Ionospheric annual asymmetry observed by the COSMIC radio occultation measurements and simulated by the TIEGCM

Zeng, Zhen; Burns, A. G.; Wang, Wenbin; Lei, Jiuhou; Solomon, Stanley C.; Syndergaard, Stig; Qian, Liying; Kuo, Ying‐Hwa

doi:10.1029/2007ja012897

Cited by 109 publications

(155 citation statements)

References 25 publications

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“…One of which is the definition of winter and summer and how the winter anomaly can interact with the annual anomaly, which apparently has a different source [e.g., Zeng et al, 2008]. If winter and summer values of N m F 2 are those measured at one station, then the annual anomaly cannot be uniquely separated from the differences due to a seasonal anomaly.…”

Section: Discussionmentioning

confidence: 99%

“…Burns et al [2012] suggested that this problem should be addressed by defining the winter anomaly as being the relationship between the electron density at the F 2 peak in the winter hemisphere and the equivalent electron density at the conjugate latitude in the opposite hemisphere at the same longitude (to remove any longitudinal effects) and on the same day of the year. This definition removes contamination by the annual anomaly (or asymmetry-[e.g., Zeng et al, 2008]). …”

Section: Introductionmentioning

confidence: 99%

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On the solar cycle variation of the winter anomaly

et al. 2014

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Constellation Observing System for Meteorology, Ionosphere and Climate, Ionosonde, and Global Ultraviolet Imager data have been used to investigate the solar cycle changes in the winter anomaly (the winter anomaly is defined as the enhancement of the F 2 peak electron density in the winter hemisphere over that in the summer hemisphere) in the last solar cycle. There is no winter anomaly in solar minimum, and an enhancement of about 50% in winter over summer ones on the same day of the year at solar maximum. This solar cycle variation in the winter anomaly is primarily due to greater winter to summer differences of [O]/[N 2 ] in solar maximum than in solar minimum, with a secondary contribution from the effects of temperature on the recombination coefficient between O + and the molecular neutral gas. The greater winter increases in electron density in the Northern Hemisphere than in the Southern Hemisphere appear to be related to the greater annual variation of [O]/[N 2 ] in the north than in the south.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the solar cycle variation of the winter anomaly

et al. 2014

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“…At the equator, the OH nightglow intensity at the December solstice was stronger than that at the June solstice. We calculated the asymmetry index using the method used by Zeng et al [26] to study the annual asymmetry in ionosphere, namely,…”

Section: Seasonal Variations Of Oh and O 2 Nightglowmentioning

confidence: 99%

Global distributions of OH and O2 (1.27 μm) nightglow emissions observed by TIMED satellite

Gao

Chen

et al. 2011

Sci. China Technol. Sci.

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In order to investigate the global distributions of temporal variations of OH and O 2 nightglow emissions, we statistically analyzed their variations with altitude, local time, and season, using the OH and O 2 airglow emission rate data observed by the TIMED satellite between 2002 and 2009. The results indicated that the OH nightglow emission was stronger than dayglow emission and the O 2 nightglow emission was weaker than dayglow emission. In the tropics, the OH nightglow intensity reached its maximum near midnight; at higher latitudes, the OH nightglow intensities after sunset and before sunrise were much strong. At the equinoxes, the O 2 nightglow intensity in the tropics decreased with local time; at the solstices, the local time-latitude distribution of the O 2 nightglow intensity had a valley (with weak emission). As for the altitude-latitude distributions of nightglow emission rates, the distribution for OH nightglow at the equinoxes had one peak (with strong emission) at the equator, with a peak height around 85 km; the peak for the March equinox was stronger than that for the September equinox. The distribution for O 2 nightglow at the equinoxes had three peaks, lying at 30° in the spring and autumn hemispheres and at the equator, and the peak height at the equator was the lowest. The distributions for both OH and O 2 nightglow emissions at the solstices had three peaks. Both nightglow intensities in the tropics had obvious annual and semi-annual variations, the peaks and valleys for semi-annual variations appeared near the equinoxes and solstices, respectively, and the peak at the March equinox was larger than that at the September equinox. The distributions of both OH and O 2 nightglow intensities showed a hemispheric asymmetry.

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“…The FORMOSAT-3 is a scientific satellite, developed by the US and Taiwan, that orbits at an altitude of approximately 500 km. Approximately 1000-2500 ionospheric RO events registered per day by the COSMIC mission have been used to study the various ionospheric phenomena (e.g., He et al, 2009;Liu et al, 2008, Luan et al, 2008Potula et al, 2011;Yue et al, 2010;Zeng et al, 2008). For ground-based observations, we used data from Ascension Island (345.6 • E, 8.0 • S) located in the low latitudes area in the Southern Hemisphere.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the characteristics of ionospheric parameters obtained from FORMOSAT-3 and digisonde over Ascension Island

et al. 2013

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Electron density profile data obtained from the FORMOSAT-3 radio occultation (RO) measurements over Ascension Island are used to study the bottomside thickness parameter B0 in the International Reference Ionosphere (IRI) model, scale height around the F region peak height, and other F2 region parameters. The RO data were collected when the radio occultation occurred at Ascension Island (345.6° E, 8.0° S) during the solar minimum activity period from May 2006 to April 2008. Results show that the B0 values are in moderate agreement with the ground-based observations in the equinox period (correlation coefficient r = 0.682) and winter (r = 0.570), with a strong correlation in summer (r = 0.750). The seasonal and diurnal variations in B0 over Ascension Island show peak values during the daytime and in winter. In addition, the B0 values were underestimated and overestimated in the RO measurements during the daytime and nighttime, respectively. Moreover, the comparison of scale heights shows that scale heights obtained from the retrieved data and digisonde observations are weakly correlation in all three seasons. Furthermore, although the effective scale height (H_T) values were reverse of those obtained from the RO measurements and are higher during the nighttime than in the daytime, they are in good agreement with those from ground-based observations. This paper also provides a comprehensive discussion of the effect of the asymmetric ionospheric electron density profiles on RO measurements

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Ionospheric annual asymmetry observed by the COSMIC radio occultation measurements and simulated by the TIEGCM

Cited by 109 publications

References 25 publications

On the solar cycle variation of the winter anomaly

On the solar cycle variation of the winter anomaly

Global distributions of OH and O2 (1.27 μm) nightglow emissions observed by TIMED satellite

Comparison of the characteristics of ionospheric parameters obtained from FORMOSAT-3 and digisonde over Ascension Island

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