Electron precipitation in the auroral zone

Brown, R. R.

doi:10.1007/bf02653249

Cited by 77 publications

(19 citation statements)

References 116 publications

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“…If the ducts were indeed present, there are questions as to the source of the noise and how it enters the duct. It may be that the noise originated from precipitating electrons [Ho#man, 1969;Evans, 1967;Evans et al, 1967;Hartz and Brice, 1967;Westerlund, 1969;Brown, 1966] in the nearby auroral region, in view of the time of occurrence and geomagnetic latitudes of observed hiss events.…”

Section: Observation Of Narrow Bani) Lhr Hxssmentioning

confidence: 96%

VLF duct associated with the lower-hybrid-resonance frequency in a multi-ion upper ionosphere

Gross¹

1970

J. Geophys. Res.

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As a result of the presence of two or more ions with different height profiles in the upper F region of the ionosphere, propagation ducts that are associated with the lower‐hybrid‐resonance frequency may form. Such ducts are generally oriented along a horizontal direction. These ducts were originally suggested as a mechanism for the explanation of certain VLF hiss bands observed by a number of satellites with electric antennas. They were questioned, however, as a result of detections of VLF noise components at frequencies well above their trapping bands. The conditions in a diffusive equilibrium region under which such ducts may form are investigated. It is found that the ducts are essentially narrow‐band guides with maximum possible bandwidths of the order of 2.5 to 3.0 kHz; the bandwidths vary with altitude. Duct quality is found to depend on the parameters at the ion density crossover level and at the F region peak. Duct formation is favored by low electron density conditions, thus implying that their existence at high midlatitudes in or near the ionospheric trough is favored. Preliminary examination of data from the VLF receiver connected to the long electric antenna on Alouette 1 revealed a number of hiss events for the year 1963 with bandwidths that fit the duct properties.

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Section: Observation Of Narrow Bani) Lhr Hxssmentioning

confidence: 96%

VLF duct associated with the lower-hybrid-resonance frequency in a multi-ion upper ionosphere

Gross¹

1970

J. Geophys. Res.

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“…The parameterized auroral oval resets Q values to six when they exceed this number, so that more NO x is deposited in the polar night than should be during intense geomagnetic storms. In addition, the highest energy electrons are assumed to be distributed in the same auroral oval as the lower energy electrons when in fact relativistic electrons are deposited in the sub-auroral belt (e.g., Brown, 1966). However, the relativistic electrons account for a small fraction of the NO x production and this limitation of the scheme is not significant.…”

Section: Electron Precipitationmentioning

confidence: 99%

Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation

et al. 2011

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Abstract. The impact of NO x and HO x production by three types of energetic particle precipitation (EPP), auroral zone medium and high energy electrons, solar proton events and galactic cosmic rays on the middle atmosphere is examined using a chemistry climate model. This process study uses ensemble simulations forced by transient EPP derived from observations with one-year repeating sea surface temperatures and fixed chemical boundary conditions for cases with and without solar cycle in irradiance. Our model results show a wintertime polar stratosphere ozone reduction of between 3 and 10 % in agreement with previous studies. EPP is found to modulate the radiative solar cycle effect in the middle atmosphere in a significant way, bringing temperature and ozone variations closer to observed patterns. The Southern Hemisphere polar vortex undergoes an intensification from solar minimum to solar maximum instead of a weakening. This changes the solar cycle variation of the Brewer-Dobson circulation, with a weakening during solar maxima compared to solar minima. In response, the tropical tropopause temperature manifests a statistically significant solar cycle variation resulting in about 4 % more water vapour transported into the lower tropical stratosphere during solar maxima compared to solar minima. This has implications for surface temperature variation due to the associated change in radiative forcing.

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“…The precipitation of energetic electrons in the dawn sector related to geomagnetic activity is well known from early experiments by riometers and X‐ray detectors on balloons [ Brown , 1966; Sletten et al , 1971]. With the introduction of global auroral imagers the precipitation related to substorm injections and chorus activity has been seen to extend all the way to the noon sector during quiet periods, with a local maximum in the postdawn sector.…”

Section: Introductionmentioning

confidence: 99%

Statistical pitch angle properties of substorm‐injected electron clouds and their relation to dawnside energetic electron precipitation

et al. 2005

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[1] Using the existing large database of geosynchronous orbit particle measurements from Los Alamos instruments, statistical properties of substorm-injected electron clouds are investigated, with special focus on the pitch angle distribution (PAD) of the electrons. The electron distributions at 6.6 R E do in general show some anisotropy, and their PADs are probably caused by the combined influence of drift orbits, different for each energy and pitch angle, and pitch angle diffusion due to waves. The statistical results of this paper indicate that the PADs during intervals of increased electron flux at energies greater than 10 keV from midnight till noon are dominated by pitch angle diffusion by interaction with waves. The strength of the pitch angle diffusion is seen to initially limit the growth of anisotropy from differential drift speeds and orbits and later on to increase the anisotropy when the diffusion strength decreases. After local noon we find evidence that pitch angle diffusion is no longer important and the PADs are evolving due to differential drift effects.

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Electron precipitation in the auroral zone

Cited by 77 publications

References 116 publications

VLF duct associated with the lower-hybrid-resonance frequency in a multi-ion upper ionosphere

VLF duct associated with the lower-hybrid-resonance frequency in a multi-ion upper ionosphere

Middle atmosphere response to the solar cycle in irradiance and ionizing particle precipitation

Statistical pitch angle properties of substorm‐injected electron clouds and their relation to dawnside energetic electron precipitation

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