Bibliography

Hemispheric Asymmetries in the Mid-latitude Ionosphere During the September 7--8, 2017 Storm: Multi-instrument Observations

Hemispheric asymmetries of the Vertical Total Electron Content (VTEC) were observed during the first recovery phase of the geomagnetic storm on September 7–8, 2017. These asymmetries occurred at the mid latitudes at two different local times simultaneously: In the European-African sector (early morning), the storm time VTEC in the southern/northern hemisphere was higher/lower than the quiet time value, suggesting the southern/northern hemisphere entered the positive/negative phase (N−S+). In the East Asian-Australian sector (afternoon), the storm time VTEC change was positive in the northern hemisphere, but negative in the southern hemisphere (N+S−). The electron density profiles from digisondes demonstrated that the asymmetries appeared in the F region density as well. The plasma drifts data from digisondes, the column-integrated [O]/[N2] ratio from GUVI onboard the TIMED satellite, and the detrended VTEC were utilized to study the drivers of the asymmetries. Traveling Ionospheric Disturbance (TID) signatures were identified in the digisonde drift and detrended VTEC data before the appearance of the asymmetry. The magnitude of TIDs was larger in the hemisphere where the negative phase occurred later. The storm time [O]/[N2] ratio change was positive in Africa (S+) and negative in Europe (N−). However, the [O]/[N2] measurements were not available in the East Asian-Australian sector during the focused period. The hemispheric differences in the vertical drifts were also observed in both sectors. Therefore, the observed hemispheric asymmetries in both sectors are suggested to be due to the hemispheric asymmetries in the thermospheric composition change, vertical drift, and TID activity.

Wang, Zihan; Zou, Shasha; Liu, Lei; Ren, Jiaen; Aa, Ercha;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2021     DOI: 10.1029/2020JA028829

Impact of Storm-Enhanced Density (SED) on Ion Upflow Fluxes During Geomagnetic Storm

The impact of the dynamic evolution of the Storm-Enhanced Density (SED) on the upward ion fluxes during the March 06, 2016 geomagnetic storm is studied using comprehensive multi-scale datasets. This storm was powered by a Corotating Interaction Region (CIR), and the minimum Sym-H reached ∼−110 nT. During the ionospheric positive storm phase, the SED formed and the associated plume and polar cap patches occasionally drifted anti-sunward across the polar cap. When these high-density structures encountered positive vertical flows, large ion upward fluxes were produced, with the largest upward flux reaching 3 × 1014 m−2s−1. These upflows were either the type-1 ion upflow associated with fast flow channels, such as the subauroral polarization stream (SAPS) channel, or the type-2 ion upflow due to soft particle precipitations in the cusp region. The total SED-associated upflow flux in the dayside cusp can be comparable to the total upflow flux in the nightside auroral zone despite the much smaller cusp area compared with the auroral zone. During the ionospheric negative storm phase, the ionospheric densities within the SED and plume decreased significantly and thus led to largely reduced upward fluxes. This event analysis demonstrates the critical role of the ionospheric high-density structures in creating large ion upward fluxes. It also suggests that the dynamic processes in the coupled ionosphere-thermosphere system and the resulting state of the ionospheric storm are crucial for understanding the temporal and spatial variations of ion upflow fluxes and thus should be incorporated into coupled geospace models for improving our holistic understanding of the role of ionospheric plasma in the geospace system.

Zou, Shasha; Ren, Jiaen; Wang, Zihan; Sun, Hu; Chen, Yang;

Published by: Frontiers in Astronomy and Space Sciences      Published on:

YEAR: 2021     DOI:

Multi-scale ionosphere responses to the May 2017 magnetic storm over the Asian sector

We investigate multi-scale ionospheric responses to the May 27, 2017, geomagnetic storm over the Asian sector by using multi-instrumental observations, including ground-based global navigation satellite systems (GNSS) network, constellation observing system for meteorology, ionosphere and climate radio occultation, the FengYun-3C (FY-3C) GNSS occultation sounder electron density profiles and in situ plasma density observations provided by both Swarm and defense meteorological satellite program missions. This geomagnetic storm was an intense storm with the minimum symmetric horizontal component reaching - 150\ nT and was caused by a coronal mass ejection released on May 23. The main observations are summarized below: (1) two ionospheric positive storm periods were observed. The first one was observed in the noon\textendashafternoon sector during the main phase of the storm on May 28, with nearly 120\% TEC enhancement. The second one was of a smaller scale and occurred on the nightside during the recovery phase of the storm on May 29. The first dayside positive storm was initiated by the interplanetary magnetic field (IMF) Bz southward turning and eastward penetration electric field, while the second nightside one was terminated by a later southward turning of the IMF Bz since the Asian sector was on the nightside and the penetration electric field changed westward. (2) A negative storm occurred from 00:00 to 12:00 UT on May 30 over the Asian sector, nearly 2\ days after the main phase, which was due to the thermospheric composition change, i.e., decrease in the O/N₂ ratio, as shown in the TIMED/GUVI measurements. (3) A band-like TEC enhancement was observed aligning in the northwest\textendashsoutheast direction and propagated slowly southwestward from 15:00 to 20:00 UT (23:00\textendash04:00 LT, near midnight) on May 28 during the recovery phase of the storm. In situ density observations from the Swarm B and DMSP F15\&16 satellites confirmed the density enhancement at 510\ km and 850\ km, respectively, and revealed that this band-like TEC enhancement structure resembles the so-called plasma blob. The similarities of the observed plasma blob characteristics in terms of spatial structure, propagation trend and temporal evolution with the nighttime traveling ionospheric disturbance (TID) are consistent with the TID-blob theory.

