JGR:Space physics

Syndicate content Wiley: Journal of Geophysical Research: Space Physics: Table of Contents
Table of Contents for Journal of Geophysical Research: Space Physics. List of articles from both the latest and EarlyView issues.
Updated: 1 day 19 hours ago

Statistical Analysis of Mercury's Magnetotail Lobe Field Using MESSENGER Observations

Mon, 02/05/2024 - 11:34
Abstract

The magnetotail lobe region at Mercury is characterized by low plasma density and low magnetic field variability compared to the nightside magnetosheath and central plasma sheet. At Mercury, as well as other planets, lobe magnetic fields play a crucial role in storing and releasing magnetic flux in response to changing upstream solar wind conditions such as interplanetary magnetic field (IMF) orientation and solar wind dynamic pressure (P dyn ). This makes the region significant for studying the magnetospheric interaction with the intense solar wind conditions at Mercury's orbit. Here, we identify and analyze magnetotail lobe observations made by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft during its 4 years orbital phase. We empirically determined a set of criteria using magnetometer (MAG) and the Fast Imaging Plasma Spectrometer instruments onboard MESSENGER to identify lobe magnetic field intervals. From 3,332 MESSENGER orbits, we identify 1,242 lobe field intervals. We derive an expression for the average lobe magnetic field strength in nanotesla with respect to radial distance downtail: B lobe (r) = (135 ± 8) * r (−2.1±0.3) + (31 ± 8). The lobe magnetic field exhibits both small-scale (∼3 min) and orbit-to-orbit (∼8–12 hr) variability in magnetic field strength compared to this averaged field strength expression. The orbit-to-orbit variability in lobe field strength is not significantly correlated with estimated IMF orientation, but is directly correlated with P dyn . Thus, our findings provide evidence for the pressure balance between the inward facing P dyn on the nightside magnetopause and the outward facing magnetic pressure supplied by the lobes.

Seasonal and Interannual Variations of Global Tides in the Mesosphere and Lower Thermosphere Neutral Winds: I. Diurnal Tides

Mon, 02/05/2024 - 08:00
Abstract

In the mesosphere and lower thermosphere, diurnal tides are responsible for the dynamics and structures at low latitudes since they have largest amplitudes there. Based on the 20-year (2002−2021) observations from Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics Doppler interferometer (TIDI), we investigate the seasonal variations of three diurnal tidal components (DW1, DE3, DW2), and their responses to stratospheric quasi-biennial oscillation (SQBO) and solar cycle globally. The results show that: (a) DW1, DE3 and DW2 show prominent semiannual (SAO) and annual oscillations (AO) in their peak regions where the ratio of their annual mean amplitude to their maximum annual mean amplitude is larger than 0.8. DW1 also exhibit strong terannual oscillations (TAO) especially in meridional wind. (b) The responses of the amplitudes of seasonal variations of DW1, DE3 and DW2 to SQBO and solar cycle are comparable in magnitude to those of their annual mean amplitudes (for response to solar cycle, even stronger in some cases), and thus cannot be neglected. (c) In their respective peak regions, the responses of annual mean amplitudes of these diurnal tidal components to SQBO are uniformly positive except DW2, and their responses to solar cycle are uniformly negative. For these diurnal tides, the amplitudes of the dominant seasonal variations exhibit consistent response patterns with those of annual means to the SQBO/solar cycle. (d) Empirical formulas are given, which well describe the seasonal and interannual variations of dominant diurnal tidal components in their peak regions.

Response Time of Joule Heating Rate and Nitric Oxide Cooling Emission During Geomagnetic Storms: Correlated Ground‐Based and Satellite Observations

Fri, 02/02/2024 - 17:34
Abstract

Joule heating is the primary source of the high latitude thermospheric energy dissipation during geomagnetic storm period. The nitric oxide (NO) emission at 5.3 μm accounts for the majority of Joule heating energy due to its radiative nature. It is the dominating cooling agent above 100 km that effectively regulates the thermospheric temperature. We studied the relationship between the response time of NO cooling emission and Joule heating rate during geomagnetic storm periods by using the NO emission observations by Sounding of Atmosphere using Broadband Emission Radiometry (SABER) onboard NASA’s Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite and the Joule heating rate measured by the European incoherent scatter (EISCAT) radar over Tromsø (geographic:69.59°N, 19.22°E), Norway, and the thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM) simulation. We selected seven geomagnetic storms during which there were continuous measurements of the Pederson conductivity and electric fields when the TIMED/SABER satellite was in the northview mode. The TIEGCM gives a fair description of NO cooling. However, it was found that the Joule heating rates obtained with the TIEGCM often do not show good agreement with those from EISCAT observations. The Joule heating rate peaks with 3–7 hr of storm' onset. The NO cooling flux takes longer time to respond to the energy input during storm period. The fastest response of the NO cooling emission to the Joule heating rate is found during the strongest storm. The weakest storm does not have the longest response time. No correlation between the response time of NO cooling flux with respect to the Joule heating rate and storm’s intensity was observed.

The Medium Energy Electron Telescope (MEET): Geant4‐Based Instrument Design and Analysis

Thu, 02/01/2024 - 10:20
Abstract

While the recent Van Allen Probes mission has provided a wealth of trapped particle measurements, questions still arise from analysis of their data. In particular, 10–100s of keV electrons exhibit dynamics not well understood with current data. Injections of 33–80 keV electrons can occur during both storm and quiet times as shown by Van Allen Probes data. However, due to the Probes' orbit, they can not distinguish precipitation during these events, necessary to quantify injection rates. Analysis of a Low Earth Orbit (LEO) mission measuring these electron populations found enhancements not explained with current injection sources. Future measurements including the quasi-trapped and precipitating populations are necessary to resolve these dynamics. We present the Medium Energy Electron Telescope to resolve these uncertainties surrounding 10–100s of keV electrons in the inner belt. This solid-state particle telescope is optimized for these measurements in the high-flux inner belt environment, with flight heritage from prior instruments. However, novel instrument design is required to measure these populations at fine energy resolution and fit the instrument into a 1U volume, including that of the detectors, electronics, instrument housing, and collimator components. The design is guided by Geant4 analysis and consideration for expected fluxes using the AE9 and AP9 models for a LEO mission and associated tradeoffs are discussed. We develop 59 energy channels with fine nominal resolution (<20%) for 30–800 keV electrons and show proton measurement capabilities for 1.1–>60 MeV populations. Instrument saturation and proton contamination are quantified by analysis of the instrument's response.

On the Linkage Between Daytime E Region Field‐Aligned Irregularities and Sporadic E Layer at Low Latitude

Thu, 02/01/2024 - 10:03
Abstract

We investigate the generation of low latitude daytime E region field-aligned irregularities (FAIs) and focus on whether the FAIs are exclusively linked with sporadic E (Es) and whether the FAIs are driven by wind-driven gradient-drift instability (GDI). For this investigation, we use observations of FAIs made by the 30 MHz Gadanki Ionospheric Radar Interferometer (GIRI) and Es made by the DPS-4D digital ionosonde, both collocated at Gadanki. We have also examined simultaneous GIRI and Ionospheric Connection Explorer wind observations to substantiate our results. Results show that daytime E region FAIs are closely linked with Es activity and FAIs are not formed when Es is absent. FAIs are formed when blanketing frequency of Es (fbEs) exceeds frequency of the E layer. Both signal-to-noise ratio (SNR) and spectral width of the FAIs echoes display close relationship with top frequency of Es (ftEs). Further, SNR and spectral width of the FAIs echoes display a near-linear relationship with minimum deviation when Es activity is moderate and show dispersion from near-linear relationship when Es activity is strong. Zonal drift of the FAIs are predominantly eastward displaying both positive and negative vertical shear. Results also show that Es activity in terms of fbEs and ftEs is found to be closely related to the vertical shear in the zonal drift of the FAIs. Considering the height region of FAIs being highly collisional, we argue that zonal drifts are dominated by zonal wind and vertical shear in the zonal neutral wind is responsible for the formation/maintenance of Es layer and the eastward neutral wind is primarily responsible for the generation of the FAIs through the GDI.

The Magnetopause Deformation Indicated by Fast Cold Ion Motion

Thu, 02/01/2024 - 09:49
Abstract

The magnetopause deformation due to the upstream magnetosheath pressure perturbations is important to understand the solar wind-magnetosphere coupling process, but how to identify such events from in situ spacecraft observations is still challenging. In this study, we investigate magnetopause crossing events with fast-moving cold ions in the magnetosphere from Magnetospheric Multiscale observations, and find when fast-moving cold ions are present at the magnetopause, they are closely associated with the magnetopause deformation, which is featured by fast magnetopause motion and significant magnetopause normal deflection from model predictions. Therefore, fast-moving cold ions can be a useful indicator to search for magnetopause deformation events. By integrating the cold ion speed, the inferred magnetopause deformation amplitude varies from 0.1 to 2.0 RE. Further statistics indicate that such magnetopause deformation events prefer to occur under quasi-radial interplanetary magnetic field and fast solar wind conditions, suggesting high-speed magnetosheath jets could be one direct cause of magnetopause deformations.

Non‐Thermal Oxygen Escape on Mars in the Presence of Gravity Waves

Thu, 02/01/2024 - 09:15
Abstract

Extensive measurements made over the past two decades have indicated the widespread and frequent occurrence of gravity waves in the atmosphere of Mars. Gravity waves are able to significantly modify the atmospheric structure and potentially affect atmospheric escape. This study is devoted to examining the hot O escape variability on Mars in the presence of gravity waves with the aid of the Wentzel–Kramers–Brillouin approximation and the multi collision model as well as the multi-instrument MAVEN data set. Our calculations suggest that the hot O escape probability tends to be enhanced or suppressed in the presence of gravity waves near the Martian exobase and the impacts vary substantially with the ejection angle and nascent energy of hot O, and gravity wave characteristics. Further study indicates that although gravity waves play a negligible role in the averaged hot O escape probability, they are able to enhance hot O escape flux by 20% via altering the hot O production rate rather. Since gravity waves are omnipresent on any planetary body with a permanent atmosphere, they are expected to affect the non-thermal escape on solar system and extrasolar bodies.

Statistical Study on the Azimuthal Mode Number of Pc5 ULF Wave in the Inner Magnetosphere

Tue, 01/30/2024 - 21:53
Abstract

The azimuthal mode number, m, of ultra-low frequency (ULF) waves is a significant contributing factor for radiation belt electron energization, because it determines the conditions for resonant interaction between waves and particles. Based on multi-point magnetic field measurements of GOES satellites from January to September of 2011, we statistically analyze the distributions of the characteristics of m of Pc5 ULF waves. In the dayside, the local peaks in the distributions of wave power spectra density locate at ∼10 and ∼13 MLT for m < 0 (westward propagation) and m > 0 (eastward propagation) waves respectively, suggesting the waves generally propagate anti-sunward. In the nightside, the local peaks are at 22–23 MLT for both m < 0 and m > 0 waves, suggesting possible relation to substorm activities. Further investigation shows that, with increasing solar wind activities, the enhancements of dayside peaks are primarily contributed by |m| ≤ 3 waves, whereas the enhancements of nightside peak are contributed by both |m| ≤ 3 and |m| > 3 waves. With increasing AE index, the enhancements are more significant for the nightside peaks comparing to dayside peaks, and for |m| > 3 waves comparing to |m| ≤ 3 waves. The results of this study provide inputs for further investigation on the radial diffusion coefficient of radiation belt electrons with considering mode number information.

Localized Hybrid Simulation of Martian Crustal Magnetic Cusp Regions: Vertical Electric Potential Drop and Plasma Dynamics

Tue, 01/30/2024 - 21:33
Abstract

The localized crustal magnetic fields of Mars play an important role in the planet’s ionosphere-solar wind interaction. Various physical processes in the induced magnetosphere, such as particle precipitation, field-aligned currents, and ion outflow, are usually associated with the crustal magnetic cusp regions, where field lines are mostly vertical and open to space. Due to the small spatial scale (a few hundred km) of the Martian crustal magnetic cusps, localized models with high spatial resolutions and ion kinetics are needed to understand the physical processes. We adapt the simulation platform HYB developed at the Finnish Meteorological Institute to a moderately strong magnetic cusp above the Martian exobase with a 2-D simulation domain assuming periodic boundary conditions on the third dimension. Two plasma sources are included in the simulation: hot protons from the induced magnetosphere and cold heavy ions (O+) from the ionosphere. Our model results can qualitatively reproduce the vertical electric potential drop, particle transport, and field aligned current in the cusp region. The vertical electric potential is built up mostly by the Hall electric field as a result of the separation between ion and electron fluxes of the downward plasma flow. By varying the model inputs, we found that the vertical potential drop depends on ionospheric ion density and magnetic field strength. These results tell us that energy is transferred from magnetospheric plasma to ionospheric plasma through the vertical electric potential buildup in magnetic cusps and how this process may affect electron precipitation, ion escape, and ionosphere conditions at Mars.

