scholarly journals Energetic particle observations at the subsolar magnetopause

2002 ◽  
Vol 20 (4) ◽  
pp. 445-460 ◽  
Author(s):  
A. A. Eccles ◽  
T. A. Fritz
Keyword(s):  
Pitch Angle ◽  
Energetic Particle ◽  
Three Dimensional ◽  
Extended Period ◽  
Energetic Particles ◽  
Current Layer ◽  
Particle Distributions ◽  
Magnetospheric Configuration And Dynamics ◽  
Subsolar Point ◽  
Magnetospheric Configuration

Abstract. The pitch-angle distributions (PAD) of energetic particles are examined as the ISEE-1 satellite crosses the Earth’s magnetopause near the subsolar point. The investigation focuses on the possible existence of a particular type of distribution that would be associated with a source of energetic particles in the high-latitude magnetosphere. PADs, demonstrating broad, persistent field-aligned fluxes filling a single hemisphere (upper/northern or lower/southern), were observed just sunward of the magnetopause current layer for an extended period of many minutes. These distributions are a direct prediction of a possible source of energetic particles located in the high altitude dayside cusp and we present five examples in detail of the three-dimensional particle distributions to demonstrate their existence. From these results, other possible causes of such PADs are examined.Key words. Magnetospheric physics (energetic particles, precipitating; magnetopause, cusp and boundary layers; magnetospheric configuration and dynamics)

scholarly journals On the Turbulent Reduction of Drifts for Solar Energetic Particles

2021 ◽  
Vol 922 (2) ◽  
pp. 200
Author(s):  
J. P. van den Berg ◽  
N. E. Engelbrecht ◽  
N. Wijsen ◽  
R. D. Strauss
Keyword(s):  
Pitch Angle ◽  
Cosmic Ray ◽  
Energetic Particles ◽  
Solar Energetic Particles ◽  
Particle Distributions ◽  
Magnetic Turbulence ◽  
Field Diffusion ◽  
Background Magnetic Field ◽  
Perpendicular Diffusion ◽  
Inner Heliosphere

Abstract Particle drifts perpendicular to the background magnetic field have been proposed by some authors as an explanation for the very efficient perpendicular transport of solar energetic particles (SEPs). This process, however, competes with perpendicular diffusion caused by magnetic turbulence, which can also disrupt the drift patterns and reduce the magnitude of drift effects. The latter phenomenon is well known in cosmic-ray studies, but not yet considered in SEP models. Additionally, SEP models that do not include drifts, especially for electrons, use turbulent drift reduction as a justification of this omission, without critically evaluating or testing this assumption. This article presents the first theoretical step for a theory of drift suppression in SEP transport. This is done by deriving the turbulence-dependent drift reduction function with a pitch-angle dependence, as is applicable for anisotropic particle distributions, and by investigating to what extent drifts will be reduced in the inner heliosphere for realistic turbulence conditions and different pitch-angle dependencies of the perpendicular diffusion coefficient. The influence of the derived turbulent drift reduction factors on the transport of SEPs are tested, using a state-of-the-art SEP transport code, for several expressions of theoretically derived perpendicular diffusion coefficients. It is found, for realistic turbulence conditions in the inner heliosphere, that cross-field diffusion will have the largest influence on the perpendicular transport of SEPs, as opposed to particle drifts.

Study on the variation of energetic particle pitch angle caused by NWC VLF transmitter

2020 ◽  
Author(s):  
Wei Chu ◽  
Song Xu ◽  
ZhenXia Zhang ◽  
Jianping Huang ◽  
Zhima Zeren ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Energetic Particle ◽  
Electron Flux ◽  
Energetic Electron ◽  
Energetic Particles ◽  
Observation Data ◽  
Electron Loss ◽  
Loss Mechanism ◽  
Central Location ◽  
The North

