scholarly journals A Comparison of Radial Diffusion Coefficients in 1-D and 3-D Long-Term Radiation Belt Simulations

2020 ◽  
Author(s):  
Alexander Drozdov ◽  
Hayley Allison ◽  
Yuri Shprits ◽  
Nikita Aseev
Keyword(s):  
Radiation Belt ◽  
Low Frequency ◽  
Radial Diffusion ◽  
Ulf Waves ◽  
Electron Radiation ◽  
Particle Interactions ◽  
Physical Mechanisms ◽  
Modeling And Forecasting ◽  
Radiation Belt Electrons

<p>Radial diffusion is one of the dominant physical mechanisms that drives acceleration andloss of the radiation belt electrons due to wave-particle interactions with ultra-low frequency (ULF) waves, which makes it very important for radiation belt modeling and forecasting.  We investigate the sensitivity of several parameterizations of the radial diffusion including Brautigam and Albert (2000), Ozeke et al. (2014), Ali et al. (2016), and Liu et al. (2016) on long-term radiation belt modeling using the Versatile Electron Radiation Belt (VERB) code.  Following previous studies, we first perform 1-D radial diffusion simulations.  To take into account effects of local acceleration and loss, we perform additional 3-D simulations, including pitch-angle, energy and mixed diffusion.</p>

The magnetospheric interactions of predicted ULF wave power

2021 ◽  
Author(s):  
Sarah Bentley ◽  
Rhys Thompson ◽  
Clare Watt ◽  
Jennifer Stout ◽  
Teo Bloch
Keyword(s):  
Solar Wind ◽  
Radiation Belt ◽  
Internal State ◽  
Low Frequency ◽  
Ulf Waves ◽  
Wave Power ◽  
Ulf Wave ◽  
Radiation Belt Electrons ◽  
Spatial Parameters ◽  
The Given

<p>We present and analyse a freely-available model of the power found in ultra-low frequency waves (ULF, 1-15 mHz) throughout Earth’s magnetosphere. Predictions can be used to test our understanding of magnetospheric dynamics, while accurate models of these waves are required to characterise the energisation and transport of radiation belt electrons in space weather.</p><p>This model is constructed using decision tree ensembles, which iteratively partition the given parameter space into variable size bins. Wave power is determined by physical driving parameters (e.g. solar wind properties) and spatial parameters of interest (magnetic local time MLT, magnetic latitude and frequency). As a parameterised model, there is no guarantee that individual physical processes can be extracted and analysed. However, by iteratively considering smaller scale driving processes, we identify predominant wave drivers and find that solar wind driving of ULF waves are moderated by internal magnetospheric conditions. Significant remaining uncertainty occurs with mild solar wind driving, suggesting that the internal state of the magnetosphere should be included in future.</p><p>Models such as this may be used to create global magnetospheric “maps” of predicted wave power which may then be used to create radial diffusion coefficients determining the effect of ULF waves on radiation belt electrons.</p>

Global models of the inner electron radiation belt and slot region investigating the effects of VLF transmitter waves

2020 ◽  
Author(s):  
Johnathan Ross ◽  
Sarah Glauert ◽  
Richard Horne ◽  
Nigel Meredith ◽  
Mark Clilverd
Keyword(s):  
Radiation Belt ◽  
Low Frequency ◽  
Particle Interactions ◽  
Electron Dynamics ◽  
Global Models ◽  
Inner Magnetosphere ◽  
The Earth ◽  
Radiation Belt Electrons ◽  
Wave Particle Interactions ◽  
Earth Orbits

<p>Signals from man-made very low frequency (VLF) transmitters can leak from the Earth-ionosphere wave guide into the inner magnetosphere, where they propagate in the whistler mode and contribute to electron dynamics in the inner radiation belt and slot region through wave-particle interactions. These inner regions of the magnetosphere are becoming increasingly important from a satellite perspective. For instance, the newly populated Medium Earth Orbits pass though the slot region, and satellites launched via electric orbit raising are exposed to the inner belt and slot region for extended periods of time.</p><p>We have calculated diffusion coefficients associated with wave-particle interactions between radiation belt electrons and waves from each of the strongest VLF transmitters using Van Allen Probe observations. These coefficients are included into global models of the radiation belts to assess the importance of the effects of VLF transmitters individually and collectively on electron populations.</p>

scholarly journals A first approach to model the low-frequency wave activity in the plasmasphere

