Energization of radiation belt electrons by ring current ion driven ULF waves

Ozeke, L. G.; Mann, I. R.

doi:10.1029/2007ja012468

Cited by 59 publications

(64 citation statements)

References 49 publications

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“…Other MLT sectors (analysed in this study but not shown here) demonstrate similar dependencies on solar wind variability. We only show the dependence of radial (B x ) magnetic component corresponding to the poloidal Alfvén waves expected to be the most relevant to drift resonance interactions with radiation belt electrons (Ozeke and Mann, 2008). The other two magnetic components (azimuthal B y and compressional B z ) demonstrate similar solar wind dependencies supporting the conclusions below.…”

Section: Solar Wind Datasupporting

confidence: 50%

The influence of solar wind variability on magnetospheric ULF wave power

Pokhotelov¹,

Rae²,

Murphy

et al. 2015

Ann. Geophys.

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Abstract. Magnetospheric ultra-low frequency (ULF) oscillations in the Pc 4-5 frequency range play an important role in the dynamics of Earth's radiation belts, both by enhancing the radial diffusion through incoherent interactions and through the coherent drift-resonant interactions with trapped radiation belt electrons. The statistical distributions of magnetospheric ULF wave power are known to be strongly dependent on solar wind parameters such as solar wind speed and interplanetary magnetic field (IMF) orientation. Statistical characterisation of ULF wave power in the magnetosphere traditionally relies on average solar wind-IMF conditions over a specific time period. In this brief report, we perform an alternative characterisation of the solar wind influence on magnetospheric ULF wave activity through the characterisation of the solar wind driver by its variability using the standard deviation of solar wind parameters rather than a simple time average. We present a statistical study of nearly one solar cycle (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)) of geosynchronous observations of magnetic ULF wave power and find that there is significant variation in ULF wave powers as a function of the dynamic properties of the solar wind. In particular, we find that the variability in IMF vector, rather than variabilities in other parameters (solar wind density, bulk velocity and ion temperature), plays the strongest role in controlling geosynchronous ULF power. We conclude that, although time-averaged bulk properties of the solar wind are a key factor in driving ULF powers in the magnetosphere, the solar wind variability can be an important contributor as well. This highlights the potential importance of including solar wind variability especially in studies of ULF wave dynamics in order to assess the efficiency of solar wind-magnetosphere coupling.

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Section: Solar Wind Datasupporting

confidence: 50%

The influence of solar wind variability on magnetospheric ULF wave power

Pokhotelov¹,

Rae²,

Murphy

et al. 2015

Ann. Geophys.

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“…For example, Ozeke and Mann [2001] modeled the drift bounce instability in the magnetosphere and found that high-m number waves can be driven by ring current ions. These high-m number waves in turn become potential accelerators for radiation belt electrons through drift resonance [Ozeke and Mann, 2008]. The ST-5 observations reveal that these waves have a very high occurrence rate in the dayside magnetosphere (Figure 4) even though the observations are made mostly during quiet and moderately active geomagnetic conditions.…”

Section: High-m Number Ulf Wavesmentioning

confidence: 99%

Observations of a unique type of ULF wave by low-altitude Space Technology 5 satellites

Strangeway

et al. 2011

J. Geophys. Res.

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[1] We report a unique type of ULF waves observed by low-altitude Space Technology 5 (ST-5) constellation mission. ST-5 is a three-microsatellite constellation deployed into a 300 × 4500 km dawn-dusk and Sun-synchronous polar orbit with 105.6°inclination angle. Because of the Earth's rotation and the dipole tilt effect, the spacecraft's dawn-dusk orbit track can reach as low as subauroral latitudes during the course of a day. Whenever the spacecraft traverse the dayside closed field line region at subauroral latitudes, they frequently observe strong transverse oscillations at 30-200 mHz, or in the Pc2-3 frequency range. These Pc2-3 waves appear as wave packets with durations in the order of 5-10 min. As the maximum separations of the ST-5 spacecraft are in the order of 10 min, the three ST-5 satellites often observe very similar wave packets, implying these wave oscillations occur in a localized region. The coordinated ground-based magnetic observations at the spacecraft footprints, however, do not see waves in the Pc2-3 band; instead, the waves appear to be the common Pc4-5 waves associated with field line resonances. We suggest that these unique Pc2-3 waves seen by ST-5 are in fact the Doppler-shifted Pc4-5 waves as a result of rapid traverse of the spacecraft across the resonant field lines azimuthally at low altitudes. The observations with the unique spacecraft dawn-dusk orbits at proper altitudes and magnetic latitudes reveal the azimuthal characteristics of field line resonances.

