Equatorial pitch angle distributions in Earth's radiation belts: an empirical model from Van Allen Probes data

2020 ◽  
Author(s):  
Artem Smirnov ◽  
Yuri Shprits ◽  
Hayley Allison ◽  
Nikita Aseev
Keyword(s):  
Solar Activity ◽  
Empirical Model ◽  
Pitch Angle ◽  
Electron Flux ◽  
Dynamic Pressure ◽  
Radiation Belts ◽  
Data Set ◽  
Van Allen Probes ◽  
Flux Measurements ◽  
Solar Wind Parameters

<p><span>Earth’s radiation belts comprise complex and dynamic systems, depending substantially on solar activity. The pitch angle distributions (PADs) play an important role for radiation belts modelling, as they yield information on the particle transport, source and loss processes. Yet, many missions flying in the radiation belts provide omni-directional or uni-directional electron flux measurements and do not resolve pitch angles. We propose an empirical model of the equatorial PADs and a method to retrieve PADs from omni-directional flux measurements at different energies and locations along the inclined orbits. We use the entire dataset of MagEIS and REPT instruments aboard the Van Allen Probes (RBSP) mission to analyze the equatorial pitch angle distributions in the energy range from 30 keV to 6.2 MeV. The fitting method resolves all main types of PADs, including butterfly and cap distributions, and the resulting coefficients are directly related to the PAD shapes. The developed model can be used to obtain pitch angle resolved fluxes for GPS, Arase and other missions. The proposed algorithm is applied to the GPS electron flux data set to obtain the pitch-angle resolved fluxes, which are compared to the RBSP data at a number of GPS-RBSP conjunctions. The proposed model also allows one to reconstruct the pitch-angle resolved data using LEO measurements. The dynamics of the fitting coefficients based on solar activity is discussed with respect to AE, Kp, Dst indices and solar wind parameters: velocity, density and dynamic pressure.</span></p>

scholarly journals Electron acceleration at Jupiter: input from cyclotron-resonant interaction with whistler-mode chorus waves

2013 ◽  
Vol 31 (10) ◽  
pp. 1619-1630 ◽  
Author(s):  
E. E. Woodfield ◽  
R. B. Horne ◽  
S. A. Glauert ◽  
J. D. Menietti ◽  
Y. Y. Shprits
Keyword(s):  
Pitch Angle ◽  
Electron Flux ◽  
Electron Acceleration ◽  
Resonant Interaction ◽  
Radiation Belts ◽  
Resonant Wave ◽  
Resonant Interactions ◽  
Energy Diffusion ◽  
Chorus Waves ◽  
L 14

Abstract. Jupiter has the most intense radiation belts of all the outer planets. It is not yet known how electrons can be accelerated to energies of 10 MeV or more. It has been suggested that cyclotron-resonant wave-particle interactions by chorus waves could accelerate electrons to a few MeV near the orbit of Io. Here we use the chorus wave intensities observed by the Galileo spacecraft to calculate the changes in electron flux as a result of pitch angle and energy diffusion. We show that, when the bandwidth of the waves and its variation with L are taken into account, pitch angle and energy diffusion due to chorus waves is a factor of 8 larger at L-shells greater than 10 than previously shown. We have used the latitudinal wave intensity profile from Galileo data to model the time evolution of the electron flux using the British Antarctic Survey Radiation Belt (BAS) model. This profile confines intense chorus waves near the magnetic equator with a peak intensity at ∼5° latitude. Electron fluxes in the BAS model increase by an order of magnitude for energies around 3 MeV. Extending our results to L = 14 shows that cyclotron-resonant interactions with chorus waves are equally important for electron acceleration beyond L = 10. These results suggest that there is significant electron acceleration by cyclotron-resonant interactions at Jupiter contributing to the creation of Jupiter's radiation belts and also increasing the range of L-shells over which this mechanism should be considered.

scholarly journals A background correction algorithm for Van Allen Probes MagEIS electron flux measurements

2015 ◽  
Vol 120 (7) ◽  
pp. 5703-5727 ◽  
Author(s):  
S. G. Claudepierre ◽  
T. P. O'Brien ◽  
J. B. Blake ◽  
J. F. Fennell ◽  
J. L. Roeder ◽  
...  
Keyword(s):  
Electron Flux ◽  
Background Correction ◽  
Correction Algorithm ◽  
Van Allen Probes ◽  
Flux Measurements

scholarly journals Statistical study of the proton isotropy boundary

2005 ◽  
Vol 23 (4) ◽  
pp. 1311-1316 ◽  
Author(s):  
E. A. Lvova ◽  
V. A. Sergeev ◽  
G. R. Bagautdinova
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Empirical Relationship ◽  
Large Data ◽  
Magnetic Activity ◽  
Least Square ◽  
Quiet Time ◽  
Data Set ◽  
Ae Index ◽  
Solar Wind Parameters

