Major Achievements in 2020
1. Papers and Conference Presentations in 2020
Papers of the FST Team Members: 17
(8 papers have been published, and additional 9 papers have been submitted for publication)
.
Conference Presentations of the FST Team Members: 25
Special Sessions Convened by the FST Team Members in National and International Conferences: 22
2. Major Accomplishments in 2020
Equatorial Westward Ion Drifts during Severe Magnetic Storms
Equatorial zonal ion drifts measured by the Defense Meteorological Satellite Program satellites during
ten severe magnetic storms with a minimum Dst < -200 nT in the solar maximum years of 2000-2003 are
analyzed. Strong westward plasma drifts (200-400 m/s) are observed in the dusk-evening sector.
The westward drifts occur immediately after the storm onset and are well correlated with the Dst index.
The features and variations of the equatorial westward ion drifts cannot be explained with storm-time
disturbance winds, and a new mechanism is proposed. This new mechanism is that the poleward electric
fields associated with the subauroral polarization stream penetrate or extend to low latitudes,
producing the westward plasma drifts in the equatorial region.
Huang, C.-S. (2020). Westward plasma drifts in the nighttime equatorial ionosphere during severe
magnetic storms: A new type of penetration electric fields caused by subauroral polarization stream.
Journal of Geophysical Research: Space Physics, 125, 2020JA028300. https://doi.org/10.1029/2020JA028300.
Rapid Establishment of Ionospheric Disturbance Current System
A rapid re-construction of global ionospheric disturbance currents in response to a sudden enhancement in
the solar wind dynamic pressure, measured by ~180 ground magnetometers, is identified. The time scale of
1 minute for global ionospheric current system to fully establish or reconstruct is identified for the first
time. This new current system remains stable for 20-30 minutes. The equivalent current system is
characterized by a large, single counterclockwise vortex at middle and low latitudes (below ~60o MLat) and
a much smaller clockwise vortex at high latitudes. A scenario is proposed to explain the global distribution
and fast reconstruction of the ionospheric current systems.
Huang, C.-S. (2020). Systematical analyses of global ionospheric disturbance current systems caused by
multiple processes: Penetration electric fields, solar wind pressure impulses, magnetospheric substorms, and
ULF waves. Journal of Geophysical Research: Space Physics, 125, 2020JA027942.
https://doi.org/10.1029/2020JA027942.
Global Ionospheric Currents Systems Caused by Multiple Processes
Global ionospheric disturbance current systems caused by multiple solar wind and magnetospheric processes,
including penetration and shielding electric fields, sudden enhancement and decrease in the solar wind dynamic
pressure, magnetospheric sawtooth substorms, and ultra-low frequency (ULF) waves, are systematically
identified for the first time. A surprising result is that the equivalent disturbance current systems are
very similar, although the driving processes are completely different. The similar disturbance current
systems caused by different solar wind and magnetospheric processes suggest that the global distribution
of the ionospheric currents is determined by the intrinsic property of the ionosphere.
Huang, C.-S. (2020). Systematical analyses of global ionospheric disturbance current systems caused by
multiple processes: Penetration electric fields, solar wind pressure impulses, magnetospheric substorms,
and ULF waves. Journal of Geophysical Research: Space Physics, 125, 2020JA027942.
https://doi.org/10.1029/2020JA027942.
Multimodel Ensemble Prediction System for Specifying and Predicting Space Weather
Multimodel Ensemble Prediction System (MEPS) of data assimilation models are used to elucidate the
similarities and differences in the individual data assimilation model reconstructions of the mid-low
latitude ionosphere. Ensemble model averages are also obtained. Five data assimilation models and one
physics-based model were used to produce an ensemble mean output for multiple ionospheric parameters.
The data assimilated included ground-based Global Positioning Satellite TEC and topside plasma densities
near 800 km altitude derived from the COSMIC (Constellation Observing System for Meteorology, Ionosphere,
and Climate) satellites. The MEPS system we have constructed will be delivered to the NASA Community
Coordinated Modeling Center.
Schunk, R. W., Scherliess, L., Eccles, V., Gardner, L. C., Sojka, J. J., Zhu, L., et al. (2021).
