Studies of the motion of equatorial 630.0 nm airglow depletions

Sipler, D. P.; Biondi, Manfred A.; Hake, R. D.

doi:10.1016/0032-0633(81)90131-8

Cited by 16 publications

(7 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The structures in ESF, particularly those with largescale sizes, have been studied using scanning optical photometers (Takahashi et al, 1989;Sipler et al, 1981) and allsky imagers (Weber et al, 1978;Sahai et al, 1994;Mendillo et al, 1997;Sinha et al, 1996). Depletions and enhancements in airglow intensities during ESF events (Mendillo et al, 1985;Sinha et al, 1996) have been recorded by imagers.…”

Section: Introductionmentioning

confidence: 99%

“…In view of these aspects, both these thermospheric emission line intensities are used to infer the modulations in the F-region ionosphere. The modulations in the temporal variation of nocturnal airglow intensities have been found to be associated with the variations in the F-layer heights (Barbier, 1959), with the well-known equatorial reverse plasma fountain (Kulkarni and Rao, 1972;Sridharan et al, 1993;Sekar et al, 1993), with the meridional wind reversal associated with midnight temperature anomaly (Herrero and Meriwether, 1980) and plasma depletions (Sipler et al, 1981). Most of the earlier studies have been carried out using photometers having a broad spectral range (band width ranging from 0.6-nm to a few nm) and as a consequence, without the requirement of stringent temperature tuning of the interference filters used.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, the airglow imagers which have been usually deployed for ESF investigations are devices aimed at having large spatial coverage (large field of view) and hence filters with large bandwidth are used. A narrow band (∼0.3-nm) photometer, along with the ALTAIR radar (Sipler et al, 1981), was operated to obtain all-sky map of airglow intensities which revealed airglow depletions. Although the plasma drift velocities obtained by the photometer were compared with the line-of-sight neutral wind velocities measured by a collocated airglow spectrometer, the variations in the airglow intensity were not compared with the ESF structures obtained by the radar.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Characterization of VHF radar observations associated with equatorial Spread F by narrow-band optical measurements

et al. 2004

View full text Add to dashboard Cite

Abstract. The VHF radars have been extensively used to investigate the structures and dynamics of equatorial Spread F (ESF) irregularities. However, unambiguous identification of the nature of the structures in terms of plasma depletion or enhancement requires another technique, as the return echo measured by VHF radar is proportional to the square of the electron density fluctuations. In order to address this issue, co-ordinated radar backscatter and thermospheric airglow intensity measurements were carried out during March 2003 from the MST radar site at Gadanki. Temporal variations of 630.0-nm and 777.4-nm emission intensities reveal smallscale ("micro") and large-scale ("macro") variations during the period of observation. The micro variations are absent on non-ESF nights while the macro variations are present on both ESF and non-ESF nights. In addition to the well-known anti-correlation between the base height of the F-region and the nocturnal variation of thermospheric airglow intensities, the variation of the base height of the F-layer, on occasion, is found to manifest as a bottomside wave-like structure, as seen by VHF radar on an ESF night. The micro variations in the airglow intensities are associated with large-scale irregular plasma structures and found to be in correspondence with the "plume" structures obtained by VHF radar. In addition to the commonly observed depletions with upward movement, the observation unequivocally reveals the presence of plasma enhancements which move downwards. The observation of enhancement in 777.4-nm airglow intensity, which is characterized as plasma enhancement, provides an experimental verification of the earlier prediction based on numerical modeling studies.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of VHF radar observations associated with equatorial Spread F by narrow-band optical measurements

et al. 2004

View full text Add to dashboard Cite

show abstract

“…Optical studies of the 630.0 nm brightness distribution of the airglow emanating from the bottomside of the equatorial Fregion often show regions of significant depletion [Weber et al, 1982;Mendillo and Baumgardner, 1982;Sipler et al, 1981;Malcolm et al, 1984] that are usually aligned in the meridional geomagnetic direction and have widths ranging between 50 and 200 km. The 630.0 nm airglow line is emitted by O[•D] atoms produced by the dissociative recombination of 02 + ions with F-region electrons.…”

Section: Introductionmentioning

confidence: 99%

Equatorial airglow depletions induced by thermospheric winds

Meriwether

Biondi

Anderson

1985

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

Interferometric observations of the 630.0 nm nightglow brightness at the equatorial station of Arequipa, Peru [16.2°S, 71.4°W geographic, 3.2°S dip latitude] have revealed widespread areas of airglow depletion, with reductions in intensity as large as factors of 3 or 4. These depletions correlated closely with large increases of the equatorward (northward) wind and the 630.0 nm kinetic temperature. On occasion, the usually small meridional wind reached a velocity of 100 m/s near 22h LT lasting for 1 to 2 hours. The temperature increases of 100 K or more existed only in the poleward (southward) direction. Comparisons with modelling calculations suggest that this effect results from an upward movement of the ionosphere along the inclined magnetic field lines, driven by the equatorward neutral wind. The airglow column integrated emission rate is consequently decreased by the slower rate of formation and subsequent dissociative recombination of molecular oxygen ions within the higher F‐layer. We conclude that the transient period of equatorward wind is a result of the passage of the midnight pressure bulge.

show abstract

“…The ground based and spacecraft measurements of the equatorial and low latitude ionosphere have established clearly that the various phenomena such as airglow enhancements, VHF scintillations, TEC variations and equatorial spread-F (ESF) are coupled to each other and can be explained by the generation of g x B plasma instability which occurs initially at the bottom of the F layer (Anderson, 1981;Sipler et al, 1981;Zalesak et al, 1982). Subsequently the irregularities move up nonlinearly by polarization E x B motion.…”

Section: Introductionmentioning

confidence: 99%