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 Diurnal and Seasonal Variations of Equivalent Slab thickness over Low and Mid Latitude Regions

2019 ◽  
Vol 16 (1) ◽  
pp. 64-78
Author(s):  
Temitope Pascal Owolabi ◽  
Emmanuel Ariyibi ◽  
Olatunbosun Lilian ◽  
Ayomide O Olabode
Keyword(s):  
Complex Dynamics ◽  
Electron Density Profile ◽  
Slab Thickness ◽  
Electron Content ◽  
Low Latitude ◽  
Ionospheric Electron Density ◽  
Total Electron ◽  
Maximum Value ◽  
Latitude Station ◽  
Monthly Variations

The equivalent slab-thickness  is very important in the study of the complex dynamics of the ionosphere as a result of its ability to determine the skewness of the ionospheric electron density profile. This study involves the day to day and monthly variations of . Ionosonde  (FoF2) and Total electron content (TEC) data at the low latitude station of Sao Luis (Glat 2.60° S, Glong 315.80° E and Mlat 6.05° N and Mlong 28.40° E), Brazil and mid latitude station of Chilton (Glat 51.50° N, Glong 359.40° E and Mlat 53.35° N and Mlong 84.34° E), United Kingdom from January 2013 to December 2015 were used in the study of  . For Sao Luis station, the diurnal pattern for the different days are characterized by day time (08:00 – 16:00 UT) high values and nighttime (20:00 – 04:00 UT) low values; however, Chilton shows signatures, such as day time low values and nighttime high values. Also, the daytime values (~600 km) of  for the low latitude station (Sao Luis) is more than double the mid latitude station (Chilton) maximum value (~235 km) over the years considered. The monthly variation of  also indicate a seasonal variation with highest daytime values (400 km) during winter months and lowest (below 300 km) during summer months for the low latitude station (Sao Luis). However, the nighttime values are of the same order (about 200 km) for the low latitude station (Sao Luis). Also, highest daytime values (above 250 km) are observed during summer months and the nighttime values are below 200 km over the years for the mid latitude station (Chilton).

scholarly journals Obtaining Ionospheric Conditions according to Data of Navigation Satellites

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Olga Maltseva ◽  
Natalia Mozhaeva
Keyword(s):  
Critical Frequency ◽  
Bench Mark ◽  
Slab Thickness ◽  
Electron Content ◽  
Efficiency Coefficient ◽  
Low Latitude ◽  
Total Electron ◽  
Average Value ◽  
Middle Latitudes ◽  
Critical Frequency Fof2

Defining ionospheric conditions, the deviation of the observational value of the total electron content TEC(obs), measured by means of navigation satellites, from a median is a bench mark. According to more than 40 ionospheric stations during April 2014 it is shown that synchronism of change of deviations of TEC and critical frequency foF2 of the ionosphere is kept under quiet and moderate disturbed conditions. This fact allows to use a median of the equivalent slab thicknessτ(med) as a reliable calibration factor to calculate foF2 from TEC(obs). The efficiency coefficient of joint use ofτ(med) and TEC(obs) changes from 1.5 to 4 with average value 2.2 across the globe. The highest coefficient corresponds to middle latitudes, however the estimations obtained for high- and low-latitude areas indicate possibility to useτ(med) and TEC(obs) in these areas.

scholarly journals Climatology of ionospheric slab thickness

2004 ◽  
Vol 22 (1) ◽  
pp. 25-33 ◽  
Author(s):  
B. Jayachandran ◽  
T. N. Krishnankutty ◽  
T. L. Gulyaeva
Keyword(s):  
High Latitude ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Magnetic Activity ◽  
Slab Thickness ◽  
Electron Content ◽  
Night Time ◽  
Total Electron ◽  
Ionospheric Physics ◽  
F Region

Abstract. The ionospheric slab thickness τ defined as a ratio of the total electron content (TEC) to the F-region peak electron density (NmF2) has been analysed during the solar maximum (1981) and minimum (1985) phases of an intense, the 21st, solar cycle. Hourly values of TEC and NmF2 collected at Hawaii (low-latitude), Boulder (mid-latitude) and Goosebay (high-latitude) are used in the study. Climatology of the slab thickness is described by the diurnal, seasonal, solar and magnetic activity variations of τ for the different latitude zones. It is found that, for magnetically quiet days of solar maximum, increased ionization of NmF2 and TEC during the daytime is accompanied by an increased thickness of the ionosphere compared to the night-time for non-auroral latitudes. However, the reverse is found to be true during the solar minimum compensating TEC against a weak night-time ionization of NmF2. For the high-latitude the night-time slab thickness is higher compared to the daytime for both the solar phases. Ratios of daily peak to minimum values of slab thickness vary from 1.3 to 3.75 with the peaks of τ often observed at pre-sunrise and post-sunset hours. The average night-to-day ratios of τ vary from 0.68 to 2.23. The day-to-day variability of τ, expressed in percentage standard deviation, varies from 10% by day (equinox, high-latitude) to 67% by night (summer, mid-latitude) during solar minimum and from 10% by day (winter and equinox, mid-latitude) to 56% by night (equinox, high-latitude) during solar maximum. A comprehensive review of slab thickness related literature is given in the paper. Key words. Ionospheric physics

scholarly journals On the response of the equatorial and low latitude ionospheric regions in the Indian sector to the large magnetic disturbance of 29 October 2003

2009 ◽  
Vol 27 (6) ◽  
pp. 2539-2544 ◽  
Author(s):  
G. Manju ◽  
T. Kumar Pant ◽  
S. Ravindran ◽  
R. Sridharan
Keyword(s):  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Equatorial Station ◽  
Neutral Winds ◽  
Storm Sudden Commencement ◽  
Magnetometer Data ◽  
Ionospheric Height ◽  
Electric Field Penetration ◽  
Low Latitude Ionosphere

