned currents. Near the center, precipitating electrons were substantially accelerated to ~10 keV. The hurricane imparted large energy and momentum deposition into the ionosphere despite otherwise extremely quiet conditions. The observations and simulations reveal that the space hurricane is generated by steady high-latitude lobe magnetic reconnection and current continuity during a several hour period of northward interplanetary magnetic field and very low solar wind density and speed.

Anapole mode is excited by the destructive interference between the toroidal-and electric-dipole moments, resulting in a highquality (Q) factor. In this paper, we designed a high-Q-factor metamaterial that shows anapole behaviors in the terahertz region. Through the introduction of graphene, the destructive interference condition is disturbed and tunability can be realized. This pattern reflects a brilliant tunability performance in which frequency movements above 250 GHz per 0.1 eV can be verified. Ingenious adjustment by the position of graphene offers the possibility of diversified tuning capabilities. Such a tunable terahertz metamaterial has great potential in reconfigurable sensors.

Inspired by the development of terahertz (THz) technology, the demand for THz sensors with high quality and high sensitivity is significantly increasing. In this study, one-dimensional metallic metamaterials based on cavity mode resonance are proposed for sensing applications in the THz regime. Owing to the strong energy concentration in the cavity, metamaterials with a high quality factor were obtained. Thus, the presented device not only achieved narrowband selective absorption but also exhibited excellent refractive index sensing with high sensitivity, figure of merit, and quality factor. The physical mechanism was verified by comparing the simulation results with that of the coupled mode theory. The polarization dependence of absorption and dual-band sensing, which can be actively tuned by the broken symmetry between two adjacent units, were also discussed. Consequently, this study may open up new avenues for the development of biosensing and imaging applications.

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