Variability in the Energetic Electron Bombardment of Ganymede

Abstract. Several possible mechanisms for the production of sporadic sodium layers have been discussed in the literature, but none of them seem to explain all the accumulated observations. The hypotheses range from direct meteoric input, to energetic electron bombardment on meteoric smoke particles, to ion neutralization, to temperature dependent chemistry. The varied instrumentation located on Andøya and near Tromsø in Norway gives us an opportunity to test the different theories applied to high latitude sporadic sodium layers. We use the ALOMAR Weber sodium lidar to monitor the appearance and characteristics of a sporadic sodium layer that was observed on 5 November 2005. We also monitor the temperature to test the hypotheses regarding a temperature dependent mechanism. The EISCAT Tromsø Dynasonde, the ALOMAR/UiO All-sky camera and the SKiYMET meteor radar on Andøya are used to test the suggested relationships of sporadic sodium layers and sporadic E-layers, electron precipitation, and meteor deposition during this event. We find that more than one candidate is eligible to explain our observation of the sporadic sodium layer.

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Variations in Cathodoluminescent Intensity of Spacecraft Materials Exposed to Energetic Electron Bombardment

IEEE Transactions on Plasma Science ◽

10.1109/tps.2015.2480086 ◽

2015 ◽

Vol 43 (11) ◽

pp. 3948-3954 ◽

Cited By ~ 1

Author(s):

Justin Dekany ◽

Justin Christensen ◽

John Robert Dennison ◽

Amberly Evans Jensen ◽

Gregory Wilson ◽

...

Keyword(s):

Energetic Electron ◽

Electron Bombardment

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Surface Characterization and Secondary Electron Emission Properties of Alumina Containing MgO Film on Ag-Mg-Al Alloy

Metals ◽

10.3390/met8080570 ◽

2018 ◽

Vol 8 (8) ◽

pp. 570 ◽

Cited By ~ 3

Author(s):

Fan Zhou ◽

Quan Zhang ◽

Feifei Wang ◽

Jing Wang ◽

Yunfei Yang ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Surface Characterization ◽

Secondary Electron ◽

Energetic Electron ◽

Electron Bombardment ◽

Mg Alloy ◽

Al Alloy ◽

Activation Process ◽

Low Oxygen ◽

Electron Multiplier

Ag-Mg alloy is used as a dynode material in electron multiplier tubes due to the high secondary electron yields (δ) of the surface of MgO film. However, MgO film is readily degraded under strong electron or ion bombardment, which results in a decrease in the lifetime of devices. In this study, alumina-containing MgO films of ~50–150 nm were developed on a Ag-2Mg-2Al alloy (silver alloy containing 2 wt % Mg and 2 wt % Al) after a thermal activation process performed at 500–600 °C under low oxygen pressures of 5.0–20.0 Pa. Auger electron spectroscopy and X-ray photoelectron spectroscopy analyses reveal that the film consists of a thin layer of pure MgO and a relatively thicker layer of alumina-containing MgO located beneath the top MgO layer. The alumina-containing MgO film exhibits high δ value of 7.7 at a primary electron energy of 580 eV and a much better stability under energetic electron bombardment than pure MgO film on Ag-Mg alloy. Alumina has higher bond dissociation energy than MgO, and the presence of alumina in the film contributes to mitigating the dissociation of the MgO film under electron bombardment. The Ag-2Mg-2Al alloy with alumina-containing MgO film is a promising candidate as a dynode material for electron multiplier tubes.

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Space and Time Distribution of Hard X-Ray Emission in a Loop at the Beginning of a Flare

International Astronomical Union Colloquium ◽

10.1017/s0252921100025446 ◽

1994 ◽

Vol 144 ◽

pp. 275-277

Author(s):

M. Karlický ◽

J. C. Hénoux

Keyword(s):

Time Distribution ◽

Electron Bombardment ◽

Spatial Evolution ◽

Superthermal Electrons ◽

Flare Loop ◽

X Ray ◽

Superthermal Electron ◽

Flare Loops ◽

Chromospheric Evaporation ◽

Temporal And Spatial

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.

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Electron beam induced effects in Cu/GeSe2amorphous films

MRS Proceedings ◽

10.1557/proc-777-t4.7 ◽

2003 ◽

Vol 777 ◽

Author(s):

J.S. Romero ◽

A.G. Fitzgerald

Keyword(s):

Thin Films ◽

Electron Beam ◽

Simple Model ◽

Copper Concentration ◽

Negative Charge ◽

Electron Bombardment ◽

Continuous Operation ◽

Electron Radiation ◽

Crystalline Product ◽

Intense Electron

AbstractCopper migration is observed in the SEM in amorphous GeSe2/Cu thin films when an electron beam is focused in pulsed or continuous operation on the surface of these thin films. The phenomenon can be explained using a simple model in which the population of D- centers is considered to increase upon electron irradiation. The increase in the D- center population is envisaged as due to the breaking of bonds by the electron radiation and by the constant presence of negative charge in irradiated regions. Changes in copper concentration of 20%-30% have been obtained. Additionally we have observed the local crystallization of amorphous GeSe2/Cu thin films in the TEM when the samples were subjected to intense electron bombardment. The crystalline product has been identified as Berzelianite (Cu2Se).

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