Bibliography

FUV observations of variations in thermospheric composition and topside ionospheric density during the November 2004 magnetic superstorm

We revisited the November 2004 superstorm by analyzing TIMED/GUVI data. The 135.6 nm limb radiances at 520-km are mainly due to the O+ and electron radiative recombination and represent the daytime ionosphere density at the altitude. The 135.6 nm radiances clearly showed a signature of ionospheric equatorial arcs and their variations during the November 2004 magnetic superstorm. When an intense eastward Interplanetary Electric Field (IEF) occurred, the dayside equatorial arcs were enhanced and their latitude separation increased. The enhanced equatorial arcs were hemispherically symmetric or asymmetric in the region with non-depleted O/N2 or hemispherically asymmetric O/N2 depletion, respectively. When O/N2 depletion reached the magnetic equator, there was no observable enhancement in the equatorial arcs regardless the IEF conditions, indicating O/N2 condition significantly modulated the variations in storm-time equatorial arcs. GUVI observations also showed that a westward IEF and/or disturbance dynamo electric field could also suppress the dayside equatorial arcs.

Zhang, Yongliang; Paxton, LarryJ.; Huang, Chaosong; Wang, Wenbin;

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

YEAR: 2022     DOI: 10.1016/j.jastp.2022.105832

geomagnetic storm; penetration electric field; Thermosperic composition; topside ionosphere

Diurnal and Seasonal Characteristics of the Longitudinal Variations of Electron Densities in the Topside Ionosphere at Middle Latitudes

The ionosphere experiences strong diurnal and seasonal changes. The longitudinal variations of electron density (Ne) in the ionosphere at the middle latitudes also show strong diurnal and seasonal changes. In this paper, we use in situ Ne measurements from the DEMETER satellite and electron density profiles retrieved from the COSMIC data to study the local time (LT) and seasonal dependence of the longitudinal variations of topside Ne at middle latitudes during 2007–2009. With regard to the diurnal trend, the reversal phase of longitudinal peaks/valleys of topside Ne with a 12 hr interval occurred in less than half of the cases, and there were less cases with eastward phase shift of the longitudinal variations of topside Ne with LT in winter than those in other seasons. The seasonal trends of transition longitudes of topside Ne might be westward from winter to summer and eastward from summer to winter in the daytime and in the opposite direction at night in both hemispheres in some cases and sometimes they were located within 20° of longitude at 52°N in other cases. The longitudinal peaks/valleys of hmF2 and/or NmF2 and the longitudinal peaks/valleys of topside Ne were within 30° of longitude in most cases at all local times, in all seasons, and in both hemispheres. Exceptions to this were independent of season or LT.

Su, Fanfan; Wang, Wenbin;

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

YEAR: 2022     DOI: 10.1029/2022JA030308

Electron density; middle latitude; season; topside ionosphere

The Ionosphere at Middle and Low Latitudes Under Geomagnetic Quiet Time of December 2019

The ionospheric electron density shows remarkable day-to-day variability due to solar radiance, geomagnetic activity and lower atmosphere forcing. In this report, we investigated the ionospheric variations at middle and low latitudes during a period under geomagnetic quiet time (Kpmax = 1.7) from November 30 to December 8, 2019. During the quiescent period, the ionosphere is not undisturbed as expected in the Asian-Australian and the American sectors. Total electron content (TEC) has multiple prominent enhancements at middle and low latitudes in the two sectors, and TEC depletions also occur repeatedly in the Asian-Australian sector. The low-latitude electric fields vary significantly, which is likely to be modulated by the notably changing tides in the mesosphere and lower thermosphere region. It is worth noting that the variations of TEC and the electric fields are not consistent in the two sectors, particularly on December 4–6. Further investigation reveals that the increase in TEC depends on altitude. The TEC enhancements are mainly contributed by the altitude below 500 km in both two sectors, which indirectly reflects that the driving sources may come from the lower atmosphere. Especially, a mid-latitude band structure continuously appears at all local times in the North American sector on December 6–8, which is also mainly contributed by the altitude below 500 km.