Issue Information

Tue, 01/30/2024 - 11:38

No abstract is available for this article.

Commencement and Interruption of Relativistic Electron Dropout in the Heart of the Outer Radiation Belt Induced by a Magnetic Cloud Event

Sun, 01/28/2024 - 20:03
Abstract

We analyze and discuss the commencement and interruption of the relativistic electron dropout in the heart of the outer radiation belt (L* = 4–5) induced by a typical magnetic cloud (MC) event. This MC event impinged the Earth’s magnetosphere on 31 October 2012 and caused a moderate geomagnetic storm with a special prolonged initial phase lasting for >13 hr. The relativistic electrons phase space density (PSD) dropout commenced at L* > 5 during the initial phase. The PSD dropout penetrated deep beyond the heart of the radiation belt (reached L* < 4) at the onset of the main phase, while it was partially enhanced with a local PSD maximum around L* = 4.5, thus causing the interruption of the PSD dropout. The dropout became pronounced at L* > ∼4.7 while the local PSD maximum was maintained throughout the main phase. During the recovery phase, the dropout totally disappeared at L* < 5.5 with relativistic electron PSD gradually recovering to pre-event level or higher. Further investigations on solar wind parameters and plasma waves give evidence that (a) persistent high dynamic pressure and the triggered Ultra-Low Frequency waves contribute to the dropout of electrons to interplanetary space during the initial phase and the onset of the main phase; (b) local acceleration by chorus waves during the main phase and recovery phase could explain the interruption of the dropout. Our study underlines the persistent high dynamic pressure competing with intense chorus waves in triggering the commencement and interruption of the relativistic electrons PSD dropout in the heart of the outer radiation belt.

A Statistical Study of Quasi‐Electrostatic Magnetosonic Waves

Sun, 01/28/2024 - 19:53
Abstract

Quasi-electrostatic magnetosonic (QEMS) waves have been recently reported, referring to a distinct type of magnetosonic (MS) wave with only the electric fluctuation being detectable. Here a statistical study of QEMS waves is carried out with the Van Allen Probes data. 83% of 40,466 QEMS samples are observed with plasma density n e  < 20 cm−3, and intense QEMS waves tend to appear in the lower density region. QEMS waves become strong in the case of more pronounced proton rings around 10 keV and larger suprathermal proton populations. High occurrence rates and large amplitudes of QEMS waves are confined near the dayside equator (|MLAT| < 3°). The wave frequencies are typically slightly below the nth harmonic of proton gyro-frequency, and the wave intensity gradually decreases with an increasing harmonic number n. Our results further demonstrate that low plasma densities and abundant suprathermal protons are beneficial for intensifying QEMS waves and contribute to the establishment of QEMS wave model.

Characterizing Radiation‐Belt Energetic Electron Precipitation Spectra: A Comparison of Quasi‐Linear Diffusion Theory With In Situ Measurements

Sun, 01/28/2024 - 07:00
Abstract

High energy electron precipitation from the Earth's radiation belts is important for loss from the radiation belts and atmospheric chemistry. We follow up investigations presented in Reidy et al. (2021, https://doi.org/10.1029/2020ja028410) where precipitating flux is calculated inside the field of view of the POES T0 detector using quasi-linear theory and pitch angle diffusion coefficients (D αα ) from the British Antarctic Survey (BAS). These results showed good agreements at >30 keV for L* >5 on the dawnside but the flux were too low at higher energies. We have investigated the effect of changing parameters in the calculation of the precipitating flux to improve the results for the higher energies using comparisons of in situ flux and cold plasma measurements from GOES-15 and RBSP. We find that the strength of the diffusion coefficients rather than the shape of the source spectrum has the biggest effect on the calculated precipitation. In particular we find decreasing the cold plasma density used in the calculation of D αα increases the diffusion and hence the precipitation at the loss cone for the higher energies, improving our results. The method of calculating D αα is also examined, comparing co-located rather than averaged RBSP measurements. We find that the method itself has minimal effect but using RBSP derived D αα improved our results over using D αα calculated using the entire BAS wave data base; this is potentially due to better measurements of the cold plasma density from RBSP than the other spacecraft included in the BAS wave data base (e.g., THEMIS).

