Article
Engineering, Aerospace
Igor Belokonov, Ivan Timbai, Petr Nikolaev
Summary: This paper discusses the possibility of reconstructing the motion of a LEO nanosatellite relative to its center of mass using satellite position measurements. It is important for developers to understand the nanosatellite's behavior in case of radio communication failure after deployment. The study focuses on the aerodynamically stabilized SamSat-218D nanosatellite, which entered a near-circular orbit in April 2016 and was destroyed in March 2022 without achieving aerodynamic stability.
Article
Engineering, Chemical
E. M. Ofuchi, H. L. V. Silva, D. Bertoldi, E. Mancilla, H. Stel, R. E. M. Morales
Summary: Single bubbles flowing in a centrifugal rotor were studied using numerical and experimental methods. The effects of rotating speed, flow coefficient, and bubble diameter on the bubble trajectories and drag coefficient were analyzed. The results showed that the bubble trajectory was influenced by the flow rate and rotating speed, while the drag coefficient curves were affected by the bubble diameter and rotating speed. Additionally, a comparison between the estimated drag coefficient and several drag coefficient correlations was conducted, showing a good agreement with a model based on the Reynolds, Weber, and Eotvos numbers. Furthermore, a dependence between the drag coefficient and a dimensionless number considering the rotational acceleration of the rotor was identified.
CHEMICAL ENGINEERING SCIENCE
(2022)
Article
Engineering, Aerospace
N. Cimmino, R. Opromolla, G. Fasano
Summary: The increase in Resident Space Objects poses a serious threat to satellite safety. Estimating the physical characteristics that affect their orbits, such as the area-to-mass ratio, is crucial for predicting their trajectories. This study proposes a machine learning-based regression approach to estimate the ballistic coefficient in Low Earth Orbit using a variety of orbital parameters. The performance of different machine learning techniques is evaluated using synthetic space catalogues, and the applicability of the approach is tested using both real and synthetic datasets.
ADVANCES IN SPACE RESEARCH
(2023)
Article
Astronomy & Astrophysics
J. Martin Laming, Natsuha Kuroda
Summary: This article discusses a model to explain the enhanced abundances of trans-Fe elements in impulsive solar energetic particle events, which are frequently characterized by large mass-dependent abundance enhancements. The model is a variation of the ponderomotive force model for the first ionization potential effect, where elements like Fe, Mg, and Si have higher abundances in the solar corona compared to neutral ones. The model proposes that the fractionation region is located in the chromosphere, connected to the solar envelope, allowing for significant abundance variations.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Sumanth Rotti, Berkay Aydin, Manolis K. Georgoulis, Petrus C. Martens
Summary: We present a catalog of solar energetic particle (SEP) events covering solar cycles 22, 23 and 24 and integrate three existing catalogs based on satellite data. The catalog includes 341 SEP events, of which 245 events reach the threshold for significant proton events. Researchers can access time-series data and intensity profiles of proton fluxes for each event, aiding understanding of SEPs and their source eruption characteristics for space weather prediction.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2022)
Article
Astronomy & Astrophysics
S. W. Kahler, D. Brown
Summary: The study found that the He/H peak intensity ratios of 43 solar energetic particle events observed in four energy channels vary significantly, with correlations to solar wind and event peak intensities.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
S. W. Kahler, A. G. Ling, D. V. Reames
Summary: The longitudinal extents of solar energetic particle (SEP) events in the heliosphere have been studied with Gaussian fits to peak intensities or fluences at each spacecraft. The widths of the events are increasing throughout the event, while the projected Gaussian centers move westward from SEP onset and remain stationary before moving west again as the event amplitudes decrease. Late decay phases are characterized by eastward movements away from the flare longitudes. Schematic Buffett plots are introduced to show successive snapshots of event longitudes and amplitudes.
ASTROPHYSICAL JOURNAL
(2023)
Article
Engineering, Aerospace
Phillip Logan Sheridan, Smriti Nandan Paul, Guillermo Avendano-Franco, Piyush M. Mehta
Summary: Researchers at Los Alamos National Laboratory have developed a toolkit called Response Surface Modeling (RSM) for simulating and modeling satellite drag coefficients. The toolkit provides computational benefits and extended capabilities for analyzing drag coefficients of satellites with complex geometries, using Python and C programming languages.
ADVANCES IN SPACE RESEARCH
(2022)
Article
Astronomy & Astrophysics
Wen Wang, Linghua Wang, Sam Krucker, Glenn M. Mason, Yang Su, Radoslav Bucik
Summary: The study of 16 solar energetic electron events and associated western hard X-ray flares suggests that the energetic electron source is likely high in the corona, while the observed hard X-rays are produced mainly by bremsstrahlung processes at the bottom of the corona.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Kosuke Kihara, Ayumi Asai, Seiji Yashiro, Nariaki V. Nitta
Summary: This study investigates two solar energetic particle events with different TO in the western hemisphere, despite similar CME speed and source region longitude. The reasons for the difference in TO, or proton release times, are examined by analyzing CME height-time profiles and radio dynamic spectra. The study also explores how CME-CME interactions and active region properties may affect proton release times.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
G. M. Mason, M. E. Greenspan, S. G. Kanekal, R. A. Leske, M. D. Looper, J. E. Mazur, R. A. Mewaldt
Summary: The detection of energetic neutral hydrogen atoms (ENAs) >0.8 MeV in several large solar energetic particle events observed between 1997 and 2004 suggests that these particles penetrate Earth's magnetic field and undergo charge exchange in the upper atmosphere. These findings indicate that the ENAs associated with large solar flares may be generated as coronal mass ejections move through the corona.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Wen Wang, Linghua Wang, Saem Krucker, Robert F. F. Wimmer-Schweingruber
Summary: We investigated the energy spectrum of 458 solar energetic electron (SEE) events and classified them into five spectral types: downward double-power-law (DDPL), upward double-power-law (UDPL), single-power-law (SPL), Ellison-Ramaty (ER), and logarithmic-parabola (LP) events. These events showed different spectral indices and exhibited variations during the solar cycle. The spectral shape of most SEE events appeared to be unrelated to the estimated electron path lengths, suggesting complex processes/sources involved in the formation of SEE events.
ASTROPHYSICAL JOURNAL
(2023)
Article
Multidisciplinary Sciences
Junxiang Hu, Vladimir S. Airapetian, Gang Li, Gary Zank, Meng Jin
Summary: The discovery of frequent superflares on active cool stars is crucial in understanding the properties of eruptive events and their impact on exoplanetary environments. Research suggests that solar and young solar-like stars' flares can produce high-energy particle events that influence the atmospheric biosignatures of exoplanets and the chemistry and isotopic composition of circumstellar disks.
Article
Chemistry, Multidisciplinary
Miguel Espinoza, Ernesto Olguin-Diaz, Vicente Parra-Vega, Rogelio Alvarez-Vargas
Summary: Passive LEO satellites are a preferred option for telecommunications, but they require stringent specifications on resolution, precision, and repeatability, as well as advanced antenna technology for signal downlink. This paper proposes a method for designing, path planning, and controlling a six degrees of freedom robotic antenna to track LEO satellites with precision. Simulation results demonstrate the feasibility of practical tracking using off-the-shelf-component actuators, without requiring knowledge of the dynamics and while withstanding disturbances.
APPLIED SCIENCES-BASEL
(2022)
Article
Astronomy & Astrophysics
Bin Zhuang, Noe Lugaz, Tingyu Gou, Liuguan Ding
Summary: The study revealed that in the scenario of twin coronal mass ejections (CMEs), the speed of the primary CME (priCME) has the highest correlation with the peak intensity of solar energetic particles (SEPs). Furthermore, the combination of CME speed and propagation direction showed a higher correlation with SEP peak intensity. This indicates the dominant role of priCME in controlling SEP enhancements and emphasizes the consideration of latitudinal effects.
ASTROPHYSICAL JOURNAL
(2021)
Article
Geochemistry & Geophysics
Victor U. J. Nwankwo, Sandip K. Chakrabarti, Olugbenga Ogunmodimu
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS
(2016)
Article
Engineering, Aerospace
Victor U. J. Nwankwo, Sandip K. Chakrabarti
ADVANCES IN SPACE RESEARCH
(2018)
Article
Geochemistry & Geophysics
Olugbenga Ogunmodimu, Farideh Honary, Neil Rogers, Ian G. Richardson, Bamidele Adebisi, Victor U. J. Nwankwo
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS
(2020)
Article
Multidisciplinary Sciences
Matthias C. Ominyi, Augustine A. Uwakwe, Friday N. Nweke, Fedrick U. Ali, Moses E. Ogbanshi, Lilian N. Ebenyi, Victor U. Nwankwo, Emmanuel O. Ogueji
Summary: The aqueous seed extract of Dacryodes edulis showed significant therapeutic potential for doxorubicin-induced cardiac tissue damage in albino rats, with dose-dependent ameliorative effects and healing effects similar to standard drugs.
KUWAIT JOURNAL OF SCIENCE
(2021)
Review
Biology
Michael A. Olatunji, Mayeen U. Khandaker, Victor U. J. Nwankwo, Abubakr M. Idris
Summary: Proper documentation of baseline radiation data is crucial for environmental monitoring and decision making processes. This review focuses on the radioactivity levels in Nigerian environments and highlights the presence of high background radiation areas. It also discusses the potential health hazards associated with the reported radioactivity and emphasizes the need for appropriate regulations to protect the public.
RADIATION AND ENVIRONMENTAL BIOPHYSICS
(2022)
Article
Astronomy & Astrophysics
Victor U. J. Nwankwo, William Denig, Sandip K. Chakrabarti, Olugbenga Ogunmodimu, Muyiwa P. Ajakaiye, Johnson O. Fatokun, Paul Anekwe, Omodara E. Obisesan, Olufemi E. Oyanameh, Oluwaseun Fatoye
Summary: Through studying the propagation characteristics of very low-frequency (VLF) radio signals, we found that geomagnetic storms can affect the mid-latitude D region. On storm days, the signal amplitudes generally decreased, with a more significant decrease observed along the DHO-A118 propagation path. Additionally, the virtual heights and critical frequencies of the ionosphere showed significant increases and fluctuations during the storms.
ANNALES GEOPHYSICAE
(2022)
Article
Astronomy & Astrophysics
Victor U. J. Nwankwo, William Denig, Sandip K. Chakrabarti, Muyiwa P. Ajakaiye, Johnson Fatokun, AdeniyiW. Akanni, Jean-Pierre Raulin, Emilia Correia, John E. Enoh, Paul I. Anekwe
Summary: This study simulated the atmospheric drag effect on small satellites in low Earth orbit under different solar-geomagnetic conditions, showing that solar-geomagnetic activity significantly influences satellite orbit decay rates, and that a satellite's ballistic coefficient affects the atmospheric drag force.
ANNALES GEOPHYSICAE
(2021)
Article
Physics, Multidisciplinary
V. U. J. Nwankwo, S. K. Chakrabarti
INDIAN JOURNAL OF PHYSICS
(2015)