Challenges in specifying and predicting space weather. Space Weather, 19, 2019SW002404.
https://doi.org/10.1029/2019SW002404.
Polar Topside TEC Enhancement Revealed by Jason-2 Measurements
Significant polar topside total electron content (topTEC) enhancement (PTTE) above 1,336 km altitude,
observed by the Jason-2 satellite, is reported for the first time. PTTE mostly occurs on the dayside,
with a seasonal preference of southern summer, and preferentially during geomagnetically disturbed days but
can also occur during quiet days. Our case analysis indicates that PTTE is observed simultaneously with the
effect of tongue of ionization. This suggests that the during storms, dayside F region plasma moving poleward
following the antisunward plasma convection may also be part of the PTTE source, and the plasma upflow driven
by the polar wind may act to cause PTTE.
Pi, X., Mannucci, A. J., & Verkhoglyadova, O. (2021). Polar topside TEC enhancement revealed by Jason-2
measurements. Earth and Space Science, 8, 2020EA001429. https://doi.org/10.1029/2020EA001429.
New Empirical Model for High-Latitude Electron Precipitation and Electric Field
A new high-latitude empirical model, named for Auroral energy Spectrum and High-Latitude Electric field
variabilitY (ASHLEY), is developed to improve specifications of soft electron precipitations and electric
field variability that are not well represented in existing high-latitude empirical models. This new model
is developed based on the electron precipitation and bulk ion drift measurements from the Defense
Meteorological Satellite Program (DMSP) satellites during the most recent solar cycle. ASHLEY provides
consistent mean electric field and electric field variability under different geophysical conditions.
This is different from most existing electric field models which only focus on the large-scale mean
electric field and ignore the electric field variability.
Zhu, Q., Deng, Y., Maute, A., Kilcommons, L., Knipp, D., & Hairston, M. (2021). ASHLEY: A new empirical
model for the high-latitude electron precipitation and electric field. Space Weather, 19, 2020SW002671.
https://doi.org/10.1029/2020SW002671.
New Observations of Postsunset OI 135.6 nm Radiance by the GOLD Mission
The Global-scale Observation of Limb and Disk (GOLD) mission, for the first time, provides synoptic
two-dimensional maps of OI 135.6 nm observations. These maps describe the unambiguous and dynamic evolution
of nighttime ionospheric F2-peak electron densities (NmF2) as the 135.6 nm airglow emission radiance
correlates well with NmF2 at night. The equatorial ionization anomaly hemispheric asymmetry, which
included both different densities and movement of two crests in a short time period (&<2h), is captured.
Equatorial plasma bubbles (EPBs) and third peaks of electron density poleward of the southern EIA crests
are evident in GOLD nighttime OI 135.6 radiance.
Cai, X., Burns, A. G., Wang, W., Qian, L., Liu, J., Solomon, S. C., et al. (2021). Observation of
postsunset OI 135.6 nm radiance enhancement over South America by the GOLD mission. Journal of
Geophysical Research: Space Physics, 126, 2020JA028108. https://doi.org/10.1029/2020JA028108.
Statistical Results of Equatorial Plasma Irregularities Retrieved From Swarm 2013–2019 Observations
In situ plasma density measurements of the Swarm constellation from 2013 to 2019 are used for a statistical
analysis of equatorial plasma irregularities (EPIs). The occurrence patterns for both postsunset and
postmidnight EPIs with respect to longitude, season, local time, latitude, solar activity, and geomagnetic
activity level are investigated. It is found that the postsunset and postmidnight EPIs occurrence rates
exhibit different longitudinal and seasonal dependence and solar activity dependence. The EPIs occurrence
rate increases with increasing geomagnetic activity level. The main controlling factors for the distribution
of postsunset EPIs are the magnetic declination angle, equatorial vertical E × B drift, and thermospheric
zonal wind.
Aa, E., Zou, S., & Liu, S. (2020). Statistical analysis of equatorial plasma irregularities retrieved from
Swarm 2013–2019 observations. Journal of Geophysical Research: Space Physics, 125, 2019JA027022.
https://doi.org/10.1029/2019JA027022.