Bibliography

Ionosphere equatorial ionization anomaly observed by GPS radio occultations during 2006--2014

A large number of Global Position System (GPS) radio occultation (RO) observations have been accumulated in the University Corporation for Atmospheric Research (UCAR) Constellation Observation System for Meteorology, Ionosphere and Climate (COSMIC) Data Analysis and Archive Center (CDAAC) especially since the launch of COSMIC mission. This study made use of these RO data to study the morphology of ionosphere equatorial ionization anomaly (EIA) statistically during 2006\textendash2014. The ionospheric peak density (NmF2) and peak height (hmF2) derived from the RO electron density profiles as well as the derived magnetic latitude of both crests and trough, the trough width, and the crest-to-trough ratio (CTR) of NmF2 are analyzed systematically. The corresponding seasonal, local time, and solar activity variations and the hemispheric asymmetry are identified and discussed. Most morphology agree well with previous studies and could be explained by the corresponding variations of neutral wind/composition and ExB vertical drift. We also found some interesting features. During May\textendashAugust, magnetic latitude of the trough could be up to ~5\textdegree north of the equator especially around noontime, and the local time difference corresponding best developed EIA between both hemispheres could be up to ~6\ h. Both crests even move equator-ward with the increase of solar activity in the morning sector except June solstice.

Yue, Xinan; Schreiner, William; Kuo, Ying-Hwa; Lei, Jiuhou;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 07/2015

YEAR: 2015     DOI: 10.1016/j.jastp.2015.04.004

Meteor radar wind over Chung-Li (24.9 N, 121 E), Taiwan, for the period 10--25 November 2012 which includes Leonid meteor shower: Comparison with empirical model and satellite measurements

The neutral winds in the mesosphere and lower thermosphere (MLT) region are measured by a newly installed meteor trail detection system (or meteor radar) at Chung-Li, Taiwan, for the period 10\textendash25 November 2012, which includes the Leonid meteor shower period. In this study, we use the 3 m field-aligned plasma irregularities in the sporadic E (E_s) region in combination with the International Geomagnetic Reference Field model to calibrate the system phase biases such that the true positions of the meteor trails can be correctly determined with interferometry technique. The horizontal wind velocities estimated from the radial velocities of the meteor trails and their locations by using a least squares method show that the diurnal tide dominates the variation of the MLT neutral wind with time over Chung-Li, which is in good agreement with the horizontal wind model (HWM07) prediction. However, harmonic analysis reveals that the amplitudes of the mean wind, diurnal, and semidiurnal tides of the radar-measured winds in height range 82\textendash100 km are systematically larger than those of the model-predicted winds by up to a factor of 3. A comparison shows that the overall pattern of the height-local time distribution of the composite radar-measured meteor wind is, in general, consistent with that of the TIMED Doppler Interferometer-observed wind, which is dominated by a diurnal oscillation with downward phase progression at a rate of about 1.3 km/h. The occurrences of the E_s layers retrieved from fluctuations of the amplitude and excess phase of the GPS signal received by the FORMOSAT-3/COSMIC satellites during the GPS radio occultation (RO) process are compared with the shear zones of the radar-measured meteor wind and HWM07 wind. The result shows that almost all of the RO-retrieved E_s layers occur within the wind shear zones that favor the E_s layer formation based on the wind shear theory, suggesting that the primary physical process responsible for the E_s layer events retrieved from the scintillations of the GPS RO signal is very likely the plasma convergence effect of the neutral wind shear.

Su, C.; Chen, H.; Chu, Y.; Chung, M.; Kuong, R.; Lin, T.; Tzeng, K.; Wang, C; Wu, K.; Yang, K.;

Published by: Radio Science      Published on: 08/2014

YEAR: 2014     DOI: 10.1002/2013RS005273

HWM07; radar meteor wind; tide

GNSS radio occultation (RO) derived electron density quality in high latitude and polar region: NCAR-TIEGCM simulation and real data evaluation

Global Navigation Satellite System (GNSS) based radio occultation (RO) technique has shown powerful ability in ionospheric electron density profiling in the past decade. The most frequently used Abel inversion method in electron density retrieval has some biases because of the used spherical symmetry assumption. Our previous series simulations and evaluations mainly concentrated in the middle and low latitude regions have shown some systematical bias especially in lower altitude of low latitude region. However, the RO derived electron density quality in the high latitude and polar region is rarely investigated and not quantitatively clear yet. In this study, the Abel inversion error over high latitude and polar regions are systematically investigated for the first time based on NCAR-TIEGCM simulations and real data evaluations. The TIMED data driven NCAR-TIEGCM modeled electron density during 2008 are used to simulate the COSMIC RO events. The Abel inversion error can then be estimated by comparing Abel retrievals from TIEGCM simulated occultation with the original TIEGCM simulations. The Abel inversion can reproduce the season, altitude, latitude, and local time variation patterns of electron density and auroral zone electron density nighttime enhancement well in high latitude and polar region. The Abel inversion tends to underestimate the electron density in the auroral zone and overestimate it on both the equatorward and poleward sides of the auroral zone. As simulated by the TIEGCM model, the significant relative error (\>25\%) mainly occurs in lower altitude (\<250\ km) inside and around auroral zone region. Above 250\ km, the relative error mostly is less than 25\%. Specifically, RMSE (root mean square error) of NmF2 error from simulation is \~8.5\%. The Abel error under real ionosphere situation would be worse because the ionosphere could be more complicated and noisier than the model simulation. The error distribution and its seasonal, local time and latitude variations can be explained by the spherical symmetry assumption used in the Abel inversion associated with the corresponding ionospheric electron density variations. The comparisons between PFISR and COSMIC RO electron density during 2007\textendash2011 and some previous validation studies agree well with our simulation results. We hope these results can stimulate more studies in high latitude ionospheric research using RO data.

Yue, Xinan; Schreiner, William; Kuo, Ying-Hwa; Wu, Qian; Deng, Yue; Wang, Wenbin;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 06/2013

YEAR: 2013     DOI: 10.1016/j.jastp.2013.03.009

Abel inversion; AURORA; COSMIC; Electron density; GNSS radio occultation; TIEGCM

Artificial plasma cave in the low-latitude ionosphere results from the radio occultation inversion of the FORMOSAT-3/COSMIC

Liu, J; Lin, C; Lin, C.; Tsai, H.; Solomon, S.; Sun, Y; Lee, I.; Schreiner, W.; Kuo, Y.;

Published by: Journal of Geophysical Research      Published on: Jan-01-2010

YEAR: 2010     DOI: 10.1029/2009JA015079

Spectral analysis of ionospheric electron density and mesospheric neutral wind diurnal nonmigrating tides observed by COSMIC and TIMED satellites

Wu, Quian; Solomon, SC; Kuo, Y-H; Killeen, TL; Xu, JiYao;

Published by: Geophysical research letters      Published on:

YEAR: 2009     DOI: