Article
Astronomy & Astrophysics
Khan-Hyuk Kim, Dong-Hee Kim, Junho Back, Hyuck-Jin Kwon, Geonhwa Jee, Young-Bae Ham, Changsup Lee, Jeong-Han Kim
Summary: Noticeable F-region electron density depletions (NmF2) were observed in the winter-nighttime polar cap ionosphere during solar minimum. The depletion events, known as polar holes, occurred over a wide range of magnetic local time, with the peak occurrence at 01-03 MLT. The exponential decrease in NmF2 and the positive correlation between NmF2 and horizontal ion drift velocity (V-hor) prior to the polar hole formation were discussed in relation to the formation mechanisms.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Bishwas L. Shrestha, Eric J. Zirnstein, David J. McComas
Summary: In this study, the evolution of polar coronal holes (PCHs) is investigated using high-time resolution ENA flux measurements from IBEX-Hi. The PCHs are identified by ENA spectral indices <1.8. The results show a periodic evolution of the ENA spectral index over the poles, with a slight increase in the surface area with flatter ENA spectra from 2009-2011 and a gradual decrease from 2012-2014. The PCH completely disappears in 2016 and reappears starting in 2017, gradually growing until 2019, showing a clear correlation with the change in the PCH area observed at the Sun.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Yi Liu, Zhongxin Deng, Tong Xu, Jian Kong, Chen Zhou, Yibin Yao, Qiong Tang, Zhengyu Zhao
Summary: Using Qujing VHF radar, daytime F region echoes were observed at the equatorial ionization anomaly crest. Simultaneous observations of ionospheric disturbance and atmospheric gravity wave activities revealed that daytime F region echoes could be excited by ionospheric disturbance during the strong atmospheric gravity wave activities. Our results provided observational evidence of links among different ionospheric disturbances in the daytime region of China.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Article
Astronomy & Astrophysics
Zhenning Shen, Gang Qin, Pingbing Zuo, Fengsi Wei, Xiaojun Xu
Summary: This study investigates the latitudinal distribution of galactic cosmic-ray protons in the inner heliosphere using a numerical model, and finds that the latitudinal-dependent magnetic turbulence magnitude and anisotropic perpendicular diffusion coefficient are crucial for proton gradient, especially during the negative-polarity solar cycle. In addition, during the A > 0 period, the latitudinal diffusion coefficient and reduced drift velocity in the polar region play a more important role in modulating the proton distribution.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2021)
Article
Astronomy & Astrophysics
R. Remya, M. G. Manoj, V Rakesh, K. Mohanakumar, C. Sivan
Summary: The study demonstrates the evidence of dynamic coupling between high-latitude sudden stratospheric warming (SSW) events and changes in wind patterns in the lower stratosphere and troposphere. The research also reveals the occurrence of sudden fluctuations in vertical wind and unusual rainfall in the tropical region associated with SSW events. Further comprehensive observational and numerical modeling studies are required to understand the mechanisms behind SSW events and associated convective activity and precipitation in the low latitude region.
EARTH AND SPACE SCIENCE
(2021)
Article
Astronomy & Astrophysics
D. Telloni, E. Antonucci, L. Adhikari, G. P. Zank, S. Giordano, M. Vai, L. -l. Zhao, V. Andretta, A. Burtovoi, G. E. Capuano, V. Da Deppo, Y. De Leo, S. Fineschi, C. Grimani, P. Heinzel, G. Jerse, F. Landini, A. Liberatore, J. D. Moses, G. Naletto, G. Nicolini, M. Pancrazzi, M. Romoli, G. Russano, C. Sasso, A. Slemer, D. Spadaro, M. Stangalini, R. Susino, L. Teriaca, M. Uslenghi, L. Sorriso-Valvo, R. Marino, D. Perrone, R. D'Amicis, R. Bruno
Summary: This article reports the first estimate of the expansion rate of polar coronal flows performed by the Metis coronagraph on board Solar Orbiter. By extending observations of the outflow velocity of the main component of the solar wind from polar coronal holes, the results suggest that a magnetohydrodynamic turbulence model can satisfactorily reproduce the observations.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Matti Ala-Lahti, Tuija I. Pulkkinen, Julia Ruohotie, Mojtaba Akhavan-Tafti, Simon W. Good, Emilia K. J. Kilpua
Summary: This study investigates the front boundary of interplanetary coronal mass ejections (ICMEs) and their interaction with the ambient medium using multipoint observations. The observations reveal a two-sided jet and multiple reconnection sites associated with ICME erosion. The study also highlights the incoherence of the mixed plasma and emphasizes the importance of continuous plasma and field measurements in the solar wind.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