Abstract. The present paper investigates the response of the equatorial and low latitude ionosphere over the Indian longitudes to the events on 29 October 2003 using ionosonde data at Trivandrum (8.5° N (0.5° N geomagnetic), 77° E) and SHAR (13.7° N (5.7° N geomagnetic), 80.2° E), ground-based magnetometer data from Trivandrum and Total Electron Content (TEC) derived from GPS data at the locations of Ahmedabad (23° N (15° N geomagnetic), 72° E), Jodhpur (26.3° N (18.3° N geomagnetic), 73° E) and Delhi (28° N (20° N geomagnetic), 77° E). Following the storm sudden commencement, the TEC at all the three stations showed an overall enhancement in association with episodes of inter-planetary electric field penetration. Interestingly, real ionospheric height profiles derived using the ionosonde data at both Trivandrum and SHAR showed significant short-term excursions and recoveries. In the post noon sector, these features are more pronounced over SHAR, an off equatorial station, than those over Trivandrum indicating the increased effects of neutral winds.

scholarly journals Global equivalent slab thickness model of the Earth’s ionosphere

2021 ◽  
Author(s):  
Norbert Jakowski ◽  
Mohammed Mainul Hoque
Keyword(s):  
Solar Activity ◽  
Electron Density ◽  
Total Electron Content ◽  
Local Time ◽  
Slab Thickness ◽  
Electron Content ◽  
Night Time ◽  
Total Electron ◽  
First Time ◽  
Model Approach

The shape of the vertical electron density profile is a result of production, loss and transportation of plasma in the Earth’s ionosphere. Therefore, the equivalent slab thickness of the ionosphere that characterizes the width of vertical electron density profiles is an important parameter for a better understanding of ionospheric processes under regular as well as under perturbed conditions. The equivalent slab thickness is defined by the ratio of the vertical total electron content over the peak electron density and is therefore easy to compute by utilizing powerful data sources nowadays available thanks to ground and space based GNSS techniques. Here we use peak electron density data from three low earth orbiting (LEO) satellite missions, namely CHAMP, GRACE and FORMOSAT-3/COSMIC, as well as total electron content data obtained from numerous GNSS ground stations. For the first time, we present a global model of the equivalent slab thickness (Neustrelitz equivalent Slab Thickness Model – NSTM). The model approach is similar to a family of former model approaches successfully applied for Total Electron Content (TEC), peak electron density NmF2 and corresponding height hmF2 at DLR. The model description focuses on an overall view of the behaviour of the equivalent slab thickness as a function of local time, season, geographic/geomagnetic location and solar activity on a global scale. In conclusion, the model agrees quite well with the overall observation data within a RMS range of 70 km. There is generally a good correlation with solar heat input that varies with local time, season and level of solar activity. However, under non-equilibrium conditions, plasma transport processes dominate the behaviour of the equivalent slab thickness. It is assumed that night-time plasmasphere-ionosphere coupling causes enhanced equivalent slab thickness values like the pre-sunrise enhancement. The overall fit provides consistent results with the mid-latitude bulge (MLB) of the equivalent slab thickness, described for the first time in this paper. Furthermore, the model recreates quite well ionospheric anomalies such as the Night-time Winter Anomaly (NWA) which is closely related to the Mid-latitude Summer Night Anomaly (MSNA) like the Weddell Sea Anomaly (WSA) and Okhotsk Sea Anomaly (OSA). Further model improvements can be achieved by using an extended model approach and considering the particular geomagnetic field structure.

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 Climatology of the ionospheric slab thickness along the longitude of 120° E in China and its adjacent region during the solar minimum years of 2007–2009

2015 ◽  
Vol 33 (10) ◽  
pp. 1311-1319 ◽  
Author(s):  
Z. Huang ◽  
H. Yuan
Keyword(s):  
Electron Density ◽  
Solar Minimum ◽  
Slab Thickness ◽  
Electron Content ◽  
Radio Waves ◽  
Signal Delay ◽  
Dual Frequency ◽  
Adjacent Region ◽  
Night Time ◽  
Total Electron

Abstract. The ionospheric slab thickness is defined as the ratio of the total electron content (TEC) to the ionospheric F2 layer peak electron density (NmF2). In this study, the slab thickness is determined by measuring the ionospheric TEC from dual-frequency Global Positioning System (GPS) data and the NmF2 from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC). A statistical analysis of the diurnal, seasonal and spatial variation in the ionospheric slab thickness is presented along the longitude of 120° E in China and its adjacent region during the recent solar minimum phase (2007–2009). The diurnal ratio, defined as the maximum slab thickness to the minimum slab thickness, and the night-to-day ratio, defined as the slab thickness during daytime to the slab thickness during night-time, are both analysed. The results show that the TEC of the northern crest is greater in winter than in summer, whereas NmF2 is greater in summer than in winter. A pronounced peak of slab thickness occurs during the post-midnight (00:00–04:00 LT) period, when the peak electron density is at the lowest level. A large diurnal ratio exists at the equatorial ionization anomaly, and a large night-to-day ratio occurs near the equatorial latitudes and mid- to high latitudes. It is found that the behaviours of the slab thickness and the F2 peak altitude are well correlated at the latitudes of 30–50° N and during the period of 10:00–16:00 LT. This current study is useful for improvement of the regional model and accurate calculation of the signal delay of radio waves propagating through the ionosphere.

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 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 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.

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