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7 results on '"Ephrem Beshir Seba"'

1. TEC disturbances caused by CME-triggered geomagnetic storm of September 6–9, 2017

Author

Chali Idosa Uga, Sujan Prasad Gautam, and Ephrem Beshir Seba

Subjects
Geomagnetic Storm, Solar Activity, Coronal Mass Ejection, Ionospheric Disturbances, Total Electron Content, Science (General), Q1-390, Social sciences (General), H1-99
Abstract

This study investigates the ionospheric response to a geomagnetic storm triggered by a Coronal Mass Ejection (CME) during 6–9 September 2017, across GPS stations located in diverse geographical regions. We analyze the changes in the magnetic field component (ΔH), the Prompt Penetration Electric Fields (PPEF), and the Total Electron Content (TEC). We find that ΔH exhibits latitude-dependent responses during the storm, with high-latitude stations experiencing more significant reductions compared to low-latitude stations. The PPEF behavior is found to be directly correlated with solar wind disturbances. Particularly during the main phase of the storm, fluctuations in PPEF were clearly associated with negative values in the Dst index. The KIRU station, located at a high latitude, shows the most pronounced PPEF effects, indicating the increased susceptibility of high-latitude regions to solar wind interactions. The time series plot of TEC, covering a full month at different stations, shows a distinct diurnal pattern driven by solar ionization. Equatorial stations such as HYDE, BOU, HON (HNLC), and DODM exhibit the highest daily TEC values. During the geomagnetic storm, TEC disturbances are evident across all stations, with significant disturbances and varying trends in TEC depletion rate observed at different locations. The TEC values differ by 5–25 TECU during the storm period, suggesting intricate ionospheric responses to geomagnetic storms at different stations. This highlights the importance of considering different geographical regions to fully understand the ionospheric dynamics related to solar activities.

Published
2024
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2. Modeling Equatorial to Mid‐Latitudinal Global Night Time Ionospheric Plasma Irregularities Using Machine Learning

Author

Ephrem Beshir Seba and Giovanni Lapenta

Subjects
Meteorology. Climatology, QC851-999, Astrophysics, QB460-466
Abstract

Abstract This study focuses on modeling the characteristics of nighttime topside Ionospheric Plasma Irregularities (PI) on a global scale. We utilize Random Forest (RF) and a one‐dimensional Convolutional Neural Network (1D‐CNN) model, incorporating data from the Swarm A, B, and C satellites, space weather data from the OMNIWeb data center, as well as zonal and meridional wind model data. Our objective is to simulate monthly global PI characteristics using a multilayer 1D‐CNN model trained on 12 space weather and ionospheric parameters. In addition, we investigate the most influential input parameters for predicting global nighttime PI characteristics. Our findings indicate that non‐equinox months exhibit the highest equatorial PI magnitude over the American‐African longitudinal sector, contrary to the expected higher Rayleigh‐Taylor instability growth rate during equinox months. Winter months display the most intense and widespread vertically and horizontally distributed equatorial PI patterns. We also observe double peaks across geomagnetic latitudes and longitudinally varying wavelike irregularity structures, particularly in May, August, and predominantly in September. Furthermore, north‐south hemispherical asymmetry in PI observed across different seasons. Through the RF parameter importance analysis method, we determine that temporal, geographical, and magnetic disturbance‐related factors play a crucial role in predicting global PI variabilities. These findings emphasize the significance of these variables in controlling the strongest PI characteristics observed in the Atlantic sector, which has garnered considerable attention in PI research. The employed 1D‐CNN model demonstrates exceptional predictive capabilities, exhibiting a strong correlation of 0.98 for global PI characteristics across all months and satellites.

Published
2024
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5. First Ethiopian Remote Sensing Satellite (ETRSS-1): Mission information and overview

Author

Salem Sintayehu Gizie, Chen Yuanwei, Messay Woldehana Elsea, Denekew Ejigu Alebel, Natnael Agegnehu Ayele, Solomon Belay Tessema, Samuel Tilahun Ayele, Alemiye Mamo, Eskedar Gebeyehu Ayele, Dawit Kassaw Gedefaw, Bethelem Bilata Woldeyes, Eshete Tesfaye Tafes, Melaku Muka Mulatu, Seblu Humne Negu, Tesfay Yemane Tesfu, Ghion Ashenafi Getahun, Abdissa Yilma Tiky, Daniel Atnafu Chekole, Shore Salle Chota, Etsegenet Getachew Alemu, Nigussie Mezgebe Giday, Yufu Cui, Titike Kassa Bahaga, Noah Diriba Debar, Sebhat Tadesse Ademu, Gemechu Fanta Garuma, Eyoas Ergatu Aredo, Shimels Kebede Tegaw, Amarech Alebie Addisuu, Jerusalem Tamirat Teklu, Eyasu Leta Alemu, Dugasa Belay Zeleke, Befkadu Sata, Yeshurun Alemayehu Adde, Selima Wolela Kedit, Mirjana Pović, Yilkal Chanie Eshete, Wudu Worku Wodaj, Biruk Abreham Abate, Getachew Wollel Tiru, Lidya Rezene Elias, Ephrem Beshir Seba, Getnet Gebreezgiabher Fikru, Daniel Fekadu Asefa, Solomon Gerra Cherie, Wondmagegn Melaku Asres, Firaol Lenjinsa Gadisa, Feleke Zerihun Terefe, Yekoye Asmare Tariku, Tsegaye Demsis Lema, Tsegazeab Hailegebriel Assgedom, Yonas Negash Mekonnen, Dinaol Zelalem Gadisa, Alazar Siyoum Demissie, Ermyas Aklilu Feleke, Samson Tilahun Moges, Zelalem Wudu Addis, Michael Abebe Wossene, and Milliyard Likesa Shanko

Subjects
Remote sensing satellite, business.industry, media_common.quotation_subject, Urbanization, Environmental resource management, Environmental science, Climate change, Population growth, Quality (business), Plan (drawing), business, media_common
Abstract

The amount and quality of land, water and atmospheric information is critical to plan, monitor, predict and mitigate the impacts of climate change, urbanization and population growth. To get reason...