E. K. J. Kilpua, S. W. Good, N. Dresing, R. Vainio, E. E. Davies, R. J. Forsyth, J. Gieseler, B. Lavraud, E. Asvestari, D. E. Morosan, J. Pomoell, D. J. Price, D. Heyner, T. S. Horbury, V Angelini, H. O'Brien, V Evans, J. Rodriguez-Pacheco, R. Gomez Herrero, G. C. Ho, R. Wimmer-Schweingruber
Summary: This study provides new insights into the internal structure of CME-driven sheaths with a focus on energetic particle enhancements, using multi-point in-situ observations made by spacecraft at different locations. Various smaller-scale substructures were identified within the sheaths, indicating potential acceleration sites for charged particles in interplanetary space.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Meteorology & Atmospheric Sciences
Beatriz Canadillas, Shuhan Wang, Yasmin Ahlert, Bughsin Djath, Mares Barekzai, Richard Foreman, Astrid Lampert
Summary: The transition from land to sea affects the wind field in coastal regions. This study uses ERA5 reanalysis data to quantify the average horizontal wind speed gradients at progressively increasing distances from the German coast and explores the dependence of wind speed gradients on various factors. The results show good agreement between the ERA5 data and observational reference, suggesting the potential of utilizing the horizontal wind speed gradient information in offshore resource assessment.
METEOROLOGISCHE ZEITSCHRIFT
(2023)
Article
Engineering, Ocean
Yunli Nie, Xin Luan, Hua Yang, Xu Chen, Dalei Song, Xiuyan Liu, Shengmei Liu, Xianghua Hiu
Summary: The study focused on the characteristics of turbulent mixing in the Yellow Sea continental shelf. It found that the vertical thermohaline structure of the water column was nonstratified during the observation period, leading to consistent distribution of turbulence dissipation and diapycnal diffusivity. Wind energy was identified as a dominant driver of elevated turbulent mixing in the area.
MARINE TECHNOLOGY SOCIETY JOURNAL
(2021)
Proceedings Paper
Engineering, Electrical & Electronic
V. Cheshm Siyahi, V. N. Kudryavtsev, M. Yurovskaya
Summary: This study investigates surface waves generated by Polar Lows (PLs) in the Barents and Norwegian seas, revealing that PLs can generate abnormally high waves comparable to tropical cyclones. Unlike TCs, wind field and trajectory in PLs are highly variable, but there is also group velocity resonance mechanism between generating waves and moving wind field in PLs which leads to abnormal waves. Comma-type PLs play a major role in generating abnormally high waves in the Arctic.
2021 PHOTONICS & ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS 2021)
(2021)
Article
Environmental Sciences
Sunkara Eswaraiah, Kyong-Hwan Seo, Kondapalli Niranjan Kumar, Andrey V. Koval, Madineni Venkat Ratnam, Chalachew Kindie Mengist, Gasti Venkata Chalapathi, Huixin Liu, Young-Sil Kwak, Eugeny Merzlyakov, Christoph Jacobi, Yong-Ha Kim, Sarangam Vijaya Bhaskara Rao, Nicholas J. Mitchell
Summary: Using a network of meteor radar observations, this study presents observational evidence of polar-to-tropical mesospheric coupling during the 2018 major sudden stratosphere warming (SSW) event in the northern hemisphere. The study detected a maximum zonal wind reversal in the tropical lower mesosphere and noted a time delay in the wind reversal between the tropical/polar stations and the mid-latitudes. The wind reversal is attributed to the propagation of dominant intra-seasonal oscillations (ISOs) and the presence of planetary waves (PWs).
Article
Astronomy & Astrophysics
Q. Nenon, A. R. Poppe
Summary: This study found that the flux of out-of-ecliptic ions influences the lunar polar craters with a flux of 10(-3) times that of the solar wind. The northward and southward ions impacting the Moon mainly originate from shocked thermalized solar wind ions in the terrestrial magnetosheath and the isotropic component of ion distributions in the terrestrial magnetotail. The energy spectrum of out-of-ecliptic ions was found to be flatter than the solar wind spectrum.
PLANETARY SCIENCE JOURNAL
(2021)
Article
Optics
V. V. Zuev, E. S. Savelieva, A. V. Pavlinsky
Summary: This study examines the features of weakening a stratospheric polar vortex and its preceding breakdown. By analyzing the abnormal dynamics and utilizing ERA5 reanalysis data, the criteria for the abnormal weakening of the polar vortex before its breakdown are identified: a decrease in vortex area to less than 10 million km(2), and a subsequent decrease in mean wind speed along the vortex edge below 30 m/s and 45 m/s in the lower and middle stratosphere, respectively. In this case, the polar vortex transforms into a small cyclone characterized by high temperatures and the absence of a dynamic barrier, ultimately collapsing within three weeks.
