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 Modification of the low-latitude ionosphere before the 26 December 2004 Indonesian earthquake

2006 ◽  
Vol 6 (5) ◽  
pp. 817-823 ◽  
Author(s):  
I. E. Zakharenkova ◽  
A. Krankowski ◽  
I. I. Shagimuratov
Keyword(s):  
Electron Content ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Total Electron ◽  
Ionospheric Effects ◽  
Earthquake Preparation ◽  
Low Latitude Ionosphere ◽  
Positive Effect ◽  
Possible Cause ◽  
Gps Observations

Abstract. This paper investigates the features of pre-earthquake ionospheric anomalies in the total electron content (TEC) data obtained on the basis of regular GPS observations from the IGS network. For the analysis of the ionospheric effects of the 26 December 2004 Indonesian earthquake, global TEC maps were used. The possible influence of the earthquake preparation processes on the main low-latitude ionosphere peculiarity – the equatorial anomaly – is discussed. Analysis of the TEC maps has shown that modification of the equatorial anomaly occurred a few days before the earthquake. For 2 days prior to the event, a positive effect was observed in the daytime amplification of the equatorial anomaly. Maximal enhancement in the crests reached 20 TECU (50–60%) relative to the non-disturbed state. In previous days, during the evening and night hours (local time), a specific transformation of the TEC distribution had taken place. This modification took the shape of a double-crest structure with a trough near the epicenter, though usually in this time the restored normal latitudinal distribution with a maximum near the magnetic equator is observed. It is assumed that anomalous electric field generated in the earthquake preparation zone could cause a near-natural "fountain-effect" phenomenon and might be a possible cause of the observed ionospheric anomaly.

Analysis of Plasma Bubble Signatures in Total Electron Content Maps of the Low-Latitude Ionosphere: A Simplified Methodology

2020 ◽  
Vol 41 (4) ◽  
pp. 897-931 ◽  
Author(s):  
César Buchile Abud de Oliveira ◽  
Teddy Modesto Surco Espejo ◽  
Alison Moraes ◽  
Emanoel Costa ◽  
Jonas Sousasantos ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Plasma Bubble ◽  
Low Latitude ◽  
Total Electron ◽  
Low Latitude Ionosphere

scholarly journals Observations in equatorial anomaly region of total electron content enhancements and depletions

2005 ◽  
Vol 23 (7) ◽  
pp. 2449-2456 ◽  
Author(s):  
N. Dashora ◽  
R. Pandey
Keyword(s):  
Total Electron Content ◽  
Scintillation Index ◽  
Electron Content ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Total Electron ◽  
First Results ◽  
Spread F ◽  
New Feature ◽  
Low Latitude Ionosphere

Abstract. A GSV 4004A GPS receiver has been operational near the crest of the equatorial anomaly at Udaipur, India for some time now. The receiver provides the line-of-sight total electron content (TEC), the phase and amplitude scintillation index, σφ and S4, respectively. This paper presents the first results on the nighttime TEC depletions associated with the equatorial spread F in the Indian zone. The TEC depletions are found to be very well correlated with the increased S4 index. A new feature of low-latitude TEC is also reported, concerning the observation of isolated and localized TEC enhancements in the nighttime low-latitude ionosphere. The TEC enhancements are not correlated with the S4 index. The TEC enhancements have also been observed along with the TEC depletions. The TEC enhancements have been interpreted as the manifestation of the plasma density enhancements reported by Le et al. (2003). Keywords. Ionosphere (Equatorial ionosphere; Ionospheric irregularities)

scholarly journals Storm-time total electron content and its response to penetration electric fields over South America

2011 ◽  
Vol 29 (10) ◽  
pp. 1765-1778 ◽  
Author(s):  
P. M. de Siqueira ◽  
E. R. de Paula ◽  
M. T. A. H. Muella ◽  
L. F. C. Rezende ◽  
M. A. Abdu ◽  
...  
Keyword(s):  
South America ◽  
Total Electron Content ◽  
Electric Fields ◽  
Equatorial Region ◽  
Electron Content ◽  
The South ◽  
Low Latitude ◽  
Total Electron ◽  
Vertical Drift ◽  
Magnetometer Data

Abstract. In this work the response of the ionosphere due to the severe magnetic storm of 7–10 November 2004 is investigated by analyzing GPS Total Electron Content (TEC) maps constructed for the South America sector. In order to verify the disturbed zonal electric fields in South America during the superstorm, ionospheric vertical drift data obtained from modeling results are used in the analysis. The vertical drifts were inferred from ΔH magnetometer data (Jicamarca-Piura) following the methodology presented by Anderson et al. (2004). Also used were vertical drifts measured by the Jicamarca ISR. Data from a digisonde located at São Luís, Brazil (2.33° S, 44.2° W, dip latitude 0.25°) are presented to complement the Jicamarca equatorial data. Penetration electric fields were observed by the comparison between the equatorial vertical drifts and the Interplanetary Electric Field (IEF). The TEC maps obtained from GPS data reflect the ionospheric response over the South America low-latitude and equatorial region. They reveal unexpected plasma distributions and TEC levels during the main phase of the superstorm on 7 November, which is coincident with the local post-sunset hours. At this time an increase in the pre-reversal enhancement was expected to develop the Equatorial Ionization Anomaly (EIA) but we observed the absence of EIA. The results also reveal well known characteristics of the plasma distributions on 8, 9, and 10 November. The emphasized features are the expansion and intensification of EIA due to prompt penetration electric fields on 9 November and the inhibition of EIA during post-sunset hours on 7, 8, and 10 November. One important result is that the TEC maps provided a bi-dimensional view of the ionospheric changes offering a spatial description of the electrodynamics involved, which is an advantage over TEC measured by isolated GPS receivers.

