scholarly journals Statistical Observation of Thunderstorm-Induced Ionospheric Gravity Waves above Low-Latitude Areas in the Northern Hemisphere

2019 ◽  
Vol 11 (23) ◽  
pp. 2732 ◽  
Author(s):  
Tang ◽  
Chen ◽  
Chen ◽  
Louis
Keyword(s):  
Gravity Waves ◽  
Southern China ◽  
Concave Function ◽  
Thunderstorm Activity ◽  
Lower Atmosphere ◽  
Electron Content ◽  
Night Time ◽  
Low Latitude ◽  
Total Electron ◽  
Total Electron Content Data

Gravity waves (GWs) generated in the lower atmosphere can propagate upwards to ionospheric height. In this study, we investigated the correlation between ionospheric GWs detected by Global Navigation Satellite System (GNSS)-derived total electron content data and thunderstorm events recorded by a local lightning-detection network in the low-latitude region of Southern China during a four-year period, from 2014 to 2017. Ionospheric GWs were detected on both thunderstorm and non-thunderstorm days. Daytime ionospheric GW activity on high-thunderstorm days showed a similar convex-function-like diurnal variation to thunderstorm activity, which is different to the concave-function-like pattern on non-thunderstorm days. Daytime ionospheric GW activity on low-thunderstorm days showed an approximately linear rising trend and was of a larger magnitude than that of high-thunderstorm days, suggesting it may be mixed by non-thunderstorm origins. Night-time enhancement of ionospheric GW activity was observed on thunderstorm days but not on non-thunderstorm days. Furthermore, ionospheric GW activity on thunderstorm days showed a positive correlation to solar activity. These findings can effectively distinguish thunderstorm-related ionospheric GWs from those of non-thunderstorm origins and provide more comprehensive knowledge of thunderstorm–ionosphere coupling in low-latitude areas.

scholarly journals Observation of Ionospheric Gravity Waves Introduced by Thunderstorms in Low Latitudes China by GNSS

2021 ◽  
Vol 13 (20) ◽  
pp. 4131
Author(s):  
Tong Liu ◽  
Zhibin Yu ◽  
Zonghua Ding ◽  
Wenfeng Nie ◽  
Guochang Xu
Keyword(s):  
Gravity Waves ◽  
Propagation Speed ◽  
Satellite System ◽  
Lower Atmosphere ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Cycle Slips ◽  
Short Period ◽  
Low Latitudes

The disturbances of the ionosphere caused by thunderstorms or lightning events in the troposphere have an impact on global navigation satellite system (GNSS) signals. Gravity waves (GWs) triggered by thunderstorms are one of the main factors that drive short-period Travelling Ionospheric Disturbances (TIDs). At mid-latitudes, ionospheric GWs can be detected by GNSS signals. However, at low latitudes, the multi-variability of the ionosphere leads to difficulties in identifying GWs induced by thunderstorms through GNSS data. Though disturbances of the ionosphere during low-latitude thunderstorms have been investigated, the explicit GW observation by GNSS and its propagation pattern are still unclear. In this paper, GWs with periods from 6 to 20 min are extracted from band-pass filtered GNSS carrier phase observations without cycle-slips, and 0.2–0.8 Total Electron Content Unit (TECU) magnitude perturbations are observed when the trajectories of ionospheric pierce points fall into the perturbed region. The propagation speed of 102.6–141.3 m/s and the direction of the propagation indicate that the GWs are propagating upward from a certain thunderstorm at lower atmosphere. The composite results of disturbance magnitude, period, and propagation velocity indicate that GWs initiated by thunderstorms and propagated from the troposphere to the ionosphere are observed by GNSS for the first time in the low-latitude region.

scholarly journals Ionospheric response to total solar eclipse of 22 July 2009 in different Indian regions

2013 ◽  
Vol 31 (9) ◽  
pp. 1549-1558 ◽  
Author(s):  
S. Kumar ◽  
A. K. Singh ◽  
R. P. Singh
Keyword(s):  
Total Electron Content ◽  
Solar Eclipse ◽  
Total Solar Eclipse ◽  
Lower Atmosphere ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Total Electron ◽  
Ionospheric Response ◽  
Total Electron Content Data ◽  
Photoionization Process

