The Super Dual Auroral Radar Network (SuperDARN) is a network of high-frequency (HF) radars located in the high- and mid-latitude regions of both hemispheres that is operated under international cooperation. The network was originally designed for monitoring the dynamics of the ionosphere and upper atmosphere in the high-latitude regions. However, over the last approximately 15 years, SuperDARN has expanded into the mid-latitude regions. With radar coverage that now extends continuously from auroral to sub-auroral and mid-latitudes, a wide variety of new scientific findings have been obtained. In this paper, the background of mid-latitude SuperDARN is presented at first. Then, the accomplishments made with mid-latitude SuperDARN radars are reviewed in five specified scientific and technical areas: convection, ionospheric irregularities, HF propagation analysis, ion-neutral interactions, and magnetohydrodynamic (MHD) waves. Finally, the present status of mid-latitude SuperDARN is updated and directions for future research are discussed.

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Review of the accomplishments of mid-latitude Super Dual Auroral Radar Network (SuperDARN) HF radars

[1] We investigate the response of the equatorial ionosphere at dusk to the intense magnetic storms of 30 October 2003 and 20 November 2003, different aspects of which have been widely studied by the community. We present here a very complete set of space and ground-based diagnostics that provide the vertical and latitudinal structures of the ionosphere within the South Atlantic magnetic anomaly (SAMA) region and the contiguous parts of South America and Africa. We show that for both storms, the dusk sector corresponding to the universal time (UT) interval between the fast decrease of the SYM-H index and minimum SYM-H value determines uniquely the longitude interval populated by equatorial plasma bubbles and depletions. Further, we find that the UT of these storms is such that the ionospheric density perturbations occur in the SAMA region, which are most extended in latitude and altitude compared with other regions of the globe. In the dusk sector, the eastward penetration electric field, associated with rapid SYM-H decrease, adds to the postsunset eastward E-field because of the F region dynamo, which may be specially enhanced in this longitude interval because of the increased zonal conductivity gradient caused by energetic particle precipitation. This enhanced E-field at dusk causes a rapid uplift of the ionosphere and sets off plasma instabilities to form bubbles or bite-outs. The decreased ion density seen in the Defense Meteorological Satellite Program (DMSP) in situ data at 840 km indicates that the ionospheric plasma has been lifted above the DMSP altitude and transported away from the region by diffusion along magnetic field lines. Plasma bubbles and bite-outs impact satellite communication and navigation systems by introducing scintillations and steep density gradients. This paper corroborates that intense magnetic storms follow the framework, developed by Su. Basu et al. (2001) for moderate storms, that specifies the longitude interval in which such disturbances are most likely to occur.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006JA012192

Response of the equatorial ionosphere at dusk to penetration electric fields during intense magnetic storms

Penetration electric fields: Efficiency and characteristic time scale

[1] There is great interest in understanding how the thermosphere-ionosphere system responds to geomagnetic storms. New insights are possible using the new generation of fully coupled three-dimensional models, together with extensive ionospheric databases. The period of postsolar maximum geomagnetic storms in October and November 2003 were some of the largest storms ever recorded. In this paper, we explore how the thermosphere-ionosphere system responded to the onset of the 20 November 2003 geomagnetic storm, using the NCAR TIMEGCM. The model simulates dramatic changes in the thermospheric equatorward winds, O/N 2 , and corresponding ionospheric electron densities. The model is used as a framework to interpret an increase in the observed ionospheric total electron content, and F region electron density, in the European and North African sector, in terms of changes in the neutral gas. Corresponding compositional effects observed by the GUVI instrument on the TIMED satellite lend credence to the model results. We describe some of the important physical processes that will affect planning for the utilization of measurements from the Geospace investigations in NASA's Living With a Star Program. The study illustrates the value of measuring both the neutral and ionized gases, of obtaining quasi-global views from imaging instruments, and the synergy between satellite data, ground-based measurements, and models.

Global thermosphere‐ionosphere response to onset of 20 November 2003 magnetic storm

[1] Development or inhibition of ESF during magnetically active periods has been an important space weather topic of interest during the recent past in view of its applications in the satellite based navigational systems. Particularly, the postsunset period exhibits significant variability for storm time development of ESF versus longitude. In this paper, we report the results of a multi-instrumental (ground based and space-borne) and multistation study on the development/inhibition of postsunset ESF during five moderate to intense geomagnetic storms occurred during the low and descending phase of the solar activity period, 2004–2006. It has been observed that, the prompt penetration of eastward electric fields into low latitudes and subsequent development of ESF occurred in all longitudinal sectors where the local time corresponds to postsunset hours during the entire main phase of the storm. In this paper, we show the development of plasma bubble irregularities over a wide longitudinal extent of 92° owing to the dusk time penetration of eastward electric fields into low latitudes. Either the sudden increase in AE-index and/or a marked decrease in Sym-H index may be used as proxies to determine the occurrence as well as the time of penetration of electric fields into equatorial and low latitudes. However, in such cases where the AE-index does not represent any sudden increase, the dSymH/dt seems to be the better index to determine the time of penetration. In this paper, is also presented an interesting case where the prompt penetration eastward electric fields dominated the existing strong westward electric fields and subsequently caused the onset of spread-F and scintillations at both VHF (244 MHz) as well as L-band (1.5 GHz) frequencies.

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Local time dependent response of postsunset ESF during geomagnetic storms

The ‘convection’ electric field, set up in the magnetosphere by the interaction of the solar wind plasma flowing around the Earth's magnetic field, projects along magnetic field lines to low altitudes where it drives the high-latitude ionospheric convection. During active times, ionospheric electric fields are thought to originate from two sources: a disturbed wind dynamo and electric fields that penetrate from high latitudes. In the latter, when the magnetospheric convection is enhanced following a southward turning of the interplanetary magnetic field (IMF), the initial high-latitude electric field will penetrate to the equatorial latitudes.

Islav Sazykin

Papers

Storm-Time Penetration Electric Fields and Their Effects