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Your search keyword '"Kashcheyev, Anton"' showing total 23 results
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23 results on '"Kashcheyev, Anton"'

2. Simulation of Focusing Effect of Traveling Ionospheric Disturbances on Meter-Decameter Solar Dynamic Spectra

Author

Koval, Artem, Chen, Yao, Stanislavsky, Aleksander, Kashcheyev, Anton, and Zhang, Qing-He

Subjects
Astrophysics - Solar and Stellar Astrophysics, Physics - Space Physics
Abstract

For the first time we present simulation results of the focusing effect of the ionospheric plasma density irregularities, namely, Medium Scale Traveling Ionospheric Disturbances (MSTIDs), on solar radio emission by applying a ray-tracing method to the Earth's ionosphere with MSTIDs. With this technique we investigate the focusing effect which manifests itself in the form of peculiar spectral disturbances in intensity with specific morphology, so-called Spectral Caustics (SCs), occasionally appearing in dynamic spectra of different solar radio instruments operating in the meter-decameter wavelength range. We show that the simulated spectral shapes of SCs are in good agreement with the ones detected in real solar radio spectrograms. In particular, SCs that are classified as inverted V-like, V-like, X-like, and fiber-like types have been reproduced. It is also found that the seasonal dependence in the occurrence of SCs, which has been discovered recently, can be understood through a strong relation between the focusing frequency - the most important characteristic point in most SCs patterns - and the elevation angle of the Sun. We find that under typical parameters of MSTIDs with spatial and temporal periods set to be 300 km and 40 min, respectively, the focusing frequency decreases with the growth of the elevation angle. Physical interpretations of the results and implications on the analysis of solar radio data with SCs are discussed.

Published
2018
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4. Westward PPEF Plays Important Role in the Suppression of Post‐Midnight Plasma Irregularities: A Case Study of the November 2021 Geomagnetic Storm.

Author

Imtiaz, Nadia, Dugassa, Teshome, Calabia, Andres, Anoruo, Chukwuma, and Kashcheyev, Anton

Subjects
MAGNETIC storms, EQUATORIAL ionization anomaly, GLOBAL Positioning System, ELECTRIC currents, EQUATORIAL electrojet, LATITUDE
Abstract

We use multiple instruments data to investigate the behavior of the equatorial and low‐latitude ionosphere during the geomagnetically active and quiet period of November 1–6, 2021. In this context, total electron content (TEC) data obtained from the Global Positioning System (GPS) receivers in the equatorial and low‐latitude regions of Asia, Africa, and America are used to assess variations in plasma density during the storm. The storm‐time ionization levels were found to vary significantly in the crests of the Equatorial Ionization Anomaly (EIA) region over the 3 longitudes. The Rate of Change TEC Index (ROTI) derived from GPS receiver measurements, is used to study the equatorial/low‐latitude ionospheric plasma irregularities at various longitudes under geomagnetically quiet and disturbed conditions. Observations showed longitudinal variations in the ionospheric irregularities under both quiet and disturbed conditions. Some days exhibit a decrease in the strength of the midnight plasma irregularities toward the East, that is, the irregularities are more pronounced in West America, less common in East America, and almost non‐existent in Africa and Asia. Our investigations show this storm prevented the occurrence of plasma irregularities at the equatorial/low‐latitude region in the American sector during the night following the main phase. In general, no significant storm effects were observed at the target locations in Africa and Asia. The existence of westward Prompt Penetration Electric Field (PPEF) and the Equatorial Electrojet (EEJ) during the main phase, from midnight to noon, is clearly related with the constriction of plasma diffusion and the consequent suppression of plasma irregularities. Thus, the longitudinal dependence for the generation of midnight plasma irregularities during this storm is mainly influenced by local time occurrence of maximum ring current, and the ionospheric electric fields. Key Points: On certain days, the midnight plasma irregularities are most pronounced in America, and almost absent in Africa and AsiaUnder geomagnetically active conditions, midnight plasma irregularities inhibited in the American sector during the main phase of stormPhysical factors such as time of maximum ring current and ionospheric electric fields are responsible for this longitudinal variability [ABSTRACT FROM AUTHOR]

Published
2024
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6. Two components spectrum in the phase scintillation observed in the auroral region

Author

Song, Kaili, P. Thayyil, Jayachandran, Meziane, Karim, and Kashcheyev, Anton

Abstract

Global Positioning Satellite (GPS) measurements made by the Canadian High Arctic Ionospheric Network (CHAIN) are used to scrutinize the distortion seen in the trans-ionospheric radio signal. The analysis of ground measurements of the radio signal can therefore contribute for the understanding the plasma instability mechanisms thatgenerate electron density structures in the ionosphere (irregularities). Inthis work, we describe the radio signal spectral characteristics in the auroral region (Churchill).We present examples of phase spectrum with two-components characterized by a stepper spectral slope at smallscales irregularities, and a shallower slope at larger scales. The breaking point frequency is larger than the Fresnel frequency in the most cases. In return, the amplitude scintillation spectra always exhibit a single slope power behaviour. The phase spectra are examined within a two-components model developed byFremouw et al.[1980]. In this model, the component associated with large scale electron density fluctuations is responsible for low frequency phase variations (geometrical-optics), while the small-scales produce diffractive patterns responsible for the generation of the high frequency fluctuations., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Published
2023