2002 ◽  
Vol 20 (7) ◽  
pp. 981-996 ◽  
Author(s):  
R. André ◽  
F. Lefeuvre ◽  
F. Simonet ◽  
U. S. Inan
Keyword(s):  
Wave Field ◽  
Radiation Belt ◽  
Low Frequency ◽  
Plasma Waves ◽  
Particle Interactions ◽  
Frequency Wave ◽  
Magnetic Wave ◽  
Amplitude Spectra ◽  
Radiation Belt Electrons ◽  
Instruments And Techniques

Abstract. A comprehensive empirical model of waves is developed in the objective to simulate wave-particle interactions involved in the loss and acceleration of radiation belt electrons. Three years of measured magnetic wave field components from the Plasma Wave Instrument on board the DE-1 satellite are used to model the amplitude spectral density of the magnetic wave field of each type of emission observed in the equatorial regions of the plasmasphere: VLF transmitter emissions, chorus emissions, plasmaspheric hiss emissions and equatorial emissions below ~ 200 Hz. Each model is a function of the wave frequency f , the MLT, L and Mlat parameters, and the Kp values. The performances of the plasmaspheric hiss and chorus models are tested on amplitude spectra recorded on board the OGO-5 and GEOS-1 satellites.Key words. Magnetospheric physics (plasmasphere; plasma waves and instabilities; instruments and techniques)

ULF Wave Power During Geomagnetic Storms and Implications for Radial Diffusion Processes

2021 ◽  
Author(s):  
Jasmine Sandhu ◽  
Jonathan Rae ◽  
John Wygant ◽  
Aaron Breneman ◽  
Sheng Tian ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Diffusion Coefficients ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Radial Diffusion ◽  
Ulf Waves ◽  
Wave Power ◽  
Outer Radiation Belt ◽  
Large Variability ◽  
Ulf Wave

<p>Ultra Low Frequency (ULF) waves drive radial diffusion of radiation belt electrons, where this process contributes to and, at times, dominates energisation, loss, and large scale transport of the outer radiation belt. In this study we quantify the changes and variability in ULF wave power during geomagnetic storms, through a statistical analysis of Van Allen Probes data for the time period spanning 2012 – 2019. The results show that global wave power enhancements occur during the main phase, and continue into the recovery phase of storms. Local time asymmetries show sources of ULF wave power are both external solar wind driving as well as internal sources from coupling with ring current ions and substorms.</p><p>The statistical analysis demonstrates that storm time ULF waves are able to access lower L values compared to pre-storm conditions, with enhancements observed within L = 4. We assess how magnetospheric compressions and cold plasma distributions shape how ULF wave power propagates through the magnetosphere. Results show that the Earthward displacement of the magnetopause is a key factor in the low L enhancements. Furthermore, the presence of plasmaspheric plumes during geomagnetic storms plays a crucial role in trapping ULF wave power, and contributes significantly to large storm time enhancements in ULF wave power.</p><p>The results have clear implications for enhanced radial diffusion of the outer radiation belt during geomagnetic storms. Estimates of storm time radial diffusion coefficients are derived from the ULF wave power observations, and compared to existing empirical models of radial diffusion coefficients. We show that current Kp-parameterised models, such as the Ozeke et al. [2014] model, do not fully capture the large variability in storm time radial diffusion coefficients or the extent of enhancements in the magnetic field diffusion coefficients.</p>

scholarly journals Magnetospheric Response to Solar Wind Forcing: ULF Wave – Particle Interaction Perspective

2021 ◽  
Author(s):  
Qiugang Zong
Keyword(s):  
Solar Wind ◽  
Radiation Belt ◽  
Ring Current ◽  
Dynamic Pressure ◽  
Plasma Heating ◽  
Interplanetary Shock ◽  
Wind Forcing ◽  
Ulf Waves ◽  
Radiation Belt Electrons ◽  
The Impact