Kuai, Jiawei; Li, Qiaoling; Zhong, Jiahao; Zhou, Xu; Liu, Libo; Yoshikawa, Akimasa; Hu, Lianhuan; Xie, Haiyong; Huang, Chaoyan; Yu, Xumin; Wan, Xin; Cui, Jun;

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

YEAR: 2021     DOI: 10.1029/2020JA028964

low-latitude electric fields; the ionosphere variations in solar minimum; the ionospheric day-to-day variations; the ionospheric disturbance; the ionospheric variations; topside ionosphere

The responses of ionospheric topside diffusive fluxes to two geomagnetic storms in October 2002

O⁺ field-aligned ambipolar diffusive velocities V_d and fluxes Ф_d in the topside ionosphere have been calculated from the observed profiles of electron density, ion, and electron temperatures during a 30 day incoherent scatter radar experiment conducted at Millstone Hill (288.5\textdegreeE, 42.6\textdegreeN) from 4 October to 4 November 2002. Two geomagnetic storms took place during this period. During the negative phases (depleted electron densities) of these two storms, the magnitudes of the daytime upward V_d and Ф_d were less than their averaged quiet time values. Whereas at nighttime, the downward V_d and Ф_d were sometimes larger than the averaged quiet time values. The variations in diffusive velocity and flux during the storm main and recovery phases were caused by changes in the ionospheric scale height or the shapes of ionospheric density profiles. The negative storm effect further reduced daytime diffusive flux. During these two storms, positive ionosphere phases (enhanced electron densities) were also observed. The diffusive velocity was much smaller during the period of positive storm effect, which led to a smaller diffusive flux than the quiet time one, although electron density was higher. It appears that storm time variations in diffusive velocity were more the results of storm time changes in the plasma vertical profile, rather than the cause of these plasma density changes.

Chen, Guang-Ming; Xu, JiYao; Wang, Wenbin; Lei, Jiuhou; Zhang, Shun-Rong;

Published by: Journal of Geophysical Research: Space Physics      Published on: 08/2014

YEAR: 2014     DOI: 10.1002/2014JA020013

diffusion; geomagnetic storm; scale height; topside ionosphere

The Ionospheric Bubble Index deduced from magnetic field and plasma observations onboard Swarm

In the post-sunset tropical ionospheric F-region plasma density often exhibits depletions, which are usually called equatorial plasma bubbles (EPBs). In this paper we give an overview of the Swarm Level 2 Ionospheric Bubble Index (IBI), which is a standard scientific data of the Swarm mission. This product called L2-IBI is generated from magnetic field and plasma observations onboard Swarm, and gives information as to whether a Swarm magnetic field observation is affected by EPBs. We validate the performance of the L2-IBI product by using magnetic field and plasma measurements from the CHAMP satellite, which provided observations similar to those of the Swarm. The L2-IBI product is of interest not only for ionospheric studies, but also for geomagnetic field modeling; modelers can de-select magnetic data which are affected by EPBs or other unphysical artifacts.

Park, J.; Noja, M.; Stolle, C.; Lühr, H.;

Published by: Earth, Planets and Space      Published on: 11/2014

YEAR: 2013     DOI: 10.5047/eps.2013.08.005

Equatorial ionosphere; Plasma irregularity; topside ionosphere

Retrieval of thermospheric parameters from routine ionospheric observations: assessment of method\textquoterights performance at mid-latitudes daytime hours