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“…Because of the known energy dependence of ω d and ω b , the resonance energy can be determined in theory if the wave properties are known. For the case of electrons, it should be noted that the bounce frequency is usually much higher than the other two frequencies [27,59]. Figure 6 gives a schematic view of the behavior of resonant particles in the poloidal standing waves with different harmonics.…”

Section: Fast Acceleration Of Ions By Poloidal Ulf Wavesmentioning

confidence: 99%

Fast acceleration of “killer” electrons and energetic ions by interplanetary shock stimulated ULF waves in the inner magnetosphere

et al. 2011

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Energetic electrons and ions in the Van Allen radiation belt are the number one space weather threat. Understanding how these energetic particles are accelerated within the Van Allen radiation belt is one of the major challenges in space physics. This paper reviews the recent progress on the fast acceleration of "killer" electrons and energetic ions by ultralow frequency (ULF) waves stimulated by the interplanetary shock in the inner magnetosphere. Very low frequency (VLF) wave-particle interaction is considered to be one of the primary electron acceleration mechanisms because electron cyclotron resonances can easily occur in the VLF frequency range. Recently, using four Cluster spacecraft observations, we have found that, after interplanetary shocks impact the Earth's magnetosphere, energetic electrons in the radiation belt are accelerated almost immediately and continue to accelerate for a few hours. The time scale (a few days) for traditional acceleration mechanisms, based on VLF wave-particle interactions to accelerate electrons to relativistic energies, is too long to explain our observations. Furthermore, we have found that interplanetary shocks or solar wind pressure pulses, with even small dynamic pressure changes, can play a non-negligible role in radiation belt dynamics. Interplanetary shocks interaction with the Earth's magnetosphere manifests many fundamental space physics phenomena including energetic particle acceleration. The mechanism of fast acceleration of energetic electrons in the radiation belt responding to interplanetary shock impacts consists of three contributing parts: (1) the initial adiabatic acceleration due to strong shock-related magnetic field compression; (2) followed by the drift-resonant acceleration with poloidal ULF waves excited at different L-shells; and (3) particle acceleration due to the quickly damping electric fields associated with ULF waves. Particles end up with a net acceleration because they gain more energy in the first half of this cycle than they lose in the second. The results reported in this paper cast a new light on understanding the acceleration of energetic particles in the Earth's Van Allen radiation belt. The results of this study can likewise be applied to interplanetary shock interaction with other planets such as Mercury, Jupiter, Saturn, Uranus and Neptune, and other astrophysical objects with magnetic fields."killer" electrons, radiation belt, energetic particles acceleration, ULF wave, VLF wave, wave-particle interaction, resonance Citation:Zong Q G, Wang Y F, Yuan C J, et al. Fast acceleration of "killer" electrons and energetic ions by inter-planetary shock stimulated ULF waves in the inner magnetosphere.

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Energization of radiation belt electrons by ring current ion driven ULF waves

Cited by 59 publications

References 49 publications

The influence of solar wind variability on magnetospheric ULF wave power

The influence of solar wind variability on magnetospheric ULF wave power

Observations of a unique type of ULF wave by low-altitude Space Technology 5 satellites

Fast acceleration of “killer” electrons and energetic ions by interplanetary shock stimulated ULF waves in the inner magnetosphere

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