scholarly journals Wavenumber-4 patterns of the total electron content over the low latitude ionosphere

2008 ◽  
Vol 35 (12) ◽  
pp. n/a-n/a ◽  
Author(s):  
W. Wan ◽  
L. Liu ◽  
X. Pi ◽  
M.-L. Zhang ◽  
B. Ning ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Low Latitude Ionosphere

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 An additional layer in the low-latitude ionosphere in Indian longitudes: Total electron content observations and modeling

2007 ◽  
Vol 112 (A6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Smitha V. Thampi ◽  
N. Balan ◽  
Sudha Ravindran ◽  
Tarun Kumar Pant ◽  
C. V. Devasia ◽  
...  
Keyword(s):  
Total Electron Content ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Additional Layer ◽  
Low Latitude Ionosphere

scholarly journals Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone

2009 ◽  
Vol 27 (5) ◽  
pp. 1803-1820 ◽  
Author(s):  
N. Dashora ◽  
S. Sharma ◽  
R. S. Dabas ◽  
S. Alex ◽  
R. Pandey
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Geomagnetic Storm ◽  
High Latitude ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
H Index ◽  
The Mean ◽  
Low Latitude Ionosphere

Abstract. Results pertaining to the response of the equatorial and low latitude ionosphere to a major geomagnetic storm that occurred on 15 May 2005 are presented. These results are also the first from the Indian zone in terms of (i) GPS derived total electron content (TEC) variations following the storm (ii) Local low latitude electrodynamics response to penetration of high latitude convection electric field (iii) effect of storm induced traveling atmospheric disturbances (TAD's) on GPS-TEC in equatorial ionization anomaly (EIA) zone. Data set comprising of ionospheric TEC obtained from GPS measurements, ionograms from an EIA zone station, New Delhi (Geog. Lat. 28.42° N, Geog. Long. 77.21° E), ground based magnetometers in equatorial and low latitude stations and solar wind data obtained from Advanced Composition Explorer (ACE) has been used in the present study. GPS receivers located at Udaipur (Geog. Lat. 24.73° N, Geog. Long. 73.73° E) and Hyderabad (Geog. Lat. 17.33° N, Geog. Long. 78.47° E) have been used for wider spatial coverage in the Indian zone. Storm induced features in vertical TEC (VTEC) have been obtained comparing them with the mean VTEC of quiet days. Variations in solar wind parameters, as obtained from ACE and in the SYM-H index, indicate that the storm commenced on 15 May 2005 at 02:39 UT. The main phase of the storm commenced at 06:00 UT on 15 May with a sudden southward turning of the Z-component of interplanetary magnetic field (IMF-Bz) and subsequent decrease in SYM-H index. The dawn-to-dusk convection electric field of high latitude origin penetrated to low and equatorial latitudes simultaneously as corroborated by the magnetometer data from the Indian zone. Subsequent northward turning of the IMF-Bz, and the penetration of the dusk-to-dawn electric field over the dip equator is also discernible. Response of the low latitude ionosphere to this storm may be characterized in terms of (i) enhanced background level of VTEC as compared to the mean VTEC, (ii) peaks in VTEC and foF2 within two hours of prompt penetration of electric field and (iii) wave-like modulations in VTEC and sudden enhancement in hmF2 within 4–5 h in to the storm. These features have been explained in terms of the modified fountain effect, local low latitude electrodynamic response to penetration electric field and the TIDs, respectively. The study reveals a strong positive ionospheric storm in the Indian zone on 15 May 2005. Consequences of such major ionospheric storms on the systems that use satellite based navigation solutions in low latitude, are also discussed.

scholarly journals Investigation of the response time of the equatorial ionosphere in context of the equatorial electrojet and equatorial ionization anomaly

2011 ◽  
Vol 29 (7) ◽  
pp. 1267-1275 ◽  
Author(s):  
L. Jose ◽  
S. Ravindran ◽  
C. Vineeth ◽  
T. K. Pant ◽  
S. Alex
Keyword(s):  
Time Delay ◽  
Response Time ◽  
Large Scale ◽  
Equatorial Electrojet ◽  
Equatorial Ionosphere ◽  
Electron Content ◽  
Low Latitude ◽  
Total Electron ◽  
Equatorial Ionization Anomaly ◽  
Low Latitude Ionosphere

Abstract. Equatorial Electrojet (EEJ) and Equatorial Ionization Anomaly (EIA) are two large-scale processes in the equatorial/low latitude ionosphere, driven primarily by the eastward electric field during daytime. In the present paper we investigate the correlation between the Integrated EEJ strength (IEEJ) and the EIA parameters like the total electron content at the northern crest, location of crest in Magnetic latitude and strength of the EIA for the Indian sector. A good correlation has been observed between the IEEJ and EIA when a time delay is introduced between IEEJ and EIA parameters. This time delay is regarded as the response time of equatorial ionosphere in context of the evolution of EIA vis-à-vis EEJ. Further, a seasonal variation in the time delay has been observed, which is believed to be due to changes in thermospheric wind. Using the response time and the linear relationship obtained, the possibility of near-real time prediction of EIA parameters has been attempted and found that the prediction holds well during the geomagnetically quiet periods. The paper discusses these aspects in detail.

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