TY  - GEN
A1  - Sadovnichii, V. A.
A1  - Panasyuk, M. I.
A1  - Amelyushkin, A. M.
A1  - Benghin, V. V.
A1  - Garipov, G. K.
A1  - Kalegaev, V. V.
A1  - Klimov, P. A.
A1  - Khrenov, B. A.
A1  - Petrov, V. L.
A1  - Sharakin, S. A.
A1  - Shirokov, A. V.
A1  - Svertilov, S. I.
A1  - Zotov, M. Y.
A1  - Yashin, I. V.
A1  - Gorbovskoy, E. S.
A1  - Lipunov, V. M.
A1  - Park, I. H.
A1  - Lee, J.
A1  - Jeong, S.
A1  - Kim, M. B.
A1  - Jeong, H. M.
A1  - Shprits, Yuri Y.
A1  - Angelopoulos, V.
A1  - Russell, C. T.
A1  - Runov, A.
A1  - Turner, D.
A1  - Strangeway, R. J.
A1  - Caron, R.
A1  - Biktemerova, S.
A1  - Grinyuk, A.
A1  - Lavrova, M.
A1  - Tkachev, L.
A1  - Tkachenko, A.
A1  - Martinez, O.
A1  - Salazar, H.
A1  - Ponce, E.
T1  - "Lomonosov" satellite-space observatory to study extreme phenomena in space
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The "Lomonosov" space project is lead by Lomonosov Moscow State University in collaboration with the following key partners: Joint Institute for Nuclear Research, Russia, University of California, Los Angeles (USA), University of Pueblo (Mexico), Sungkyunkwan University (Republic of Korea) and with Russian space industry organi-zations to study some of extreme phenomena in space related to astrophysics, astroparticle physics, space physics, and space biology. The primary goals of this experiment are to study:

-Ultra-high energy cosmic rays (UHECR) in the energy range of the Greizen-ZatsepinKuzmin (GZK) cutoff;

-Ultraviolet (UV) transient luminous events in the upper atmosphere;

-Multi-wavelength study of gamma-ray bursts in visible, UV, gamma, and X-rays;

-Energetic trapped and precipitated radiation (electrons and protons) at low-Earth orbit (LEO) in connection with global geomagnetic disturbances;

-Multicomponent radiation doses along the orbit of spacecraft under different geomagnetic conditions and testing of space segments of optical observations of space-debris and other space objects;

-Instrumental vestibular-sensor conflict of zero-gravity phenomena during space flight.

This paper is directed towards the general description of both scientific goals of the project and scientific equipment on board the satellite. The following papers of this issue are devoted to detailed descriptions of scientific instruments.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 959 
KW  - gamma-ray bursts
KW  - ultra-high energy cosmic rays
KW  - radiation belts
KW  - space mission
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-428185
SN  - 1866-8372
IS  - 959
SP  - 1705
EP  - 1738
ER  - 
TY  - JOUR
A1  - Sadovnichii, V. A.
A1  - Panasyuk, M. I.
A1  - Amelyushkin, A. M.
A1  - Bogomolov, V. V.
A1  - Benghin, V. V.
A1  - Garipov, G. K.
A1  - Kalegaev, V. V.
A1  - Klimov, P. A.
A1  - Khrenov, B. A.
A1  - Petrov, V. L.
A1  - Sharakin, S. A.
A1  - Shirokov, A. V.
A1  - Svertilov, S. I.
A1  - Zotov, M. Y.
A1  - Yashin, I. V.
A1  - Gorbovskoy, E. S.
A1  - Lipunov, V. M.
A1  - Park, I. H.
A1  - Lee, J.
A1  - Jeong, S.
A1  - Kim, M. B.
A1  - Jeong, H. M.
A1  - Shprits, Yuri Y.
A1  - Angelopoulos, V.
A1  - Russell, C. T.
A1  - Runov, A.
A1  - Turner, D.
A1  - Strangeway, R. J.
A1  - Caron, R.
A1  - Biktemerova, S.
A1  - Grinyuk, A.
A1  - Lavrova, M.
A1  - Tkachev, L.
A1  - Tkachenko, A.
A1  - Martinez, O.
A1  - Salazar, H.
A1  - Ponce, E.
