Calculated photoelectron pitch angle and energy spectra

Mantas, G. P.; Bowhill, S. A.

doi:10.1016/0032-0633(75)90140-3

Cited by 34 publications

(14 citation statements)

References 40 publications

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“…The observed fluxes of electrons below 120 km at WSMR are photoelectrons. Their fluxes and spectra below 100 eV are consistent with those calculated by Mantas and Bowhill [1975] but approach the values reported by Schlegel [1974] near 1000 eV. We have presented both fluxes and spectra as a function of altitude.…”

Section: Discussionsupporting

confidence: 87%

Mid-LatitudeERegion: An Examination of the Existence of a Corpuscular Source

Morse¹,

Rice²

1976

J. Geophys. Res.

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We present new data from two rocket flights and examine the published evidence for the existence of a corpuscular source of ionization at E region heights. The rockets were launched from White Sands Missile Range (magnetic latitude of ∼43°) to provide measurements of energetic electrons and protons between 40 eV and 5.5 keV in the E region below 120 km. A daytime flight (solar zenith angle χ of 58°) launched during a geomagnetically disturbed period (Kp = 5‐) provided measurements of a small flux of electrons which exhibits a strong altitude dependence below 500 eV but essentially none above that energy. The observed electron energy flux at 116 km is ∼ 1.8 × 10−3 erg/cm² s. We interpret these to be photoelectrons. During the nighttime flight we observed an energy flux which was less than 10−5 erg/cm² s. Upper limits for proton fluxes are given. The electron flux values contrast sharply with much higher values reported by some other investigators. The implications of and some possible reasons for the differences are discussed. After reviewing our data and the relevant literature we conclude that (1) data obtained from one location must be carefully interpreted with regard to implications about the general ionosphere, since a real geographic variability exists; (2) since we observe no significant fluxes of energetic particles in a geomagnetically disturbed ionosphere, even in the presence of fluctuating nighttime E region ionization, the presence of such fluctuations cannot be taken as evidence of precipitating particles; and (3) many reports of corpuscular radiation contain high flux values which are not supported by observations of 391.4‐nm radiation from N2+.

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Section: Discussionsupporting

confidence: 87%

Mid-LatitudeERegion: An Examination of the Existence of a Corpuscular Source

Morse¹,

Rice²

1976

J. Geophys. Res.

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“…Quantitative estimates of the effect of pitch angle diffusion through collisions in the plasmasphere on the magnitude of the flux buildup will be made later. However, we qualitatively note here that in addition to injecting a fraction of photoelectrons into magnetically trapped orbits, collisions inhibit transport (the same effect as that found in the ionosphere, which has been discussed by Banks and Nagy [1970] and Mantas and Bowhill [1975]). Both effects tend to retain a larger fraction of photoelectrons in the plasmasphere than when they are neglected.…”

Section: Photoelectron Fluxes In the Plasmaspherementioning

confidence: 77%

“…By taking the mean thermal electron density in a magnetospheric field tube as 5 X 1!Y cm -3 the therma!ization time for a 20-eV photoelectron (approximately equal to the mean energy of the escape flux [see Mantas and Bowhill, 1975]) confined in the plasmasphere is about 80 s. In this time interval the photoelectron will cover a distance As • 2 X 10 x• X (E•/Ne) -• 1.5 X 10 •ø Cm. The path length of an electron entering a field tube with L = !.5 at 1000 kin, with a pitch angle of, say, 87 ø, through the magnetosphere to the magnetic conjugate is about !.73 X l lY cm (collisions neglected) and decreases by about a factor of 2 as the initial pitch angle (measured from the forward direction) goes to zero.…”

Section: General Considerations Regarding Photoelectrons In the Ionosmentioning

confidence: 99%

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Photoelectron flux buildup in the plasmasphere

Mantas¹,

Carlson²,

Wickwar³

1978

J. Geophys. Res.

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Processes which confine photoelectrons to the plasmasphere (e.g., collisional backscattering from the thermosphere and magnetic trapping due to pitch angle redistribution through Coulomb collisions in the plasmasphere) tend to increase the steady state photoelectron flux in the plasmasphere above the amplitude level that would otherwise have been attained. Theoretical calculations are presented of steady state photoelectron fluxes in the plasmasphere, for specified atmospheric and ionospheric conditions. (Observational plasma line intensity data for these conditions exist and will be compared elsewhere.) General features of the angular distribution are presented and compared with observations. The transparency of the plasmasphere and the backscattering properties of the thermosphere are investigated. The buildup effect due to collisional backscatter alone is calculated, and the combined buildup effect of pitch angle diffusion and backscatter is estimated. It is found that the inclusion of these effects increases the steady state photoelectron flux amplitude in the plasmasphere by about 50% over the value obtained when the buildup effects are neglected. The calculated steady state photoelectron fluxes in the plasmasphere are in good agreement with the available observations.

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“…Hanson (1963) first drew attention to the potential importance of transport, and recent literature (Nisbet, 1968;Nagy and Banks, 1970;Banks and Nagy, 1970;Cicerone and Bowhill, 1971;Cicerone et QL, 1973;Mantas, 1975;Mantas and Bowhill, 1975;Swartz, 1976;Oran and Strickland, 1976;Lejeune and Wormser, 1976) has emphasized attempts to devise a unified theory for both local and non-local regimes. A variety of approaches have been devised to treat the complexities introduced by transport, including models based on Monte Carlo techniques, analogies with molecular diffusion, and theories for radiative transfer.…”

mentioning

confidence: 99%