Monitoring of Sudden Ionospheric Disturbance (SID) with 0–50 kHz Frequency Receiver over Aliero, Nigeria
Joshua Benjamin Wisdom,
Suleiman Muhammed Yushau,
Gwani Muhammad,
Umar Muhammad Kangiwa,
Abbas Mustapha,
Oladipo Mumin Olatunji
Issue:
Volume 9, Issue 3, September 2021
Pages:
37-44
Received:
3 September 2021
Accepted:
18 September 2021
Published:
12 October 2021
Abstract: Solar flares are known to produce fast Corona Mass Ejections (CMEs) that can lead to the occurrence of different classes of geomagnetic storms. Severe geomagnetic storms can generate disturbances in the magnetosphere and the ionosphere that can affect communication channels; by disrupting Satellite and navigation systems, such as GPS, Galileo, Compass and GLONASS. During intense Solar flares, enhancement in the ionospheric electron density usually occurs, leading to the absorption of the High Frequency (HF) signals by the ionosphere. Enhancement in the Very Low Frequency (VLF) radio waves (3 – 30 kHz) usually takes place during solar flares. This phenomenon is called Sudden Ionospheric Disturbance (SID). These SIDs serves as an opportunity for the tracking of solar flares using VLF. In this study, the diurnal variation of the VLF signals transmitted from six locations selected from USA, Australia and Japan were used to monitor SIDs. The signals were received using the 0-50 kHz frequency receiver (Super SID Monitor) installed at the Kebbi State University of Science and Technology (KSUST), Aliero, Nigeria (latitude: 12.31°N and Longitude: 4.50°E). The diurnal variation of the VLF signals alongside some magnetic indices (Dst, kp, and ap), solar wind speed and density as well as the solar flux index (f10.7) for the month of February, 2020 was investigated. Results from this study reveal that; the VLF amplitudes appeared to be stronger when the lowest level of the geomagnetic activity was recorded across all stations on the quietest day of the month. During this day, the intensity of the signals received vary across the stations, ranging from 2*104 to 4*107dB. During the disturbed period, decrease in the Disturbance Storm Time (Dst) index was observed to have two minimum excursion with values of -31 and -33 nT, thus indicating a weak geomagnetic storm (-30-50) event. Consequently a gradual increase in the solar wind speed with a peak value of 520 km/s, significant decrease in the VLF amplitude ranging from 50 – 7*105dB was observed during the weak geomagnetic storm, on 19 February, 2020. It is also evident from this study that the intensity/strength of the VLF signal and its pattern of propagation are greatly affected by the geomagnetic storm. In spite of the changes in the VLF amplitude observed, there was no trace of solar flares during the weak geomagnetic storm. This therefore suggests that not all classes of geomagnetic storms are connected to solar flares.
Abstract: Solar flares are known to produce fast Corona Mass Ejections (CMEs) that can lead to the occurrence of different classes of geomagnetic storms. Severe geomagnetic storms can generate disturbances in the magnetosphere and the ionosphere that can affect communication channels; by disrupting Satellite and navigation systems, such as GPS, Galileo, Comp...
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Density, Alternative Determinant of Star Formation Efficiency of the Milky Way GMCs: Core Reason for Low Star Formation Efficiency
Okezuonu Patrick Chinedu,
Ogwo Jemima Ngozi
Issue:
Volume 9, Issue 3, September 2021
Pages:
45-50
Received:
11 October 2021
Accepted:
5 November 2021
Published:
24 November 2021
Abstract: The overall efficiency with which Milky Way Giant Molecular Clouds (GMCs) is forming stars was determined by deriving an equation using density of cloud (i.e. stellar density/ total cloud density), which is the core parameter that determines star formation other than the mass of cloud, and comparing with mass (i.e. stellar mass/ total gas mass) as was propounded by previous researchers, to ascertain the reasons the observed star formation efficiency of Milky Way Giant Molecular Clouds (ϵ_GMC) is low. This will aid understanding the physical factors behind the formation of stars from interstellar gas and develop a predictive theory of star formation and evolution of galaxies. A total of 191 star formation complexes-giant molecular cloud (SFC-GMC) complexes was used in estimating the following cloud parameters: density as 93.8218 solar mass/parsec squared, average stellar density as 2.67872 solar mass/parsec squared, average luminosity as 9.87E24 solar luminosity, average effective temperature as 498,647 solar temperature, average stellar radius as 51.4522 parsec and average cloud radius as 325507 parsec as well as the total mass in stars M_⋆ harbored by the individual clouds (20,831 solar mass), which was inferred from Wilkinson Microwave Anisotropy probe (WMAP) free-free. Finally, the overall efficiency with which Milky Way Giant Molecular Clouds is forming star gave 0.0289573 which is less than the previous estimate as 0.030849, showing that not all the masses of the cloud were present at the end of the star formation, and this reduction in mass are caused by magnetic field, supersonic turbulence, self-regulation and unbound states of its internal structure, which are the reasons the observed star formation efficiencies are low.
Abstract: The overall efficiency with which Milky Way Giant Molecular Clouds (GMCs) is forming stars was determined by deriving an equation using density of cloud (i.e. stellar density/ total cloud density), which is the core parameter that determines star formation other than the mass of cloud, and comparing with mass (i.e. stellar mass/ total gas mass) as ...
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