Patches of ionization are common in the polar ionosphere, where their motion and associated density gradients give variable disturbances to high-frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication. Their formation and evolution are poorly understood, particularly under disturbed space weather conditions. We report direct observations of the full evolution of patches during a geomagnetic storm, including formation, polar cap entry, transpolar evolution, polar cap exit, and sunward return flow. Our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a "tongue" of ionization (TOI).

Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to 'scan the horizon' to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone.

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Observational properties of throat aurora are investigated in detail by using 7 year continuous auroral observations obtained at Yellow River Station (magnetic latitude 76.24°N). From our inspection, throat aurora is often observed under the condition of stripy diffuse aurora contacting with the persistent discrete auroral oval, and the long‐period throat aurora observations generally consist of intermittent subsequences of throat aurora brightening followed by poleward moving auroral form and throat aurora dimming. We also noticed that the orientation of throat aurora is aligned along the ionospheric convection flow, and its local time distribution shows clear dependence on the interplanetary magnetic field (IMF) By component. These observational results indicate that factors inside the magnetosphere may play important role on occurrence of throat aurora. We thus suggest that throat aurora may present the ionospheric signature of redistribution of reconnection rate on the magnetopause by cold magnetospheric plasma flowing into the reconnection site. In addition, we also found that the occurrence rate of throat aurora clearly decreases with increase of the IMF cone angle (arccos(|Bx|/B)), which is very similar with the occurrence rate of high‐speed jet (HSJ) observed in magnetosheath depending on the IMF cone angle. This is suggested as that the HSJs occurred outside the magnetosphere may also play important role for generation of throat aurora by triggering magnetopause reconnection or by direct impacting. Although further studies are needed to clarify how the throat auroras are generated in detail, the relevant observations about throat aurora have presented important implications on a variety open questions, such as distribution and generation of cold plasma structures in the outer magnetosphere, magnetopause deformation, and possible relation between HSJ and reconnection.

[1] A number of poleward moving events were observed between 1130 and 1300 UT on 11 February 2004, during periods of southward interplanetary magnetic field (IMF), while the steerable antenna of the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) and the Tromsø VHF radar pointed nearly northward at low elevation. In this interval, simultaneous SuperDARN CUTLASS Finland radar measurements showed poleward moving radar aurora forms (PMRAFs) which appeared very similar to the density enhancements observed by the ESR northward pointing antenna. These events appeared quasiperiodically with a period of about 10 min. Comparing the observations from the above three radars, it is inferred that there is an almost one-to-one correspondence between the poleward moving plasma concentration enhancements (PMPCEs) observed by the ESR and the VHF radar and the PMRAFs measured by the CUTLASS Finland radar. These observations are consistent with the interpretation that the polar cap patch material was generated by photoionization at subauroral latitudes and that the plasma was structured by bursts of magnetopause reconnection giving access to the polar cap. There is clear evidence that plasma structuring into patches was dependent on the variability in IMF |B y |. The duration of these events implies that the average evolution time of the newly opened flux tubes from the subauroral region to the polar cap was about 33 min.