Abstract. Based on a large data set of polar NOAA-type satellite observations we studied the latitude-MLT shape of the 80keV proton isotropy boundary (IB) as a function of the solar wind parameters and magnetic activity. Using "snapshots" of isotropy boundaries near-simultaneously crossed at four points we found that its equatorward expansion, as well as its dawn-dusk shift, depends mostly on the AE-index and on the corrected Dst*, whereas the amplitude of the IB daily variation is mostly controlled by the solar wind dynamic pressure. Applying a nonlinear, multi-parametric, least-square regression procedure, the empirical relationship describing the IB latitude as a function of MLT and AE, Pd, Dst* parameters was obtained. Comparing it with the predictions from the Tsyganenko-2001 model we found a good agreement during the quiet time but some important differences during the disturbed periods. Interpretation of these results in terms of the properties of the magnetospheric configuration is briefly discussed.

scholarly journals An Empirical Model of Radiation Belt Electron Pitch Angle Distributions Based On Van Allen Probes Measurements

2018 ◽  
Vol 123 (5) ◽  
pp. 3493-3511 ◽  
Author(s):  
H. Zhao ◽  
R. H. W. Friedel ◽  
Y. Chen ◽  
G. D. Reeves ◽  
D. N. Baker ◽  
...  
Keyword(s):  
Empirical Model ◽  
Pitch Angle ◽  
Radiation Belt ◽  
Van Allen Probes

Electron filling and proton loss in radiation belts and SAA during 2018 storm based on ZH-1 satellite observations

2021 ◽  
Author(s):  
Zhenxia Zhang
Keyword(s):  
Geomagnetic Storm ◽  
Radiation Belt ◽  
Electron Flux ◽  
Outer Boundary ◽  
Energetic Electron ◽  
High Energy ◽  
Radiation Belts ◽  
High Energy Particle ◽  
Van Allen Probes ◽  
Proton Loss

<p>Based on data from the ZH-1 satellites, companied with Van Allen Probes and NOAA observations, we analyze the high energy particle evolutions in radiation belts, slot region and SAA during August 2018 major geomagnetic storm (minimum Dst ≈ −190 nT). </p><p>  1) Relativistic electron enhancements in extremely low L-shell regions (reaching L ∼ 3) were observed during storm. Contrary to what occurs in the outer belt, such an intense and deep electron penetration event is rare and more interesting. Strong whistler-mode (chorus and hiss) waves, with amplitudes 81–126 pT, were also observed in the extremely low L-shell simultaneously (reaching L ∼ 2.5) where the plasmapause was suppressed. The bounce-averaged diffusion coefficient calculations support that the chorus waves can play a significantly important role in diffusing and accelerating the 1–3 MeV electrons even in such low L-shells during storms.</p><p>2) A robust evidence is clearly demonstrated that the energetic electron flux with energy 30∼600 keV are increased by 2∼3 times in the inner radiation belt near equator and SAA region on dayside during the major geomagnetic storm. This is the first time that the 100s keV electron flux enhancement is reported to be potentially induced by the interaction with magnetosonic waves in extremely low L-shells (L<2) observed by Van Allen Probes. Proton loss in outer boundary of inner radiation belt takes place in energy of 2~220 MeV extensively during the occurrence of this storm but the loss mechanism is energy dependence which is consistent with some previous studies. It is confirmed that the magnetic field line curvature scattering plays a significant role in the proton loss phenomenon in energy 30-100 MeV during this storm. This work provides a beneficial help to comprehensively understand the charged particles trapping and loss in SAA region and inner radiation belt dynamic physics.</p>

Plasma Sheet Convection Velocities Inferred From Electron Flux Measurements at Synchronous Altitude

Radio Science ◽  
1971 ◽  
Vol 6 (2) ◽  
pp. 305-313 ◽  
Author(s):  
E. G. Shelley ◽  
R. G. Johnson ◽  
R. D. Sharp
Keyword(s):  
Plasma Sheet ◽  
Electron Flux ◽  
Flux Measurements

scholarly journals Building prediction models for coronary heart disease by synthesizing multiple longitudinal research findings

2005 ◽  
Vol 12 (5) ◽  
pp. 459-464 ◽  
Author(s):  
Guizhou Hu ◽  
Martin M. Root
Keyword(s):  
Coronary Heart Disease ◽  
Heart Disease ◽  
Prediction Model ◽  
Empirical Model ◽  
Complex Disease ◽  
Prediction Models ◽  
Longitudinal Research ◽  
Study Data ◽  
Individual Risk ◽  
Data Set

