Climatologies of nighttime upper thermospheric winds measured by ground‐based Fabry‐Perot interferometers during geomagnetically quiet conditions: 1. Local time, latitudinal, seasonal, and solar cycle dependence

Emmert, J. T.; Faivre, M.; Hernández, G.; Jarvis, M. J.; Meriwether, J. W.; Niciejewski, R. J.; Sipler, D. P.; Tepley, C. A.

doi:10.1029/2006ja011948

Cited by 74 publications

(148 citation statements)

References 50 publications

(77 reference statements)

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“…Poleward winds tend to decrease electron density; so if they are more equatorward in solar minimum, it would be expected that the winter anomaly would be more pronounced in solar minimum than in solar maximum. Emmert et al [2006] [Drob et al, 2008], the solar cycle variation of these winds has not yet been included explicitly in a scientific publication. Solar cycle variations in 557.7 nm emissions have been analyzed [Liu and Shepherd, 2007].…”

Section: The Possible Effects Of Transport On Solar Cycle Variations mentioning

confidence: 99%

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: The Possible Effects Of Transport On Solar Cycle Variations mentioning

confidence: 99%

On the solar cycle variation of the winter anomaly

et al. 2014

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“…However, there The thermospheric winds over Mount John and Millstone Hill are likely more affected by aurora heating from high latitude (Hagan, 1993) than those over Xinglong. On the other hand, since the Arecibo station is located at low geographical latitude and middle geomagnetic latitude, the thermospheric winds over Arecibo have typical characteristics of middle latitudes (Emmert et al, 2006a).…”

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confidence: 99%

“…As for the nighttime zonal wind, it was mainly eastward with a peak of ∼ 150 m s −1 . Emmert et al (2006a) have shown that the thermospheric zonal wind over Arecibo exhibited annual variation during solar minimum and exhibited semiannual variation during solar maximum.…”

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confidence: 99%

“…Whereas observational studies on thermospheric winds are confined to the data from a few incoherent scatter radar (ISR), FPI, and satellite observations (e.g., Drob et al, 2008;Emmert et al, 2006aEmmert et al, , b, 2008Santos et al, 2011;Wu et al, 2012;Shepherd et al, 2012). It has been generally accepted that the middle-atmospheric winds at middle latitudes are mainly influenced by the states of the lower atmosphere and are less influenced by solar and geomagnetic activities (Kazimirovsky and Vergasova, 2009).…”

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confidence: 99%

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FPI observations of nighttime mesospheric and thermospheric winds in China and their comparisons with HWM07

Yuan

Liu

et al. 2013

Ann. Geophys.

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We analyzed the nighttime horizontal neutral winds in the middle atmosphere (~ 87 and ~ 98 km) and thermosphere (~ 250 km) derived from a Fabry–Perot interferometer (FPI), which was installed at Xinglong station (40.2° N, 117.4° E) in central China. The wind data covered the period from April 2010 to July 2012. We studied the annual, semiannual and terannual variations of the midnight winds at ~ 87 km, ~ 98 km and ~ 250 km for the first time and compared them with Horizontal Wind Model 2007 (HWM07). Our results show the following: (1) at ~ 87 km, both the observed and model zonal winds have similar phases in the annual and semiannual variations. However, the HWM07 amplitudes are much larger. (2) At ~ 98 km, the model shows strong eastward wind in the summer solstice, resulting in a large annual variation, while the observed strongest component is semiannual. The observation and model midnight meridional winds agree well. Both are equatorward throughout the year and have small amplitudes in the annual and semiannual variations. (3) There are large discrepancies between the observed and HWM07 winds at ~ 250 km. This discrepancy is largely due to the strong semiannual zonal wind in the model and the phase difference in the annual variation of the meridional wind. The FPI annual variation coincides with the results from Arecibo, which has similar geomagnetic latitude as Xinglong station. In General, the consistency of FPI winds with model winds is better at ~ 87 and ~ 98 km than that at ~ 250 km. We also studied the seasonally and monthly averaged nighttime winds. The most salient features include the following: (1) the seasonally averaged zonal winds at ~ 87 and ~ 98 km typically have small variations throughout the night. (2) The model zonal and meridional nighttime wind variations are typically much larger than those of observations at ~ 87 km and ~ 98 km. (3) At ~ 250 km, model zonal wind compares well with the observation in the winter. For spring and autumn, the model wind is more eastward before ~ 03:00 LT but more westward after. The observed nighttime zonal and meridional winds on average are close to zero in the summer and autumn, which indicates a lack of strong stable tides. The consistency of FPI zonal wind with model wind at ~ 250 km is better than the meridional wind

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“…The diurnal amplitudes of the wind decrease with increasing solar activity and vice versa (Igi et al, 1999). Emmert et al (2006) reported that the dependence of the neutral wind on the F10.7 solar flux either weakens or saturates around F10.7=150 at most latitudes and local times. As TEC is an integrated parameter of production, loss and transport processes, the above-mentioned effects may be reflected in the TEC variation.…”

Section: Resultsmentioning

confidence: 99%

Solar control of ambient ionization of the ionosphere near the crest of the equatorial anomaly in the Indian zone

Chakraborty¹,

Hajra²

2008

Ann. Geophys.

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Abstract. Long-term (1978Long-term ( -1990 total electron content (TEC) data have been analyzed to show the dependence of ambient ionization on EUV radiation from the Sun. TEC observations were made at Calcutta (22.58 • N, 88.38 • E geographic, dip: 32 • N), situated virtually below the northern crest of the equatorial ionization anomaly. Day-to-day changes in TEC at different local times do not show any significant correlation with F10.7 solar flux. A good correlation is, however, observed between the F10.7 solar flux and the monthly mean TEC when both are considered on a long-term basis, i.e. either in the ascending (1986)(1987)(1988)(1989)(1990) or in the descending (1979-1985) phase. In the early morning hours the correlation coefficient maximizes around the 08:00-10:00 h IST interval. The flux independent nature of diurnal TEC is evident around the noon time hours of only a few months in the descending phase for F10.7 values greater than 150 unit. Variation of TEC for the whole time period (1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)) also exhibits a prominent hysteresis effect. The remarkable feature of the hysteresis effect is its local time dependence, leading to a temporal flip-over. Solar flux-normalized TEC values show a clear seasonal dependence with asymmetrical variations in the two equinoxes. The amplitudes of the equinoctial peaks reveal a prominent local time dependence. A further normalization leads to a typical local time variation of TEC. Based on solar flux, seasonal and local time dependent features of TEC, an empirical formula has been developed to represent the TEC variation in the early morning hours. It yields a quantitative estimate of the solar flux dependent nature of the TEC variation. The formula has been validated using the available TEC data and data from the neural network.

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Climatologies of nighttime upper thermospheric winds measured by ground‐based Fabry‐Perot interferometers during geomagnetically quiet conditions: 1. Local time, latitudinal, seasonal, and solar cycle dependence

Cited by 74 publications

References 50 publications

On the solar cycle variation of the winter anomaly

On the solar cycle variation of the winter anomaly

FPI observations of nighttime mesospheric and thermospheric winds in China and their comparisons with HWM07

Solar control of ambient ionization of the ionosphere near the crest of the equatorial anomaly in the Indian zone

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