T1  - "Lomonosov" Satellite-Space Observatory to Study Extreme Phenomena in Space
JF  - Space science reviews
N2  - The "Lomonosov" space project is lead by Lomonosov Moscow State University in collaboration with the following key partners: Joint Institute for Nuclear Research, Russia, University of California, Los Angeles (USA), University of Pueblo (Mexico), Sungkyunkwan University (Republic of Korea) and with Russian space industry organi-zations to study some of extreme phenomena in space related to astrophysics, astroparticle physics, space physics, and space biology. The primary goals of this experiment are to study: -Ultra-high energy cosmic rays (UHECR) in the energy range of the Greizen-ZatsepinKuzmin (GZK) cutoff; -Ultraviolet (UV) transient luminous events in the upper atmosphere; -Multi-wavelength study of gamma-ray bursts in visible, UV, gamma, and X-rays; -Energetic trapped and precipitated radiation (electrons and protons) at low-Earth orbit (LEO) in connection with global geomagnetic disturbances; -Multicomponent radiation doses along the orbit of spacecraft under different geomagnetic conditions and testing of space segments of optical observations of space-debris and other space objects; -Instrumental vestibular-sensor conflict of zero-gravity phenomena during space flight. This paper is directed towards the general description of both scientific goals of the project and scientific equipment on board the satellite. The following papers of this issue are devoted to detailed descriptions of scientific instruments.
KW  - Gamma-ray bursts
KW  - Ultra-high energy cosmic rays
KW  - Radiation belts
KW  - Space mission
Y1  - 2017
U6  - https://doi.org/10.1007/s11214-017-0425-x
SN  - 0038-6308
SN  - 1572-9672
VL  - 212
SP  - 1705
EP  - 1738
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Ripoll, Jean-Francois
A1  - Loridan, Vivien
A1  - Denton, Michael H.
A1  - Cunningham, Gregory
A1  - Reeves, G.
A1  - Santolik, O.
A1  - Fennell, Joseph
A1  - Turner, Drew L.
A1  - Drozdov, Alexander
A1  - Cervantes Villa, Juan Sebastian
A1  - Shprits, Yuri Y.
A1  - Thaller, Scott A.
A1  - Kurth, William S.
A1  - Kletzing, Craig A.
A1  - Henderson, Michael  G.
A1  - Ukhorskiy, Aleksandr Y.
T1  - Observations and Fokker-Planck Simulations of the L-Shell, Energy, and Times
JF  - Journal of geophysical research : Space physics
N2  - The evolution of the radiation belts in L-shell (L), energy (E), and equatorial pitch angle (alpha(0)) is analyzed during the calm 11-day interval (4-15 March) following the 1 March 2013 storm. Magnetic Electron and Ion Spectrometer (MagEIS) observations from Van Allen Probes are interpreted alongside 1D and 3D Fokker-Planck simulations combined with consistent event-driven scattering modeling from whistler mode hiss waves. Three (L, E, alpha(0)) regions persist through 11 days of hiss wave scattering; the pitch angle-dependent inner belt core (L similar to <2.2 and E < 700 keV), pitch angle homogeneous outer belt low-energy core (L > similar to 5 and E similar to < 100 keV), and a distinct pocket of electrons (L similar to [4.5, 5.5] and E similar to [0.7, 2] MeV). The pitch angle homogeneous outer belt is explained by the diffusion coefficients that are roughly constant for alpha(0) similar to <60 degrees, E > 100 keV, 3.5 < L < L-pp similar to 6. Thus, observed unidirectional flux decays can be used to estimate local pitch angle diffusion rates in that region. Top-hat distributions are computed and observed at L similar to 3-3.5 and E = 100-300 keV.
KW  - radiation belts
KW  - wave-particle interactions
KW  - electron lifetime
KW  - pitch angle diffusion coefficient
KW  - hiss waves
Y1  - 2018
U6  - https://doi.org/10.1029/2018JA026111
SN  - 2169-9380
SN  - 2169-9402
VL  - 124
IS  - 2
SP  - 1125
EP  - 1142
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Long, Minyi
A1  - Ni, Binbin
A1  - Cao, Xing
A1  - Gu, Xudong
A1  - Kollmann, Peter
A1  - Luo, Qiong
A1  - Zhou, Ruoxian
A1  - Guo, Yingjie
A1  - Guo, Deyu
A1  - Shprits, Yuri Y.