Rapid Relativistic Electron Enhancements and Associated Particle Injections: A Multi‐Spacecraft Statistical Study

Sun, 01/28/2024 - 06:50
Abstract

Rapid relativistic electron enhancements (REE) in the outer radiation belt have long been an intriguing phenomenon for space weather. In this study, we investigate rapid REE from October 2012 to December 2017 using multi-spacecraft observations. A total of 27 rapid REE events are identified from the Van Allen Probes (RBSP) measurements with a 5 times increase of MeV electrons at the center of the outer radiation belt (L = 4.5–5.5) in a half RBSP orbit (∼4.5 hr). All REE events are found to be in association with pulse-like injections of MeV electrons in the outer radiation belt. Electron fluxes in each injection at L ∼ 6.6 and the overall electron enhancements at L = 4.5–5.5 are quantified. The 500 keV and 0.8–1 MeV electron fluxes are correlated in injections and in overall enhancements. Substorm strength is more intense before/during the REE than intervals after the REE. The statistical study suggests that substorm-associated MeV electron injections are highly correlated with rapid REE in the outer radiation belt.

Influence of the Jovian Current Sheet Models on the Mapping of the UV Auroral Footprints of Io, Europa, and Ganymede

Sun, 01/28/2024 - 06:44
Abstract

The in situ characterization of moon-magnetosphere interactions at Jupiter and the mapping of moon auroral footpaths require accurate global models of the magnetospheric magnetic field. In this study, we compare the ability of two widely-used current sheet models, Khurana-2005 (KK2005) and Connerney-2020 (CON2020) combined with the most recent internal magnetic field model of Jupiter (JRM33) to match representative Galileo and Juno measurements acquired at low, medium, and high latitudes. With the adjustments of the KK2005 model to JRM33, we show that in the outer and middle magnetosphere (R > 15R J), JRM33 + KK2005 is found to be the best model to reproduce the magnetic field observations of Galileo and Juno as it accounts for local time effects. JRM33 + CON2020 gives the most accurate representation of the inner magnetosphere. This finding is drawn from comparisons with Juno in situ magnetic field measurements and confirmed by contrasting the timing of the crossings of the Io, Europa, and Ganymede flux tubes identified in the Juno particles data with the two model estimates. JRM33 + CON2020 also maps more accurately the UV auroral footpath of Io, Europa, and Ganymede observed by Juno than JRM33 + KK2005. The JRM33 + KK2005 model predicts a local time asymmetry in position of the moons' footprints, which is however not detected in Juno's UV measurements. This could indicate that local time effects on the magnetic field are marginal at the orbital locations of Io, Europa, and Ganymede. Finally, the accuracy of the models and their predictions as a function of hemisphere, local time, and longitude is explored.

Automatic Encoding of Unlabeled Two Dimensional Data Enabling Similarity Searches: Electron Diffusion Regions and Auroral Arcs

Sun, 01/28/2024 - 06:34
Abstract

Critically important phenomena in Earth’s magnetosphere often occur briefly, or in small spatial regions. These processes are sampled with orbiting spacecraft or by fixed ground observatories and so rarely appear in data. Identifying such intervals can be an incredibly time consuming task. We apply a novel, powerful method by which two dimensional data can be automatically processed and embeddings created that contain key features of the data. The distance between embedding vectors serves as a measure of similarity. We apply the state-of-the-art method to two example datasets: MMS electron velocity distributions and auroral all sky images. We show that the technique creates embeddings that group together visually similar observations. When provided with novel example images the method correctly identifies similar intervals: when provided with an electron distribution sampled during an encounter with an electron diffusion region the method recovers similar distributions obtained during two other known diffusion region encounters. Similarly, when provided with an interesting auroral structure the method highlights the same structure observed from an adjacent location and at other close time intervals. The method promises to be a useful tool to expand interesting case studies to multiple events, without requiring manual data labeling. Further, the models could be fine-tuned with relatively small set of labeled example data to perform tasks such as classification. The embeddings can also be used as input to deep learning models, providing a key intermediary step—capturing the key features within the data.