Published
2020
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6. The relationship between equatorial ionization anomaly and nighttime equatorial spread F in East Africa

Author

Ephrem Beshir Seba, Mark B. Moldwin, and Melessew Nigussie

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, TEC, Anomaly (natural sciences), Aerospace Engineering, Magnitude (mathematics), Magnetic dip, Astronomy and Astrophysics, Zonal and meridional, Geodesy, 01 natural sciences, Latitude, Geophysics, Space and Planetary Science, 0103 physical sciences, General Earth and Planetary Sciences, Crest, 010303 astronomy & astrophysics, Trough (meteorology), Geology, 0105 earth and related environmental sciences
Abstract

We study the relationship of equatorial ionization anomaly (EIA) to the occurrence of nighttime equatorial spread F (ESF) using data from ground-based GPS stations and a horizontal meridional neutral wind model for the East African sector. Anomaly strength, symmetry of anomaly crests, horizontal meridional wind magnitude and direction, and magnitude of rate of TEC index (ROTI) are computed and analyzed. We find mean crest to trough ratio (CTR) greater than or equal to 1.4 and mean north crest to south crest ratio (CCR) within 0.9 and 1.1 in the time between 16:00 UT (19:00 LT) and 18:00 UT (21:00 LT) as good conditions for the occurrence of ESF. EIA strength and symmetry of anomaly crests are better related with ESF occurrence between conjugate stations (≈ ± 11.5o magnetic latitudes) than between other north-south stations. ROTI is found to be relatively large when CCR of EIA are symmetrical (CCR between 0.9 and 1.1) and CTR is greater than or equal to 1.4, but decreases as the CCR of EIA shows asymmetry and/or CTR of EIA is less than 1.4. EIA strength and symmetry of anomaly crests between 18:00 UT to 20:45 UT are not well related with spread F occurrences. Post-sunset spread F occurrence close to anomaly crest locations are found to be greater than spread F occurrence at magnetic equatorial station. Shifting of EIA crest locations on either side of the magnetic equator is found to depend on season and meridional wind magnitude and direction. The relative difference in spread F occurrence among the four seasons is also discussed.

Published
2018
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7. Investigating the effect of geomagnetic storm and equatorial electrojet on equatorial ionospheric irregularity over East African sector

Author

Ephrem Beshir Seba and Melessew Nigussie

Subjects
Geomagnetic storm, Atmospheric Science, Ionospheric dynamo region, Daytime, 010504 meteorology & atmospheric sciences, Meteorology, TEC, Aerospace Engineering, Astronomy and Astrophysics, Equatorial electrojet, Geodesy, 01 natural sciences, Physics::Geophysics, Geophysics, Interplanetary scintillation, Space and Planetary Science, Physics::Space Physics, 0103 physical sciences, General Earth and Planetary Sciences, Interplanetary magnetic field, Ionosphere, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences
Abstract

The variability of the equatorial ionosphere is still a big challenge for ionospheric dependent radio wave technology users. To mitigate the effect of equatorial ionospheric irregularity on trans-ionospheric radio waves considerable efforts are being done to understand and model the equatorial electrodynamics and its connection to the creation of ionospheric irregularity. However, the effect of the East-African ionospheric electrodynamics on ionospheric irregularity is not yet well studied due to lack of multiple ground based instruments. But, as a result of International Heliophysical Year (IHY) initiative, which was launched in 2007, some facilities are being deployed in Africa since then. Therefore, recently deployed instruments, in the Ethiopian sector, such as SCINDA-GPS receiver (2.64°N dip angle) for TEC and amplitude scintillation index (S 4 ) data and two magnetometers, which are deployed on and off the magnetic equator, data collected in the March equinoctial months of the years 2011, 2012, and 2015 have been used for this study in conjunction with geomagnetic storm data obtained from high resolution OMNI WEB data center. We have investigated the triggering and inhibition mechanisms for ionospheric irregularities using, scintillation index (S 4 ), equatorial electrojet (EEJ), interplanetary electric field (IEF y ), symH index, AE index and interplanetary magnetic field (IMF) B z on five selected storm and two storm free days. We have found that when the eastward EEJ fluctuates in magnitude due to storm time induced electric fields at around noontime, the post-sunset scintillation is inhibited. All observed post-sunset scintillations in equinox season are resulted when the daytime EEJ is non fluctuating. The strength of noontime EEJ magnitude has shown direct relation with the strength of the post-sunset scintillations. This indicates that non-fluctuating EEJ stronger than 20 nT, can be precursor for the occurrence of the evening time ionospheric irregularities. It is also found that prolonged eastward undershielding electric field during the daytime intensified the daytime EEJ magnitude and resulted in strong post-sunset scintillations. We have also observed that the rate of change of B Z (i.e. electric field produced by Faraday’s Induction law) and eastward IEF y around the PRE hour is nicely correlated with strong post-sunset scintillations. Moreover, discussions about the causes for the appearance and disappearance of ionospheric scintillation are presented in this paper.

Published
2016
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