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Features of horizontal magnetic field intensity over northern island of Malaysia


Abbas, M and Abidin, ZZ and Jusoh, MH and Bolaji, OS and Yoshikawa, A, Features of horizontal magnetic field intensity over northern island of Malaysia, Indian Journal of Physics, 93, (10) pp. 1247-1257. ISSN 0973-1458 (2019) [Refereed Article]

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Copyright 2019 IACS

DOI: doi:10.1007/s12648-019-01388-9


This study utilized magnetic field records of the horizontal component obtained from magnetic data acquisition system at northern island of Malaysia to delineate the diurnal variations of SqH and their monthly mean MSqH for a period of 4 years. The results show that for the entire period of study, the daytime SqH amplitudes increase from ∼20 to ∼160 nT and their MSqH amplitudes increased from ∼40 to about 135 nT in 2008 to 2013, respectively. These variabilities of SqH and MSqH reached peak amplitudes between 10:00 and 12:00 LT hrs. The standard deviation fairly responds to the daily variability of SqH with a phase shift in January 2008 and 2013 which may likely have connection to the sudden stratospheric warming event that occurred in these months. We observed the extension of eastward field that continued beyond the sunset (18:00 LT) hours is more prevalent with higher magnitudes during the deep minimum solar activity and the probable causes are discussed. The observed counter equatorial electrojet associated with late reversal of night-time westward electric field (WEF) shows inverse relationship with increasing solar activity and those that are not associated to late reversal of night-time WEF seems to indicate linear relationship exception of deep minimum solar activity year (2008). We also observed a gradual shift of ECEJ to the morning sector with increasing solar activity. Throughout the years, days with stronger morning counter equatorial electrojet magnitudes generally weaken the expected strong eastward current and shifted its peak to earlier local time. The annual and seasonal variations of SqH show semiannual variation with equinoctial maxima and solstitial minima. About 40% of the SqH shows positive night-time to pre-sunrise variations which suggest the existence of weak electric currents not necessarily of ionospheric origin with appreciable influence at this longitude sector. The extension of eastward field beyond the sunset hours suggests likely modification of the evening side ionosphere over this region.

Item Details

Item Type:Refereed Article
Keywords:ionosphere, solar quiet field, counter equatorial electrojet, electric field
Research Division:Physical Sciences
Research Group:Space sciences
Research Field:Mesospheric, thermospheric, ionospheric and magnetospheric physics
Objective Division:Environmental Management
Objective Group:Air quality, atmosphere and weather
Objective Field:Atmospheric processes and dynamics
UTAS Author:Bolaji, OS (Dr Olawale Bolaji)
ID Code:140021
Year Published:2019
Deposited By:Physics
Deposited On:2020-07-22
Last Modified:2020-08-24

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