Abstract. The variability of ionospheric response to the total solar eclipse of 22 July 2009 has been studied analyzing the GPS data recorded at the four Indian low-latitude stations Varanasi (100% obscuration), Kanpur (95% obscuration), Hyderabad (84% obscuration) and Bangalore (72% obscuration). The retrieved ionospheric vertical total electron content (VTEC) shows a significant reduction (reflected by all PRNs (satellites) at all stations) with a maximum of 48% at Varanasi (PRN 14), which decreases to 30% at Bangalore (PRN 14). Data from PRN 31 show a maximum of 54% at Kanpur and 26% at Hyderabad. The maximum decrement in VTEC occurs some time (2–15 min) after the maximum obscuration. The reduction in VTEC compared to the quiet mean VTEC depends on latitude as well as longitude, which also depends on the location of the satellite with respect to the solar eclipse path. The amount of reduction in VTEC decreases as the present obscuration decreases, which is directly related to the electron production by the photoionization process. The analysis of electron density height profile derived from the COSMIC (Constellation Observing System for Meteorology, Ionosphere & Climate) satellite over the Indian region shows significant reduction from 100 km altitude up to 800 km altitude with a maximum of 48% at 360 km altitude. The oscillatory nature in total electron content data at all stations is observed with different wave periods lying between 40 and 120 min, which are attributed to gravity wave effects generated in the lower atmosphere during the total solar eclipse.

scholarly journals Study of TEC, slab-thickness and neutral temperature of the thermosphere in the Indian low latitude sector

2011 ◽  
Vol 29 (9) ◽  
pp. 1635-1645 ◽  
Author(s):  
K. Venkatesh ◽  
P. V. S. Rama Rao ◽  
D. S. V. V. D. Prasad ◽  
K. Niranjan ◽  
P. L. Saranya
Keyword(s):  
Early Morning ◽  
Electron Density Profile ◽  
Slab Thickness ◽  
Electron Content ◽  
Night Time ◽  
Low Latitude ◽  
Total Electron ◽  
Equatorial Station ◽  
Ionization Density ◽  
Neutral Temperature

Abstract. The ionospheric equivalent slab-thickness is an important parameter which measures the skewness of the electron density profile of the ionosphere. In this paper, the diurnal, seasonal, day-to-day and latitudinal variations of ionospheric parameters namely total electron content (TEC), the peak ionization density of F-layer (NmF2), equivalent slab-thickness (τ) and neutral temperature (Tn) are presented. The simultaneous data of GPS-TEC and NmF2 from Trivandrum (8.47° N, 76.91° E), Waltair (17.7° N, 83.3° E) and Delhi (28.58° N, 77.21° E) are used to compute the slab-thickness (τ = TEC/NmF2) of the low sunspot period, 2004–2005. The day-time TEC values at Waltair are found to be greater than those at Trivandrum, while at Delhi the day-time TEC values are much lower compared to those at Trivandrum and Waltair. The trends of variation in the monthly mean diurnal variation of TEC and NmF2 are similar at Delhi, while they are different at Trivandrum and Waltair during the day-time. The slab-thickness (τ) has shown a pre-sunrise peak around 05:00 LT at all the three stations, except during the summer months over Delhi. A consistent secondary peak in slab-thickness around noon hours has also been observed at Trivandrum and Waltair. During equinox and winter months a large night-time enhancement in the slab-thickness (comparable to the early morning peak in slab-thickness) is observed at Delhi. The latitudinal variation of slab-thickness has shown a decrease from the equatorial station, Trivandrum to the low-mid latitude station, Delhi. The neutral temperatures (Tn) computed from the slab-thickness (τ) has shown a sharp increase around 05:00 LT over Trivandrum and Waltair. Whereas at Delhi, a double peaking around 05:00 and 23:00 LT is observed during winter and equinoctial months. The neutral temperatures computed are compare well with those of the MSIS-90 model derived temperatures.

scholarly journals Some characteristics of atmospheric gravity waves observed by radio-interferometry

1996 ◽  
Vol 14 (1) ◽  
pp. 42-58 ◽  
Author(s):  
Claude Mercier
Keyword(s):  
Gravity Waves ◽  
Horizontal Gradient ◽  
Electron Content ◽  
Radio Sources ◽  
Cosmic Radio ◽  
Night Time ◽  
Total Electron ◽  
Acoustic Gravity Waves ◽  
Atmospheric Gravity

