GPS observations at quasi-conjugate points under disturbed conditions

Momani, Mohammad; Ali, Mohd; Yatim, Baharudin; Abdullah, Mardina; Misran, Norbahiah

doi:10.2478/s11600-008-0048-4

Cited by 9 publications

(4 citation statements)

References 20 publications

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“…The TEC values were corrected from the receiver and satellite biases by using the AIUB Data Center of Bern University in Switzerland (AIUB, 2000). The equivalent absolute vertical TEC, Percentage deviation of the GPS TEC and the rate of change of TEC (ROT) have been calculated using standered methods (Rashid et al, 2006;Momani et al, 2008;2010;Abdullah et al, 2009).…”

Section: Methodsmentioning

confidence: 99%

GPS Ionospheric Total Electron Content and Scintillation Measurements during the October 2003 Magnetic Storm

Momani¹

2011

American Journal of Engineering and Applied Sciences

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Problem Statement: Ionospheric scintillations, cause significant effects on satellite signals for communication and navigation in equatorial region and polar regions mainly during sever magnetic storms periods. This phenomenon is not fully understood due to few studies performed. The study investigates variability of Total Electron Content (TEC) and ionospheric scintillation during October 2003 magnetic storm over Antarctica using ground based GPS technique. Approach: The TEC/scintillation measuring system at Scott Base station, consists of Trimble TS5700 24-channel (a high-precision dual-frequency GPS receiver), a Trimble Zephyr Geodetic antenna and a notebook computer for data logging. The absolute GPS TEC was calculated from differential phase advance GPS observables (1-L2). The GPS signal-to-noise ratios (C/No) and 1/L2 carrier frequencies were employed to determine the scintillation index S 4 every 60 s, amplitude scintillation (in dB-Hz) and phase scintillation. Results: The GPS measurements during storm periods at Scott Base show pronounced phase and amplitude scintillation activities, sudden increase in TEC followed by trough-like figure depletions. The maximum value of phase scintillation during the main phase of third episode was 8.3 times the value during Sudden Storm Commencement (SSC) period. Measured amplitude scintillation and S4 index on both 1 and L2 signals are >15dB-Hz and >0.4dB-Hz respectively. Conclusion/Recommendation: The timing and intensity of TEC and scintillation measurements during the storm event were are in a good agreement with WDC measurements. For this particular event, the duration of enhanced periods were approximately 12 h while periods of TEC depletions were more than 30 h. This value implies better understanding of the polar ionospheric response to magnetic storm and eases efforts for better space weather prediction in this region.

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Section: Methodsmentioning

confidence: 99%

GPS Ionospheric Total Electron Content and Scintillation Measurements during the October 2003 Magnetic Storm

Momani¹

2011

American Journal of Engineering and Applied Sciences

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“…The mapping function is the elevation angle dependent function which represents the ratio between VTEC and STEC [22] . The equivalent VTEC, percentage deviation of the GPS TEC (ΔTEC) and the rate of change of TEC (ROT) have been calculated using the standard methods discussed in open literature [23][24][25][26] .…”

Section: Measurement Techniquementioning

confidence: 99%

Large-scale traveling ionospheric disturbances observed by GPS receivers in Antarctica

Momani

Yatim

Ali

2010

Wuhan Univ. J. Nat. Sci.

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The paper examines the propagation direction and velocity of large-scale traveling ionospheric disturbances (LSTIDs) during extreme geomagnetic storms in the 23rd solar cycle (e.g., October 2003 and November 2003 storms) using GPS observations. In the analysis, the time delay between the vertical total electron content (VTEC) structures at Scott Base, McMurdo, Davis and Casey GPS stations and the distance between these stations were the main parameters in the determination of LSTIDs propagation speed and direction. The observations during October and November 2003 storms show obvious time delay between the total electron content (TEC) enhancement signatures at these stations. The time delay suggests a movement of the ionospheric disturbances from higher to lower latitudes during the October storm with a velocity of 800-1 200 m/s and poleward propagation of LSTIDs during the November storm with a velocity of 300-400 m/s. The equatorward or poleward expansion of LSTIDs during the October and November 2003 storms is probably caused by the disturbances of the neutral temperature occurring close to the dayside convection throat or by the neutral wind oscillation induced by atmospheric gravity waves (AGW) launched from the aurora region.