T1  - Losses of radiation belt energetic particles by encounters with four of the inner Moons of Jupiter
JF  - Journal of geophysical research, Planets
N2  - Based on an improved model of the moon absorption of Jovian radiation belt particles, we investigate quantitatively and comprehensively the absorption probabilities and particle lifetimes due to encounters with four of the inner moons of Jupiter (Amalthea, Thebe, Io, and Europa) inside L < 10. Our results demonstrate that the resultant average lifetimes of energetic protons and electrons vary dramatically between similar to 0.1 days and well above 1,000 days, showing a strong dependence on the particle equatorial pitch angle, kinetic energy and moon orbit. The average lifetimes of energetic protons and electrons against moon absorption are shortest for Io (i.e., similar to 0.1-10 days) and longest for Thebe (i.e., up to thousands of days), with the lifetimes in between for Europa and Amalthea. Due to the diploe tilt angle absorption effect, the average lifetimes of energetic protons and electrons vary markedly below and above alpha eq ${\alpha }_{\mathrm{e}\mathrm{q}}$ = 67 degrees. Overall, the average electron lifetimes exhibit weak pitch angle dependence, but the average proton lifetimes are strongly dependent on equatorial pitch angle. The average lifetimes of energetic protons decrease monotonically and substantially with the kinetic energy, but the average lifetimes of energetic electrons are roughly constant at energies <similar to 10 MeV, increase substantially around the Kepler velocities of the moons (similar to 10-50 MeV), and decrease quickly at even higher energies. Compared with the averaged electron lifetimes, the average proton lifetimes are longer at energies below a few MeV and shorter at energies above tens of MeV.
KW  - moon absorption
KW  - Jupiter's magnetosphere
KW  - energetic electrons
KW  - energetic
KW  - protons
Y1  - 2022
U6  - https://doi.org/10.1029/2021JE007050
SN  - 2169-9097
SN  - 2169-9100
VL  - 127
IS  - 2
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Shprits, Yuri Y.
A1  - Menietti, J. D.
A1  - Drozdov, Alexander
A1  - Horne, Richard B.
A1  - Woodfield, Emma E.
A1  - Groene, J. B.
A1  - de Soria-Santacruz, M.
A1  - Averkamp, T. F.
A1  - Garrett, H.
A1  - Paranicas, C.
A1  - Gurnett, Don A.
T1  - Strong whistler mode waves observed in the vicinity of Jupiter’s moons
JF  - Nature Communications
N2  - Understanding of wave environments is critical for the understanding of how particles are accelerated and lost in space. This study shows that in the vicinity of Europa and Ganymede, that respectively have induced and internal magnetic fields, chorus wave power is significantly increased. The observed enhancements are persistent and exceed median values of wave activity by up to 6 orders of magnitude for Ganymede. Produced waves may have a pronounced effect on the acceleration and loss of particles in the Jovian magnetosphere and other astrophysical objects. The generated waves are capable of significantly modifying the energetic particle environment, accelerating particles to very high energies, or producing depletions in phase space density. Observations of Jupiter’s magnetosphere provide a unique opportunity to observe how objects with an internal magnetic field can interact with particles trapped in magnetic fields of larger scale objects.
Y1  - 2018
U6  - https://doi.org/10.1038/s41467-018-05431-x
SN  - 2041-1723
VL  - 9
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Yamazaki, Yosuke
A1  - Matzka, Jürgen
A1  - Stolle, Claudia
A1  - Kervalishvili, Guram N.
A1  - Rauberg, Jan
A1  - Bronkalla, Oliver
A1  - Morschhauser, Achim
A1  - Bruinsma, Sean L.
A1  - Shprits, Yuri Y.
A1  - Jackson, David R.
T1  - Geomagnetic activity index Hpo
JF  - Geophysical research letters
N2  - The geomagnetic activity index Kp is widely used but is restricted by low time resolution (3-hourly) and an upper limit. To address this, new geomagnetic activity indices, Hpo, are introduced. Similar to Kp, Hpo expresses the level of planetary geomagnetic activity in units of thirds (0o, 0+, 1-, 1o, 1+, 2-, horizontal ellipsis ) based on the magnitude of geomagnetic disturbances observed at subauroral observatories. Hpo has a higher time resolution than Kp. 30-min (Hp30) and 60-min (Hp60) indices are produced. The frequency distribution of Hpo is designed to be similar to that of Kp so that Hpo may be used as a higher time-resolution alternative to Kp. Unlike Kp, which is capped at 9o, Hpo is an open-ended index and thus can characterize severe geomagnetic storms more accurately. Hp30, Hp60 and corresponding linearly scaled ap30 and ap60 are available, in near real time, at the GFZ website (https://www.gfz-potsdam.de/en/hpo-index).
KW  - Hpo
KW  - Hp30
KW  - Hp60
KW  - apo
KW  - ap30
KW  - ap60
Y1  - 2022
U6  - https://doi.org/10.1029/2022GL098860
SN  - 0094-8276
SN  - 1944-8007
VL  - 49
IS  - 10
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - GEN
A1  - Woodfield, Emma E.
