Thermospheric planetary wave‐type oscillations observed by FPIs over Xinglong and Millstone Hill

Self Cite

An 11 year (1989–1995 and 2010–2013) nighttime thermospheric wind (at ~250 km) data set from Fabry‐Perot interferometer at Millstone Hill (42.6°N, 71.5°W) is used to investigate multiday oscillations (6–30 days) in the thermospheric nighttime winds. Dependencies of multiday oscillations on solar radiation (F10.7), solar wind speed (SW), and geomagnetic activity (Kp) are determined. We found that (1) there exist prominent quasi 27 day oscillations in the thermospheric zonal (meridional) wind, which appears to be more correlated to the same periodic oscillations in Kp and SW than in F10.7 during the solar maximum (solar declining phase and minimum); (2) quasi 13.5 day oscillations in the zonal wind occur during the solar maximum and increasing phases and are also more correlated to the same periodic oscillations in Kp and SW; and (3) in general, the correlations of the multiday oscillations in the thermospheric winds are more correlated with Kp and SW than F10.7. Our analyses also show that the zonal wind is more sensitive to SW than the meridional wind. We further find that (4) for high F10.7, the premidnight zonal wind is more westward toward increasing SW; for low F10.7, the postmidnight zonal wind is also more westward toward increasing SW; and (5) meridional winds tend to be more southward with increasing SW for medium and high F10.7.

Section: Data Set and Methodsmentioning

confidence: 99%

Section: Data Set and Methodsmentioning

confidence: 99%

Section: Oscillations Extraction Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Solar activity dependency of multiday oscillations in the nighttime thermospheric winds observed by Fabry‐Perot interferometer

Liu

Zhang

et al. 2015

Self Cite

“…Their studies indicate that thermospheric density multiday oscillations are mainly associated with the periodic variations in high-speed solar wind streams and their resultant recurrent geomagnetic activity. The multiday oscillations in thermospheric winds were reported as well [Liu et al, 2014]. Hecht et al [2012] used Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Global Ultraviolet Imager (TIMED/GUVI) observations of thermospheric composition (O/N 2 ) from 2002 to 2006 to show that thermospheric O/N 2 had multiday periodic oscillations.…”

Section: Introductionmentioning

confidence: 96%

“…Their studies indicate that thermospheric density multiday oscillations are mainly associated with the periodic variations in high‐speed solar wind streams and their resultant recurrent geomagnetic activity. The multiday oscillations in thermospheric winds were reported as well [ Liu et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Multiday thermospheric density oscillations associated with variations in solar radiation and geomagnetic activity

Wang

Zhang

et al. 2015

Self Cite

Thermospheric densities observed by Challenging Minisatellite Payload and Gravity Recovery and Climate Experiment satellites during 2002-2010 and the globally averaged thermospheric densities from 1967 to 2007 have been used to investigate latitudinal, longitudinal, and height dependences of the multiday oscillations of thermospheric densities. The data show that the main multiday oscillations in thermospheric densities are 27, 13.5, 9, and 7 day oscillations. The high-correlation coefficients between the density oscillations and the F 10.7 or Ap index indicate that these oscillations are externally driven. The 27 day density oscillation, being the strongest, is induced by variations in solar radiation, as well as recurrent geomagnetic activity that is the result of corotating interaction regions (CIRs) and high-speed solar wind streams of coronal hole origin. Density oscillations at periods of 13.5, 9, and 7 days at solar minimum and during the declining phase are stronger than those at solar maximum. These oscillations are mainly associated with recurrent geomagnetic activity due to coronal hole high-speed streams and CIRs. The multiday, periodic oscillations of thermospheric density exhibit strong latitudinal and longitudinal variations in the geomagnetic coordinate and oscillate synchronously at different heights. Oscillations with zonal wave number 0 oscillate globally, whereas those with nonzero wave numbers are strong at high geomagnetic latitudes, and hemispherically asymmetric. They are stronger in the Southern Hemisphere. The spectral distributions of thermospheric densities at different heights have almost the same latitude and longitude structures, but the spectral magnitudes increase with height.

Mesoscale field‐aligned irregularity structures (FAIs) of airglow associated with medium‐scale traveling ionospheric disturbances (MSTIDs)

Sun

Wang

et al. 2015

Self Cite

In this paper, we report the evolution (generation, amplification, and dissipation) of optically observed mesoscale field-aligned irregularity structures (FAIs) (~150 km) associated with a medium-scale traveling ionospheric disturbance (MSTID) event. There have not been observations of mesoscale FAIs of airglow before. The mesoscale FAIs were generated in an airglow-depleted front of southwestward propagating MSTIDs that were simultaneously observed by an all-sky imager, a GPS monitor, and a digisonde around Xinglong (40.4°N, 30.5°magnetic latitude), China, on 17/18 February 2012. A normalized cross-correlation method has been used to obtain the velocities of mesoscale FAIs and MSTIDs. The mesoscale FAIs had an obvious northwestward relative velocity to main-body MSTIDs (about 87.0 m/s on average). The direction of this relative velocity was roughly parallel to the depleted fronts. Furthermore, the evolution of the mesoscale FAIs was mostly controlled by the intensity of the depleted fronts. Occurred in a highly elevated ionosphere that had a total electron content depletion associated with large negative airglow perturbations (À25%), the mesoscale FAIs grew rapidly when they experienced southeastward wind, which had a speed of about 100 m/s and were measured by a Fabry-Perot interferometer. A northeastward polarization electric field within a depleted airglow front can play a controlling role in the development of the mesoscale FAIs. The electric field can significantly elevate the ionosphere and move the mesoscale FAIs northwestward by the E × B drift. The processes for the generation and development of the polarization electric field and the mesoscale FAIs, however, need further study. Hemisphere, a northwestward (NW) preferable propagation of nighttime MSTIDs was found [Candido et al., 2008;Pimenta et al., 2008;Amorim et al., 2011]. In the statistical analyses cited above, Kubota et al. [2011] recently showed that the SW propagating MSTIDs in Alaska are atmospheric gravity waves (AGWs), whereas SUN ET AL.FAIS OF AIRGLOW ASSOCIATED WITH MSTIDS 9839 PUBLICATIONS Key Points:• An evolution of medium-scale traveling ionospheric disturbances (MSTIDs) is presented • Mesoscale field-aligned irregularity structures (FAIs) (~150 km) of airglow are firstly presented • We first find the mesoscale FAIs had a northwestward relative velocity to main-body MSTIDs (2015), Mesoscale field-aligned irregularity structures (FAIs) of airglow associated with medium-scale traveling ionospheric disturbances (MSTIDs), J. Geophys.