<p>Based on the observation data collected by the Energetic Particles Detector Package(HEPP) on board CSES satellite during the period of 2018 and 2019.We analyzed the characterizes of pitch angle spectrum of energetic electron precipitated caused by NWC. Our analysis revealed in details the transient properties of the space electrons induced by the man-made VLF wave emitted by the transmitter at NWC.The center location of the NWC electron flux locates in the north hemisphere other than in the south hemisphere during both quiet and disturbance period which is surprising.And the central location of NWC electron belt move westwards during the geomagnetic storm.The pitch angle distributions of the precipitation electron have the maximum flux at about 60-70 degree other than at 90 degree.The pitch angle distributions presented here are examined for evidence of the transportation mechanism especially for the electron loss mechanism.</p><p> </p>

Linear dispersion relation of geodesic acoustic modes driven by trapped and circulating energetic particles

2021 ◽  
Vol 87 (4) ◽  
Author(s):  
I. Chavdarovski ◽  
M. Schneller ◽  
A. Biancalani
Keyword(s):  
Dispersion Relation ◽  
Pitch Angle ◽  
Energetic Particle ◽  
Energetic Particles ◽  
Ion Beams ◽  
Mean Velocity ◽  
Local Dispersion ◽  
Acoustic Modes ◽  
Slowing Down ◽  
Tail Distribution

We derive the local dispersion relation of energetic-particle-induced geodesic acoustic modes (EGAMs) for both trapped and circulating ion beams with single pitch angle slowing-down and Maxwellian distributions, as well as a bump-on-tail distribution in tokamak plasmas. For slowing-down and Maxwellian particles, the solutions of the local dispersion relation give the spectrum, growth rate and thresholds of excitation as functions of the pitch angle, beam density and frequency of the energetic particles bounce motion. For circulating ions there is only one unstable branch with frequency below the GAM continuum and a threshold of excitation in the pitch angle, for both the slowing-down and single pitch Maxwellian distributions. Trapped particles cause no excitation of a mode for neither slowing-down nor Maxwellian ion beams, but they can excite a mode with a bump-on-tail distribution when the mean velocity of the beam is larger than the threshold and the energetic particle bounce frequency is high enough.

scholarly journals Energetic particles observed by ISEE-1 and ISEE-2 in a cusp diamagnetic cavity on 29 September 1978

2007 ◽  
Vol 25 (12) ◽  
pp. 2633-2640 ◽  
Author(s):  
B. M. Walsh ◽  
T. A. Fritz ◽  
N. M. Lender ◽  
J. Chen ◽  
K. E. Whitaker
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Pitch Angle ◽  
Energetic Particle ◽  
Electron Flux ◽  
Energetic Particles ◽  
Local Magnetic Field ◽  
Local Source ◽  
Magnetospheric Cusp ◽  
The Magnetic Field

Abstract. Observations by the ISEE-1 and ISEE-2 spacecraft on 29 September 1978 show large CEP (Cusp Energetic Particle) fluxes while passing through the dayside magnetospheric cusp in near coincident orbits. The event was observed around 11:00 MLT between roughly 12:30 and 13:00 UT by ISEE-1 and 12:00 and 13:00 UT by ISEE-2. During these periods, both electron and ion fluxes increased by more than two orders of magnitude, with the electron flux showing a strong peak at a pitch angle of 90°. The solar wind was ~710 km s−1 and the Dst was ~−200 nT, suggesting the occurrence of a strong geomagnetic storm. The ISEE-1 and ISEE-2 observations, however, show no time-energy dispersion of the CEPs, leading us to believe that these particles could not be the result of substorm processes in the magnetotail. The local magnetic field was depressed and extremely turbulent. Changes in the magnitude of the magnetic field anticorrelate closely to variations of the electron flux. The observations in electron flux peaking at 90° and the close anticorrelation between the local magnetic field strength and electron flux are unique and provide evidence of a potential local source for these energetic particles.

scholarly journals Precession drift reversal and rapid transport of trapped energetic particles due to an energetic particle driven instability in the Large Helical Device

2021 ◽  
Vol 28 (8) ◽  
pp. 080701
Author(s):  
M. Idouakass ◽  
Y. Todo ◽  
H. Wang ◽  
J. Wang ◽  
R. Seki ◽  
...  
Keyword(s):  
Energetic Particle ◽  
Energetic Particles ◽  
Rapid Transport