ATMOSPHERIC AND OCEANIC OPTICS
(2022)
Article
Meteorology & Atmospheric Sciences
Coltin Grasmick, Bart Geerts, Xia Chu, Jeffrey R. French, Robert M. Rauber
Summary: Kelvin-Helmholtz (KH) waves are a common source of turbulence in stratiform precipitation systems over mountainous terrain, introducing large eddies and small-scale turbulence into laminar flow. Dynamics associated with KH waves influence microphysical processes in clouds, impacting precipitation growth and fallout. Observations and modeling suggest that KH waves may increase precipitation by enhancing depositional and accretional growth and ice nucleation within mixed-phase clouds.
JOURNAL OF THE ATMOSPHERIC SCIENCES
(2021)
Article
Geosciences, Multidisciplinary
E. E. Woodfield, S. A. Glauert, J. D. Menietti, R. B. Horne, A. J. Kavanagh, Y. Y. Shprits
Summary: Plasmaspheric hiss waves at Saturn accelerate electrons instead of causing losses, due to the different plasma density environment. The interaction between electrons and hiss occurs at high latitudes, resulting in acceleration with mid to low pitch angles.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geochemistry & Geophysics
Minyi Long, Binbin Ni, Xing Cao, Xudong Gu, Peter Kollmann, Qiong Luo, Ruoxian Zhou, Yingjie Guo, Deyu Guo, Yuri Y. Shprits
Summary: This study quantitatively and comprehensively investigates the absorption probabilities and particle lifetimes due to encounters with four of Jupiter's inner moons. The results show that the particle lifetimes vary dramatically depending on the particle equatorial pitch angle, kinetic energy, and moon orbit. The lifetimes are shortest for encounters with Io and longest for encounters with Thebe. Additionally, the lifetimes of energetic protons decrease with increasing kinetic energy, while the lifetimes of energetic electrons remain roughly constant at higher energies.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2022)
Article
Astronomy & Astrophysics
Yingjie Guo, Binbin Ni, Song Fu, Dedong Wang, Y. Y. Shprits, I. S. Zhelavskaya, Minghang Feng, Deyu Guo
Summary: Using feature selection techniques, this study identified the key geomagnetic and solar wind factors influencing magnetospheric chorus waves, with the AE index with zero-time delay, solar wind speed, and IMF B-z identified as important controlling factors for chorus wave intensity. By combining these factors, a neural network model was developed to predict chorus wave intensity, with the model using the Random Forest method showing the best performance.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Fadil Inceoglu, Yuri Y. Shprits, Stephan G. Heinemann, Stefano Bianco
Summary: In this study, unsupervised machine learning method k-means clustering was used to classify solar images. The results were found to be compatible with complex methods, and the importance of establishing a coronal hole database was emphasized.
ASTROPHYSICAL JOURNAL
(2022)
Article
Geosciences, Multidisciplinary
A. Y. Drozdov, H. J. Allison, Y. Y. Shprits, M. E. Usanova, A. Saikin, D. Wang
Summary: In this study, a statistical analysis of PSD minima was conducted to quantify the association between EMIC waves and radiation belt depletions, highlighting the importance of EMIC waves in the dynamics of the radiation belts. Additionally, it was found that approximately 53% of electron depletions in the outer radiation belt core are associated with PSD minima, indicating the common and crucial role of fast localized loss due to interactions with EMIC waves for ultra-relativistic electron populations.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Y. Yamazaki, J. Matzka, C. Stolle, G. Kervalishvili, J. Rauberg, O. Bronkalla, A. Morschhauser, S. Bruinsma, Y. Y. Shprits, D. R. Jackson
Summary: The study introduces a new geomagnetic activity index Hpo, which has higher time resolution and can accurately characterize severe geomagnetic storms compared to the traditional index Kp.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
D. A. Landis, A. A. Saikin, I Zhelavskaya, A. Y. Drozdov, N. Aseev, Y. Y. Shprits, M. F. Pfitzer, A. G. Smirnov
Summary: This study introduces two new empirical models of radiation belt electron flux at geostationary orbit, utilizing NARX neural network for GOES-15 flux modeling and application in VERB code reconstruction. The results demonstrate that factors such as magnetic local time, Dst, and Kp are effective predictors of GOES-15 flux.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Review
Astronomy & Astrophysics
Yuri Y. Shprits, Hayley J. Allison, Dedong Wang, Alexander Drozdov, Matyas Szabo-Roberts, Irina Zhelavskaya, Ruggero Vasile
