Electron Dump Research Articles

A stretched betatron

We have demonstrated trapping, confinement, acceleration, and dumping of electrons in a betatron which has a geometry similar to the Astron. 76±22 nC were accelerated to 800±100 keV. This corresponds to a circulating electron current of 60 A. The betatron has a 6-cm orbit radius and is 1 m long. Electrons are injected tangentially from a 70-kV, 15-A field emission diode. A toroidal field roughly equal to the betatron field is used.

Effect of a heated patch of auroral ionosphere on VLF-radio wave propagation

In the early 1960s, during the period of atmospheric nuclear tests, much theoretical interest developed in the effects of localized ionospheric depressions on the propagation of very low frequency (VLF) radio waves1–4. Similar VLF-propagation effects are also produced by the localized dumping of electrons from the radiation belts after wave–particle interactions5,6. Both nuclear explosions and particle precipitation events are of a transient nature, however, and no experimental study has yet been made to confirm these early theoretical predictions. With the development of a unique high frequency (HF) heating facility near Tromso, Norway, the generation of movable controlled anomalies in the D-region has become possible. We describe here some initial observations, made in Norway, of the effect of such a movable D-region anomaly on the VLF signals received from the 12.1-kHz Omega transmitter at Aldra. The observations confirm the validity of earlier theoretical predictions.

The design and fabrication of a 30 s pulsed plasma generator

The design and fabrication techniques for a large hybrid magnetic cusp plasma generator developed for 30 s pulse length are described. Included are the magnetic cusp geometry features, water cooling characteristics, filament structures, and the high energy density actively cooled anode and electron dump employed.

Electron precipitation of evening diffuse aurora and its conjugate electron fluxes near the magnetospheric equator

A more precise and definitive relation between diffuse auroras and their particle source region was determined by examining simultaneously the particle observations at the geosynchronous orbit and the auroral display as well as the auroral electron precipitations near its field line conjugate observed by the polar‐orbiting DMSP 32 satellite. It is found that the spectral shape and differential fluxes of precipitated auroral electrons of diffuse auroras are very similar, and sometimes almost identical, to those of the trapped plasma sheet electrons located simultaneously in the conjugate magnetospheric equator. The characteristics of auroral electron precipitations are determined by the particle features in the conjugate magnetospheric equator, and diffuse auroras are produced by the direct dumping of the plasma sheet electrons.

Electron precipitations and polar auroras

In the first part (Sections I–III) a brief historical review of the progress of our knowledge of the precipitation of auroral electrons is given. Observations by different techniques, in terms of detectors aboard balloons, sounding rockets, and polar-orbiting satellites, are reviewed (Sections I). The precipitation morphology is examined in terms of synoptic statistical results (Section II) and of latitudinal survey along individual satellite passes (Section III). In the second part (Section IV), a large number of simultaneous observations of auroras and precipitating auroral electrons by DMSP satellites are examined in detail, and it is shown that precipitation characteristics of auroral electrons are distinctly different for the discrete aurora and the diffuse aurora. In the third part (Section V), the source region of auroral electrons is discussed by comparing the auroral electron precipitation at low altitudes observed by DMSP satellites with the simultaneous ATS-6 observations near the magnetospheric equatorial plane approximately along the same geomagnetic field line. It is shown that the diffuse aurora is caused by direct dumping of the plasma sheet electrons from the equatorial region, whereas discrete auroras require acceleration of electrons between the plasma sheet and the polar atmosphere. The parallel electric field along the geomagnetic field line above the ionosphere is a likely candidate for the acceleration mechanism.

Evidence suggesting dumping of semitrapped electrons on the night side of the Earth

Processes leading to the production of energetic electrons and their precipitation into the auroral atmosphere are believed to take place in the earth's magnetosphere. Details as to how these electrons appear on and are removed from the magnetic lines linking the distant field and the auroral atmosphere are currently unknown, although all processes presumably result from interactions with the solar wind. The older interpretation of particle precipitation as simply dumping of the statically trapped radiation from the outer zone has largely given way to the concept of local acceleration for a number of compelling reasons [O'Brien, 1962; Winckler, 1962]. Nevertheless, the character of the precipitation may, in some instances, still be related to the local quasi-trapped reservoir of particles.

Direct observations of dumping of electrons at 1000-kilometer altitude and high latitudes

Quiescent dumping of electrons with energy above 40 kev in intensities of the order of 104 particles (cm2 sec ster)−1 was detected by the Injun I satellite at altitudes about 1000 km and high latitudes around July 1, 1961. In 16 passes between longitudes of 230°E and 340°E, the angular distribution of electrons about the magnetic vector B showed there was dumping in every one of 8 passes between 1200 and 1500 local time, and in only one of 8 passes between 1900 and 2300. When there was no dumping, the directional intensity of electrons at ∼20° from the normal to B was less than 1 per cent of that normal to B. When there was dumping, the corresponding value was of the order of 100 per cent, and the intensity at about 50° from the normal to B was of the order of 10 per cent of that normal to B. Appreciable intensities of electrons were backscattered. Dumping was seen over very wide ranges of latitude between L∼2 and L∼10 and was uncorrelated with Kp. It is pointed out that the dumped electrons may be either new, freshly injected or accelerated particles, or they may be old, formerly trapped particles, which were perturbed in their orbits. The obervations are further evidence that acceleration mechanisms must occur frequently at altitudes above 1000 km.

Atmospheric phenomena, energetic electrons, and the geomagnetic field

Abstract : X-ray measurements associated with the dumping of electrons from the magnetic field, made with balloons and rockets are discussed. It is shown that in the normal auroral zone the x-ray bursts occur throughout the 24-hour period, have peak intensities corresponding to e ectron fluxes of 10 to the 6th to 10 to the 7th power/sq cm/sec, and have integrated fluxes over a 24-hour period of 10 to the 10th power/sq cm. In the auroral zone the x-ray bursts arising from 30-kv or higher electrons are not correlated with visible aurorae. Direct rocket measurements of bright aurorae in the auroral zone confirm this by showing the absence of appreciable electron fluxes above 20 kv. At lower latitudes, the x-rays are well-correlated with visible aurorae, have peak burst intensities of 10 to the 9th power electrons/sq cm/sec greater than 30 kv, and are also strongly correlated with negative bays in the local magnetic field. (Author)