A1  - Horne, Richard B.
A1  - Glauert, Sarah A.
A1  - Menietti, John D.
A1  - Shprits, Yuri Y.
A1  - Kurth, William S.
T1  - Formation of electron radiation belts at Saturn by Z-mode wave acceleration
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - At Saturn electrons are trapped in the planet's magnetic field and accelerated to relativistic energies to form the radiation belts, but how this dramatic increase in electron energy occurs is still unknown. Until now the mechanism of radial diffusion has been assumed but we show here that in-situ acceleration through wave particle interactions, which initial studies dismissed as ineffectual at Saturn, is in fact a vital part of the energetic particle dynamics there. We present evidence from numerical simulations based on Cassini spacecraft data that a particular plasma wave, known as Z-mode, accelerates electrons to MeV energies inside 4 R-S (1 R-S = 60,330 km) through a Doppler shifted cyclotron resonant interaction. Our results show that the Z-mode waves observed are not oblique as previously assumed and are much better accelerators than O-mode waves, resulting in an electron energy spectrum that closely approaches observed values without any transport effects included.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1032 
KW  - astrophysical plasmas
KW  - giant planets
KW  - magnetospheric physics
KW  - diffusion
KW  - pitch angle
KW  - plasma
KW  - radio
KW  - region
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-468342
SN  - 1866-8372
IS  - 1032
ER  - 
TY  - JOUR
A1  - Guo, Yingjie
A1  - Ni, Binbin
A1  - Fu, Song
A1  - Wang, Dedong
A1  - Shprits, Yuri Y.
A1  - Zhelavskaya, Irina
A1  - Feng, Minghang
A1  - Guo, Deyu
T1  - Identification of controlling geomagnetic and solar wind factors for magnetospheric chorus intensity using feature selection techniques
JF  - Journal of geophysical research : A, Space physics
N2  - Using over-5-year EMFISIS wave measurements from Van Allen Probes, we present a detailed survey to identify the controlling factors among the geomagnetic indices and solar wind parameters for the 1-min root mean square amplitudes of lower band chorus (LBC) and upper band chorus (UBC). 
A set of important features are automatically determined by feature selection techniques, namely, Random Forest and Maximum Relevancy Minimum Redundancy. Our analysis results indicate the AE index with zero-time-delay dominates the intensity evolution of LBC and UBC, consistent with the evidence that chorus waves prefer to occur and amplify during enhanced substorm periods. Regarding solar wind parameters, solar wind speed and IMF B-z are identified as the controlling factors for chorus wave intensity. Using the combination of all these important features, a predictive neural network model of chorus wave intensity is established to reconstruct the temporal variations of chorus wave intensity, for which application of Random Forest produces the overall best performance. 

Plain Language Summary
Whistler mode chorus waves are electromagnetic waves observed in the low-density region near the geomagnetic equator outside the plasmapause. The dynamics of Earth's radiation belts are largely influenced by chorus waves owing to their dual contributions to both radiation belt electron acceleration and loss. In this study, we use feature selection techniques to identify the controlling geomagnetic and solar wind factors for magnetospheric chorus waves. Feature selection techniques implement the processes which can select the features most influential to the output. 
In this study, the inputs are geomagnetic indices and solar wind parameters and the output is the chorus wave intensity. The results indicate that AE index with zerotime delay dominates the chorus wave intensity. Furthermore, solar wind speed and IMF B-z are identified as the most important solar wind drivers for chorus wave intensity. 
On basis of the combination of all these important geomagnetic and solar wind controlling factors, we develop a neural network model of chorus wave intensity, and find that the model with the inputs identified using the Random Forest method produces the overall best performance.
Y1  - 2021
U6  - https://doi.org/10.1029/2021JA029926
SN  - 2169-9380
SN  - 2169-9402
VL  - 127
IS  - 1
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Prol, Fabricio S.
A1  - Smirnov, Artem G.
A1  - Hoque, M. Mainul
A1  - Shprits, Yuri Y.
T1  - Combined model of topside ionosphere and plasmasphere derived from radio-occultation and Van Allen Probes data
JF  - Scientific reports
N2  - In the last years, electron density profile functions characterized by a linear dependence on the scale height showed good results when approximating the topside ionosphere. The performance above 800 km, however, is not yet well investigated. 
This study investigates the capability of the semi-Epstein functions to represent electron density profiles from the peak height up to 20,000 km. Electron density observations recorded by the Van Allen Probes were used to resolve the scale height dependence in the plasmasphere. 
