Characterization of internal inertia gravity wave over a low latitude: results from the RONAC-2012 campaign

Abstract. The advantages of using a composite day analysis for all-sky interferometric meteor radars when measuring mean winds and tides are widely known. On the other hand, problems arise if this technique is applied to Hocking's (2005) gravity wave analysis for all-sky meteor radars. In this paper we describe how a simple change in the procedure makes it possible to use a composite day in Hocking's analysis. Also, we explain how a modified composite day can be constructed to test its ability to measure gravity wave momentum fluxes. Test results for specified mean, tidal, and gravity wave fields, including tidal amplitudes and gravity wave momentum fluxes varying strongly with altitude and/or time, suggest that the modified composite day allows characterization of monthly mean profiles of the gravity wave momentum fluxes, with good accuracy at least at the altitudes where the meteor counts are large (from 89 to 92.5 km). In the present work we also show that the variances measured with Hocking's method are often contaminated by the tidal fields and suggest a method of empirical correction derived from a simple simulation model. The results presented here greatly increase our confidence because they show that our technique is able to remove the tide-induced false variances from Hocking's analysis.

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Characterization of Ionospheric Scintillation Index over Low Latitude: Nepal Region

10.20944/preprints202002.0404.v1 ◽

2020 ◽

Author(s):

Kutubuddin Ansari ◽

Tae-Suk Bae ◽

Punyawi Jamjareegulgarn ◽

Shakera Khan ◽

Soo-Hyeon Lim

Keyword(s):

Satellite Communication ◽

Scintillation Index ◽

Ionospheric Scintillation ◽

Small Scale ◽

Low Latitude ◽

Rapid Phase ◽

Global Positioning ◽

Low Latitudes ◽

Communication Space

The ionospheric scintillation is a rapid phase and amplitude fluctuation of satellite signals due to the small-scale irregularity of electron density in the ionosphere. The characterization of the scintillation index in a proper way is a crucial aspect of the Global Positioning System (GPS) satellite signals for the purpose of space-based navigation, satellite communication, space weather as well as earth observation applications. In the current study, we analyzed the ionospheric scintillation index during the year of 2018 to 2019 over the Nepal region which locates itself almost being sandwiched between India and China and in the vicinity of low latitudes. The characteristic variations of scintillation occurrence are studied during the several geomagnetic storm and quiet days. The results show that the S4 indexes are varying from the 0.05 to 0.45 during the whole year. The S4 indexes behave higher variations during the whole day in the starting of the year and start to decrease at end of the day as well as at the ending months of the year 2019. The S4 values become completely less during the sunset time, while they have higher values during the sunrise. Especially, the S4 index during the storm days are larger than during the quiet days. It is worthy to note that the variations of S4 index studied in this current study do not follow the sunset property during the year of 2019. Consequently, the causes should be discovered and discussed additionally in the next research paper.

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Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

Annales Geophysicae ◽

10.5194/angeo-22-3241-2004 ◽

2004 ◽

Vol 22 (9) ◽

pp. 3241-3250 ◽

Cited By ~ 26

Author(s):

D. Pallamraju ◽

S. Chakrabarti ◽

C. E. Valladares

Keyword(s):

Gravity Wave ◽

Magnetic Storm ◽

Geomagnetic Storm ◽

Local Time ◽

Direct Effect ◽

Spatial Structures ◽

Low Latitude ◽

Equatorial Ionization Anomaly ◽

Low Latitudes ◽

Spread F

Abstract. We describe the effect of the 6 November 2001 magnetic storm on the low latitude thermospheric composition. Daytime red line (OI 630.0nm) emissions from Carmen Alto, Chile showed anomalous 2-3 times larger emissions in the morning (05:30-08:30 Local Time; LT) on the disturbed day compared to the quiet days. We interpret these emission enhancements to be caused due to the increase in neutral densities over low latitudes, as a direct effect of the geomagnetic storm. As an aftereffect of the geomagnetic storm, the dayglow emissions on the following day show gravity wave features that gradually increase in periodicities from around 30min in the morning to around 100min by the evening. The integrated dayglow emissions on quiet days show day-to-day variabilities in spatial structures in terms of their movement away from the magnetic equator in response to the Equatorial Ionization Anomaly (EIA) development in the daytime. The EIA signatures in the daytime OI 630.0nm column-integrated dayglow emission brightness show different behavior on days with and without the post-sunset Equatorial Spread F (ESF) occurrence.

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Large- and small-scale periodicities in the mesosphere as obtained from variations in O<sub>2</sub> and OH nightglow emissions

Annales Geophysicae ◽

10.5194/angeo-35-227-2017 ◽

2017 ◽

Vol 35 (2) ◽

pp. 227-237 ◽

Cited By ~ 3

Author(s):

Ravindra P. Singh ◽

Duggirala Pallamraju

Keyword(s):

Gravity Wave ◽

Statistical Study ◽

Small Scale ◽

Radio Flux ◽

Low Latitude ◽

Atmospheric Processes ◽

Solar Influence ◽

Seasonal Dependence

Abstract. Using 3 years (2013–2015) of O2(0–1) and OH(6–2) band nightglow emission intensities and corresponding rotational temperatures as tracers of mesospheric dynamics, we have investigated large- and small-timescale variations in the mesosphere over a low-latitude location, Gurushikhar, Mount Abu (24.6° N, 72.8° E), in India. Both O2 and OH intensities show variations similar to those of the number of sunspots and F10.7 cm radio flux with coherent periodicities of 150 ± 2.1, 195 ± 3.6, 270 ± 6.4, and 420 ± 14.8 days, indicating a strong solar influence on mesospheric dynamics. In addition, both mesospheric airglow intensities also showed periodicities of 84 ± 0.6, 95 ± 0.9, and 122 ± 1.3 days which are of atmospheric origin. With regard to the variability of the order of a few days, O2 and OH intensities were found to be correlated, in general, except when altitude-dependent atmospheric processes were operative. To understand mesospheric gravity wave behavior over the long term, we have carried out a statistical study using the periodicities derived from the nocturnal variations in all four parameters (O2 and OH intensities and their respective temperatures). It was found that the major wave periodicity of around 2 h duration is present in all the four parameters. Our analyses also reveal that the range of periods in O2 and OH intensities and temperatures is 11 to 24 and 20 to 60 min, respectively. Periods less than 15 min were not present in the temperatures but were prevalent in both emission intensities. No seasonal dependence was found in either the wave periodicities or the number of their occurrence.

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