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A Very Low Frequency (VLF) wave detection system has been designed at Wuhan University (WHU) and recently deployed by the Polar Research Institute of China at the Chinese Great Wall station (GWS, 62.22°S, 58.96°W) in Antarctica. With a dynamic range of ∼110 dB and timing accuracy of ∼100 ns, this detection system can provide observational data with a resolution that can facilitate space physics and space weather studies. This paper presents the first results of the wave measurements by the WHU VLF wave detection system at GWS to verify the performance of the system. With the routine operation for 3 months, the system can acquire the dynamic changes of the wave amplitudes and phases of various ground‐based VLF transmitter signals emitted in both North America and Europe. A preliminary analysis indicates that the properties of the VLF transmitter signals observed at GWS during the X‐class solar flare events are consistent with previous studies. As the HWU‐GWS path crosses the South Atlantic Anomaly region, the observations also imply a good connection in space and time between the VLF wave disturbances and the lower ionosphere variation potentially caused by magnetospheric electron precipitation during the geomagnetic storm period. It is therefore well expected that the acquisition of VLF wave data at GWS, in combination with datasets from other instruments, can be beneficial for space weather studies related to the radiation belt dynamics, terrestrial lightning discharge, whistler wave propagation, and the lower ionosphere disturbance, etc., in the polar region. Plain Language Summary: Considering the good coverage and quiet electromagnetic environment, Antarctica is an ideal place for plasma wave measurements. Various stations have been established in Antarctica, of which Palmer station is particularly noteworthy and has historically provided valuable VLF data for atmospheric, ionospheric, and magnetospheric studies. An Extremely Low Frequency/Very Low Frequency (VLF) wave detection system has been designed by Wuhan University and recently set up at Great Wall station (GWS) in Antarctica. This device can effectively record VLF signals with frequencies of 1–50 kHz, including artificial transmitter signals and natural emissions. This paper gives the broadband spectrum of 1–50 kHz signals in the north‐south and east‐west directions recorded at GWS for the first time. VLF signatures from lightning discharges, environmental disturbances, and navy transmitters in North America and Europe can be clearly identified. The overall trend of amplitude and phase of transmitter signals is consistent with the X‐ray fluxes measured by the Geostationary Operational Environment Satellite satellite. Based on the GWS observations, it is expected to reveal some significant new phenomena reflected in VLF signals and further study the distribution and propagation characteristics of VLF waves. These are of great significance for physical research and application, especially in the unique geographical location of the South Pole. Key Points: A high‐sensitivity Very Low Frequency (VLF) wave detection system with a dynamic range of ∼110 dB and timing accuracy of ∼100 ns has been designedThis system has been recently deployed by the Polar Research Institute of China in Antarctica and operated routinely for 3 monthsThe VLF wave data collected by this system can be widely used to monitor and study space weather events in the polar region [ABSTRACT FROM AUTHOR]

The ionospheric density displays hemispheric asymmetries in the polar region due to various hemispheric differences, for example, in the offset between geographic and geomagnetic poles and in the geomagnetic field strength. Using ground‐based ionospheric measurements from Vertical Incidence Pulsed Ionospheric Radar with Dynasonde analysis at Jang Bogo Station (JBS), Antarctica and from EISCAT Svalbard Radar (ESR) where both sites are located mostly in the polar cap, we investigate the hemispheric differences in the ionospheric density between the northern and southern hemispheres for geomagnetically quiet and solar minimum condition. The results are also compared with Thermosphere Ionosphere Electrodynamic Global Circulation Model (TIEGCM) simulations. The observations show larger density and stronger diurnal and seasonal variations at JBS in the southern hemisphere than at Svalbard in the northern hemisphere. The diurnal variations of the density peak height are also observed to be much larger at JBS. In both hemispheres, the ionospheric density is significantly reduced in winter due to the limited solar production at high geographic latitudes, but TIEGCM considerably overestimates winter density, which is even larger than summer density, especially in the northern hemisphere. Also existed are the differences in the equinoctial asymmetry between the observations and the simulations: the daytime F‐region density is observed to be larger in fall than in spring in both hemispheres, but TIEGCM shows the opposite. In general, most of the observed asymmetrical density are much weaker in the model simulation, which may result from lack of proper magnetospheric forcings and neutral dynamics in the model. Plain Language Summary: The global ionospheric density is not symmetric around the equator due to various reasons. The main reason for the asymmetry would be the asymmetric characteristics of the geomagnetic field. The ionospheric plasma motions are strongly controlled by the magnetic field lines and the magnetospheric energy inputs dominate the polar ionosphere. Therefore, the asymmetric geometry of the magnetic field lines and the offset between the geomagnetic and geographic poles can produce asymmetric density distributions of the ionosphere. However, the investigation of the hemispheric asymmetry has been mostly restricted to the low and mid‐latitude ionosphere and little study has been conducted in the polar ionosphere, mainly due to the lack of observations in the southern hemisphere. Since the establishment of the Jang Bogo Station (JBS), Antarctica in 2014, Korea Polar Research Institute (KOPRI) has been operating various instruments to observe the ionosphere in association with the thermosphere and the magnetosphere. These observations allow us to investigate the hemispheric asymmetry of the ionospheric density by comparing with the observations in the northern polar region. It is found that the diurnal and seasonal variations of the ionospheric density are much stronger at JBS in the southern hemisphere than in Svalbard in the northern hemisphere. Key Points: The polar ionospheric density shows larger magnitude and stronger diurnal and seasonal variations at Jang Bogo Station than in SvalbardThe daytime density shows an equinoctial asymmetry which is larger in fall equinox than in spring equinoxThermosphere Ionosphere Electrodynamic Global Circulation Model significantly overestimates the winter density at high latitudes and shows the opposite equinoctial asymmetry to the observations [ABSTRACT FROM AUTHOR]

