Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx)

Abstract

Abstract. The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in plasma bubble seeding at the bottomside F layer. Our purpose here is to employ these results to estimate gravity wave characteristics at the bottomside F layer, and to assess their possible contributions to optimal seeding conditions for ESF and plasma instability growth rates. We also assess expected tidal influences on the environment in which plasma bubble seeding occurs, given their apparent large wind and temperature amplitudes at these altitudes. We conclude 1) that gravity waves can achieve large amplitudes at the bottomside F layer, 2) that tidal winds likely control the orientations of the gravity waves that attain the highest altitudes and have the greatest effects, 3) that the favored gravity wave orientations enhance most or all of the parameters influencing plasma instability growth rates, and 4) that gravity wave and tidal structures acting together have an even greater potential impact on plasma instability growth rates and plasma bubble seeding.

Reconstruction of the gravity wave field from convective plumes via ray tracing

“…We then calculated the zonal velocity amplitudes of GWs excited from a single convective plume and a small convective cluster at the OH layer as a function of λ H and λ z . These spectra were used to infer GW amplitudes at higher altitudes in the TI during this SpreadFEx campaign Fritts et al, 2008b). They were also used to constrain the amplitudes of medium-scale GWs detected in the OH airglow layer and reverse ray traced to deep convective plumes (Vadas et al, 2009a).…”

“…16 were also used to infer GW amplitudes at higher altitudes in the TI for this SpreadFEx campaign Fritts et al, 2008b). GWs with λ z > ∼ 100 km are those we expect to penetrate to the greatest altitudes, based on the viscous dispersion relation developed by VF2005 and the ray tracing studies by Vadas (2007) and Fritts and Vadas (2008).…”

“…GWs with λ z > ∼ 100 km are those we expect to penetrate to the greatest altitudes, based on the viscous dispersion relation developed by VF2005 and the ray tracing studies by Vadas (2007) and Fritts and Vadas (2008). Fritts et al (2008b) employed the results of this study to infer maximum horizontal velocities near z∼80 km of ∼1−2 ms −1 for GWs with λ z ∼150 km and λ H ∼200−400 km arising from a single convective plume, with amplitudes ∼2 times larger in response to a small convective cluster. Assuming that these GWs penetrate to higher altitudes, they then inferred corresponding GW horizontal velocities as large as ∼100 ms −1 or larger at altitudes of ∼250 to 300 km for GWs propagating against the tidal winds and refracting to higher intrinsic frequencies.…”

“…Note that Fritts and Vadas (2008) employ the GW amplitudes and spectra determined in this paper to anticipate general GW propagation, filtering, and amplitude growth accompanying various thermospheric temperature and wind profiles. Fritts et al (2008b) also employ these results to infer specific neutral and plasma responses at the bottomside F layer.…”

An Investigation into Height Variation of Ionospheric Signature Due To the Cyclonic Storm Formation Using COSMIC-RO Measurements

“…In this respect, Low Earth Orbiting (LEO) satellite Radio Occultation (RO) information could be an apposite alternative source to evolve the evolutions in ionospheric layers during different geophysical phenomenon, like, thunderstorm, cyclone etc. In this study, COSMIC-RO observation profiles have been used to determine and estimate the precursor and/or postcursor signature, if any, at ionospheric heights due to the existence of two CSs: Mahasen (10)(11)(12)(13)(14)(15)(16) th May 2013) and Phailin (8)(9)(10)(11)(12)(13)(14) th October 2013). This kind of study, using space based measurements, is first over this region.…”