Research Article
Features of Quiet-time Magnetic Field and Simple Approach to Estimate the Variability Strength of Equatorial Electrojet (EEJ) Current Intensity
Issue:
Volume 14, Issue 6, December 2025
Pages:
215-224
Received:
10 May 2025
Accepted:
26 May 2025
Published:
28 November 2025
Abstract: It is a widely accepted fact that the quiet-time equatorial electrojet (EEJ) is a prominent narrow band of enhanced daytime eastward current flowing basically in the ionospheric E-region within ± 3° latitude of the dip equator. Studies have shown over the years that at least two magnetic stations are required to estimate the daytime variability strength of the EEJ. One station must be situated within the EEJ strip (station whose EEJ strength is to be determined) and the other displaced just outside the EEJ influence. One of the open issues in estimating the strength of the EEJ has been the actual latitudinal distance of the off-equatorial station from the equatorial region. This has given rise to different schools of thought in estimating the variability strength of the EEJ. This paper outlined for the first time the latitudinal extent required of the off-equatorial station which is longitudinally aligned with the equatorial station and step-by-step procedure required for estimating the daytime equatorial electrojet and the latitudinal extent ideal for choosing the off-equatorial station aligned to the equatorial station. The result from this study will clarify on the latitudinal extent required for estimating the variability strength of the EEJ in the African sector and invariably provide to some extent the role of equatorial electrojet on the distribution of equatorial ionization at low latitude in this region.
Abstract: It is a widely accepted fact that the quiet-time equatorial electrojet (EEJ) is a prominent narrow band of enhanced daytime eastward current flowing basically in the ionospheric E-region within ± 3° latitude of the dip equator. Studies have shown over the years that at least two magnetic stations are required to estimate the daytime variability str...
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Research Article
Karst Regions of Montenegro and Environmental Degradation and Remediation
Milutin Ljesevic,
Ivana Medojevic*
Issue:
Volume 14, Issue 6, December 2025
Pages:
225-231
Received:
13 October 2025
Accepted:
29 October 2025
Published:
9 December 2025
Abstract: Montenegro is an area of vast mountain ridges and terrain, deep and narrow river valleys, and only a small number of low-level planes. In its total area, with just over 90% share, the area over 200 meters above sea level dominates. Hilly and mountainous areas of 200 - 1000 meters above sea level cover about 35% of the territory. The mountainous region of 1000-1500 meters above sea level covers about 45%, while the highest parts of the mountains over 1500 meters above sea level accounts for about 15% of the territory. Below 1000 m above sea level is approximately 45% of the territory, in which about 15% are areas up to 500 meters above sea level and 29% of the area of 500 - 1000 meters above sea level. The territory of over 1700 meters above sea level qualifies as a very high mountain, and thus, in terms of the development of restrictive category area covers about 8.5% of the area. Karst in Montenegro covers more than 75%. Here, deep karst (Holokarst) is represented, followed by Jure-type karst, and shallow karst is the least present, with about 12% of total karst. Karst is most stronlgly pronounced in the mountainous area from Orjen via Lovcen to Rumija. High mountain karst covers the Central Zone of Montenegro, and shallow karst is represented in the northeastern zone towards the Serbian border.
Abstract: Montenegro is an area of vast mountain ridges and terrain, deep and narrow river valleys, and only a small number of low-level planes. In its total area, with just over 90% share, the area over 200 meters above sea level dominates. Hilly and mountainous areas of 200 - 1000 meters above sea level cover about 35% of the territory. The mountainous reg...
