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Browsing Observatories_and_Data_Analysis by Author "Alex, S."

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The activities at world data center for geomagnetism Mumbai, India

Doiphode, M.G.; Nimje, R.; Alex, S. (2013)

The World Data Centre for Geomagnetism, Mumbai has functioned as a division of the Indian Institute of Geomagnetism, Navi Mumbai since its full fledged activities commenced in 1991 in coordination with the International ...
Analysis of vertical drifts in the post sunset equatorial F-region during geomagnetically quiet and disturbed periods

Simi, K.G.; Vineeth, C.; Pant, T.K.; Alex, S. (2013)

This paper reports the HF Doppler Radar measured post sunset F-region vertical drift (Vd) over Trivandrum (8.5°N, 77°E, 0.5°N dip latitude) during quiet and disturbed periods. In general, Vd showed significant day-to-day ...
Association between equatorial and tropical spread-F

Alex, S.; Chandra, H.; Rastogi, R.G. (2003)

Comparative study of spread-F is made from the quarter-hourly ionograms at Huancayo, near the magnetic equator and Bogota, close to the anomaly crest region in the same longitude sector. The occurrence of equatorial spread-F ...
Can a nightside geomagnetic Delta H observed at the equator manifest a penetration electric field?

Wei, Y.; Fraenz, M.; Dubinin, E.; He, M.; Ren, Z.; Zhao, B.; Liu, J.; Wan, W.; Yumoto, K.; Watari, S.; Alex, S. (2013)

A prompt penetration electric field (PPEF) usually manifests itself in the form of an equatorial ionospheric electric field being in correlation with a solar wind electric field. Due to the strong Cowling conductivity, a ...
Complexities in the variation of declination component (D) of the geomagnetic field in the Indian region

Alex, S.; Jadhav, L.; Rao, D.R.K. (1992)
Corotating interaction region (CIR) induced magnetic storms during solar minimum and their effects on low-latitude geomagnetic field and ionosphere

Veenadhari, B.; Kumar, Sandeep; Tulasiram, S.; Singh, Rajesh; Alex, S. (2012)

The corotating interaction region (CIR) induced magnetic storms which occurred during solar minimum are investigated to study their effects on equatorial and low-latitude ionosphere and geomagnetic field at Indian sector. ...
Counter equatorial electrojet: Analysis of the variability in daytime mesopause temperature and winds

Vineeth, C.; Pant, T.K.; Kumar, K.K.; Jose, Lijo; Sumod, S.G.; Alex, S. (2012)

This paper reports the variation of the daytime zonal wind and OH temperature at upper mesospheric altitudes during the afternoon equatorial counter electrojet (CEJ) events over a geomagnetic dip equatorial station, ...
Day-to-day variability in the occurrence characteristics of Sq focus during d-months and its association with diurnal changes in the Declination component

Alex, S.; Jadhav, Madhavi (2007)

Scrutiny of the geomagnetic observations of the Declination component “D” from equatorial and low-latitude locations in the Indian longitude revealed anomalous variations during d-months. Examination of the Quiet day (Ap≤7) ...
Equatorial electrojet characteristics and its longitudinal dependence

Alex, S.; Mukherjee, S.; Jadhav, Madhavi; Rao, D.R.K. (2000)
Evolution of equatorial irregularities under varying electrodynamical conditions: A multitechnique case study from Indian longitude zone

Hajra, R.; Chakraborty, S.K.; Mazumdar, S.; Alex, S. (2012)

A comprehensive multitechnique study on the postsunset evolutions of equatorial ionization anomaly (EIA) and equatorial plasma density irregularities in the context of the varying electrodynamical conditions under normal ...
Geomagnetic signatures during the intense geomagnetic storms of 29 October and 20 November 2003

Alex, S.; Mukherjee, S.; Lakhina, G.S. (2006)

Solar cycle 23 in its declining phase witnessed the most pronounced space weather events during October–November 2003. A series of powerful solar flares and associated geoeffective Coronal Mass Ejections (CMEs) travelling ...
Geomagnetic storm characteristics under varied interplanetary conditions

Rawat, Rahul; Alex, S.; Lakhina, G.S. (2007)

Solar cycle-23 witnessed many successive intense X-ray solar flares and coronal mass ejections (CME) during the peak activity period, as well as in the descending phase of the cycle. Some of these emissions had large solar ...
An intense SFE & SSC event in geomagnetic H,Y,Z fields at the Indian chain of observatories

Rastogi, R.G.; Rao, D.R.K.; Alex, S.; Pathan, B.M. (1997)

Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent ...
Investigation of the response of equatorial MLTI region during a partial solar eclipse through ground-based daytime optical technique

Vineeth, C.; Pant, T.K.; Thampi, Smitha V.; Sridharan, R.; Ravindran, Sudha; Devasia, C.V.; Kumar, K. Kishore; Alex, S. (2008)

[1] First experimental evidence for solar eclipse induced changes in the equatorial mesopause and the thermosphere ionosphere regions using daytime optical photometer is presented. The photometer was operated in scanning ...
Investigation of the response time of the equatorial ionosphere in context of the equatorial electrojet and equatorial ionization anomaly

Jose, L.; Ravindran, S.; Vineeth, C.; Pant, T.K.; Alex, S. (2011)

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 ...
Ionospheric current systems on days of low equatorial ΔH

Alex, S.; Kadam, B.D.; Rao, D.R.K. (1998)

Examination of the day to day variability in the equatorial electrojet strength, in the Indian region, shows that certain quiet days (Ap ≤ 6) are characterized by an abnormally low magnitude of the jet strength. Geomagnetic ...
Ionospheric response to a geomagnetic storm during November 8–10, 2004

Simi, K.G.; Manju, G.; Haridas, M. K. Madhav; Nayar, S. R. Prabhakaran; Pant, Tarun Kumar; Alex, S. (2013)

This paper investigates the response of the equatorial, and near equatorial, ionosphere to geomagnetic disturbances during the period November 8–10, 2004. Ionosonde data from Trivandrum (8.5°N 77°E and dip 0.5°N) and SHAR ...
Large enhancements in low latitude total electron content during 15 May 2005 geomagnetic storm in Indian zone

Dashora, N.; Sharma, S.; Dabas, R.S.; Alex, S.; Pandey, R. (2009)

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 ...
Local time dependence of the equatorial counter electrojet effect in a narrow longitudinal belt

Alex, S.; Mukherjee, S. (2001)

Irregular occurrence characteristics of the equatorial counter electrojet phenomena at different longitudinal zones are investigated using the magnetic data of the horizontal component ‘H’ at the two equatorial stations ...
Low latitude geomagnetic signatures following two major solar energetic particle events at different phases of solar cycle-23

Rawat, Rahul; Alex, S.; Lakhina, G.S. (2006)

Occurrence of transient astrophysical phenomena is well known to enhance greatly during the solar maximum period. Acceleration of energetic particles takes place in abundance at heliosphere by different transient processes, ...

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