Climatology of middle‐ and low‐latitude daytime F region disturbance neutral winds measured by Wind Imaging Interferometer (WINDII)

Emmert, J. T.; Fejer, Bela G.; Fesen, C. G.; Shepherd, G. G.; Solheim, B. H.

doi:10.1029/2000ja000372

Cited by 61 publications

(86 citation statements)

References 37 publications

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“…Hence, in the absence of simultaneous observations of the altitude distribution of the neutral composition during this storm, it can only be inferred that the increase in observed emissions are most likely due to a significant increase in the neutral densities over low latitudes during the 6 November storm. The decrease in the observed emissions around 09:00 LT on the disturbed day can be attributed to the decrease in mass transport of neutral species, due to a decrease in the storm strength from K p =9 − to K p =7 in 9 h. This is commensurate with the measurements (Emmert et al, 2001) that showed a decrease in the equatorward wind strengths with the decrease in the storm strength.…”

Section: Discussionsupporting

confidence: 77%

“…Zhang and Shepherd (2000) reported WINDII measured winds of 650 ms −1 at 200 km in the polar region for a storm with K p =7.7. The wind-strengths reduce as they propagate towards the low and equatorial latitudes (Emmert et al, 2001). The wind strengths also increase with an increase in the intensity and the duration of the magnetic storm.…”

Section: Discussionmentioning

confidence: 90%

“…Further, there is ample evidence in the literature to show that the measured and modeled winds, and TADs during storm time show large equatorward velocities (e.g. Fujiwara et al, 1996;Zhang and Shepherd, 2000;Emmert et al, 2001). Zhang and Shepherd (2000) reported WINDII measured winds of 650 ms −1 at 200 km in the polar region for a storm with K p =7.7.…”

Section: Discussionmentioning

confidence: 99%

“…This heating also causes an upwelling of the neutral species over the auroral oval, which generates a large wave that is capable of propagating to the magnetic equator in a few hours (Mayr et al, 1978;Prolss, 1993). There are ample evidences of an increase in the neutral temperature and winds at low latitudes during magnetic storms (Mayr and Volland, 1973;Meriwether et al, 1973;Mayr et al, 1978;Prolss, 1980;Burrage et al, 1992;Prolss, 1993;Burns et al, 1995;Fuller-Rowell et al, 1996;Pant and Sridharan, 1998;Fujiwara et al, 1996;Emmert et al, 2001). The thermospheric winds and composition changes are intimately coupled and as a consequence, the F-region electron densities also change accordingly.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(1D) dayglow measurements from Chile

2004

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Abstract.We describe the effect of the 6 November 2001 magnetic storm on the low latitude thermospheric composition. Daytime red line (OI 630.0 nm) emissions from Carmen Alto, Chile showed anomalous 2-3 times larger emissions in the morning (05:30-08:30 Local Time; LT) on the disturbed day compared to the quiet days. We interpret these emission enhancements to be caused due to the increase in neutral densities over low latitudes, as a direct effect of the geomagnetic storm. As an aftereffect of the geomagnetic storm, the dayglow emissions on the following day show gravity wave features that gradually increase in periodicities from around 30 min in the morning to around 100 min by the evening. The integrated dayglow emissions on quiet days show day-to-day variabilities in spatial structures in terms of their movement away from the magnetic equator in response to the Equatorial Ionization Anomaly (EIA) development in the daytime. The EIA signatures in the daytime OI 630.0 nm column-integrated dayglow emission brightness show different behavior on days with and without the post-sunset Equatorial Spread F (ESF) occurrence.

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Section: Discussionsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(1D) dayglow measurements from Chile

2004

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“…12 24 12 24 12 24 12 24 12 24 12 24 Manila SLT (hours) Effects of the E×B plasma drift on hmF2 and NmF2 over the Kokubunji and Darwin sounders and over the MU radar, whose locations are far enough from the geomagnetic equator, are much less than those caused by the plasma drift along magnetic field lines due to the neutral wind (Rishbeth, 2000;Souza et al, 2000;Pincheira et al, 2002;Pavlov, 2003;Pavlov et al, 2004a, b), and variations of hmF2 are predominantly determined by variations in the thermospheric wind over these sounders and the MU radar. The HWM90 wind velocities are known to differ from observations (Titheridge, 1995;Kawamura et al, 2000;Emmert et al, 2001;Fejer et al, 2002). The meridional, W, and the zonal components of the neutral wind are produced by the HWM90 wind model of Hedin et al (1991) in geographical frame of reference, so that the meridional wind is directed northward for W>0 and southward for W<0.…”

