Relative Contribution of ULF Waves and Whistler‐mode Chorus to the Radiation Belt Variation during the May 2017 Storm

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 &#8211; 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.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.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.

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On the effect of ULF waves on the outer radiation belt during geomagnetic storms

10.5194/egusphere-egu21-5977 ◽

2021 ◽

Author(s):

Christopher Lara ◽

Pablo S. Moya ◽

Victor Pinto ◽

Javier Silva ◽

Beatriz Zenteno

Keyword(s):

Relativistic Electron ◽

Radiation Belt ◽

Geomagnetic Storms ◽

Cumulative Effect ◽

Radiation Belts ◽

Ulf Waves ◽

Relativistic Electrons ◽

Relative Role ◽

Outer Radiation Belt ◽

Ulf Wave

The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.

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

10.5194/angeo-2021-57 ◽

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.

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Simultaneous Influence of Whistler-Mode Chorus and EMIC Waves on Electron Loss in the Earth’s Radiation Belt

Journal of the Korean Physical Society ◽

10.3938/jkps.77.707 ◽

2020 ◽

Vol 77 (8) ◽

pp. 707-713

Author(s):

Dae-Young Lee ◽

Joonsung Kim

Keyword(s):

Radiation Belt ◽

Electron Loss ◽

Whistler Mode ◽

Simultaneous Influence ◽

Earth’S Radiation Belt ◽

Emic Waves

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How Whistler-Mode Waves and Thermal Plasma Density Control the Global Distribution of the Diffuse Aurora and the Dynamical Evolution of Radiation Belt Electrons

Magnetosphere-Ionosphere Coupling in the Solar System - Geophysical Monograph Series ◽

10.1002/9781119066880.ch9 ◽

2016 ◽

pp. 115-125

Author(s):

Richard M. Thorne ◽

Jacob Bortnik ◽

Wen Li ◽

Lunjin Chen ◽

Binbin Ni ◽

...

Keyword(s):

Plasma Density ◽

Thermal Plasma ◽

Radiation Belt ◽

Dynamical Evolution ◽

Global Distribution ◽

Whistler Mode ◽

Density Control ◽

Radiation Belt Electrons ◽

Whistler Mode Waves ◽

Diffuse Aurora

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A survey of Galileo plasma wave instrument observations of Jovian whistler-mode chorus

Annales Geophysicae ◽

10.5194/angeo-26-1819-2008 ◽

2008 ◽

Vol 26 (7) ◽

pp. 1819-1828 ◽

Cited By ~ 21

Author(s):

J. D. Menietti ◽

R. B. Horne ◽

D. A. Gurnett ◽

G. B. Hospodarsky ◽

C. W. Piker ◽

...

Keyword(s):

Plasma Wave ◽

Radiation Belt ◽

Good Reason ◽

Radial Distance ◽

Local Times ◽

Whistler Mode ◽

Jovian Magnetosphere ◽

Spacecraft Trajectory ◽

Almost All ◽

The Magnetic Field

Abstract. A survey of plasma wave observations at Jupiter obtained by the plasma wave instrument on board the Galileo spacecraft is presented. The observations indicate that chorus emissions are observed commonly in the Jovian magnetosphere near the magnetic equator in the approximate radial range 6<r<10 RJ. The survey includes almost all local times but not equally sampled in radial distance due to the spacecraft trajectory. The data suggest that chorus emissions are somewhat more intense on the dayside, but this may be a result of insufficient nightside observations. The orbit of Galileo is also restricted to ±3° of the Jovigraphic equator, but the tilt of the magnetic field permits coverage of a range of magnetic latitudes of −13°<λmag<+13°. The similarities of chorus emissions to terrestrial observations are a good reason to speculate that Jovian chorus emission may play a significant role in the stochastic acceleration of electrons in the radial range 6–10 RJ as recent studies indicate. These electrons may then be transported inward by radial diffusion where they are additionally accelerated to form the synchrotron radiation belt source.

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

10.5194/egusphere-egu2020-13703 ◽

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

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.&#160; 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. &#160;

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