TY - JOUR A1 - Kim, Kyung-Chan A1 - Shprits, Yuri Y. T1 - Survey of the Favorable Conditions for Magnetosonic Wave Excitation JF - Journal of geophysical research : Space physics N2 - The ratio of the proton ring velocity (VR) to the local Alfven speed (VA), in addition to proton ring distributions, plays a key factor in the excitation of magnetosonic waves at frequencies between the proton cyclotron frequency fcp and the lower hybrid resonance frequency fLHR in the Earth's magnetosphere. Here we investigate whether there is a statistically significant relationship between occurrences of proton rings and magnetosonic waves both outside and inside the plasmapause using particle and wave data from Van Allen Probe-A during the time period of October 2012 to December 2015. We also perform a statistical survey of the ratio of the ring energy (ER, corresponding to VR) to the Alfven energy (EA, corresponding to VA) to determine the favorable conditions under which magnetosonic waves in each of two frequency bands (fcp < f ≤ 0.5 fLHR and 0.5 fLHR < f < fLHR) can be excited. The results show that the magnetosonic waves in both frequency bands occur around the postnoon (12–18 magnetic local time, MLT) sector outside the plasmapause when ER is comparable to or lower than EA, and those in lower-frequency bands (fcp < f ≤ 0.5 fLHR) occur around the postnoon sector inside the plasmapause when ER/EA > ~9. However, there is one discrepancy between occurrences of proton rings and magnetosonic waves in low-frequency bands around the prenoon sector (6–12 MLT) outside the plasmapause, which suggests either that the waves may have propagated during active time from the postnoon sector after being excited during quiet time, or they may have locally excited in the prenoon sector during active time. Y1 - 2018 U6 - https://doi.org/10.1002/2017JA024865 SN - 2169-9380 SN - 2169-9402 VL - 123 IS - 1 SP - 400 EP - 413 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Shprits, Yuri Y. A1 - Kellerman, Adam C . A1 - Aseev, Nikita A1 - Drozdov, Alexander A1 - Michaelis, Ingo T1 - Multi-MeV electron loss in the heart of the radiation belts JF - Geophysical research letters N2 - Significant progress has been made in recent years in understanding acceleration mechanisms in the Earth's radiation belts. In particular, a number of studies demonstrated the importance of the local acceleration by analyzing the radial profiles of phase space density (PSD) and observing building up peaks in PSD. In this study, we focus on understanding of the local loss using very similar tools. The profiles of PSD for various values of the first adiabatic invariants during the previously studied 17 January 2013 storm are presented and discussed. The profiles of PSD show clear deepening minimums consistent with the scattering by electromagnetic ion cyclotron waves. Long-term evolution shows that local minimums in PSD can persist for relatively long times. During considered interval of time the deepening minimums were observed around L* = 4 during 17 January 2013 storm and around L* = 3.5 during 1 March 2013 storm. This study shows a new method that can help identify the location, magnitude, and time of the local loss and will help quantify local loss in the future. This study also provides additional clear and definitive evidence that local loss plays a major role for the dynamics of the multi-MeV electrons. Y1 - 2017 U6 - https://doi.org/10.1002/2016GL072258 SN - 0094-8276 SN - 1944-8007 VL - 44 IS - 3 SP - 1204 EP - 1209 PB - American Geophysical Union CY - Washington ER - TY - GEN A1 - Shprits, Yuri Y. A1 - Zhelavskaya, Irina A1 - Green, Janet C. A1 - Pulkkinen, Antti A. A1 - Horne, Richard B. A1 - Pitchford, David A1 - Glover, Alexi T1 - Discussions on Stakeholder Requirements for Space Weather-Related Models T2 - Space Weather: The International Journal of Research and Applications N2 - Participants of the 2017 European Space Weather Week in Ostend, Belgium, discussed the stakeholder requirements for space weather-related models. It was emphasized that stakeholders show an increased interest in space weather-related models. Participants of the meeting discussed particular prediction indicators that can provide first-order estimates of the impact of space weather on engineering systems. KW - 7924 KW - 7934 KW - 7959 Y1 - 2018 U6 - https://doi.org/10.1002/2018SW001864 SN - 1542-7390 VL - 16 IS - 4 SP - 341 EP - 342 PB - American Geophysical Union CY - Washington 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 - Kollmann, Peter A1 - Roussos, Elias A1 - Clark, George A1 - Cooper, John F. A1 - Sturner, Steven J. A1 - Kotova, Anna A1 - Regoli, Leonardo A1 - Shprits, Yuri Y. A1 - Aseev, Nikita A1 - Krupp, Norbert T1 - Spectra of Saturn's proton belts revealed JF - Icarus N2 - Saturn is permanently surrounded by 6 discrete proton radiation belts that are rigidly separated by the orbits of its inner moons and dense rings. These radiation belts are ideal environments to study the details of radial diffusion and the CRAND source process, yet progress has been hindered by the fact that the energy spectra are not known with certainty: Reanalysis of the response functions of the LEMMS instrument on-board the Cassini orbiter has shown that measurements of less than or similar to 10 MeV protons may be easily contaminated by greater than or similar to 10 MeV protons and that many available measurements characterize a very broad energy range, so that the calculation of an energy-resolved spectrum is not as straightforward as previously assumed. Here we use forward modeling of the measurements based on the instrument response and combine this technique where useful with numerical modeling of the proton belt physics in order to determine Saturn's spectra with higher certainty. We find significant proton intensities up to approximate to 1 GeV. While earlier studies reported on proton spectra roughly following a power law with exponent approximate to -2, our more advanced analysis shows harder spectra with exponent approximate to -1. The observed spectra provide independent confirmation that Saturn's proton belts are sourced by CRAND and are consistent with the provided protons being subsequently cooled in the tenuous gas originating from Saturn or Enceladus. The intensities at Saturn are found to be lower than at Jupiter and Earth, which is also consistent with the source of Saturn being exclusively CRAND, while the other planets can draw from additional processes. Our new spectra can be used in the future to further our understanding of Saturn's proton belts and the respective physical processes that occur at other magnetized planets in general. Also, the spectra have applications for several topics of planetary science, such as space weathering of Saturn's moons and rings, and can be useful to constrain properties of the main rings through their production of secondary particles. KW - Radiation belts KW - Saturn KW - CRAND KW - Proton Y1 - 2022 U6 - https://doi.org/10.1016/j.icarus.2021.114795 SN - 0019-1035 SN - 1090-2643 VL - 376 PB - Elsevier CY - San Diego 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