Daytime sodium airglow emission measurements over Trivandrum using a scanning monochromator: first results

This paper presents measurement of daytime Sodium (Na) airglow emissions at 589.6 nm wavelength using a ground based 1-m scanning monochromator from Trivandrum (8.5° N, 77° E, 0.5° N dip latitude), a near-equatorial station in India. The Na emission intensity exhibits significant temporal variability within a day and from one day to another. The Na intensity has been compared with the daytime OH airglow intensity at 731.6 nm simultaneously measured using the unique Multiwavelength Dayglow Photometer (MWDPM). The temporal variabilities of the Na and OH intensities corroborate each other in most of the occasions without any appreciable time delay, although a small time delay up to ˜10 min has been observed at times. It appears that the variability of daytime Na emissions is influenced too by the photo-chemical excitations. The observed similarities in the Na and OH intensities are believed to be due to the similar roles played by [O] and O3 (in their photo-chemical excitations) and the dynamics occurring at about the same altitude region (˜90 km). It has also been found that the gravity waves play significant role in producing the short-scale oscillations in these emissions

Electrodynamics of the equatorial F-region ionosphere during pre-sunrise period

The electrodynamics of the pre-sunrise equatorial F-region is investigated using HF Doppler radar and digital ionosonde. The observations are limited to those days for which the radar probing frequency is below the ƒoF2 value. The ionosphere observation using HF Doppler radar exhibit interesting features during pre-sunrise period similar to the post sunset pre-reversal enhancement. The most striking feature observed during pre-sunrise period is the sudden downward excursion in the vertical drift around local sunrise followed by an upward turning. Pre-sunrise observations of vertical plasma drift and the sunrise downward excursion followed by an upward turning after the ground sunrise related to the zonal electric field at the equatorial F-region are the most significant results not reported earlier

Redescription of Congrhynchus talabonoides Fowler, 1934 (Anguilliformes: Congridae) based on specimens collected from the Philippines, Taiwan and India

Smith, David G., Ho, Hsuan-Ching, Sumod, K. S. (2018): Redescription of Congrhynchus talabonoides Fowler, 1934 (Anguilliformes: Congridae) based on specimens collected from the Philippines, Taiwan and India. Zootaxa 4454 (1): 228-232, DOI: 10.11646/zootaxa.4454.1.1

On the variability of the observed HF Doppler derived equatorial F-region plasma drifts during evening and morning hours and the chemical corrections therein

130-140The radar derived F-region vertical plasma drift measurements, especially during evening/morning hours are apparent mainly because of the additional contribution from photochemical loss and/or production. As a consequence, it is very important to delineate the role of chemistry from these drift measurements in order to have a meaningful/realistic interpretation of the actual movement of the plasma in the ionosphere. In this paper, two chemical schemes have been employed separately for evening and morning hours to estimate the apparent drifts produced solely due to the chemistry. This study has been carried out by taking into account the important chemical reactions over equator during these times and for the computation, the neutral density of N2, O2, and neutral temperature Tn have been obtained from the Mass Spectrometer and Incoherent Scatter (MSIS) model. The temporal, altitudinal and seasonal variations of the chemical contributions have been theoretically estimated. The observed F-region vertical plasma drift measurements obtained from a multi-frequency HF Doppler radar over Trivandrum (8.5°N, 77°E, 0.5°N dip latitude) are then corrected, by taking into account the reflection height variation. The study reveals that (i) the apparent drift due to chemistry is strongly altitude dependent and can indeed be as high as 10-15 m s-1; (ii) there is a clear cut seasonal pattern for these correction factors with a northern hemispheric (NH) summer (June) minima and a maxima during the NH winter solstice (December)

Planetary wave-tidal interactions over the equatorial mesosphere-lower thermosphere region and their possible implications for the equatorial electrojet