It was found that the linear dependence of the scale height in the topside ionosphere cannot be directly used to extrapolate profiles above 800 km. 
We find that the dependence of scale heights on altitude is quadratic in the plasmasphere. A statistical model of the scale heights is therefore proposed. After combining the topside ionosphere and plasmasphere by a unified model, we have obtained good estimations not only in the profile shapes, but also in the Total Electron Content magnitude and distributions when compared to actual measurements from 2013, 2014, 2016 and 2017. 
Our investigation shows that Van Allen Probes can be merged to radio-occultation data to properly represent the upper ionosphere and plasmasphere by means of a semi-Epstein function.
Y1  - 2022
U6  - https://doi.org/10.1038/s41598-022-13302-1
SN  - 2045-2322
VL  - 12
IS  - 1
PB  - Macmillan Publishers Limited, part of Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Ni, Binbin
A1  - Cao, Xing
A1  - Shprits, Yuri Y.
A1  - Summers, Danny
A1  - Gu, Xudong
A1  - Fu, Song
A1  - Lou, Yuequn
T1  - Hot Plasma Effects on the Cyclotron-Resonant Pitch-Angle Scattering Rates of Radiation Belt Electrons Due to EMIC Waves
JF  - Geophysical research letters
N2  - To investigate the hot plasma effects on the cyclotron-resonant interactions between electromagnetic ion cyclotron (EMIC) waves and radiation belt electrons in a realistic magnetospheric environment, calculations of the wave-induced bounce-averaged pitch angle diffusion coefficients are performed using both the cold and hot plasma dispersion relations. The results demonstrate that the hot plasma effects have a pronounced influence on the electron pitch angle scattering rates due to all three EMIC emission bands (H+, He+, and O+) when the hot plasma dispersion relation deviates significantly from the cold plasma approximation. For a given wave spectrum, the modification of the dispersion relation by hot anisotropic protons can strongly increase the minimum resonant energy for electrons interacting with O+ band EMIC waves, while the minimum resonant energies for H+ and He+ bands are not greatly affected. For H+ band EMIC waves, inclusion of hot protons tends to weaken the pitch angle scattering efficiency of >5MeV electrons. The most crucial differences introduced by the hot plasma effects occur for >3MeV electron scattering rates by He+ band EMIC waves. Mainly due to the changes of resonant frequency and wave group velocity when the hot protons are included, the difference in scattering rates can be up to an order of magnitude, showing a strong dependence on both electron energy and equatorial pitch angle. Our study confirms the importance of including hot plasma effects in modeling the scattering of ultra-relativistic radiation belt electrons by EMIC waves.
Y1  - 2018
U6  - https://doi.org/10.1002/2017GL076028
SN  - 0094-8276
SN  - 1944-8007
VL  - 45
IS  - 1
SP  - 21
EP  - 30
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - GEN
A1  - Smirnov, Artem G.
A1  - Kronberg, Elena A.
A1  - Daly, Patrick W.
A1  - Aseev, Nikita
A1  - Shprits, Yuri Y.
A1  - Kellerman, Adam C.
T1  - Adiabatic Invariants Calculations for Cluster Mission: A Long-Term Product for Radiation Belts Studies
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The Cluster mission has produced a large data set of electron flux measurements in the Earth's magnetosphere since its launch in late 2000. Electron fluxes are measured using Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector as a function of energy, pitch angle, spacecraft position, and time. However, no adiabatic invariants have been calculated for Cluster so far. In this paper we present a step-by-step guide to calculations of adiabatic invariants and conversion of the electron flux to phase space density (PSD) in these coordinates. The electron flux is measured in two RAPID/IES energy channels providing pitch angle distribution at energies 39.2-50.5 and 68.1-94.5 keV in nominal mode since 2004. A fitting method allows to expand the conversion of the differential fluxes to the range from 40 to 150 keV. Best data coverage for phase space density in adiabatic invariant coordinates can be obtained for values of second adiabatic invariant, K, similar to 10(2), and values of the first adiabatic invariant mu in the range approximate to 5-20 MeV/G. Furthermore, we describe the production of a new data product "LSTAR," equivalent to the third adiabatic invariant, available through the Cluster Science Archive for years 2001-2018 with 1-min resolution. The produced data set adds to the availability of observations in Earth's radiation belts region and can be used for long-term statistical purposes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1192 
KW  - L-Asterisk
KW  - magnetosphere
KW  - electrons
KW  - model
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-523915
SN  - 1866-8372
IS  - 2
ER  - 
TY  - JOUR
A1  - Smirnov, Artem
A1  - Shprits, Yuri Y.