Background No methodology is currently available to allow the combining of individual risk factor information derived from different longitudinal studies for a chronic disease in a multivariate fashion. This paper introduces such a methodology, named Synthesis Analysis, which is essentially a multivariate meta-analytic technique. Design The construction and validation of statistical models using available data sets. Methods and results Two analyses are presented. (1) With the same data, Synthesis Analysis produced a similar prediction model to the conventional regression approach when using the same risk variables. Synthesis Analysis produced better prediction models when additional risk variables were added. (2) A four-variable empirical logistic model for death from coronary heart disease was developed with data from the Framingham Heart Study. A synthesized prediction model with five new variables added to this empirical model was developed using Synthesis Analysis and literature information. This model was then compared with the four-variable empirical model using the first National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-up Study data set. The synthesized model had significantly improved predictive power ( x2 = 43.8, P < 0.00001). Conclusions Synthesis Analysis provides a new means of developing complex disease predictive models from the medical literature.

scholarly journals Evaluation of the geometry of ionospheric current systems related to rapid geomagnetic variations

2004 ◽  
Vol 22 (1) ◽  
pp. 63-72 ◽  
Author(s):  
S. V. Apatenkov ◽  
V. A. Sergeev ◽  
R. Pirjola ◽  
A. Viljanen
Keyword(s):  
Dynamic Pressure ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Middle Part ◽  
Magnetic Storms ◽  
Geomagnetically Induced Currents ◽  
Geomagnetic Variations ◽  
Ionospheric Current ◽  
Solar Wind Parameters ◽  
Current Systems

Abstract. To learn about the geometry and sources of the ionospheric current systems which generate strong geomagnetically induced currents, we categorize differential equivalent current systems (DEC) for events with strong dB/dt by decomposing them into the contributions of electrojet-type and vortex-type elementary systems. By solving the inverse problem we obtain amplitudes and locations of these elementary current systems. One-minute differences of the geomagnetic field values at the IMAGE magnetometer network in 1996–2000 are analysed to study the spatial distributions of large dB/dt events. The relative contributions of the two components are evaluated. In particular, we found that the majority of the strongest dB/dt events (100–1000nT/min) appear to be produced by the vortex-type current structures and most of them occur in the morning LT hours, probably caused by the Ps6 pulsation events associated with auroral omega structures. For strong dB/dt events the solar wind parameters are shifted toward strong (tens nT) southward IMF, enhanced velocity and dynamic pressure, in order for the main phase of the magnetic storms to occur. Although these events appear mostly during magnetic storms when the auroral oval greatly expands, the area of large dB/dt stays in the middle part of the auroral zone; therefore, it is connected to the processes taking part in the middle of the magnetosphere rather than in its innermost region populated by the ring current. Key words. Geomagnetism and paleomagnetism (rapid time variations) – Ionosphere (auroral ionosphere; ionospheric disturbances)

scholarly journals Multi-satellite simultaneous observations of magnetopause and atmospheric losses of radiation belt electrons during an intense solar wind dynamic pressure pulse

2016 ◽  
Vol 34 (5) ◽  
pp. 493-509 ◽  
Author(s):  
Zheng Xiang ◽  
Binbin Ni ◽  
Chen Zhou ◽  
Zhengyang Zou ◽  
Xudong Gu ◽  
...  
Keyword(s):  
Solar Wind ◽  
Radiation Belt ◽  
Pressure Pulse ◽  
Electron Flux ◽  
Dynamic Pressure ◽  
Energetic Electron ◽  
Solar Wind Dynamic Pressure ◽  
Angle Scattering ◽  
Radiation Belt Electrons ◽  
Atmospheric Loss

<p><strong>Abstract.</strong> Radiation belt electron flux dropouts are a kind of drastic variation in the Earth's magnetosphere, understanding of which is of both scientific and societal importance. Using electron flux data from a group of 14 satellites, we report multi-satellite simultaneous observations of magnetopause and atmospheric losses of radiation belt electrons during an event of intense solar wind dynamic pressure pulse. When the pulse occurred, magnetopause and atmospheric loss could take effect concurrently contributing to the electron flux dropout. Losses through the magnetopause were observed to be efficient and significant at <i>L</i> ≳ 5, owing to the magnetopause intrusion into <i>L</i> ∼ 6 and outward radial diffusion associated with sharp negative gradient in electron phase space density. Losses to the atmosphere were directly identified from the precipitating electron flux observations, for which pitch angle scattering by plasma waves could be mainly responsible. While the convection and substorm injections strongly enhanced the energetic electron fluxes up to hundreds of keV, they could delay other than avoid the occurrence of electron flux dropout at these energies. It is demonstrated that the pulse-time radiation belt electron flux dropout depends strongly on the specific interplanetary and magnetospheric conditions and that losses through the magnetopause and to the atmosphere and enhancements of substorm injection play an essential role in combination, which should be incorporated as a whole into future simulations for comprehending the nature of radiation belt electron flux dropouts.</p>

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