The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to megaelectron volts (MeV). These plasmas rotate around the Earth longitudinally due to the gradient and curvature of the geomagnetic field and by the co-rotation motion with timescales from several tens of hours to less than 10 min. They interact with plasma waves at frequencies of mHz to kHz mainly in the equatorial plane of the magnetosphere, obtain energies up to MeV, and are lost into the ionosphere. In order to provide the global distribution and quantitative evaluation of the dynamical variation of these plasmas and waves in the inner magnetosphere, the PWING project (study of dynamical variation of particles and waves in the inner magnetosphere using ground-based network observations, http://www.isee.nagoya-u.ac.jp/dimr/PWING/) has been carried out since April 2016. This paper describes the stations and instrumentation of the PWING project. We operate all-sky airglow/aurora imagers, 64-Hz sampling induction magnetometers, 40-kHz sampling loop antennas, and 64-Hz sampling riometers at eight stations at subauroral latitudes (~ 60° geomagnetic latitude) in the northern hemisphere, as well as 100-Hz sampling EMCCD cameras at three stations. These stations are distributed longitudinally in Canada, Iceland, Finland, Russia, and Alaska to obtain the longitudinal distribution of plasmas and waves in the inner magnetosphere. This PWING longitudinal network has been developed as a part of the ERG (Arase)-ground coordinated observation network. The ERG (Arase) satellite was launched on December 20, 2016, and has been in full operation since March 2017. We will combine these ground network observations with the ERG (Arase) satellite and global modeling studies. These comprehensive datasets will © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

A critical question in ionospheric physics is the state of the ionosphere and relevant processes under extreme solar activities. The solar activity during 2007–2009 is extremely prolonged low, which offers us a unique opportunity to explore this issue. In this study, we collected the global ionosonde measurements of the F2 layer critical frequency (foF2), E layer critical frequency (foE), and F layer virtual height (h′F) and the total electron content (TEC) maps produced by the Jet Propulsion Laboratory, which were retrieved from dual‐frequency GPS receivers distributed worldwide, to investigate the ionospheric phenomena during solar minimum of cycle 23/24, particularly the difference in the ionosphere between solar minima of cycle 23/24 and the preceding cycles. The analysis indicates that the moving 1 year mean foF2 at most ionosonde stations and the global average TEC went to the lowest during cycle 23/24 minimum. The solar cycle differences in foF2 minima display local time dependence, being more negative during the daytime than at night. Furthermore, the cycle difference in daytime foF2 minima is about −0.5 MHz and even reaches to around −1.2 MHz. In contrast, a complex picture presents in global h′F and foE. Evident reduction exists prevailingly in the moving 1 year mean h′F at most stations, while no huge differences are detected at several stations. A compelling feature is the increase in foE at some stations, which requires independent data for further validation. Quantitative analysis indicates that record low foF2 and low TEC can be explained principally in terms of the decline in solar extreme ultraviolet irradiance recorded by SOHO/SEM, which suggests low solar EUV being the prevailing contributor to the unusual low electron density in the ionosphere during cycle 23/24 minimum. It also verifies that a quadratic fitting still reasonably captures the solar variability of foF2 and global average TEC at such low solar activity levels.

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We describe an automated technique to determine parameters of traveling ionospheric disturbances (TIDs) using the Super Dual Auroral Radar Network (SuperDARN) high frequency (HF) radar data. The technique is based on the analysis of minimum ground backscatter range variations corresponding to different radar beams. Using this technique, we processed the SuperDARN Hokkaido radar data for 2011 and revealed statistical distributions of medium-scale TID (MSTID) azimuth and apparent horizontal velocity. We found four peaks with a distinct diurnal and seasonal dependence in the MSTID azimuth occurrence rate distributions. Northeast MSTID azimuths (20°to 50°) are typical of the summer and equinox morning hours; southeast azimuths (100°to 140°) prevail in the winter daytime; southwest azimuths (190°to 220°) are typical mostly in the summer and equinox nighttime and in the equinox evening; northwest azimuths (280°to 320°) are typical of the summer daytime and evening. The apparent horizontal velocities are generally within the 100 to 160 m/s range. The obtained results agree well with earlier studies by other researchers. However, there are also certain differences. The summer daytime northwestward MSTIDs are not indicated in the earlier studies. The nighttime horizontal velocities are 1.5 to 2 times higher than those in the daytime. Furthermore, winter velocity values are about 1.5 times higher than those in other seasons. These differences might be associated with the peculiarities of the data recorded by different facilities, or the features of the processing techniques, and require further investigation for their interpretation.

We have carried out a comprehensive analysis of data from the high‐frequency coherent radar located near Yekaterinburg, ground‐based ionospheric, riometric, and magnetic stations, situated within the radar field of view and in the vicinity of it, as well as from eight radio paths crossing the Asian region of Russia. Using these data, we studied dynamics of ionospheric disturbances over wide longitudinal sector during the first 3 days of the St. Patrick's two‐step severe geomagnetic storm and determined the main mechanisms of their development. We showed that on 17 March during the main and early recovery storm phases, the major contribution to the generation of the ionospheric disturbances had been made by impact ionization by precipitating magnetospheric particles. This had lead to appearance of intense sporadic layers, alternating with intervals of total absorption. The main features of the storm were the large latitude width of the auroral precipitation zone and an expansion of this zone to corrected geomagnetic latitude ~ 45°. We suppose that these peculiarities were due to high variability of interplanetary magnetic field and solar wind impacted on the magnetosphere. The most probable cause of the negative ionospheric disturbance on 18 March might have been a change in the neutral atmosphere composition. Significant differences between measured and simulated values of maximal electron concentration in F2 layer point to the need to improve the existing empirical models of thermosphere, auroral precipitations, and magnetospheric convection in order to use them for modeling of ionospheric parameters during severe geomagnetic storms.