A1  - Allison, Hayley
A1  - Aseev, Nikita
A1  - Drozdov, Alexander
A1  - Kollmann, Peter
A1  - Wang, Dedong
A1  - Saikin, Anthony
T1  - An empirical model of the equatorial electron pitch angle distributions in earth's outer radiation belt
JF  - Space Weather: the International Journal of Research and Applications
N2  - In this study, we present an empirical model of the equatorial electron pitch angle distributions (PADs) in the outer radiation belt based on the full data set collected by the Magnetic Electron Ion Spectrometer (MagEIS) instrument onboard the Van Allen Probes in 2012-2019. The PADs are fitted with a combination of the first, third and fifth sine harmonics. The resulting equation resolves all PAD types found in the outer radiation belt (pancake, flat-top, butterfly and cap PADs) and can be analytically integrated to derive omnidirectional flux. We introduce a two-step modeling procedure that for the first time ensures a continuous dependence on L, magnetic local time and activity, parametrized by the solar wind dynamic pressure. We propose two methods to reconstruct equatorial electron flux using the model. The first approach requires two uni-directional flux observations and is applicable to low-PA data. The second method can be used to reconstruct the full equatorial PADs from a single uni- or omnidirectional measurement at off-equatorial latitudes. The model can be used for converting the long-term data sets of electron fluxes to phase space density in terms of adiabatic invariants, for physics-based modeling in the form of boundary conditions, and for data assimilation purposes.
KW  - pitch angle
KW  - radiation belt
KW  - model
KW  - magnetosphere
KW  - van allen probes;
KW  - electrons
Y1  - 2022
U6  - https://doi.org/10.1029/2022SW003053
SN  - 1542-7390
VL  - 20
IS  - 9
PB  - American Geophysical Union
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Zhu, Hui
A1  - Shprits, Yuri Y.
A1  - Spasojevic, M.
A1  - Drozdov, Alexander
T1  - New hiss and chorus waves diffusion coefficient parameterizations from the Van Allen Probes and their effect on long-term relativistic electron radiation-belt VERB simulations
JF  - Journal of Atmospheric and Solar-Terrestrial Physics
N2  - New wave frequency and amplitude models for the nightside and dayside chorus waves are built based on measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument onboard the Van Allen Probes. The corresponding 3D diffusion coefficients are systematically obtained. Compared with previous commonly-used (typical) parameterizations, the new parameterizations result in differences in diffusion rates that depend on the energy and pitch angle. Furthermore, one-year 3D diffusive simulations are performed using the Versatile Electron Radiation Belt (VERB) code. Both typical and new wave parameterizations simulation results are in a good agreement with observations at 0.9 MeV. However, the new parameterizations for nightside chorus better reproduce the observed electron fluxes. These parameterizations will be incorporated into future modeling efforts.
KW  - Inner magnetosphere
KW  - Radiation belts
KW  - Chorus waves
KW  - Diffusion coefficients
KW  - VERB code
Y1  - 2019
U6  - https://doi.org/10.1016/j.jastp.2019.105090
SN  - 1364-6826
SN  - 1879-1824
VL  - 193
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Shprits, Yuri Y.
A1  - Drozdov, Alexander
A1  - Spasojevic, Maria
A1  - Kellerman, Adam C.
A1  - Usanova, Maria E.
A1  - Engebretson, Mark J.
A1  - Agapitov, Oleksiy V.
A1  - Zhelavskaya, Irina
A1  - Raita, Tero J.
A1  - Spence, Harlan E.
A1  - Baker, Daniel N.
A1  - Zhu, Hui
A1  - Aseev, Nikita
T1  - Wave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts
JF  - Nature Communications
Y1  - 2016
U6  - https://doi.org/10.1038/ncomms12883
SN  - 2041-1723
VL  - 7
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Wang, Dedong
A1  - Shprits, Yuri Y.
T1  - On How High-Latitude Chorus Waves Tip the Balance Between Acceleration and Loss of Relativistic Electrons
JF  - Geophysical research letters
N2  - Modeling and observations have shown that energy diffusion by chorus waves is an important source of acceleration of electrons to relativistic energies. By performing long-term simulations using the three-dimensional Versatile Electron Radiation Belt code, in this study, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high-latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high-latitude waves can result in a net loss of MeV electrons. Variations in high-latitude chorus may account for some of the variability of MeV electrons.