Abstract. Observations of atmospheric acoustic-gravity waves (AGWs) are considered through their effect on the horizontal gradient G of the slant total electron content (slant TEC), which can be directly obtained from two-dimensional radio-interferometric observations of cosmic radio-sources with the Nançay radioheligraph (2.2°E, 47.3°N). Azimuths of propagation can be deduced (modulo 180°). The total database amounts to about 800 h of observations at various elevations, local time and seasons. The main results are: a) AGWs are partially directive, confirming our previous results. b) The propagation azimuths considered globally are widely scattered with a preference towards the south. c) They show a bimodal time distribution with preferential directions towards the SE during daytime and towards the SW during night-time (rather than a clockwise rotation as reported by previous authors). d) The periods are scattered but are larger during night-time than during daytime by about 60%. e) The effects observed with the solar radio-sources are significantly stronger than with other radio-sources (particularly at higher elevations), showing the role of the geometry in line of sight-integrated observations.

scholarly journals Investigation of Low Latitude Spread-F Triggered by Nighttime Medium-Scale Traveling Ionospheric Disturbance

2021 ◽  
Vol 13 (5) ◽  
pp. 945
Author(s):  
Zhongxin Deng ◽  
Rui Wang ◽  
Yi Liu ◽  
Tong Xu ◽  
Zhuangkai Wang ◽  
...  
Keyword(s):  
Ionospheric Disturbance ◽  
Phase Speed ◽  
Morphological Processing ◽  
Wave Number ◽  
Occurrence Rate ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Spread F

In the current study, we investigated the mechanism of medium-scale traveling ionospheric disturbance (MSTID) triggering spread-F in the low latitude ionosphere using ionosonde observation and Global Navigation Satellite System-Total Electron Content (GNSS-TEC) measurement. We use a series of morphological processing techniques applied to ionograms to retrieve the O-wave traces automatically. The maximum entropy method (MEM) was also utilized to obtain the propagation parameters of MSTID. Although it is widely acknowledged that MSTID is normally accompanied by polarization electric fields which can trigger Rayleigh–Taylor (RT) instability and consequently excite spread-F, our statistical analysis of 13 months of MSTID and spread-F occurrence showed that there is an inverse seasonal occurrence rate between MSTID and spread-F. Thus, we assert that only MSTID with certain properties can trigger spread-F occurrence. We also note that the MSTID at night has a high possibility to trigger spread-F. We assume that this tendency is consistent with the fact that the polarization electric field caused by MSTID is generally the main source of post-midnight F-layer instability. Moreover, after thorough investigation over the azimuth, phase speed, main frequency, and wave number over the South America region, we found that the spread-F has a tendency to be triggered by nighttime MSTID, which is generally characterized by larger ΔTEC amplitudes.

scholarly journals Comparison of seasonal and longitudinal variation of daytime MSTID activity using GPS observation and GAIA simulations

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Mani Sivakandan ◽  
Yuichi Otsuka ◽  
Priyanka Ghosh ◽  
Hiroyuki Shinagawa ◽  
Atsuki Shinbori ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Meridional Wind ◽  
Lower Atmosphere ◽  
Electron Content ◽  
Longitudinal Variation ◽  
Total Electron ◽  
Winter Peak ◽  
Density Perturbations ◽  
Two Peaks ◽  
Gps Observations