Optically measured daylight mean mesopause temperatures over a dip equatorial station, Trivandrum (8.5° N; 77° E; dip lat. 0.5° N), have been analyzed in conjunction with simultaneously measured equatorial electrojet (EEJ)-produced magnetic field at the surface. The signature of planetary wave-tidal interactions in the mesosphere-lower thermosphere (MLT) region has been observed for the first time in the day-to-day variability in the EEJ, i.e., the time of its peaking and the duration, as inferred from the EEJ-produced magnetic field on the ground. The present study shows that the planetary wave of quasi 16 day periodicity plays an important role in causing these variabilities, especially during the winter months. The quasi 16 day wave is found to be modulating the mesopause temperature (MT), duration, and time of the maximum EEJ intensity (D<SUB>EEJ</SUB> and T<SUB>EEJ</SUB>). During positive excursions of the planetary wave, T<SUB>EEJ</SUB> showed a shift toward evening, while the MT showed an increase and D<SUB>EEJ</SUB> showed a broadening. Similarly, all these parameters exhibited an opposite trend during negative excursions. The planetary wave-tidal interactions and subsequent modification of the tidal components have been shown to be responsible for the observed variations. This study presents a new perspective addressing the day-to-day variability of the EEJ

A new species of white-spotted moray eel, Gymnothorax smithi (Muraenidae: Muraeninae) from deep waters of Arabian Sea, India

A new species of white-spotted moray eel Gymnothorax smithi sp. nov. is described based on three specimens collected from the southeastern Arabian Sea, India. This is the first deep water report of a moray eel from Indian waters from 200 m depth. This new species is distinguishable from its congeners by the following combination of characters: greyish brown body overlain with white spots of irregular shape, dorsal-fin origin anterior to gill opening, anus positioned slightly behind the mid-point of the body, serrated teeth and a unique vertebral count 3–5 /57/130–132. [Zoobank URL: urn:lsid:zoobank.org:act:9554CE07-E9E7-4B4F-95CD-54F2BB26FF28

Effects of the intense geomagnetic storm of September-October 2012 on the equatorial, low- and mid-latitude F region in the American and African sector during the unusual 24th solar cycle

The main purpose of this paper is to investigate the response of the ionospheric F layer in the American and African sectors during the intense geomagnetic storm which occurred on 30 September-01 October 2012. In this work, we used observations from a chain of 20 GPS stations in the equatorial, low- and mid-latitude regions in the American and African sectors. Also, in this study ionospheric sounding data obtained during 29th September to 2nd October, 2012 at Jicamarca (JIC), Peru, São Luis (SL), Fortaleza (FZ), Brazil, and Port Stanley (PST), are presented. On the night of 30 September-01 October, in the main and recovery phase, the hDF variations showed an unusual uplifting of the F region at equatorial (JIC, SL and FZ) and mid- (PST) latitude stations related with the propagations of traveling ionospheric disturbances (TIDs) generated by Joule heating at auroral regions. On 30 September, the VTEC variations and foF2 observations at mid-latitude stations (American sector) showed a long-duration positive ionospheric storm (over 6h of enhancement) associated with large-scale wind circulations and equatorward neutral winds. Also, on 01 October, a long-duration positive ionospheric storm was observed at equatorial, low- and mid- latitude stations in the African sector, related with the large-scale wind circulations and equatorward neutral winds. On 01 and 02 October, positive ionospheric storms were observed at equatorial, low- and mid-latitude stations in the American sector, possibly associated with the TIDs and an equatorward neutral wind. Also, on 01 October negative ionospheric storms were observed at equatorial, low- and mid-latitude regions in the American sector, probably associated with the changes in the O/N2 ratio. On the night of 30 September-01 October, ionospheric plasma bubbles were observed at equatorial, low- and mid- latitude stations in the South American sector, possibly associated with the occurrence of geomagnetic storm.Fil: de Jesus, R.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; Brasil. Universidade do Vale do Paraíba; BrasilFil: Fagundes, P.R.. Universidade do Vale do Paraíba; BrasilFil: Coster, A.. Massachusetts Institute of Technology; Estados UnidosFil: Bolaji, O. S.. University of Lagos; NigeriaFil: Sobral, J. H. A.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: Batista, I. S.. Centro de Previsao de Tempo e Estudos Climáticos. Instituto Nacional de Pesquisas Espaciais; BrasilFil: de Abreu, A. J.. Universidade do Vale do Paraíba; Brasil. Instituto Tecnológico de Aeronáutica; BrasilFil: Venkatesh, K.. Universidade do Vale do Paraíba; BrasilFil: Gende, Mauricio Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Abalde, J. R.. Universidade do Vale do Paraíba; BrasilFil: Sumod, S. G.. Mahatma Gandhi University; Indi