Abstract. Solar wind forcing, e.g. interplanetary shock and/or solar wind dynamic pressure pulses impact on the Earth’s magnetosphere manifests many fundamental important space physics phenomena including producing electromagnetic waves, plasma heating and energetic particle acceleration. This paper summarizes our present understanding of the magnetospheric response to solar wind forcing in the aspects of radiation belt electrons, ring current ions and plasmaspheric plasma physics based on in situ spacecraft measurements, ground-based magnetometer data, MHD and kinetic simulations. Magnetosphere response to solar wind forcing, is not just a “one-kick” scenario. It is found that after the impact of solar wind forcing on the Earth’s magnetosphere, plasma heating and energetic particle acceleration started nearly immediately and could last for a few hours. Even a small dynamic pressure change of interplanetary shock or solar wind pressure pulse can play a non-negligible role in magnetospheric physics. The impact leads to generate series kind of waves including poloidal mode ultra-low frequency (ULF) waves. The fast acceleration of energetic electrons in the radiation belt and energetic ions in the ring current region response to the impact usually contains two contributing steps: (1) the initial adiabatic acceleration due to the magnetospheric compression; (2) followed by the wave-particle resonant acceleration dominated by global or localized poloidal ULF waves excited at various L-shells. Generalized theory of drift and drift-bounce resonance with growth or decay localized ULF waves has been developed to explain in situ spacecraft observations. The wave related observational features like distorted energy spectrum, boomerang and fishbone pitch angle distributions of radiation belt electrons, ring current ions and plasmaspheric plasma can be explained in the frame work of this generalized theory. It is worthy to point out here that poloidal ULF waves are much more efficient to accelerate and modulate electrons (fundamental mode) in the radiation belt and charged ions (second harmonic) in the ring current region. The results presented in this paper can be widely used in solar wind interacting with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields.

Combined Scattering of Radiation Belt Electrons by Low‐Frequency Hiss: Cyclotron, Landau, and Bounce Resonances

2020 ◽  
Vol 47 (5) ◽  
Author(s):  
Song Fu ◽  
Juan Yi ◽  
Binbin Ni ◽  
Ruoxian Zhou ◽  
Zejun Hu ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Low Frequency ◽  
Radiation Belt Electrons

ULF waves and their influence on radiation belt dynamics in Earth's magnetosphere

2020 ◽  
Author(s):  
Robert Rankin ◽  
Alexander Degeling
Keyword(s):  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Low Frequency ◽  
Recovery Phase ◽  
Ulf Waves ◽  
Wave Source ◽  
Initial Plasma ◽  
Plasma State ◽  
Van Allen Probes ◽  
Geomagnetic Fields

<p>Recent observations from the Van Allen Probes mission have established that Pc3-5 ultra-low-frequency (ULF) waves can energize ions and electrons via drift-resonance and drift-bounce resonance. The extent to which these waves contribute to the space weather of the belts is relatively poorly understood and requires sophisticated modelling and characterization of the dominant wave modes that arise in the development and recovery phase of geomagnetic storms. Despite more than four decades of observations and theoretical analysis of ULF waves, there is no framework for accurately assessing the global distribution of ULF waves and their influence on the ring current. <br>In this presentation, we describe a new global model of ULF waves that incorporates non-dipolar geomagnetic fields. The model is constrained using the GCPM of cold plasma density model and a specification of the ionosphere using the IRI and MSIS models. An algorithm is applied to adjust the initial plasma state to a quasi-static equilibrium that is then driven by a global convection electric field and ULF wave source. For specific observations by the Van Allen Probes and ARASE mission, the effect of these ULF waves on radiation belt ions and electrons is evaluated utilizing test-particle methodology and Liouville's theorem, which enables the phase space density to be followed and compared one-for-one with the satellite observations.  </p>

Controlling Effect of Wave Models and Plasma Boundaries on the Dynamic Evolution of Relativistic Radiation Belt Electrons

2020 ◽  
Author(s):  
Dedong Wang ◽  
Yuri Shprits ◽  
Irina Zhelavskaya ◽  
Alexander Drozdov ◽  
Nikita Aseev ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Dynamic Evolution ◽  
Relativistic Electrons ◽  
Electron Radiation ◽  
Energy Diffusion ◽  
Chorus Waves ◽  
Latitudinal Dependence ◽  
Shadowing Effect ◽  
Radiation Belt Electrons ◽  
Wave Models

<p>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 (VERB-3D) code, 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.</p><p>Our simulation results also show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high L*.</p>

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