Summary: Van Allen Probes measurements have shown the presence of unusual structures in the ultra-relativistic radiation belts, with electromagnetic ion cyclotron waves playing a key role in the efficient loss of ultra-relativistic electrons. The analysis also indicates that local energy diffusion and plasma density depletion are important factors in the acceleration to multi-MeV energies.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Artem Smirnov, Yuri Y. Shprits, Hayley Allison, Nikita Aseev, Alexander Drozdov, Peter Kollmann, Dedong Wang, Anthony Saikin
Summary: In this study, an empirical model of the equatorial electron pitch angle distributions (PADs) in the outer radiation belt is presented based on collected data from the MagEIS instrument onboard the Van Allen Probes. The model accurately describes various types of PADs and can be used to calculate omnidirectional flux. A two-step modeling procedure is introduced to ensure a continuous dependence on various parameters. Two methods for reconstructing equatorial electron flux using the model are proposed.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Article
Astronomy & Astrophysics
Alfredo Del Corpo, Massimo Vellante, Irina S. Zhelavskaya, Yuri Y. Shprits, Balazs Heilig, Jan Reda, Ermanno Pietropaolo, Janos Lichtenberger
Summary: This research investigates the dynamics and properties of heavy ions in the Earth's magnetosphere. The study finds that the average ion mass in the plasmasphere remains constant at around 1 amu regardless of the level of geomagnetic activity, while the ion mass loading in the plasmatrough increases with higher levels of geomagnetic disturbance.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Geosciences, Multidisciplinary
Xing Cao, Peng Lu, Binbin Ni, Danny Summers, Yuri Y. Shprits, Minyi Long, Xiaoyu Wang
Summary: By constructing an empirical model based on Cassini datasets, this study investigates the resonant interactions between ion cyclotron waves and radiation belt electrons at Saturn. It is found that the ion cyclotron waves can efficiently scatter high-energy electrons into the loss cone, inducing precipitation loss. The electron loss timescales decrease significantly with increasing L-shell and the presence of pick-up ring particles can affect the pitch angle scattering efficiency for lower energy electrons.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Astronomy & Astrophysics
Simon N. N. Walker, Richard J. J. Boynton, Yuri Y. Y. Shprits, Michael A. A. Balikhin, Alexander Y. Y. Drozdov
Summary: This study investigates the coupling of a data based model of the electron fluxes at GEO with a numerical model of the radiation belt region to improve the resulting forecasts/pastcasts of electron fluxes over the whole radiation belt region. Two coupling methods are compared and it is found that the fixed coupling method produces a more realistic forecast when compared to measurements.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Article
Environmental Sciences
Marjolijn Adolfs, Mohammed Mainul Hoque, Yuri Y. Shprits
Summary: This study proposes a neural-network-based model for predicting relative total electron content (TEC) during geomagnetic storms in the European region. The model uses inputs such as 27-day median TEC, latitude, longitude, universal time, storm time, and various indices, and predicts the relative TEC. The model shows improved performance compared to other models, accurately predicting TEC during geomagnetic storms.
Article
Geosciences, Multidisciplinary
Yuri Y. Y. Shprits, Ingo Michaelis, Dedong Wang, Hayley Allison, Ruggero Vasile, Andrei Runov, Alexander Drozdov, Christopher T. Russell, Vladimir Kalegaev, Artem Smirnov
Summary: This study used measurements from the ELFIN-L suit of instruments on the Lomonosov spacecraft to distinguish between stably trapped and drift loss cone electrons. The results show that the loss at MeV energies mainly occurs on the dawn-side, consistent with loss induced by chorus waves.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Astronomy & Astrophysics
Sanja Panovska, Stepan Poluianov, Jiawei Gao, Monika Korte, Alexander Mishev, Yuri Y. Shprits, Ilya Usoskin
Summary: The production rates of cosmogenic radionuclides in the Earth's atmosphere vary with the Earth's geomagnetic field and solar activity. This study estimated the production rates of several cosmogenic nuclides for the past 100,000 years based on global, time-dependent geomagnetic field models and moderate solar activity. The results showed that the production rates were high during the Laschamps geomagnetic excursion, with no notable latitudinal dependence. Hemispheric asymmetry and persistent overall time ranges were observed in the production rates predicted by the geomagnetic field models.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
