Relativistic electron dynamics in the inner magnetosphere — a review

Friedel, R. H. W.; Reeves, G. D.; Obara, Takao

doi:10.1016/s1364-6826(01)00088-8

Cited by 421 publications

(354 citation statements)

References 66 publications

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“…Ultra low frequency (ULF) magnetic waves are thought to interact with low-energy particle populations and accelerate them to form damaging, high energy (MeV) space radiation (e.g. Friedel et al, 2002). Wave-particle interactions are also believed to be responsible for scattering particles into the loss cone.…”

Section: Introduction and Applicationmentioning

confidence: 99%

A radiation hardened digital fluxgate magnetometer for space applications

Miles

Bennest²,

Mann

et al. 2013

Geosci. Instrum. Method. Data Syst.

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Abstract. Space-based measurements of Earth's magnetic field are required to understand the plasma processes responsible for energising particles in the Van Allen radiation belts and influencing space weather. This paper describes a prototype fluxgate magnetometer instrument developed for the proposed Canadian Space Agency's (CSA) Outer Radiation Belt Injection, Transport, Acceleration and Loss Satellite (ORBITALS) mission and which has applications in other space and suborbital applications. The magnetometer is designed to survive and operate in the harsh environment of Earth's radiation belts and measure low-frequency magnetic waves, the magnetic signatures of current systems, and the static background magnetic field. The new instrument offers improved science data compared to its predecessors through two key design changes: direct digitisation of the sensor and digital feedback from two cascaded pulse-width modulators combined with analog temperature compensation. These provide an increase in measurement bandwidth up to 450 Hz with the potential to extend to at least 1500 Hz. The instrument can resolve 8 pT on a 65 000 nT field with a magnetic noise of less than 10 pT/ √Hz at 1 Hz. This performance is comparable with other recent digital fluxgates for space applications, most of which use some form of sigma-delta ( ) modulation for feedback and omit analog temperature compensation. The prototype instrument was successfully tested and calibrated at the Natural Resources Canada Geomagnetics Laboratory.

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Section: Introduction and Applicationmentioning

confidence: 99%

A radiation hardened digital fluxgate magnetometer for space applications

Miles

Bennest²,

Mann

et al. 2013

Geosci. Instrum. Method. Data Syst.

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“…Recently, new observations and increased monitoring evidenced that other processes play an important role as well [Reeves et al, 1998]. For a review, see the studies of Friedel et al [2002], Brautigam and Albert [2000], and Green and Kivelson [2004]. Reeves et al [2003] show that the net effect of geomagnetic activity on radiation belt dynamics is a delicate balance of acceleration, transport, and losses that can lead to either increased or decreased fluxes or to almost no changes at all.…”

Section: Introductionmentioning

confidence: 99%

Identifying the radiation belt source region by data assimilation

et al. 2007

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[1] We describe how assimilation of radiation belt data with a simple radial diffusion code can be used to identify and adjust for unknown physics in the model. We study the dropout and the following enhancement of relativistic electrons during a moderate storm on 25 October 2002. We introduce a technique that uses an ensemble Kalman filter and the probability distribution of the forecast ensemble to identify if the model is drifting away from the observations and to find inconsistencies between model forecast and observations. We use the method to pinpoint the time periods and locations where most of the disagreement occurs and how much the Kalman filter has to adjust the model state to match the observations. Although the model does not contain explicit source or loss terms, the Kalman filter algorithm can implicitly add very localized sources or losses in order to reduce the discrepancy between model and observations. We use this technique with multisatellite observations to determine when simple radial diffusion is inconsistent with the observed phase space densities indicating where additional source (acceleration) or loss (precipitation) processes must be active. We find that the outer boundary estimated by the ensemble Kalman filter is consistent with negative phase space density gradients in the outer electron radiation belt. We also identify specific regions in the radiation belts (L* % 5-6 and to a minor extend also L* % 4) where simple radial diffusion fails to adequately capture the variability of the observations, suggesting local acceleration/loss mechanisms.

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“…However, the processes which are most geo-effective in energizing the belts under differing solar wind and geomagnetic conditions remain hotly debated [1][2][3][4] . Prominent candidates for dominant acceleration processes include resonance with waves in the extremely low frequency/very low frequency band such as lower band whistler mode chorus 2,4,5 , which violate the first adiabatic invariant, and interactions with ultra-low frequency (ULF) waves which violate the third invariant while conserving the first 3,[6][7][8] , or some combination thereof 9 .…”

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confidence: 99%

Discovery of the action of a geophysical synchrotron in the Earth’s Van Allen radiation belts

et al. 2013

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Although the Earth's Van Allen radiation belts were discovered over 50 years ago, the dominant processes responsible for relativistic electron acceleration, transport and loss remain poorly understood. Here we show evidence for the action of coherent acceleration due to resonance with ultra-low frequency waves on a planetary scale. Data from the CRRES probe, and from the recently launched multi-satellite NASA Van Allen Probes mission, with supporting modelling, collectively show coherent ultra-low frequency interactions which high energy resolution data reveals are far more common than either previously thought or observed. The observed modulations and energy-dependent spatial structure indicate a mode of action analogous to a geophysical synchrotron; this new mode of response represents a significant shift in known Van Allen radiation belt dynamics and structure. These periodic collisionless betatron acceleration processes also have applications in understanding the dynamics of, and periodic electromagnetic emissions from, distant plasma-astrophysical systems.

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Relativistic electron dynamics in the inner magnetosphere — a review

Cited by 421 publications

References 66 publications

A radiation hardened digital fluxgate magnetometer for space applications

A radiation hardened digital fluxgate magnetometer for space applications

Identifying the radiation belt source region by data assimilation

Discovery of the action of a geophysical synchrotron in the Earth’s Van Allen radiation belts

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