Based on in situ and ground‐based observations, a new type of “polar cap hot patch” has been identified that is different from the classical polar cap enhanced density structure (cold patches). Comparing with the classical polar cap patches, which are transported from the dayside sunlit region with dense and cold plasma, the polar cap hot patches are associated with particle precipitations (therefore field‐aligned currents), ion upflows, and flow shears. The hot patches may have the same order of density enhancement as classical patches in the topside ionosphere, suggesting that the hot patches may be produced by transported photoionization plasma into flow channels. Within the flow channels, the hot patches have low‐energy particle precipitation and/or ion upflows associated with field‐aligned currents and flow shears. Corresponding Global Navigation Satellite System (GNSS) signal scintillation measurements indicate that hot patches may produce slightly stronger radio signal scintillation in the polar cap region than classical patches. A new type of polar cap patches, “polar cap hot patches,” is identified to differentiate enhanced density structures from classical patches. Hot patches are associated with particle precipitations, ion upflows, field‐aligned currents, and shear flows in the polar cap. Hot patches may lead to slightly stronger ionospheric scintillations of GNSS signals in the polar cap region than classical patches.

A comparison tool has been developed by mapping the global GPS total electron content (TEC) and large coverage of ionospheric scintillations together on the geomagnetic latitude/magnetic local time coordinates. Using this tool, a comparison between large‐scale ionospheric irregularities and scintillations is pursued during a geomagnetic storm. Irregularities, such as storm enhanced density, middle‐latitude trough, and polar cap patches, are clearly identified from the TEC maps. At the edges of these irregularities, clear scintillations appeared but their behaviors were different. Phase scintillations (σφ) were almost always larger than amplitude scintillations (S4) at the edges of these irregularities, associated with bursty flows or flow reversals with large density gradients. An unexpected scintillation feature appeared inside the modeled auroral oval where S4 were much larger than σφ, most likely caused by particle precipitations around the exiting polar cap patches.

The Super Dual Auroral Radar Network (SuperDARN) is an international low-power high-frequency (HF) radar network, which provides continuous observations of the motion of plasma in the ionosphere. Over the past 15 years, the network has expanded dramatically in the middle latitudes of the Northern Hemisphere to improve the observation capabilities of the network during periods of strong geomagnetic disturbance. However, a large coverage gap still exists in the middle latitudes. A newly deployed middle-latitude HF radar in China (the Jiamusi radar) is about to join the network. This paper presents the first observation of the ionospheric convection from the Jiamusi radar during the strong geomagnetic storm on 26 August 2018. The Jiamusi measurements are compared with the simultaneous measurements from the SuperDARN Hokkaido East radar. The features of the high-velocity westward flows including the equatorward expansion and variation tendency of the line-of-sight velocities observed by the two radars are consistent with each other. According to joint analysis with auroral images, we can confirm that the westward flows observed by the two radars are sunward return flows of the duskside convection cell in the auroral region. The impact the Jiamusi data had on the calculation of SuperDARN convection patterns is also examined. The results show that the inclusion of the Jiamusi data can increase the number of gridded line-of-sight velocity measurements by up to 24.42%, the cross-polar cap potential can be increased by up to 13.90% during the investigated period.

A geomagnetic storm occurred on 27 February 2014 and the shock related to it arrived at Earth's magnetosphere at ∼17:00 UT. Dayside cusp region scintillation over Antarctica have been studied along with the Global Positioning System (GPS) observed total electron content (TEC), and Defense Meteorological Satellite Program (DMSP) Precipitating Particles (SSJ), Bulk Plasma Parameters (SSIES) and Magnetic Fields (SSM) data. For the first time, similar variation trend in amplitude and phase scintillation has been found near the polar latitude. Amplitude scintillation index (S 4) and phase scintillation index (σ ϕ) show the similar enhancement trend at different numerical scale. During the southward interplanetary magnetic field (IMF) Bz condition there is a significant enhancement in the particle precipitation occurred through the dayside cusp region. During southward IMF Bz and dawnward By (By < 0), high convection velocity guide solar wind plasma into the polar cap which enhances the phase scintillation, but, no amplitude scintillation enhancement at the similar numerical scale. The Halley and Dome C East radar data show that at the small to medium ionospheric irregularity speed, S 4 , and σ ϕ variations are alike. If proper variation scale is chosen, S 4 also appears an appropriate scintillation index for the polar ionosphere. The possible mechanism for S 4 occurrence similar to the σ ϕ at a dissimilar level has been discussed.

We report local secondary magnetic reconnection at Earth’s flank magnetopause by using the Magnetospheric Multiscale observations. This reconnection is found at the magnetopause boundary with a large magnetic shear between closed magnetospheric field lines and the open field lines generated by the primary magnetopause reconnection at large scales. Evidence of this secondary reconnection are presented, which include a secondary ion jet and the encounter of the electron diffusion region. Thus the observed secondary reconnection indicates a cross-scale process from a global scale to an electron scale. As the aurora brightening is also observed at the morning ionosphere, the present secondary reconnection suggests a new pathway for the entry of the solar wind into geospace, providing an important modification to the classic Dungey cycle.

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