ROCKET OBSERVATIONS OF ELECTRON PITCH-ANGLE DISTRIBUTIONS DURING AURORAL SUBSTORMS

1967 ◽  
Vol 45 (5) ◽  
pp. 1755-1769 ◽  
Author(s):  
I. B. McDiarmid ◽  
E. E. Budzinski ◽  
B. A. Whalen ◽  
N. Sckopke
Keyword(s):  
Geomagnetic Field ◽  
Pitch Angle ◽  
Angular Distributions ◽  
Intensity Increase ◽  
Ionospheric Current ◽  
Atmospheric Scattering ◽  
Auroral Substorms ◽  
Electron Intensity ◽  
Upward Moving ◽  
Particle Intensity

Electron angular distributions obtained from three rocket flights during auroral substorms are described. Pitch-angle distributions of the incident electrons vary from isotropic to strongly peaked at pitch angles near 90°. Isotropic distributions are sometimes maintained for times at least of the order of minutes with very little change in intensity. When an anisotropic distribution persists for some time, the particle intensity is usually observed to decay.Following an intensity increase the angular distribution generally becomes more isotropic. The degree of isotropy attained following an intensity increase does not appear to depend on the magnitude of the increase but rather on the degree of isotropy before the increase.The intensity of upward moving electrons (pitch angles 90–180°) can in most cases be accounted for by atmospheric scattering and mirroring in the undisturbed geomagnetic field. A few cases are observed in which the electron intensity in the pitch-angle range 90–180° is probably larger than can be accounted for by normal scattering and mirroring. The effect of an ionospheric current on the intensity of upward moving electrons is considered.

ANGULAR DISTRIBUTIONS AND ENERGY SPECTRA OF ELECTRONS ASSOCIATED WITH AURORAL EVENTS

1964 ◽  
Vol 42 (11) ◽  
pp. 2048-2062 ◽  
Author(s):  
I. B. McDiarmid ◽  
E. E. Budzinski
Keyword(s):  
Angular Distributions ◽  
Recombination Coefficient ◽  
Particle Detectors ◽  
Black Brant ◽  
Intensity Measurements ◽  
Intensity Changes ◽  
D Region ◽  
Electron Intensity ◽  
Particle Intensity ◽  
Probe Measurements

A number of Black Brant II rockets containing various charged-particle detectors have been fired during 1963 and 1964 from Fort Churchill, Manitoba. Most of the firings took place at times of auroral events and the rocket instrumentation was designed to study the particles associated with these events.Pitch-angle distributions have been observed for electrons with energies greater than 40 keV, which show varying degrees of isotropy in the pitch-angle range 0° to 90°. In no case has a distribution been observed in which the intensity increased towards small angles. In some cases electron-intensity changes appear to be correlated with changes in spectrum and angular distribution, while in other cases changes in these quantities do not appear to be related.The particle intensity measurements are used along with radio-frequency probe measurements of electron density to infer values for the nighttime recombination coefficient in the D region of the ionosphere.

ROCKET MEASUREMENTS IN PROTON AURORA

1967 ◽  
Vol 45 (10) ◽  
pp. 3247-3255 ◽  
Author(s):  
B. A. Whalen ◽  
I. B. McDiarmid ◽  
E. E. Budzinski
Keyword(s):  
Pitch Angle ◽  
Energy Spectra ◽  
Angular Distributions ◽  
Electron Spectra ◽  
Source Mechanisms ◽  
Electron Intensity ◽  
Proton Precipitation ◽  
Rocket Measurements ◽  
Short Time ◽  
Proton Aurora

Proton and electron intensities, energy spectra, and angular distributions derived from a recent rocket flight launched into a 40-rayleigh Hβ aurora are reported. High-intensity proton precipitation (~0.45 erg cm−2 s−1 for protons with energies above 30 keV) was detected throughout the flight above 100 km, whereas the electron intensity was above the limit of detectability for only a short time. The proton and electron spectra and angular distributions in the 20–60 keV energy range were found to be remarkably similar, with angular distributions being isotropic over the pitch-angle range 0–90°, and with e-folding energies of about 12 keV and 18 keV for protons and electrons respectively. The results are interpreted in terms of current magnetospheric models, and are shown to place certain restrictions on the source mechanisms.

Energy spectrum and angular distributions of electrons trapped in the geomagnetic field

1961 ◽  
Vol 66 (8) ◽  
pp. 2297-2312 ◽  
Author(s):  
J. B. Cladis ◽  
L. F. Chase ◽  
W. L. Imhof ◽  
D. J. Knecht
Keyword(s):  
Energy Spectrum ◽  
Geomagnetic Field ◽  
Angular Distributions

Wave–particle interaction and enhanced precipitation of charged particles

1985 ◽  
Vol 63 (4) ◽  
pp. 445-452
Author(s):  
R. N. Singh ◽  
R. Prasad
Keyword(s):  
Electric Fields ◽  
Geomagnetic Field ◽  
Pitch Angle ◽  
Electron Flux ◽  
Particle Interaction ◽  
Charged Particles ◽  
Lower Ionosphere ◽  
Wave Interaction ◽  
Whistler Wave ◽  
Inhomogeneity Parameter