Nearly all studies of impulsive geomagnetic disturbances (GMDs, also known as magnetic perturbation events MPEs) that can produce dangerous geomagnetically induced currents (GICs) have used data from the northern hemisphere. In this study, we investigated GMD occurrences during the first 6 months of 2016 at four magnetically conjugate high latitude station pairs using data from the Greenland West Coast magnetometer chain and from Antarctic stations in the conjugate AAL-PIP magnetometer chain. Events for statistical analysis and four case studies were selected from Greenland/AAL-PIP data by detecting the presence of >6 nT/s derivatives of any component of the magnetic field at any of the station pairs. For case studies, these chains were supplemented by data from the BAS-LPM chain in Antarctica as well as Pangnirtung and South Pole in order to extend longitudinal coverage to the west. Amplitude comparisons between hemispheres showed (a) a seasonal dependence (larger in the winter hemisphere), and (b) a dependence on the sign of the By component of the interplanetary magnetic field (IMF): GMDs were larger in the north (south) when IMF By was >0 (<0). A majority of events occurred nearly simultaneously (to within ±3 min) independent of the sign of By as long as |By| ≤ 2 |Bz|. As has been found in earlier studies, IMF Bz was <0 prior to most events. When IMF data from Geotail, Themis B, and/or Themis C in the near-Earth solar wind were used to supplement the time-shifted OMNI IMF data, the consistency of these IMF orientations was improved. [ABSTRACT FROM AUTHOR]

Poleward‐moving auroral form (PMAF) is a type of dayside auroral pattern. The distinguishing characteristic of a PMAF is its separation from the auroral oval and subsequent poleward motion. It has been reported and widely accepted that PMAFs occur more frequently during periods with dominant southward interplanetary magnetic field (IMF). However, most ground‐based optical observations were made near magnetic latitudes of 75°, close to the equatorward boundary of the dayside auroral oval; therefore, PMAFs occurring at the poleward boundary were likely missed easily. Using all‐sky images from two stations located on the similar magnetic meridian in Antarctica at 80° and 75° magnetic latitude, and taking solar wind data close to the magnetosphere by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft, we demonstrate that unlike the result from prior low‐latitude single‐station observations, the combined observations from both stations show an insignificant difference in the PMAF occurrence rate in the northward and southward IMF conditions and no clear sign suggesting that the southward IMF or southward turning of the IMF triggers PMAFs. With good agreements between PMAF occurrence rate and the intensity of the poleward drift, we suggest that PMAFs are more likely to be plasma patches torn away from the dayside auroral oval convecting antisunward and rather than direct foot points of reconnecting flux tubes. Key Points: We demonstrate that the observed frequency of PMAF occurrence and its relation with IMF depend on the choice of the observing locationCombined PMAF occurrence rates observed at two stations spanning the auroral region show no significant increase with southward BzPMAFs are more likely to be directly driven by plasma convection rather than by flux transfer events [ABSTRACT FROM AUTHOR]

Ground‐based neutron counters are a standard tool for detecting atmospheric showers from GeV range primary cosmic rays of either solar or galactic origin. Bare neutron counters, a type of lead‐free neutron monitor, function much like standard neutron monitors but have different yield functions primarily because they are more sensitive to neutrons of lower energy. When operated together with standard monitors, the different yield functions allow estimates to be made of the energy spectrum of galactic or solar particles. In 2010 a new array of 12 bare neutron detectors was installed at the South Pole to operate together with the neutron monitor there. Prior to installation, two of the detectors were operated on a ship that traveled from Sweden to Antarctica and back from November 2009 to April 2010. The purpose of this latitude survey was to use Earth's magnetic field as a spectrometer, blocking cosmic rays below the local cutoff rigidity (momentum per unit charge), from which we determined the response function versus rigidity of these bare counters. By comparing that measured response function to direct measurements of the cosmic ray spectrum taken by the PAMELA spacecraft, we were able to make a direct determination of the yield function for these detectors. Key Points: Bare neutron counters characterize the energy spectrum of high‐energy solar particles when used together with a neutron monitorBare neutron counters aboard a ship measured secondary cosmic rays over a wide range of magnetic latitudesSimultaneous measurements of the primary cosmic ray spectrum by spacecraft allow a direct determination of the bare neutron counter yield function [ABSTRACT FROM AUTHOR]

While Yi, Reid, Xue, Younger, Spargo, et al. (2017, http://doi:10.1002/2017JA024446) described the observational results showing solar wind high‐speed stream (HSS) impacts on the mesosphere over Antarctica, the specific physical mechanism behind them was not discussed. We discussed here how magnetospheric wave‐particle interactions and energetic ~20‐ to 50‐keV electron precipitation into the auroral zone atmosphere (diffuse auroras) during HSS intervals can cause the observed effects in the mesosphere. Key Points: During HSS substorm events, fresh ~10‐ to 100‐keV electrons are injected and scattered by waves creating the diffuse auroraThe ~20‐ to 50‐keV portion of the precipitating electrons deposit most of their energy at heights of ~95 km down to ~85 kmThe energy deposition creates NOx and3 O3 loss. This leads to atmospheric cooling and modulation of zonal wind speeds and neutral densities [ABSTRACT FROM AUTHOR]