Section: Solar Geophysical Conditions and Datamentioning

confidence: 99%

A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990

2006

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Abstract.We have presented a comparison between the modeled NmF2 and hmF2, and NmF2 and hmF2, which were observed in the low-latitude ionosphere simultaneously by the Kokubunji, Yamagawa, Okinawa, Manila, Vanimo, and Darwin ionospheric sounders, by the middle and upper atmosphere (MU) radar during 17-22 March 1990, and by the Arecibo radar for the time period of 20-22 March 1990. A comparison between the electron and ion temperatures measured by the MU and Arecibo radars and those produced by the model of the ionosphere and plasmasphere is presented. The empirical zonal electric field, the meridional neutral wind taken from the HWM90 wind model, and the NRLMSISE-00 neutral temperature and densities are corrected so that the model results agree reasonably with the ionospheric sounder observations, and the MU and Arecibo radar data. It is proved that the nighttime weakening of the equatorial zonal electric field (in comparison with that produced by the empirical model of Fejer and Scherliess (1997) or Scherliess and Fejer (1999)), in combination with the corrected wind-induced plasma drift along magnetic field lines, provides the development of the nighttime enhancements in NmF2 observed over Manila during 17-22 March 1990. As a result, the new physical mechanism of the nighttime NmF2 enhancement formation close to the geomagnetic equator includes the nighttime weakening of the equatorial zonal electric field and equatorward nighttime plasma drift along magnetic field lines caused by neutral wind in the both geomagnetic hemispheres. It is found that the latitudinal positions of the crests depend on the E×B drift velocity and on the neutral wind velocity. The relative role of the main mechanisms of the equatorial anomaly suppression observed during geomagnetic storms is studied for the first time in terms of storm-time variations of the model crest-to-trough ratios of the equatorial anomaly. During most of the studied time Correspondence to: A. V. Pavlov (pavlov@izmiran.rssi.ru) period, a total contribution from meridional neutral winds and variations in the zonal electric field to the equatorial anomaly changes is larger than that from geomagnetic storm disturbances in the neutral temperature and densities. Vibrationally excited N 2 and O 2 promote the equatorial anomaly enhancement during the predominant part of the studied time period, however, the role of vibrationally excited N 2 and O 2 in the development of the equatorial anomaly is not significant. The asymmetries in the neutral wind and densities relative to the geomagnetic equator are responsible for the northsouth asymmetry in NmF2 and hmF2, and for the asymmetry between the values of the crest-to-trough ratios of the Northern and Southern Hemispheres. The model simulations provide evidence in favor of an asymmetry in longitude of the energy input into the auroral region of the Northern Hemisphere on 21 March 1990.

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Nonmigrating diurnal tides observed in global thermospheric winds

2013

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Nonmigrating diurnal tides between 90 and 270 km are inferred from Upper Atmosphere Research Satellite (UARS) wind imaging interferometer (WINDII) winds. This study represents the first known effort to directly analyze tidal wave number structure and propagation direction in winds observed over this altitude range. Prominent diurnal tides include an eastward propagating wave number 3, a zonally symmetric tide, and a westward propagating wave number 2. UARS High Resolution Doppler Imager winds between 60 and 100 km were analyzed identically and show excellent consistency with WINDII tides. Observed tides were compared with tidal fits to Hough Mode Extensions. WINDII tides are generally damped more slowly above 120 km than fitted tides, and the zonally symmetric tide indicates a thermospheric source not captured by Hough Mode Extensions. Our study provides additional confirmation that tides act as direct coupling agents between the troposphere and the thermosphere (and F region), in addition to their role in the E region dynamo.

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Climatology of middle‐ and low‐latitude daytime F region disturbance neutral winds measured by Wind Imaging Interferometer (WINDII)

Cited by 61 publications

References 37 publications

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990

Nonmigrating diurnal tides observed in global thermospheric winds

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Climatology of middle‐ and low‐latitude daytime F region disturbance neutral winds measured by Wind Imaging Interferometer (WINDII)

Cited by 61 publications

References 37 publications

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(&lt;sup&gt;1&lt;/sup&gt;D) dayglow measurements from Chile

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(&lt;sup&gt;1&lt;/sup&gt;D) dayglow measurements from Chile

A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990

Nonmigrating diurnal tides observed in global thermospheric winds

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Product

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Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile