We report the influence of the atmospheric gravity waves on medium scale traveling ionospheric disturbances (MSTIDs) that are observed during the month of September 2020, using an airglow imager over Srinagar, Kashmir. Several cases of nighttime MSTIDs at similar to 250 km altitude are presented which propagate either in northwestward, northward or northeastward direction. Either the phase fronts of the observed MSTIDs are not aligned in the NW-SE direction, or the MSTIDs are not propagating in the southwest direction, these are believed to be non-electrified MSTIDs which are generally associated with gravity waves (GWs). The average horizontal wavelengths of these MSTIDs range from 185 to 469 km, horizontal phase speeds of about 162-521 m/s while the time periods range from 13 to 24 min considered as very short-period ionospheric disturbances. The detection of GWs at similar to 97 and similar to 85 km heights during the nights of MSTID detection leads to the inference that there is a strong correlation between the occurrences of these MSTIDs with mesospheric GWs. By using satellite data, including INSAT-3DR and the Atmospheric Infrared Sounder, the detection of convective clouds near the locations of the imager is observed, and by utilizing the kinetic temperature data from the Sounding of the Atmosphere using Broadband Emission Radiometry satellite, the presence of GWs near the convective systems is also seen. Such GWs are also observed in the vicinity of the imager location and it is concluded that the lower atmospheric convectively-generated GWs could be a leading factor for the generation of poleward propagating MSTIDs. The atmospheric gravity waves generally impact on some specific types of disturbances in the Earth's ionosphere known as medium-scale traveling ionospheric disturbances (MSTIDs) although there are several other electrodynamic factors responsible for their generation. Using a specialized instrument called as all-sky airglow imager over an Indian subtropical region (Srinagar), we identified several instances of nighttime MSTIDs occurring at a height of similar to 250 km above the Earth's surface traveling in different directions, such as northwestward, northward, or northeastward which otherwise propagate southwestward over the Northern Hemisphere in general. So, the observed class of the MSTIDs is not consistent with the electrified ones and can instead be associated with atmospheric gravity waves (GWs). The appearance of GWs at the mesospheric heights and even in the lower atmospheric heights suggests a strong connection between the occurrence of MSTIDs and mesospheric GWs. This study used data from airglow imager, satellites like Sounding of the Atmosphere using Broadband Emission Radiometry, INSAT-3DR and Atmospheric Infrared Sounder to reveal the relationships between the ionospheric disturbances and convectively generated GWs. Hence, we concluded that GWs originating in the lower atmosphere due to convective processes play a significant role in generating poleward propagating MSTIDs which indicates that the GW propagation plays a significant role in the troposphere-ionosphere coupling. The study identifies the poleward propagating non-electrified nighttime medium scale traveling ionospheric disturbances (MSTIDs) that don't align along the typical NW-SE directionPresence of mesospheric gravity waves (GWs) during the nights of MSTID detection indicate a strong link between the GWs and non-electrified MSTIDsLower atmospheric convection believed to be a prominent factor of generation of poleward propagating MSTIDs indicative of Troposphere-Ionosphere Coupling

In this paper, we examine the role of gravity waves (GWs) generated from tropospheric convection in initiating multiple nighttime ionospheric anomalies over Srinagar, located at 34.1 °N, 74.8 °E, and 25.91 °N MLAT. Optical airglow observations during a geomagnetic quiet night (Ap=4) of 29-30 June, 2021, show the presence of plasma depletion tilted by an angle of ∼14.9 degrees from the geographic North, quasi-periodic south eastward moving wave (QPSEMW), onset of two electrified MSTIDs and generation of plasma depletion channel between two MSTID phase fronts at ∼250 km altitude. GWs originating from deep convection in troposphere are detected at ∼85 and ∼97 km altitudes in OH and 557 nm filters respectively. The GWs in both the filters are propagating northward with almost similar characteristics. The intrinsic time period and vertical wavelength of GWs is estimated to be ∼11 minutes and ∼53 km respectively. We also present the observational indications of localised upliftment of F-layer ionosphere by ∼38 km, possibly initiated by polarization electric field generated through secondary GWs. The penetration of secondary GWs, generated by the dissipation of convective GWs, beyond the altitude of 500 km is also seen. FORMOSAT-7/COSMIC-2 RO data and SAMI3 model electron density suggest the occurrence of Sporadic-E (Es) layer at around 100 km altitude, caused by the negative gradient in eastward wind.

This paper presents the novel simultaneous observations of plasma blobs, MSTIDs and plasma depletions in OI 630 nm all sky airglow images over Srinagar, India (34.1 degrees N, 74.8 degrees E) during the night of July 29, 2019, obtained using an airglow imager. Notably, the MSTID bands that followed the plasma blob interacted with a plasma depletion structure and suddenly disappeared, resulting in a reduction in the intensity of the plasma depletion. The SWARM satellite observations during the airglow observations indicated the occurrence of the plasma blob event and showed the conjugate appearance of MSTIDs in both hemispheres. The ROTI maps indicated the absence of EPBs but the occurrence of irregularities near the transition zone just before the presence of plasma blobs in airglow images and at the time of plasma irregularity detection. These observations suggest potential interactions between these phenomena, indicating that the presence of one impacts the other. This paper discusses in detail the observed ionospheric features and time evolution of the occurrences of these events, in addition to their interactions.Utilizingthe satellite observations, including SABER, INSAT-3DR and AIRS, the presence of deep convective clouds and upward propagating gravity waves near the location of the plasma blob is demonstrated, suggesting that convective-generated gravity waves could possibly trigger the formation of plasma blobs. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.

This paper reports the observation of propagating wave structures in OI 630.0 nm airglow images captured by a CCD imager at Kashmir University (KU), Srinagar, India (34.1 degrees N, 74.8 degrees E, and 25.9 degrees N magnetic latitude). These structures were detected on the night of August 17th, 2017, with an average horizontal wavelength around 330 km and average phase velocities around 92 m/s traveling in southwest (SW) direction. The SW moving wave patterns had north-west (NW) to south-east (SE) aligned phase fronts that lasted for ~150 min and had a time period of about 1 h. Based on observed parameters such as wavelength, time span, and propagating speed, these structures are categorized as nighttime medium-scale traveling ionospheric disturbances (MSTIDs). The observed southwestward movement, phase speed, horizontal wavelength and period of these nighttime MSTIDs are consistent with the existing literature. The appearance of gravity waves in the lower atmosphere during this night means that gravity waves from below, in combination with the Perkins' instability, might be responsible candidates for generation of these MSTIDs. Near midnight the MSTID bands are seen to rotate, bifurcate and some even merging with other bands giving rise to some unique Y-shaped MSTID structures-the first such results observed from this location. These structures align along North-South direction and move westward unlike the MSTID bands before midnight which move towards southwest. In addition, we also report the shrinking phenomena of the post midnight MSTID dark bands.

As a joint research collaboration between the National Atmospheric Research Laboratory (NARL), and the University of Kashmir (KU), NARL installed an all-sky airglow CCD imager (with centre wavelengths of 630 nm, 557.7 nm [2 nm band widths] and 840 nm [150 nm wide band with blocking notch at 866 nm to avoid the contamination of molecular oxygen emissions]) in the University campus in Srinagar (75°E, 34°N, geographic), Jammu and Kashmir, India (western Himalayan region). To understand the upper atmospheric dynamics and ionospheric electrodynamics and their associated physical coupling mechanisms, the imager observes airglow emissions of OH molecules (~ 85 km height; 840 nm) and atomic oxygen occurring at the heights of ~ 97 km (557.7 nm) and ~ 250 km (630 nm). Airglow observations in Kashmir commenced in the night of August 11, 2017 and the present work reports on the characteristics of first-time observation of Medium Scale Travelling Ionospheric Disturbances (MSTIDs with horizontal wavelengths of ~ 100–300 km) over Kashmir region during 20:30—22:30 IST (Indian standard time) on August 15, 2017 (India independence day). Initially, the phase front of MSTIDs was aligned along the north-west and south-east direction and moved at ~ 57 m/s towards the south-west direction and finally the westward direction by aligning along the meridian before they disappeared. Along with SAMI-3 ionospheric model simulations, simultaneous multiwavelength airglow observations indicate that secondary gravity waves generated due to dissipation of upward propagating mesospheric gravity waves in the heights of ~ 85–95 km would have contributed to the generation of MSTIDs in the F region ionospheric plasma through electrodynamical coupling between the E and F region (Perkins instability) ionosphere.

We report some ionospheric phenomena that occurred on September 23, 2019 observed by an airglow imager installed at University of Kashmir, Srinagar, India (34.08°N, 74.79°E, and 25.91°N magnetic latitude). The various phenomena observed on this night are as follows: (1) The wave-like structures near the dusk time having phase fronts aligned along Northwest to Southeast direction and moving southwestward, classified as nighttime medium-scale traveling ionospheric disturbance. (2) Simultaneous observation of northwestward-moving nighttime medium-scale traveling ionospheric disturbances and eastward-drifting plasma irregularity and (3) The westward reversal of field-aligned plasma irregularity and K-shaped depletion structure formation post-midnight. We analyze their characteristics and evolution processes in detail. The plasma irregularity seems to be the signature of locally generated plasma irregularities at low-mid-latitude transition region as the radar observations from a geomagnetic low-latitude station (Gadanki, India; 13.5°N, 79.2°E, Magnetic latitude ~ 6.5°N) do not show any signatures of equatorial plasma bubbles during this night. It is interesting to note that the westward reversal of plasma irregularity occurred even when the geomagnetic conditions were at quiet levels (Kp ~ 0 to 1+). Though the observed nighttime MSTIDs and plasma irregularity bands are two different events, yet the structures appear to interact with each other, the apparent mechanism leading to the quiet time westward reversal of plasma irregularity structures at midnight and the development of complex K-shaped depletion structure. Interaction between these phenomena and their observed characteristic features is also discussed.

We report the observation of plasma depletions/plumes in the F region ionosphere over a low to middle latitude transition region in the Indian sector. The observation of these plasma depletions is based on the data obtained in May 2019 through the all-sky airglow CCD imager installed in the campus of University of Kashmir, Srinagar (34.12 °N, 74.83 °E, magnetic latitude 25.91 °N). The depletions on the two consecutive nights of 05 and 06 May 2019 are aligned along the North-South (N-S) direction and drift westward. Several depletion bands along with some enhancement bands are seen in the 630-nm airglow images throughout the two nights. The observed structures show certain characteristics similar to Medium Scale Traveling Ionospheric Disturbances (MSTIDs) but these airglow features are not completely periodic. Further, in the observed depletion bands some East-West asymmetries are observed along with the structured tree-like branches of the airglow depletions. Some depletion bands even bifurcate leading to the inference that the structures are signatures of plasma irregularities rather than the usual MSTIDs observed in low-mid latitude transition region. The westward drift of the depletions especially during geomagnetic quiet times over this region makes this study significant since it offers a possible evidence that shows extension of spread F irregularities from the mid latitude region to the low-mid latitude transition region. In this paper, we point out some possible mechanisms related to the occurrence of plasma depletions at this region and their westward movement during geomagnetic quiet times.

Despite an important enlargement in the preceding years, the airglow observation through sky images is immobile dwarfed by two dimensional image counterparts. To lock this hole so many images toward video conversion practices have been advised. Methods relating human workers have been the majority successful but it is time consuming plus expensive. Automatic process which is typically employs a deterministic video scene model. In this trouble-free article, we describe five uncomplicated techniques. The first method is enhancement of raw airglow dark image, second one is image cropping for confiscating non sky area , in the third method removing stars from the image, and then coordinate mapping of image pixels and spatial calibration are completed in fourth method. Finally sequences of all images with capturing time are converted into video files to prepare an excellent video for observation of dynamical airglow objects.

Simultaneous wind observations from Mesosphere Stratosphere Troposphere (MST) radar collectively with Global Positioning System (GPS) radiosonde over Gadanki, covering altitude range of 3.6-20 km (January-December 2009; 365 days), divulge the propagation of lower atmospheric waves up to the ionosphere. It is combined with temperature data (20-110 km) observed from Sounding of the Atmosphere using the Broadband Emission Radiometry (SABER) instrument onboard Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, ionosonde observations, and daily Outgoing Longwave Radiation (OLR) data acquired from the National Ocean and Atmospheric Administration (NOAA; centered around Gadanki [13.5 degrees N, 79.2 degrees E]) for the same time period. Long-period oscillations with periodicities of similar to 64, similar to 32, and similar to 21 days are witnessed along with the well-known oscillations of similar to 16, similar to 6.4, and similar to 5.3 days. Most of the long-period oscillations are dominantly perceived during the summer months (April-June 2009), which can even exist up to September. These long-period oscillations are found to propagate from lower tropospheric heights up to ionospheric heights with large vertical wavelengths (similar to 300-400 km, in some cases) near to transition zones of atmospheric layers (e.g., tropopause, stratopause, and mesopause). Signatures of vertical coupling of atmosphere through large vertical wavelengths (indicating possible intraseasonal connections) is clearly observed in the equatorial electrojet current and the peak plasma frequencies of ionospheric layers (E and F regions). Noticeable reduction of the wave oscillations in spatial scale with upsurge in spatial damping is evidently visible, in the tropical stratosphere and mesosphere, which can be attributed to stratospheric ozone.

An observational evidence of medium‐scale traveling ionospheric disturbances (MSTIDs) reaching to magnetic latitude as low as ~3.5° over the Indian sector is provided for the first time based on OI 630‐nm airglow imaging observation from a low‐latitude station, Gadanki (13.5°N, 79.2°E; 6.6° magnetic latitude), on 12 January 2016. The horizontal wavelength, horizontal phase velocity, and period of the MSTID are found to be 160 ± 6 km, 138 ± 14 m/s, and 19.5 ± 3 min, respectively. These phase fronts are observed to move toward southwest with a propagation angle of ~235° ± 1° with respect to north. In addition to the MSTID, a strong quasiperiodic southward moving wave (QPSMW) from the evening to midnight interval and a small‐scale southward moving wave structure with wavelength and periodicity different from the QPSMW are also detected on the same night. Horizontal wavelength, horizontal phase velocity, and period of the QPSMW are estimated to be 367 ± 14 km, 131 ± 18 m/s, and 46.7 ± 13 min, respectively, and those of the small‐scale southward moving wave are found to be 157 ± 4 km, 121 ± 17.8 m/s, and 21.7 ± 3.4 min, respectively. Global Positioning System‐total electron content maps suggest that the weak and asymmetric equatorial ionization anomaly helped deep ingression of the MSTID on this night. The descent of the F layer seems to have caused the dissipation of the MSTID and QPSMW closer to the dip equator on this night. Therefore, the present investigation shows that the midlatitude MSTIDs can influence the F region plasma processes even over very low latitudes under favorable background conditions.

Mesoscale convection weather events, associated with deep cumulonimbus clouds transport moisture, energy and momentum to upper troposphere and lower stratosphere (UTLS), affect the energetics and general circulation of the middle atmosphere. Therefore, it is necessary to understand the atmospheric dynamics during pre-monsoon periods (when strong mesoscale convective events occur) for improving the parameterization of model physics. The present study attempts to investigate the characteristics of high-frequency gravity waves (GWs) generated over Gadanki (13.5 degrees N, 79.2 degrees E), India during one such severe convection event in the pre monsoon period. For this purpose, the Mesosphere Stratosphere Troposphere (MST) radar at Gadanki was operated continuously for the period of similar to 10 h during 27-28 May 2015. A wide spectrum of high frequency GWs with different generation mechanisms are found during this convective event whose vertical propagation characteristics fulfill the non-hydrostatic GWs dispersion relation. The temperature and wind data of ERA (ECMWF Re-Analysis)-interim reanalysis and GPS radiosonde, launched at Gadanki, are also analyzed for ten days around the event day to determine the background atmospheric thermodynamical conditions. Strong up and downdrafts are observed in the altitude range of similar to 3.6-20 km (radar limited top height); presence of which even up to similar to 20 km height is quite rare. The WRF (Weather Research and Forecasting) model simulated relative humidity on 27-28 May 2015 clearly depicts the mid-tropospheric moisture intrusion. Presence of moisture is also observed at the higher heights similar to 17-18 km which could be due to strong low level convergence leading to high divergence value of deep cumulonimbus clouds in UTLS region. Furthermore, this is supported by the Doppler Weather Radar (DWR) and simulated reflectivity of WRF model reaching the tropopause height of similar to 18 km. The altitude profiles of phase of some oscillations during convection period depict that the sources of these waves are near 20 km which is first of its kind outcome and it is corroborated with high resolution WRF model simulations.

An observational evidence of medium‐scale traveling ionospheric disturbances (MSTIDs) reaching to magnetic latitude as low as ~3.5° over the Indian sector is provided for the first time based on OI 630‐nm airglow imaging observation from a low‐latitude station, Gadanki (13.5°N, 79.2°E; 6.6° magnetic latitude), on 12 January 2016. The horizontal wavelength, horizontal phase velocity, and period of the MSTID are found to be 160 ± 6 km, 138 ± 14 m/s, and 19.5 ± 3 min, respectively. These phase fronts are observed to move toward southwest with a propagation angle of ~235° ± 1° with respect to north. In addition to the MSTID, a strong quasiperiodic southward moving wave (QPSMW) from the evening to midnight interval and a small‐scale southward moving wave structure with wavelength and periodicity different from the QPSMW are also detected on the same night. Horizontal wavelength, horizontal phase velocity, and period of the QPSMW are estimated to be 367 ± 14 km, 131 ± 18 m/s, and 46.7 ± 13 min, respectively, and those of the small‐scale southward moving wave are found to be 157 ± 4 km, 121 ± 17.8 m/s, and 21.7 ± 3.4 min, respectively. Global Positioning System‐total electron content maps suggest that the weak and asymmetric equatorial ionization anomaly helped deep ingression of the MSTID on this night. The descent of the F layer seems to have caused the dissipation of the MSTID and QPSMW closer to the dip equator on this night. Therefore, the present investigation shows that the midlatitude MSTIDs can influence the F region plasma processes even over very low latitudes under favorable background conditions.

The Number of observable facts and structures that are accessible with an airglow images which are captured by an All Sky Imager (ASI). All of these images are required to convert from the spherical coordinating system into the rectangular coordinating image system. The spatial calibration is also most important for the perfect measurement of gravity wave characteristics, plasma characteristics and OH emission parameters in the upper atmosphere, mesosphere, ionosphere study when that calibrations are used in real life dimensions. In this paper, we expressed an effective and simple technique for the coordinate mapping and the spatial calibration for accurate dimensions used in real world life and also implemented the same procedure by using Matlab R2013a. The pixel resolutions of OH image of 840 nm, a mesospheric image of 557.7 nm and ionospheric image of 630 nm are measured. These pixel resolutions are nearly same and measuring technique is very simple than other method used in the same area.

The present study primarily focused on the characteristics of the planetary scale waves in the middle atmosphere during different phases of Quasi-Biennial Oscillation (QBO), a dominant oscillation in the low-latitude stratospheric region. The temperature profiles retrieved from the Rayleigh lidar measurements have been utilized for the 11 winter periods between 1998 and 2009 over a low-latitude station, Gadanki (13.5 degrees N 79.2 degrees E). The spectral analysis of temperature anomalies indicates two dominant planetary-scale modes, namely, quasi 12-day and quasi 16-day waves. The existence of these waves in the middle atmosphere is strongly controlled by the westerly and easterly phases of QBO. For instance, the 12-day wave is mainly observed in the QBO westerly phase, while the 16-day wave peaks at two heights; 30-40 km and above 60 km with large spread in the mesosphere due to Doppler shifting in presence of westerly winds. The QBO easterly phase indicates low wave activity with 16-day wave indicating appreciable amplitudes in the upper stratosphere and mesosphere and is absent in the lower altitudes. This indicates that the 16day wave might be generated through some in-situ mechanism due to gravity breaking or instability in the mesospheric region. Moreover, the refractive index of the two dominant planetary waves are strongly negative in the easterly phase relative to the westerly phase of QBO in the lower troposphere and stratosphere. This indicates the high probability of the planetary wave vertical propagation in the westerly phase of QBO. Therefore, the presented report re-emphasizes the importance of QBO controlling the middle atmospheric dynamics through vertical propagation of planetary scale waves in low-latitudes.

The local weather and climate of the Himalayas are sensitive and interlinked with global-scale changes in climate, as the hydrology of this region is mainly governed by snow and glaciers. There are clear and strong indicators of climate change reported for the Himalayas, particularly the Jammu and Kashmir region situated in the western Himalayas. In this study, using observational data, detailed characteristics of long- and short-term as well as localized variations in temperature and precipitation are analyzed for these six meteorological stations, namely, Gulmarg, Pahalgam, Kokarnag, Qazigund, Kupwara and Srinagar during 1980–2016. All of these stations are located in Jammu and Kashmir, India. In addition to analysis of stations observations, we also utilized the dynamical downscaled simulations of WRF model and ERA-Interim (ERA-I) data for the study period. The annual and seasonal temperature and precipitation changes were analyzed by carrying out Mann–Kendall, linear regression, cumulative deviation and Student's t statistical tests. The results show an increase of 0.8 ∘C in average annual temperature over 37 years (from 1980 to 2016) with higher increase in maximum temperature (0.97 ∘C) compared to minimum temperature (0.76 ∘C). Analyses of annual mean temperature at all the stations reveal that the high-altitude stations of Pahalgam (1.13 ∘C) and Gulmarg (1.04 ∘C) exhibit a steep increase and statistically significant trends. The overall precipitation and temperature patterns in the valley show significant decreases and increases in the annual rainfall and temperature respectively. Seasonal analyses show significant increasing trends in the winter and spring temperatures at all stations, with prominent decreases in spring precipitation. In the present study, the observed long-term trends in temperature (∘Cyear-1) and precipitation (mm year−1) along with their respective standard errors during 1980–2016 are as follows: (i) 0.05 (0.01) and −16.7 (6.3) for Gulmarg, (ii) 0.04 (0.01) and −6.6 (2.9) for Srinagar, (iii) 0.04 (0.01) and −0.69 (4.79) for Kokarnag, (iv) 0.04 (0.01) and −0.13 (3.95) for Pahalgam, (v) 0.034 (0.01) and −5.5 (3.6) for Kupwara, and (vi) 0.01 (0.01) and −7.96 (4.5) for Qazigund. The present study also reveals that variation in temperature and precipitation during winter (December–March) has a close association with the North Atlantic Oscillation (NAO). Further, the observed temperature data (monthly averaged data for 1980–2016) at all the stations show a good correlation of 0.86 with the results of WRF and therefore the model downscaled simulations are considered a valid scientific tool for the studies of climate change in this region. Though the correlation between WRF model and observed precipitation is significantly strong, the WRF model significantly underestimates the rainfall amount, which necessitates the need for the sensitivity study of the model using the various microphysical parameterization schemes. The potential vorticities in the upper troposphere are obtained from ERA-I over the Jammu and Kashmir region and indicate that the extreme weather event of September 2014 occurred due to breaking of intense atmospheric Rossby wave activity over Kashmir. As the wave could transport a large amount of water vapor from both the Bay of Bengal and Arabian Sea and dump them over the Kashmir region through wave breaking, it probably resulted in the historical devastating flooding of the whole Kashmir valley in the first week of September 2014. This was accompanied by extreme rainfall events measuring more than 620 mm in some parts of the Pir Panjal range in the south Kashmir.

An observational evidence of medium‐scale traveling ionospheric disturbances (MSTIDs) reaching to magnetic latitude as low as ~3.5° over the Indian sector is provided for the first time based on OI 630‐nm airglow imaging observation from a low‐latitude station, Gadanki (13.5°N, 79.2°E; 6.6° magnetic latitude), on 12 January 2016. The horizontal wavelength, horizontal phase velocity, and period of the MSTID are found to be 160 ± 6 km, 138 ± 14 m/s, and 19.5 ± 3 min, respectively. These phase fronts are observed to move toward southwest with a propagation angle of ~235° ± 1° with respect to north. In addition to the MSTID, a strong quasiperiodic southward moving wave (QPSMW) from the evening to midnight interval and a small‐scale southward moving wave structure with wavelength and periodicity different from the QPSMW are also detected on the same night. Horizontal wavelength, horizontal phase velocity, and period of the QPSMW are estimated to be 367 ± 14 km, 131 ± 18 m/s, and 46.7 ± 13 min, respectively, and those of the small‐scale southward moving wave are found to be 157 ± 4 km, 121 ± 17.8 m/s, and 21.7 ± 3.4 min, respectively. Global Positioning System‐total electron content maps suggest that the weak and asymmetric equatorial ionization anomaly helped deep ingression of the MSTID on this night. The descent of the F layer seems to have caused the dissipation of the MSTID and QPSMW closer to the dip equator on this night. Therefore, the present investigation shows that the midlatitude MSTIDs can influence the F region plasma processes even over very low latitudes under favorable background conditions.

An observational evidence of medium-scale traveling ionospheric disturbances (MSTIDs) reaching to magnetic latitude as low as similar to 3.5 degrees over the Indian sector is provided for the first time based on OI 630-nm airglow imaging observation from a low-latitude station, Gadanki (13.5 degrees N, 79.2 degrees E; 6.6 degrees magnetic latitude), on 12 January 2016. The horizontal wavelength, horizontal phase velocity, and period of the MSTID are found to be 160 +/- 6 km, 138 +/- 14 m/s, and 19.5 +/- 3 min, respectively. These phase fronts are observed to move toward southwest with a propagation angle of similar to 235 degrees +/- 1 degrees with respect to north. In addition to the MSTID, a strong quasiperiodic southward moving wave (QPSMW) from the evening to midnight interval and a small-scale southward moving wave structure with wavelength and periodicity different from the QPSMW are also detected on the same night. Horizontal wavelength, horizontal phase velocity, and period of the QPSMW are estimated to be 367 +/- 14 km, 131 +/- 18 m/s, and 46.7 +/- 13 min, respectively, and those of the small-scale southward moving wave are found to be 157 +/- 4 km, 121 +/- 17.8 m/s, and 21.7 +/- 3.4 min, respectively. Global Positioning System-total electron content maps suggest that the weak and asymmetric equatorial ionization anomaly helped deep ingression of the MSTID on this night. The descent of the F layer seems to have caused the dissipation of the MSTID and QPSMW closer to the dip equator on this night. Therefore, the present investigation shows that the midlatitude MSTIDs can influence the F region plasma processes even over very low latitudes under favorable background conditions. Plain Language Summary Medium-scale traveling ionospheric disturbances (MSTIDs) generated in the midlatitude are found to propagate toward the equator. While crossing the equatorial ionization anomaly crest region most of these structures dissipate due to ion drag. A deep ingression of the MSTID to a very low geomagnetic latitude (near to the geomagnetic equator) over the Indian sector is noted during the descending phase of the 24th solar cycle. Weak and asymmetric equatorial ionization anomaly formation is believed to support the deep ingression processes. On the observational night quasiperiodic southward moving waves and a small-scale southward moving wave signature are also observed in addition with the MSTID. The dissipation of all these features is possibly due to existence of the midnight pressure bulge. Present study provides an observational evidence of the midlatitude MSTID propagation into the low latitudes and their interaction with the low-latitude ionospheric/thermospheric processes, for example, midnight pressure bulge.

High intensity amplitudes due to stars introduced background noise in sky images captured by an All sky airglow imager at Gadanki, india(13.50N ,79.20E) . The maped are a of sky overhead at certain wavelengths of airglow emissions to determine characterics of atmospheric gravity waves and also to observe the attributes of ionosphere plasma irregularities/bubles in the upper atmosphere. Even though many investigators used various techniques for eliminating stars from airglow images some stars are still remain.To rise above this a new method for removing stars completely using morphological operations is projeced in this paper for better parametric evolution.