Magnetotail particle distributions associated with pitch angle isotropization

2000 ◽  
Vol 62 (6) ◽  
pp. 513-519 ◽  
Author(s):  
R.F. Martin ◽  
D. Delcourt ◽  
D.L. Holland ◽  
M.J. Asbury
Keyword(s):  
Pitch Angle ◽  
Particle Distributions

Large- and small-scale vortical motions in a shear layer perturbed by tabs

1999 ◽  
Vol 382 ◽  
pp. 307-329 ◽  
Author(s):  
JUDITH K. FOSS ◽  
K. B. M. Q. ZAMAN
Keyword(s):  
Shear Layer ◽  
Pitch Angle ◽  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Small Scale ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Cross Sectional ◽  
Scale Population

The large- and small-scale vortical motions produced by ‘delta tabs’ in a two-stream shear layer have been studied experimentally. An increase in mixing was observed when the base of the triangular shaped tab was affixed to the trailing edge of the splitter plate and the apex was pitched at some angle with respect to the flow axis. Such an arrangement produced a pair of counter-rotating streamwise vortices. Hot-wire measurements detailed the velocity, time-averaged vorticity (Ωx) and small-scale turbulence features in the three-dimensional space downstream of the tabs. The small-scale structures, whose scale corresponds to that of the peak in the dissipation spectrum, were identified and counted using the peak-valley-counting technique. The optimal pitch angle, θ, for a single tab and the optimal spanwise spacing, S, for a multiple tab array were identified. Since the goal was to increase mixing, the optimal tab configuration was determined from two properties of the flow field: (i) the large-scale motions with the maximum Ωx, and (ii) the largest number of small-scale motions in a given time period. The peak streamwise vorticity magnitude [mid ]Ωx−max[mid ] was found to have a unique relationship with the tab pitch angle. Furthermore, for all cases examined, the overall small-scale population was found to correlate directly with [mid ]Ωx−max[mid ]. Both quantities peaked at θ≈±45°. It is interesting to note that the peak magnitude of the corresponding circulation in the cross-sectional plane occurred for θ≈±90°. For an array of tabs, the two quantities also depended on the tab spacing. An array of contiguous tabs acted as a solid deflector producing the weakest streamwise vortices and the least small-scale population. For the measurement range covered, the optimal spacing was found to be S≈1.5 tab widths.

scholarly journals A note on the ring current in Saturn’s magnetosphere: Comparison of magnetic data obtained during the Pioneer-11 and Voyager-1 and -2 fly-bys

2003 ◽  
Vol 21 (3) ◽  
pp. 661-669 ◽  
Author(s):  
E. J. Bunce ◽  
S. W. H. Cowley
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Current System ◽  
Magnetic Data ◽  
Total Current ◽  
Planetary Magnetospheres ◽  
Magnetospheric Configuration And Dynamics ◽  
Magnetospheric Configuration ◽  
First Time ◽  
Current Systems

Abstract. We examine the residual (measured minus internal) magnetic field vectors observed in Saturn’s magnetosphere during the Pioneer-11 fly-by in 1979, and compare them with those observed during the Voyager-1 and -2 fly-bys in 1980 and 1981. We show for the first time that a ring current system was present within the magnetosphere during the Pioneer-11 encounter, which was qualitatively similar to those present during the Voyager fly-bys. The analysis also shows, however, that the ring current was located closer to the planet during the Pioneer-11 encounter than during the comparable Voyager-1 fly-by, reflecting the more com-pressed nature of the magnetosphere at the time. The residual field vectors have been fit using an adaptation of the current system proposed for Jupiter by Connerney et al. (1981a). A model that provides a reasonably good fit to the Pioneer-11 Saturn data extends radially between 6.5 and 12.5 RS (compared with a noon-sector magnetopause distance of 17 RS), has a north-south extent of 4 RS, and carries a total current of 9.6 MA. A corresponding model that provides a qualitatively similar fit to the Voyager data, determined previously by Connerney et al. (1983), extends radially between 8 and 15.5 RS (compared with a noon-sector magnetopause distance for Voyager-1 of 23–24 RS), has a north-south extent of 6 RS, and carries a total current of 11.5 MA.Key words. Magnetospheric physics (current systems, magnetospheric configuration and dynamics, planetary magnetospheres)

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