KW  - radiation belts
KW  - chorus waves
KW  - high latitude
KW  - acceleration
KW  - loss
KW  - modeling
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL082681
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 14
SP  - 7945
EP  - 7954
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Landis, Daji August
A1  - Saikin, Anthony
A1  - Zhelavskaya, Irina
A1  - Drozdov, Alexander
A1  - Aseev, Nikita
A1  - Shprits, Yuri Y.
A1  - Pfitzer, Maximilian F.
A1  - Smirnov, Artem G.
T1  - NARX Neural Network Derivations of the Outer Boundary Radiation Belt Electron Flux
JF  - Space Weather: the international journal of research and applications
N2  - We present two new empirical models of radiation belt electron flux at geostationary orbit. GOES-15 measurements of 0.8 MeV electrons were used to train a Nonlinear Autoregressive with Exogenous input (NARX) neural network for both modeling GOES-15 flux values and an upper boundary condition scaling factor (BF). The GOES-15 flux model utilizes an input and feedback delay of 2 and 2 time steps (i.e., 5 min time steps) with the most efficient number of hidden layers set to 10. Magnetic local time, Dst, Kp, solar wind dynamic pressure, AE, and solar wind velocity were found to perform as predicative indicators of GOES-15 flux and therefore were used as the exogenous inputs. The NARX-derived upper boundary condition scaling factor was used in conjunction with the Versatile Electron Radiation Belt (VERB) code to produce reconstructions of the radiation belts during the period of July-November 1990, independent of in-situ observations. Here, Kp was chosen as the sole exogenous input to be more compatible with the VERB code. This Combined Release and Radiation Effects Satellite-era reconstruction showcases the potential to use these neural network-derived boundary conditions as a method of hindcasting the historical radiation belts. This study serves as a companion paper to another recently published study on reconstructing the radiation belts during Solar Cycles 17-24 (Saikin et al., 2021, ), for which the results featured in this paper were used.
KW  - radiation belts
KW  - forecasting (1922, 4315, 7924, 7964)
KW  - machine learning (0555)
Y1  - 2022
U6  - https://doi.org/10.1029/2021SW002774
SN  - 1542-7390
VL  - 20
IS  - 5
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Inceoglu, Fadil
A1  - Shprits, Yuri Y.
A1  - Heinemann, Stephan G.
A1  - Bianco, Stefano
T1  - Identification of coronal holes on AIA/SDO images using unsupervised machine learning
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - Through its magnetic activity, the Sun governs the conditions in Earth's vicinity, creating space weather events, which have drastic effects on our space- and ground-based technology. 
One of the most important solar magnetic features creating the space weather is the solar wind that originates from the coronal holes (CHs). 
The identification of the CHs on the Sun as one of the source regions of the solar wind is therefore crucial to achieve predictive capabilities. 

In this study, we used an unsupervised machine-learning method, k-means, to pixel-wise cluster the passband images of the Sun taken by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory in 171, 193, and 211 angstrom in different combinations. 

Our results show that the pixel-wise k-means clustering together with systematic pre- and postprocessing steps provides compatible results with those from complex methods, such as convolutional neural networks. 
More importantly, our study shows that there is a need for a CH database where a consensus about the CH boundaries is reached by observers independently. 
This database then can be used as the "ground truth," when using a supervised method or just to evaluate the goodness of the models.
Y1  - 2022
U6  - https://doi.org/10.3847/1538-4357/ac5f43
SN  - 1538-4357
VL  - 930
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Shprits, Yuri Y.
A1  - Allison, Hayley J.
A1  - Wang, Dedong
A1  - Drozdov, Alexander
A1  - Szabo-Roberts, Matyas
A1  - Zhelavskaya, Irina
A1  - Vasile, Ruggero
T1  - A new population of ultra-relativistic electrons in the outer radiation zone
JF  - Journal of geophysical research : Space physics
N2  - Van Allen Probes measurements revealed the presence of the most unusual structures in the ultra-relativistic radiation belts. Detailed modeling, analysis of pitch angle distributions, analysis of the difference between relativistic and ultra-realistic electron evolution, along with theoretical studies of the scattering and wave growth, all indicate that electromagnetic ion cyclotron (EMIC) waves can produce a very efficient loss of the ultra-relativistic electrons in the heart of the radiation belts. Moreover, a detailed analysis of the profiles of phase space densities provides direct evidence for localized loss by EMIC waves. The evolution of multi-MeV fluxes shows dramatic and very sudden enhancements of electrons for selected storms. Analysis of phase space density profiles reveals that growing peaks at different values of the first invariant are formed at approximately the same radial distance from the Earth and show the sequential formation of the peaks from lower to higher energies, indicating that local energy diffusion is the dominant source of the acceleration from MeV to multi-MeV energies. Further simultaneous analysis of the background density and ultra-relativistic electron fluxes shows that the acceleration to multi-MeV energies only occurs when plasma density is significantly depleted outside of the plasmasphere, which is consistent with the modeling of acceleration due to chorus waves.