Liu, Lei; Zou, Shasha; Yao, Yibin; Aa, Ercha;

Published by: GPS Solutions      Published on: 12/2019

YEAR: 2020     DOI: 10.1007/s10291-019-0940-1

Blob structure; Positive and negative ionosphere responses; TID; Geomagnetic storms

Aurora in the Polar Cap: A Review

This paper reviews our current understanding of auroral features that appear poleward of the main auroral oval within the polar cap, especially those that are known as Sun-aligned arcs, transpolar arcs, or theta auroras. They tend to appear predominantly during periods of quiet geomagnetic activity or northwards directed interplanetary magnetic field (IMF). We also introduce polar rain aurora which has been considered as a phenomenon on open field lines. We describe the morphology of such auroras, their development and dynamics in response to solar wind-magnetosphere coupling processes, and the models that have been developed to explain them.

Hosokawa, Keisuke; Kullen, Anita; Milan, Steve; Reidy, Jade; Zou, Ying; Frey, Harald; Maggiolo, Romain; Fear, Robert;

Published by: Space Science Reviews      Published on: 02/2020

YEAR: 2020     DOI: 10.1007/s11214-020-0637-3

Storm-time Magnetosphere-Ionosphere-Thermosphere coupling processes revealed by distributed observations and numerical simulation

Zou, Shasha; Ren, Jiaen; Wang, Zihan;

Published by:       Published on:

YEAR: 2020     DOI:

Local Time Dependant Hemispheric Asymmetry of the Ionosphere During the September 7-8 2017 Storm: Multi-Instrument Observations

Wang, Zihan; Zou, Shasha; Ren, Jiaen; Aa, Ercha; Liu, Lei;

Published by:       Published on:

YEAR: 2020     DOI:

Dayside Aurora

Dayside aurora is related to processes in the dayside magnetosphere and especially at the dayside magnetopause. A number of dayside aurora phenomena are driven by reconnection between the solar wind interplanetary magnetic field and the Earth\textquoterights internal magnetic field at the magnetopause. We summarize the properties and origin of aurora at the cusp foot point, High Latitude Dayside Aurora (HiLDA), Poleward Moving Auroral Forms (PMAFs), aurora related to traveling convection vortices (TCV), and throat aurora. Furthermore we discuss dayside diffuse aurora, morning side diffuse aurora spots, and shock aurora.

Frey, Harald; Han, Desheng; Kataoka, Ryuho; Lessard, Marc; Milan, Stephen; Nishimura, Yukitoshi; Strangeway, Robert; Zou, Ying;

Published by: Space Science Reviews      Published on: 11/2019

YEAR: 2019     DOI: 10.1007/s11214-019-0617-7

Driving of strong nightside reconnection and geomagnetic activity by polar cap flows: application to CME shocks and possibly other situations

Lyons, LR; Gallardo-Lacourt, B; Zou, Y; Nishimura, Y; Anderson, P; , Angelopoulos; Donovan, EF; Ruohoniemi, JM; Mitchell, E; Paxton, LJ; , others;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on:

YEAR: 2018     DOI:

Driving of Dramatic Geomagnetic Activity by Enhancement of Meso-Scale Polar-cap Flows

Lyons, Larry; Gallardo-Lacourt, Bea; Zou, Ying; Nishimura, Yukitoshi; Anderson, Phillip; Angelopoulos, VASSILIS; Ruohoniemi, Michael; Mitchell, Elizabeth; Paxton, Larry; Nishitani, Nozomu;

Published by:       Published on:

YEAR: 2017     DOI:

Ionospheric scintillations at Guilin detected by GPS ground-based and radio occultation observations

The occurrence of ionospheric scintillations with S4⩾0.2 was studied using GPS measurements at Guilin, China (25.29°N, 110.33°E; geomagnetic: 15.04°N, 181.98°E), a station located near the northern crest of the equatorial anomaly. The results are presented for data collected from January 2009 to March 2010. The results show that nighttime amplitude scintillations only took place in February and March of the considered years, while daytime amplitude scintillations occurred in August and December of 2009. Nighttime amplitude scintillations, observed in the south of Guilin, always occurred with phase scintillations, TEC (Total Electron Content) depletions, and ROT (Rate Of change of TEC) fluctuations. However, TEC depletions and ROT fluctuations were weak during daytime amplitude scintillations, and daytime amplitude scintillations always took place simultaneously for most of the GPS satellites which appeared over Guilin in different azimuth directions. Ground-based GPS scintillation/TEC observations recorded at Guilin and signal-to-noise-ratio (SNR) measurements obtained from GPS-COSMIC radio occultation indicate that nighttime and daytime scintillations are very likely caused by ionospheric F region irregularities and sporadic E, respectively. Moreover, strong daytime amplitude scintillations may be associated with the plasma density enhancements in ionospheric E region caused by the Perseid and Geminid meteor shower activities.

Zou, Yuhua;

Published by: Advances in Space Research      Published on:

YEAR: 2011     DOI: https://doi.org/10.1016/j.asr.2010.11.016

Ionospheric scintillation; ionospheric irregularities; GPS; GPS-COSMIC radio occultation