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“…The TEC values were corrected from the receiver and satellite biases by using the AIUB Data Center of Bern University in Switzerland (AIUB 2005). The equivalent absolute vertical TEC, percentage deviation of the GPS TEC and the rate of change of TEC (ROT) was calculated using the standered methods discussed in Warnant and Pottiaux (2000), , Abdul Rashid et al (2006) and Momani et al (2008).…”

Section: Data Processingmentioning

confidence: 99%

ASM Sci. J., Vol. 3, No. 2, 2009

Liki

2009

ASMScJ

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First I would like to thank the Editorial Board of the ASM Sc. J. for inviting me to be their Guest Editor for this special issue of theJournal devoted to polar sciences. As the Director of the Malaysian Antarctic Research Programme (MARP) it is a pleasure to see howthe Programme has grown. When the idea of establishing the Programme was undertaken by the Task Force on Antarctic Research underthe Academy in 1998, one of the main worries of the members was the sustainability of the Programme. This sustainability is supportedon two pillars: one is the continued funding of research by the Ministry of Science, Technology and Innovation (MOSTI); and the otheris the support of the researchers participating in the programme from all the universities and research institutions in Malaysia. MARP’ssuccess is very much dependent on these two pillars and to date I have to commend MOSTI and the researchers for the support that theyhave given.In trying to develop polar research, one of the major constraints that Malaysian scientists face is the lack of local logistics support.Malaysia has no base to embark on its own scientific programme in Antarctic or the Arctic. As such, we are very much dependent on thegoodwill of our international partners. I would like to take this opportunity to thank our international partners, namely Antarctica NewZealand, Australian Antarctic Division, British Antarctic Survey, Japanese National Institute of Polar Research, Korean Polar ResearchInstitute, Instituto Antartico Argetino, Instituto Antarctico Chile, Instituto Antarctico Equador, South Africa National Antarctic Programand National Centre for Antarctic and Ocean Research of India. We are also thankful to the Scientific Committee of Antarctic Researchand Asian Forum on Polar Sciences for all the support and co-operation given to enable our scientists to embark on polar research.It is with pride that I note that our scientists and their post-graduate students have embraced our polar research initiatives withso much enthusiasm. Some spent more than two months away from their loved ones in order to undertake field work in the extremeenvironment of Antarctic. They had to assimilate different cultures and food, and for some post-graduate students the field trip was theirfirst trip overseas. However, most of them would love to be given a second and maybe a third chance to go back to Antarctic for theirfield work. MARP is lucky to have such an enthusiastic group of scientists and young researchers.However, in pursuing their love of science some have paid a higher price than others. I would like to record our condolences to thefamily of the late Omar Pozan who died while undergoing training (diving) in Tasmania for a scientific expedition.As in any scientific venture, the proof of success is in the scientific output i.e. publications and post-graduate training. In this area,MARP has been able to produce three refereed conference proceedings and a number of papers in refereed international journals suchas Polar Biology and Journal of Geophysical Research. We have trained three PhD students and there are now more than fifty postgraduates pursuing research under MARP. A testimony to this active research is that the Academy of Sciences Malaysia has kindlyundertaken to produce this special issue of their Journal devoted to polar research undertaken under the MARP and our internationalcollaborators. This issue is a demonstration of how far polar sciences in Malaysia has advanced and can be used as a milestone of ourprogress. It is my hope that R&D in Malaysian polar sciences will be further expanded and deepened so that Malaysia will be consideredas a leader in certain niche areas such as microbiology, biodiversity and tropical-polar interactions in the ocean and atmosphere. Alreadysome of our researchers are active in helping polar research developments in the field of microbiology for some of our Latin Americanpartners. We are now an active member of SCAR committee on capacity building, education and training, and helping the developingcountries in the SCAR community. I am sure this issue will not only be of interest to the Malaysian but also the international communityof polar scientists. Finally, I would like to thank again the Academy of Sciences for undertaking this special issue on Malaysian polarsciences in their prestigious Journal; acknowledge the 22 reviewers for their evaluation of the 13 articles, and Kanesan Solomalai forediting and finalizing the editorial processing of this issue.

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GPS observations at quasi-conjugate points under disturbed conditions

Cited by 9 publications

References 20 publications

GPS Ionospheric Total Electron Content and Scintillation Measurements during the October 2003 Magnetic Storm

GPS Ionospheric Total Electron Content and Scintillation Measurements during the October 2003 Magnetic Storm

Large-scale traveling ionospheric disturbances observed by GPS receivers in Antarctica

ASM Sci. J., Vol. 3, No. 2, 2009

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