AbstractThe total electron content (TEC) data derived from the GAIA (Ground-to-topside model of Atmosphere Ionosphere for Aeronomy) is used to study the seasonal and longitudinal variation of occurrence of medium-scale traveling ionospheric disturbances (MSTIDs) during daytime (09:00–15:00 LT) for the year 2011 at eight locations in northern and southern hemispheres, and the results are compared with ground-based Global Positioning System (GPS)-TEC. To derive TEC variations caused by MSTIDs from the GAIA (GPS) data, we obtained detrended TEC by subtracting 2-h (1-h) running average from the TEC, and calculated standard deviation of the detrended TEC in 2 h (1 h). MSTID activity was defined as a ratio of the standard deviation to the averaged TEC. Both GAIA simulation and GPS observations data show that daytime MSTID activities in the northern and southern hemisphere (NH and SH) are higher in winter than in other seasons. From the GAIA simulation, the amplitude of the meridional wind variations, which could be representative of gravity waves (GWs), shows two peaks in winter and summer. The winter peak in the amplitude of the meridional wind variations coincides with the winter peak of the daytime MSTIDs, indicating that the high GW activity is responsible for the high MSTID activity. On the other hand, the MSTID activity does not increase in summer. This is because the GWs in the thermosphere propagate poleward in summer, and equatorward in winter, and the equatorward-propagating GWs cause large plasma density perturbations compared to the poleward-propagating GWs. Longitudinal variation of daytime MSTID activity in winter is seen in both hemispheres. The MSTID activity during winter in the NH is higher over Japan than USA, and the MSTID activity during winter in the SH is the highest in South America. In a nutshell, GAIA can successfully reproduce the seasonal and longitudinal variation of the daytime MSTIDs. This study confirms that GWs cause the daytime MSTIDs in GAIA and amplitude and propagation direction of the GWs control the noted seasonal variation. GW activities in the middle and lower atmosphere cause the longitudinal variation.

scholarly journals Statistical study of medium-scale traveling ionospheric disturbances in low-latitude ionosphere using an automatic algorithm

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Pin-Hsuan Cheng ◽  
Charles Lin ◽  
Yuichi Otsuka ◽  
Hanli Liu ◽  
Panthalingal Krishanunni Rajesh ◽  
...  
Keyword(s):  
Climate Model ◽  
Geomagnetic Latitude ◽  
Detection Algorithm ◽  
Support Vector ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances

AbstractThis study investigates the medium-scale traveling ionospheric disturbances (MSTIDs) statistically at the low-latitude equatorial ionization anomaly (EIA) region in the northern hemisphere. We apply the automatic detection algorithm including the three-dimensional fast Fourier transform (3-D FFT) and support vector machine (SVM) on total electron content (TEC) observations, derived from a network of ground-based global navigation satellite system (GNSS) receivers in Taiwan (14.5° N geomagnetic latitude; 32.5° inclination), to identify MSTID from other waves or irregularity features. The obtained results are analyzed statistically to examine the behavior of low-latitude MSTIDs. Statistical results indicate the following characteristics. First, the southward (equatorward) MSTIDs are observed almost every day during 0800–2100 LT in Spring and Winter. At midnight, southward MSTIDs are more discernible in Summer and majority of them are propagating from Japan to Taiwan. Second, northward (poleward) MSTIDs are more frequently detected during 1200–2100 LT in Spring and Summer with the secondary peak of occurrence between day of year (DOY) 100–140 during 0000–0300 LT. The characteristics of the MSTIDs are interpreted with additional observations from radio occultation (RO) soundings of FORMOSAT-3/COSMIC as well as modeled atmospheric waves from the high-resolution Whole Atmosphere Community Climate Model (WACCM) suggesting that the nighttime MSTIDs in Summer is likely connected to the atmospheric gravity waves (AGWs).

scholarly journals Evidence of gravity waves into the atmosphere during the March 2006 total solar eclipse

2007 ◽  
Vol 7 (18) ◽  
pp. 4943-4951 ◽  
Author(s):  
C. S. Zerefos ◽  
E. Gerasopoulos ◽  
I. Tsagouri ◽  
B. E. Psiloglou ◽  
A. Belehaki ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Electron Density ◽  
Gravity Waves ◽  
Solar Eclipse ◽  
Stratospheric Ozone ◽  
Thermal Fluctuations ◽  
Ozone Layer ◽  
Total Solar Eclipse ◽  
Electron Content ◽  
Total Electron

Abstract. This study aims at providing experimental evidence, to support the hypothesis according to which the movement of the moon's shadow sweeping the ozone layer at supersonic speed, during a solar eclipse, creates gravity waves in the atmosphere. An experiment was conducted to study eclipse induced thermal fluctuations in the ozone layer (via measurements of total ozone column, ozone photolysis rates and UV irradiance), the ionosphere (Ionosonde Total Electron Content – ITEC, peak electron density height – hmF2), and the troposphere (temperature, relative humidity), before, during and after the total solar eclipse of 29 March 2006. We found the existence of eclipse induced dominant oscillations in the parameters related to the ozone layer and the ionosphere, with periods ranging between 30–40 min. Cross-spectrum analyses resulted to statistically significant square coherences between the observed oscillations, strengthening thermal stratospheric ozone forcing as the main mechanism for GWs. Additional support for a source below the ionosphere was provided by the amplitude of the oscillations in the ionospheric electron density, which increased upwards from 160 to 220 km height. Even though similar oscillations were shown in surface temperature and relative humidity data, no clear evidence for tropospheric influence could be derived from this study, due to the modest amplitude of these waves and the manifold rationale inside the boundary layer.