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Research Article
Observing Source Distributions, Interannual Variability and Transport Pathways of NOx over India During 2003-2011 Using SCIAMACHY
Issue:
Volume 14, Issue 6, December 2025
Pages:
232-238
Received:
6 September 2025
Accepted:
23 October 2025
Published:
11 December 2025
DOI:
10.11648/j.earth.20251406.13
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Abstract: The combustion of fuels, and biomass and certain industrial activities release highly toxic air pollutants in the natural environment. Nitrogen dioxide (NO2) is also an important trace gas pollutant affecting the climate. In India air pollution is monitored by various government organizations with innovative technologies developed by private sector. Such monitoring networks and tools provide necessary data to be used to frame policy decisions and communicate air quality status to the public at large. It is necessary to know the exact causes and factors responsible for air pollution in India due to certain activities as mentioned earlier. So that people could choose their mode to avoid or minimize the air pollution by adopting suitable actions by them. In this paper, Scanning Imaging Absorption Spectrometer for Atmospheric CartograpHY (SCIAMACHY) is used to observe tropospheric NO2 during 2003-2011 over India. The highest tropospheric NO2 concentration (153-137 µgm–3) is observed in the summer season of 2010-2011 over Northern Indo Gangetic (IG) plain. The NO2 mixing ratios at 350 hPa during November-May for 2003-2011 over Arabian Sea ranged from 200-230 µgm–3 and 90 µgm–3 over Bay of Bengal. It also observed that the NO2 mixing ratios decreased 80-110 µgm–3 over the Arabian Sea and 80 µgm–3 over the Bay of Bengal due to thunderstorms and long range transport of pollutants during monsoon season. These data may be useful for India’s National Clean Air Programme to be used for control of vehicular emissions and industrial emission.
Abstract: The combustion of fuels, and biomass and certain industrial activities release highly toxic air pollutants in the natural environment. Nitrogen dioxide (NO2) is also an important trace gas pollutant affecting the climate. In India air pollution is monitored by various government organizations with innovative technologies developed by private sector...
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Research Article
Peculiarities of Predicting Synthetic Seismograms and Accelerograms for Heterogeneous Foundation Beddings
Eduard Khachiyan*
Issue:
Volume 14, Issue 6, December 2025
Pages:
239-260
Received:
31 October 2025
Accepted:
14 November 2025
Published:
19 December 2025
DOI:
10.11648/j.earth.20251406.14
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Abstract: The article offers an improvement of the method for predicting strong ground motion displacements and accelerations, assuming that an earthquake is an instantaneous mechanical rupture of the Earth’s crust. The method uses derived theoretical formulas to calculate all three parameters of the ground motion: displacements, velocities and accelerations during strong (with magnitude M≥6.0) earthquakes for any heterogeneous (multilayer) ground beddings. The article addresses the case of heterogeneous two-layer beddings. The example provided involves the results obtained for 16 variants of two-layer heterogeneous sites in seismic categories I-IV at the magnitude M=7.0, and distance of 15 km from the expected earthquake’s rupture. A comparison of the results obtained for actual heterogeneous foundation beddings with the equivalent homogeneous beddings showed divergences of increase by 1.3-1.6 times, depending on the number of the five and three natural oscillation modes considered. Significant effects of various modes of foundation bedding natural oscillations on ground surface displacements and accelerations were identified when comparing a heterogeneous beddings to a homogeneous ones. A substantial reduction (by a factor of two or more) in the stiffness of the upper soil layer relative to the lower layer leads to a marked increase in surface ground accelerations. A recommendation is provided that the predicted values of displacements and accelerations for heterogeneous foundation beddings should be calculated with consideration of at least 5 natural oscillation modes of the ground bedding. The paper proposes a new analytical solution to the problem of an earthquake as an instantaneous mechanical rupture of the earth's crust with modified boundary and initial conditions of the problem, and also reveals the influence of the ratio of the rigidities coefficients and the geometric parameters of the layers on the amplitudes of seismograms and accelerograms on the Earth's surface.
Abstract: The article offers an improvement of the method for predicting strong ground motion displacements and accelerations, assuming that an earthquake is an instantaneous mechanical rupture of the Earth’s crust. The method uses derived theoretical formulas to calculate all three parameters of the ground motion: displacements, velocities and accelerations...
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