Simultaneous observation of ionospheric plasma bubbles and mesospheric gravity waves during the SpreadFEx Campaign

Abstract

Abstract. During the Spread F Experiment campaign, under NASA Living with a Star (LWS) program, carried out in the South American Magnetic Equator region from 22 September to 8 November 2005, two airglow CCD imagers, located at Cariri (7.4 • S, 36.5 • W, geomag. 11 • S) and near Brasilia (14.8 • S, 47.6 • W, geomag. 10 • S) were operated simultaneously and measured the equatorial ionospheric bubbles and their time evolution by monitoring the airglow OI 6300 intensity depletions. Simultaneous observation of the mesospheric OH wave structures made it possible to investigate the relationship between the bubble formation in the ionosphere and the gravity wave activity at around 90 km. On the evening of 30 September 2005, comb-like OI 6300 depletions with a distance of ∼130 km between the adjacent ones were observed. During the same period, a mesospheric gravity wave with a horizontal wavelength of ∼130 km was observed. From the 17 nights of observation during the campaign period, there was a good correlation between the OI 6300 depletion distances and the gravity wave horizontal wavelengths in the mesosphere with a statistically significant level, suggesting a direct contribution of the mesospheric gravity wave to plasma bubble seeding in the equatorial ionosphere.

Gravity wave amplitudes and momentum fluxes inferred from OH airglow intensities and meteor radar winds during SpreadFEx

“…However, GW penetration still depends on propitious atmospheric conditions, that is, the absence of filtering of GWs by tidal or larger scale winds and absence of turning levels between mesosphere and ionospheric F-layer. Takahashi et al (2009) have successfully investigated some cases of strong correlation between GWs motion in the mesosphere followed by plasma bubble appearing above in the F-region at Cariri. Because we had access to the same database as Takahashi et al (2009), it was possible to estimate the momentum flux and wave amplitudes at the same time intervals of those waves cited in their report.…”

“…Takahashi et al (2009) have successfully investigated some cases of strong correlation between GWs motion in the mesosphere followed by plasma bubble appearing above in the F-region at Cariri. Because we had access to the same database as Takahashi et al (2009), it was possible to estimate the momentum flux and wave amplitudes at the same time intervals of those waves cited in their report. For that comparison we used wind information, once it was available in Cariri during the campaign.…”

“…An all-sky CCD image covers a large horizontal extension of the nocturnal sky, but here it was used an area of 512×512 km centered at the zenith in order to avoid lens distortion at the edges of the images. For a complete description of the all-sky CCD imagers used in this work see Takahashi et al (2009) or Medeiros et al (2004).…”

“…General characteristics of gravity wave parameters obtained and momentum fluxes estimations were investigated in this paper. A short discussion in terms of momentum fluxes is presented for two nights with evidence of strong correlation between wave motion followed by ionospheric plasma depletion, which are compared to the results obtained by Takahashi et al (2009).…”

Statistical analysis of C/NOFS planar Langmuir probe data

“…Note that, with few exceptions (the Atlantic and the two Pacific sectors), the projection of the magnetic equator onto Earth (yellow line and left vertical axis) crosses land in most of the sectors. Thus, the above selection of longitude sectors is interesting, since topography has been listed (Friits and Alexander, 2003;Takahashi et al, 2009;Carrasco and Batista, 2012) as one of the possible drivers of gravity waves. These waves propagate vertically, reaching the bottom of the F layer to seed plasma instability processes that generate equatorial plasma bubbles and irregularities in the ionospheric density.…”