In addition to parallel electric fields, the distortions in the geomagnetic field have been considered in the study of resonant whistler wave interaction with gyrating charged particles. Mead axisymmetric distortions in the geomagnetic field have been considered and new expressions for the inhomogeneity parameter, αd, have been obtained. Considering the diffusion of charged particles in pitch angle, the variation in the precipitating electron flux under varying magnetospheric conditions has been computed. The variation in the distribution of trapped charged particles is shown to play an important role in controlling the electron flux precipitated into the lower ionosphere.

scholarly journals An intense SFE and SSC event in geomagnetic <i>H</i>, <i>Y</i> and <i>Z</i> fields at the Indian chain of observatories

1997 ◽  
Vol 15 (10) ◽  
pp. 1301-1308 ◽  
Author(s):  
R. G. Rastogi ◽  
D. R. K. Rao ◽  
S. Alex ◽  
B. M. Pathan ◽  
T. S. Sastry
Keyword(s):  
Solar Flare ◽  
Geomagnetic Storm ◽  
Geomagnetic Field ◽  
Current System ◽  
Equatorial Electrojet ◽  
Start Time ◽  
Low Latitude ◽  
Ionospheric Current ◽  
Ionospheric Current System ◽  
Solar Flare Effects

Abstract. Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC) of geomagnetic storm at 1518 h on 17 June 1991. The solar flare effects (SFE) registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in ΔH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H) at low latitude. ΔY registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. ΔZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.

scholarly journals LANL* V1.0: a radiation belt drift shell model suitable for real-time and reanalysis applications

2009 ◽  
Vol 2 (2) ◽  
pp. 113-122 ◽  
Author(s):  
J. Koller ◽  
G. D. Reeves ◽  
R. H. W. Friedel
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Space Weather ◽  
Surrogate Model ◽  
Geomagnetic Field ◽  
Pitch Angle ◽  
Radiation Belt ◽  
Equations Of Motion ◽  
Distribution Functions ◽  
Three Dimensions

Abstract. We describe here a new method for calculating the magnetic drift invariant, L*, that is used for modeling radiation belt dynamics and for other space weather applications. L* (pronounced L-star) is directly proportional to the integral of the magnetic flux contained within the surface defined by a charged particle moving in the Earth's geomagnetic field. Under adiabatic changes to the geomagnetic field L* is a conserved quantity, while under quasi-adiabatic fluctuations diffusion (with respect to a particle's L*) is the primary term in equations of particle dynamics. In particular the equations of motion for the very energetic particles that populate the Earth's radiation belts are most commonly expressed by diffusion in three dimensions: L*, energy (or momentum), and pitch angle (the dot product of velocity and the magnetic field vector). Expressing dynamics in these coordinates reduces the dimensionality of the problem by referencing the particle distribution functions to values at the magnetic equatorial point of a magnetic "drift shell" (or L-shell) irrespective of local time (or longitude). While the use of L* aids in simplifying the equations of motion, practical applications such as space weather forecasting using realistic geomagnetic fields require sophisticated magnetic field models that, in turn, require computationally intensive numerical integration. Typically a single L* calculation can require on the order of 105 calls to a magnetic field model and each point in the simulation domain and each calculated pitch angle has a different value of L*. We describe here the development and validation of a neural network surrogate model for calculating L* in sophisticated geomagnetic field models with a high degree of fidelity at computational speeds that are millions of times faster than direct numerical field line mapping and integration. This new surrogate model has applications to real-time radiation belt forecasting, analysis of data sets involving tens of satellite-years of observations, and other problems in space weather.

scholarly journals LANL<sup>*</sup> V1.0: a radiation belt drift shell model suitable for real-time and reanalysis applications

2009 ◽  
Vol 2 (1) ◽  
pp. 159-184 ◽  
Author(s):  
J. Koller ◽  
G. D. Reeves ◽  
R. H. W. Friedel
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Space Weather ◽  
Surrogate Model ◽  
Geomagnetic Field ◽  
Pitch Angle ◽  
Radiation Belt ◽  
Equations Of Motion ◽  
Distribution Functions ◽  
Three Dimensions

Abstract. We describe here a new method for calculating the magnetic drift invariant, L*, that is used for modeling radiation belt dynamics and for other space weather applications. L* (pronounced L-star) is directly proportional to the integral of the magnetic flux contained within the surface defined by a charged particle moving in the Earth's geomagnetic field. Under adiabatic changes to the geomagnetic field L* is a conserved quantity, while under quasi-adiabatic fluctuations diffusion (with respect to a particle's L*) is the primary term in equations of particle dynamics. In particular the equations of motion for the very energetic particles that populate the Earth's radiation belts are most commonly expressed by diffusion in three dimensions: L*, energy (or momentum), and pitch angle (the dot product of velocity and the magnetic field vector). Expressing dynamics in these coordinates reduces the dimensionality of the problem by referencing the particle distribution functions to values at the magnetic equatorial point of a magnetic "drift shell" (or L-shell) irrespective of local time (or longitude). While the use of L* aids in simplifying the equations of motion, practical applications such as space weather forecasting using realistic geomagnetic fields require sophisticated magnetic field models that, in turn, require computationally intensive numerical integration. Typically a single L* calculation can require on the order of 105 calls to a magnetic field model and each point in the simulation domain and each calculated pitch angle has a different value of L*. We describe here the development and validation of a neural network surrogate model for calculating L* in sophisticated geomagnetic field models with a high degree of fidelity at computational speeds that are millions of times faster than direct numerical field line mapping and integration. This new surrogate model has applications to real-time radiation belt forecasting, analysis of data sets involving tens of satellite-years of observations, and other problems in space weather.

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