Seasonal Variations of Sq Current System in Different Longitudinal Sectors and Solar Activities

Sun, 01/28/2024 - 06:24
Abstract

Years of geomagnetic observatory data during the geomagnetic quiet days (Kp ≤ 3) at the low and middle dip latitudes from INTERMAGNET and SuperMAG were utilized. Seasonal models of Sq currents for two longitudinal chains at each year and under two solar activity levels (F 10.7 index are ∼75 and 125 sfu) were constructed by spherical harmonic analysis. It is found that there are significant seasonal variations of Sq currents in the Asian-Oceanian (A-O) and North-South American (N-SA) longitude sectors under different solar activities. First, the focus intensity J increases faster in local winter than in summer for both two hemispheres as solar activity strengthens. J of ionospheric currents in the northern hemisphere (NH) during local winter is higher than that in the southern hemisphere during its winter. This asymmetric activity in the N-SA chain increases with the solar activity becomes stronger. Second, with solar activity increases, the ionospheric current focus of N-SA chain in the NH shifts toward the lower latitudes during two solstices, while internal current focus of both two chains move toward the lower latitudes during the December solstice. Seasonal variations of Sq currents in the two chains exhibit longitudinal effects. With increasing solar activity, the two hemispheric focuses of the ionospheric currents in the A-O chain both move closer to the midday longitude sector, while in the N-SA chain, only the focus in the NH shifts toward noon. The results reveal details of the seasonal variations of Sq currents.

Examining the Applicability of Direct Analytic Method (DAM) to Normal Modes of Poloidal Oscillations Under Symmetric and Asymmetric Boundary Conditions

Wed, 01/24/2024 - 15:34
Abstract

A working Direct Analytic Method (DAM) model is envisaged to explain the normal modes of poloidal Alfven waves in the Earth's magnetosphere. The model solves the ideal, cold, magnetohydrodynamic (MHD) equations associated with transverse components of the magnetic perturbations in a dipolar magnetic field. DAM model is used to study the transverse poloidal waves in different regions of magnetosphere characterized by their L-value and different plasma variability. The plasma density distribution is assumed to be governed by the standard power law, 1/r m , where r is the geocentric distance of any point of interest on the field line and m is the density index. The eigen frequencies and spatial structures are obtained analytically under different ideal ionospheric boundary conditions and the results are compared with the numerical solutions to establish the validity of the model. DAM, being an analytic model, is used to explain the distinctive structural features of transverse poloidal waves which are obtained under different boundary conditions, for different density indices. Furthermore, the application of the analytic model in the computation of eigen frequency as well as plasma density is demonstrated under different observational scenario.

Statistical Characteristics of Multi‐Scale Auroral Arc Width Based on Machine Learning

Tue, 01/23/2024 - 05:34
Abstract

Arc width is important for understanding the generation mechanism of auroral arcs. However, the continuity or discreteness of the distribution of small and meso-large scale auroral arc widths has not been determined in previous studies. This study employs machine learning techniques to investigate the distribution of arc widths across multiple scales using multi-field-of-view (multi-FOV) auroral observations. Based on the 180°, 47°, and 19° auroral observations at the Antarctic Zhongshan Station from February to October 2012, the statistical results demonstrate that the auroral arc width spectrum is continuously distributed across small, meso, and large scales, suggesting that the mechanisms responsible for their generation are capable of producing arcs at all scales. Furthermore, the arc width distribution at each FOV can be well fitted with a log-normal function. We also find that the main widths observed at different FOVs depend on the spatial resolution of the instruments. Our work provides new observational evidence for the generation mechanism of auroral arcs.

The Role of Convectively‐Generated Gravity Waves in Poleward Propagation of MSTIDs Over Srinagar (34.1°N, 74.8°E)

Mon, 01/22/2024 - 11:14
Abstract

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 ∼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 ∼97 and ∼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.

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