KW  - radiation belts
KW  - ultra-relativistic electrons
KW  - EMIC waves
KW  - modeling;
KW  - plasma density
KW  - chorus waves
Y1  - 2022
U6  - https://doi.org/10.1029/2021JA030214
SN  - 2169-9380
SN  - 2169-9402
VL  - 127
IS  - 5
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Drozdov, Alexander
A1  - Allison, Hayley J.
A1  - Shprits, Yuri Y.
A1  - Usanova, Maria E.
A1  - Saikin, Anthony
A1  - Wang, Dedong
T1  - Depletions of Multi-MeV Electrons and their association to Minima in Phase Space Density
JF  - Geophysical research letters
N2  - Fast-localized electron loss, resulting from interactions with electromagnetic ion cyclotron (EMIC) waves, can produce deepening minima in phase space density (PSD) radial profiles. Here, we perform a statistical analysis of local PSD minima to quantify how readily these are associated with radiation belt depletions. The statistics of PSD minima observed over a year are compared to the Versatile Electron Radiation Belts (VERB) simulations, both including and excluding EMIC waves. The observed minima distribution can only be achieved in the simulation including EMIC waves, indicating their importance in the dynamics of the radiation belts. By analyzing electron flux depletions in conjunction with the observed PSD minima, we show that, in the heart of the outer radiation belt (L* < 5), on average, 53% of multi-MeV electron depletions are associated with PSD minima, demonstrating that fast localized loss by interactions with EMIC waves are a common and crucial process for ultra-relativistic electron populations.
KW  - radiation belts
KW  - EMIC
KW  - VERB
KW  - PSD
Y1  - 2022
U6  - https://doi.org/10.1029/2021GL097620
SN  - 0094-8276
SN  - 1944-8007
VL  - 49
IS  - 8
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Ripoll, Jean-François
A1  - Loridan, Vivien
A1  - Cunningham, G. S.
A1  - Reeves, Geoffrey D.
A1  - Shprits, Yuri Y.
T1  - On the time needed to reach an equilibrium structure of the radiation belts
JF  - Journal of geophysical research : Space physics
N2  - In this study, we complement the notion of equilibrium states of the radiation belts with a discussion on the dynamics and time needed to reach equilibrium. We solve for the equilibrium states obtained using 1-D radial diffusion with recently developed hiss and chorus lifetimes at constant values of Kp = 1, 3, and 6. We find that the equilibrium states at moderately low Kp, when plotted versus L shell (L) and energy (E), display the same interesting S shape for the inner edge of the outer belt as recently observed by the Van Allen Probes. The S shape is also produced as the radiation belts dynamically evolve toward the equilibrium state when initialized to simulate the buildup after a massive dropout or to simulate loss due to outward diffusion from a saturated state. Physically, this shape, intimately linked with the slot structure, is due to the dependence of electron loss rate (originating from wave-particle interactions) on both energy and L shell. Equilibrium electron flux profiles are governed by the Biot number (tau(Diffusion)/tau(loss)), with large Biot number corresponding to low fluxes and low Biot number to large fluxes. The time it takes for the flux at a specific (L, E) to reach the value associated with the equilibrium state, starting from these different initial states, is governed by the initial state of the belts, the property of the dynamics (diffusion coefficients), and the size of the domain of computation. Its structure shows a rather complex scissor form in the (L, E) plane. The equilibrium value (phase space density or flux) is practically reachable only for selected regions in (L, E) and geomagnetic activity. Convergence to equilibrium requires hundreds of days in the inner belt for E>300 keV and moderate Kp (<= 3). It takes less time to reach equilibrium during disturbed geomagnetic conditions (Kp = 3), when the system evolves faster. Restricting our interest to the slot region, below L = 4, we find that only small regions in (L, E) space can reach the equilibrium value: E similar to [200, 300] keV for L= [3.7, 4] at Kp= 1, E similar to[0.6, 1] MeV for L = [3, 4] at Kp = 3, and E similar to 300 keV for L = [3.5, 4] at Kp = 6 assuming no new incoming electrons.
Y1  - 2016
U6  - https://doi.org/10.1002/2015JA022207
SN  - 2169-9380
SN  - 2169-9402
VL  - 121
SP  - 7684
EP  - 7698
PB  - American Geophysical Union
CY  - Washington
ER  -