A new method has been developed to retrieve neutral temperature T_n and composition [O], [N₂], [O₂] from electron density profiles in the daytime mid-latitude F₂-region under both quiet and disturbed conditions. A comparison with CHAMP neutral gas density observations in the vicinity of Millstone Hill Incoherent Scatter Radar (ISR) has shown that the retrieved neutral gas densities coincide with the observed ones within the announced accuracy of CHAMP observations, provided that accurate N_e(h) ISR profiles are used for the retrieval. The performance of the method has also been tested ingesting Digisonde N_e(h) profiles. In this case the agreement with CHAMP neutral gas density observations is less successful. Possible factors that can influence the performance accuracy are investigated. These are mostly related to limitations due to the ionogram scaling and inversion methods, including performance limitations of the sounding technique itself, like for instance during G-conditions. Several tests presented here demonstrate that discrepancies in the hmF2 values provided by the Digisondes could have an important impact on the performance of the method. It should be noted that in all tests performed here using Digisonde N_e(h) profiles, the topside part is approximated with the NeQuick model and any assessment concerning the impact of the topside profiler on the accuracy of the method is beyond the scope of this investigation. Despite the limitations related to the use of Digisonde profiles, the proposed method has the potential to monitor the thermosphere at least with ISR N_e(h) profiles. Digisonde electron density profiles can also be used if quality improvements are made concerning the ionogram inversion methods.

Mikhailov, A.V.; Belehaki, A.; Perrone, L.; Zolesi, B.; Tsagouri, I.;

Published by: Journal of Space Weather and Space Climate      Published on: 06/2012

YEAR: 2012     DOI: 10.1051/swsc/2012002

ionosphere/atmosphere interactions; ionosphere: instruments; Ionospheric storms; techniques; thermospheric dynamics; topside ionosphere

The equatorial ionization anomaly at the topside F region of the ionosphere along 75 E

Electron density measured by the Indian satellite SROSS C2 at the altitude of ∼500km in the 75°E longitude sector for the ascending half of the solar cycle 22 from 1995 to 1999 are used to study the position and density of the equatorial ionization anomaly (EIA). Results show that the latitudinal position and peak electron density of the EIA crest and crest to trough ratios of the anomaly during the 10:00–14:00 LT period vary with season and from one year to another. Both EIA crest position and density are found to be asymmetric about the magnetic equator and the asymmetry depends on season as well as the year of observation, i.e., solar activity. The latitudinal position of the crest of the EIA and the crest density bears good positive correlation with F10.7 and the strength of the equatorial electrojet (EEJ).

Bhuyan, P.K.; Bhuyan, K.;

Published by: Advances in Space Research      Published on:

YEAR: 2009     DOI: https://doi.org/10.1016/j.asr.2008.09.027

Ionosphere; topside ionosphere; equatorial ionization anomaly (EIA); Equatorial electrojet (EEJ); SROSS C2

Longitudinal variations of electron temperature and total ion density in the sunset equatorial topside ionosphere

Based on the DMSP F13 Satellite observations from 1995 to 2005, the longitudinal distributions of the electron temperature (Te) and total ion density (Ni) in the sunset equatorial topside ionosphere are examined. The results suggest that the longitudinal variations of both Te and Ni exhibit obvious seasonal dependence as follows: (1) wavenumber-four longitudinal structure in equinox, (2) three peaks structure in June solstice, and (3) two peaks structure in December solstice. Moreover, the longitudinal variations of Te and Ni show significant anti-correlation, and we speculate that the longitudinal variation of Te may result from that of Ni which can control Te through the electron cooling rate. The wavenumber-four longitudinal structures of both Te and Ni in equinox may relate to the eastward propagating zonal wavenumber-3 diurnal tide (DE3), which has effect on the amplitude of the daytime zonal electric field. The longitudinal variation of Te and Ni in the two solstices may be caused both by longitudinal variation of geomagnetic declination and DE3.

Ren, Zhipeng; Wan, Weixing; Liu, Libo; Zhao, Biqiang; Wei, Yong; Yue, Xinan; Heelis, Roderick;

Published by: Geophysical Research Letters      Published on:

YEAR: 2008     DOI: https://doi.org/10.1029/2007GL032998

topside ionosphere; longitudinal variation