21. MONITOR Ionospheric Network: two case studies on scintillation and electron content variability

Author

Béniguel, Yannick, primary, Cherniak, Iurii, additional, Garcia-Rigo, Alberto, additional, Hamel, Pierrick, additional, Hernández-Pajares, Manuel, additional, Kameni, Roland, additional, Kashcheyev, Anton, additional, Krankowski, Andrzej, additional, Monnerat, Michel, additional, Nava, Bruno, additional, Ngaya, Herbert, additional, Orus-Perez, Raül, additional, Secrétan, Hughes, additional, Sérant, Damien, additional, Schlüter, Stefan, additional, and Wilken, Volker, additional

Published
2017
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22. MONITOR Ionospheric Network: two case studies on scintillation and electron content variability

Author

Universitat Politècnica de Catalunya. Departament de Matemàtiques, Universitat Politècnica de Catalunya. IonSAT - Grup de determinació Ionosfèrica i navegació per SAtèl·lit i sistemes Terrestres, Beniguel, Yannick, Cherniak, Iurii, García Rigo, Alberto, Hamel, P., Hernández Pajares, Manuel, Kameni, Roland, Kashcheyev, Anton, Krankowski, Andrzej, Monnerat, Michel, Nava, Bruno, Ngaya, Herbert, Orús Pérez, Raul, Secretan, Hugues, Serant, Damien, Schlüter, Stefan, Wilken, Volken, Universitat Politècnica de Catalunya. Departament de Matemàtiques, Universitat Politècnica de Catalunya. IonSAT - Grup de determinació Ionosfèrica i navegació per SAtèl·lit i sistemes Terrestres, Beniguel, Yannick, Cherniak, Iurii, García Rigo, Alberto, Hamel, P., Hernández Pajares, Manuel, Kameni, Roland, Kashcheyev, Anton, Krankowski, Andrzej, Monnerat, Michel, Nava, Bruno, Ngaya, Herbert, Orús Pérez, Raul, Secretan, Hugues, Serant, Damien, Schlüter, Stefan, and Wilken, Volken

Abstract

The ESA MONITOR network is composed of high-frequency-sampling global navigation satellite systems (GNSS) receivers deployed mainly at low and high latitudes to study ionosphere variability and jointly with global GNSS data and ionospheric processing software in support of the GNSS and its satellite-based augmentation systems (SBAS) like the European EGNOS. In a recent phase of the project, the network was merged with the CNES/ASECNA network and new receivers were added to complement the latter in the western African sector. This paper summarizes MONITOR, presenting two case studies on scintillations (using almost 2 years of data measurements). The first case occurred during the major St. Patrick’s Day geomagnetic storm in 2015. The second case study was performed in the last phase of the project, which was supported by ESA EGNOS Project Office, when we paid special attention to extreme events that might degrade the system performance of the European EGNOS., Postprint (published version)

Published
2017

23. Assessment of the performance of the TOPGNSS and ANN-MB antennas for ionospheric measurements using low-cost u-blox GNSS receivers

Author

Okoh, Daniel, Obafaye, Aderonke, Dare-Idowu, Oluwakemi, Rabiu, Babatunde, Kashcheyev, Anton, Cesaroni, Claudio, Habarulema, John Bosco, and Nava, Bruno

Abstract

Low-cost GNSS receivers have recently been gaining reliability as good candidates for ionospheric studies. In line with these gains are genuine concerns about improving the performance of these receivers. In this work, we present a comprehensive investigation of the performances of two antennas (the u-blox ANN-MB and the TOPGNSS TOP-106) used on a low-cost GNSS receiver known as the u-blox ZED-F9P. The two antennas were installed on two identical and co-located u-blox receivers. Data used from both receivers cover the period from January to June 2022. Results from the study indicate that the signal strengths are dominantly greater for the receiver with the TOPGNSS antenna than for the receiver with the ANN-MB antenna, implying that the TOPGNSS antenna is better than the ANN-MB antenna in terms of providing greater signal strengths. Summarily, the TOPGNSS antenna also performed better in minimizing the occurrence of cycle slips on phase TEC measurements. There are no conspicuous differences between the variances (computed as 5-min standard deviations) of phase TEC measurements for the two antennas, except for a period around May–June when the TOPGNSS gave a better performance in terms of minimizing the variances in phase TEC. Remarkably, the ANN-MB antenna gave a better performance than the TOPGNSS antenna in terms of minimizing the variances in pseudorange TEC for some satellite observations. For precise horizontal (North and East) positioning, the receiver with the TOPGNSS antenna gave better results, while the receiver with the ANN-MB antenna gave better vertical (Up) positioning. The errors for the receivers of both antennas are typically within about 5 m (the monthly mean was usually smaller than 1 m) in the horizontal direction and within about 10 m (the monthly mean was usually smaller than 4 m) in the vertical direction.

Published
2023
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