scholarly journals Case study on total electron content enhancements at low latitudes during low geomagnetic activities before the storms

2008 ◽  
Vol 26 (4) ◽  
pp. 893-903 ◽  
Author(s):  
◽  
◽  
◽  
Keyword(s):  
Total Electron Content ◽  
Geomagnetic Activity ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Defense Meteorological Satellite Program ◽  
Low Latitudes ◽  
Global Ionospheric Maps ◽  
Geomagnetic Activities

Abstract. Sometimes the ionospheric total electron content (TEC) is significantly enhanced during low geomagnetic activities before storms. In this article, we investigate the characteristics of those interesting TEC enhancements using regional and global TEC data. We analyzed the low-latitude TEC enhancement events that occurred around longitude 120° E on 10 February 2004, 21 January 2004, and 4 March 2001, respectively. The TEC data are derived from regional Global Positioning System (GPS) observations in the Asia/Australia sector as well as global ionospheric maps (GIMs) produced by Jet Propulsion Laboratory (JPL). Strong enhancements under low geomagnetic activity before the storms are simultaneously presented at low latitudes in the Asia/Australia sector in regional TEC and JPL GIMs. These TEC enhancements are shown to be regional events with longitudinal and latitudinal extent. The regions of TEC enhancements during these events are confined at narrow longitude ranges around longitude 120° E. The latitudinal belts of maxima of enhancements locate around the northern and southern equatorial ionization anomaly (EIA) crests, which are consistent with those low-latitude events presented by Liu et al. (2008). During the 4 March 2001 event, the total plasma density Ni observed by the Defense Meteorological Satellite Program (DMSP) spacecraft F13 at 840 km altitude are of considerably higher values on 4 March than on the previous day in the TEC enhanced regions. Some TEC enhancement events are possibly due to contributions from auroral/magnetospheric origins; while there are also quasi-periodic enhancement events not related to geomagnetic activity and associated probably with planetary wave type oscillations (e.g. the 6 January 1998 event). Further investigation is warrented to identify/separate contributions from possible sources.

scholarly journals Assessing the performance of a Northeast Asia Japan-cantered 3-D ionosphere specification technique during the 2015 St. Patrick’s day solar storm

2021 ◽  
Author(s):  
Nicholas Ssessanga ◽  
Mamoru Yamamoto ◽  
Susumu Saito
Keyword(s):  
Northeast Asia ◽  
Three Dimensional ◽  
Satellite System ◽  
Electron Content ◽  
Potential Candidate ◽  
Storm Events ◽  
Total Electron ◽  
Total Electron Content Data ◽  
Swarm Satellites ◽  
Solar Storm

Abstract This paper demonstrates and assesses the capability of the advanced three- dimensional (3-D) ionosphere tomography technique, during severe conditions. The study area is northeast Asia and quasi-Japan-centred. Reconstructions are based on Total electron content data from a dense ground-based global navigation satellite system receiver network and parameters from operational ionosondes. We used observations from ionosondes, Swarm satellites and radio occultation (RO) to assess the 3-D picture. Specifically, we focus on St. Patrick’s day solar storm (17–19 March 2015), the most intense in solar cycle 24. During this event, the energy ingested into the ionosphere resulted in Dst and Kp and reaching values ~-223 nT and 8, respectively, and the region of interest, the East Asian sector, was characterized by a ~ 60% reduction in electron densities. Results show that the reconstructed densities follow the physical dynamics previously discussed in earlier publications about storm events. Moreover, even when ionosonde data were not available, the technique could still provide a consistent picture of the ionosphere vertical structure. Furthermore, analyses show that there is a profound agreement between the RO profiles/in-situ densities and the reconstructions. Therefore, the technique is a potential candidate for applications that are sensitive to ionospheric corrections.

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