Study of energetic electrons and their relationship to auroral absorption of radio waves

Maehlum, B.N.; O’Brien, Beverley

doi:10.1029/jz068i004p00997

Cited by 50 publications

(11 citation statements)

References 17 publications

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“…-there has been interest in relating the absorption effects to the incoming energetic particles causing them: to identify the nature of the particles and their energy; to determine the height of the absorption which depends on the energy; to be able to predict one quantity from the other; and to learn the physics involved. Maehlum and O'Brien (1963) and McDiarmid et al (1963) raised statistical arguments based on the occurrence and location of auroral absorption and of energetic electron precipitation detected by the low-orbit satellites Injun I and Alouette I, to argue that the latter was likely to be the cause of the former. The first direct connection was demonstrated by Jelly et al (1964) using measurements of >40 keV electrons on the early Canadian satellite Alouette I when passing over, or close to, the field of view of wide-beam riometers operating at, or near to, 30 MHz.…”

Section: Introductionmentioning

confidence: 99%

On the fine structure of medium energy electron fluxes in the auroral zone and related effects in the ionospheric D-region

Hargreaves

Birch

Evans³

2010

Ann. Geophys.

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Abstract. This study is based on measurements of trapped and precipitated electrons of energy >30 keV and >100 keV observed by polar orbiting environmental satellites during overpasses of the imaging riometer at Kilpisjärvi, Finland. The satellites are in sun-synchronous orbits of about 850 km altitude, recording the electron fluxes at 2-s time resolution. The riometer measures the radiowave absorption at 38.2 MHz, showing the spatial pattern within a 240 km field of view.The analysis has focussed on two areas. Having found a close correlation between the radiowave absorption and the medium-energy electron fluxes during satellite overpasses, empirical relationships are derived, enabling one quantity to be predicted from the other for three sectors of local time. It is shown that small-scale variations observed during a pass are essentially spatial rather than temporal.Other properties, such as the spectra and the relation between precipitated and trapped components, are also considered in the light of the theory of pitch angle scattering by VLF waves. It is found that the properties and behaviour depend strongly on the time of day. In the noon sector, the precipitated and trapped fluxes are highly correlated through a square law relationship.

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Section: Introductionmentioning

confidence: 99%

On the fine structure of medium energy electron fluxes in the auroral zone and related effects in the ionospheric D-region

Hargreaves

Birch

Evans³

2010

Ann. Geophys.

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“…The motion of low altitude trapping boundaries to lower latitudes during magnetic disturbances has been noted previously for 2 40 kev electrons (Maehlum and O'Brien, 1963) and for 2 280 kev electrons (Williams and Palmer, 1965). The fact that 2 40 kev and 2280 kev trapped electrons have the same nightside high latitude trapping boundary, (Williams and Mead, 1965) implies that the 140 kev electrons will also characteristically exhibit trapping boundary collapses during magnetic storms.…”

mentioning

confidence: 80%

Simultaneous trapped electron and magnetic tail field observations

Williams

Ness

1966

J. Geophys. Res.

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Using data from the polar orbiting satellite 1963 38C, the behavior of the high‐latitude energetic (≥ 280 kev) electron trapping boundary, Λc, at 1100 km is presented for the period March 15 through June 3, 1964. A sudden collapse of Λc to lower latitudes during the onset of magnetic storms, as indicated by Kp and Dst, is found to be a characteristic feature of the low‐altitude trapped electron population. Details of this behavior are presented and discussed. In addition, during this time period, the NASA IMP 1 satellite sampled field characteristics in the geomagnetic tail. Correlated observations of the simultaneously observed behavior during magnetic disturbances of the 1100‐km trapped electron population and of the field strength in the tail are presented. In three cases there is agreement and in one case disagreement with the latitude decreases that are predicted with an extended geomagnetic tail configuration. These results are considered to be direct evidence of the important influence exerted by the geomagnetic tail field in governing not only the quiet‐time trapped particle distribution, but also the behavior of the trapped particle population during magnetic storms.

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“…So far, several authors have reported a good correlation between the CNA observed with broad-beam riometers and precipitating medium-energy electrons, by comparing with data from the low-altitude satellites (Maehlum and O'Brien, 1963;Hargreaves and Sharp, 1965;Parthasarathy et al, 1966;Jelly and Brice, 1967) and from a geostationary satellite (Collis et al, 1983(Collis et al, , 1984Collis and Korth, 1985). Some of them have also shown an empirical relationship between CNA and precipitating medium-energy electrons measured at low altitude (Hargreaves and Sharp, 1965;Parthasarathy et al, 1966) and at geosynchronous orbit (Collis et al, 1983).…”

Section: Introductionmentioning

confidence: 94%

Comparison between CNA and energetic electron precipitation: simultaneous observation by Poker Flat Imaging Riometer and NOAA satellite

et al. 2005

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Abstract. The cosmic noise absorption (CNA) is compared with the precipitating electron flux for 19 events observed in the morning sector, using the high-resolution data obtained during the conjugate observations with the imaging riometer at Poker Flat Research Range (PFRR; 65.11 • N, 147.42 • W), Alaska, and the low-altitude satellite, NOAA 12. We estimate the CNA, using the precipitating electron flux measured by NOAA 12, based on a theoretical model assuming an isotropic pitch angle distribution, and quantitatively compare them with the observed CNA. Focusing on the eight events with a range of variation larger than 0.4 dB, three events show high correlation between the observed and estimated CNA (correlation coefficient (r 0 )>0.7) and five events show low correlation (r 0 <0.5). The estimated CNA is often smaller than the observed CNA (72% of all data for 19 events), which appears to be the main reason for the low-correlation events. We examine the assumption of isotropic pitch angle distribution by using the trapped electron flux measured at 80 • zenith angle. It is shown that the CNA estimated from the trapped electron flux, assuming an isotropic pitch angle distribution, is highly correlated with the observed CNA and is often overestimated (87% of all data). The underestimate (overestimate) of CNA derived from the precipitating (trapped) electron flux can be interpreted in terms of the anisotropic pitch angle distribution similar to the loss cone distribution. These results indicate that the CNA observed with the riometer may be quantitatively explained with a model based on energetic electron precipitation, provided that the pitch angle distribution and the loss cone angle of the electrons are taken into account.

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Study of energetic electrons and their relationship to auroral absorption of radio waves

Cited by 50 publications

References 17 publications

On the fine structure of medium energy electron fluxes in the auroral zone and related effects in the ionospheric D-region

On the fine structure of medium energy electron fluxes in the auroral zone and related effects in the ionospheric D-region

Simultaneous trapped electron and magnetic tail field observations

Comparison between CNA and energetic electron precipitation: simultaneous observation by Poker Flat Imaging Riometer and NOAA satellite

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