Auroral Electron Acceleration Research Articles

Low-altitude acceleration of auroral electrons during breakup observed by a mother-daughter rocket

By the use of a mother-daughter rocket combination and ground-based observations with television, time and space variations are resolved in particle measurements in breakup aurora. The spectral variations measured during a temporal variation in the aurora can be explained by a nearly uniform acceleration of all the electrons such as would be caused by an electric potential drop along the magnetic field lines. Many other explanations can be eliminated.

Space-charge regions above the aurora

Observations have shown that field-aligned currents above auroras reach such magnitudes that space-charge regions of high potential drops can be expected. Effects of the electric fields associated with such a space-charge region are acceleration of auroral electrons and horizontal motions in the visual aurora.

Theory of Auroral Bombardment.

view Abstract Citations (37) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Theory of Auroral Bombardment. Chamberlain, Joseph W. Abstract An auroral theory is developed from the point of view of particle orbits in an inhomogeneous plasma confined by a magnetic field. Specifically, a mechanism is proposed for ejection into the atmosphere of geomagnetically trapped protons and electrons. It is assumed that the energetic particles are distributed in longitude irregularly. The tendency for positive and negative particles to drift in opposite directions will then lead to momentary electrostatic fields, arising from excess charges of one sign aligned along a magnetic line of force. As particles drift into this potential, they lose transverse kinetic energy, and a portion of the particles immediately spiral out the ends of the flux tube into the atmosphere As the potential grows, the drift of particles into this "discharge tube" is inhibited, but more of those entering the potential with high velocity are ejected, regaining their lost transverse kinetic energy in accelerated motion along the magnetic field. The potential may rise sufficiently to discharge particles with energies of several kev within an interval of less than a second, which is rapid enough to render neutralization by ionospheric ions and electrons unimportant. If the density fluctuations of auroral plasma exceed a certain critical value, the electrostatic field will cause them to grow rapidly. This instability is identified with auroral-ray structure. A density fluctuation may maintain its identity, even though individual particles are constantly moving thorugh it. This characteristic may be associated with the fading and reappearance of rayed structures. The basic mechanism of electrostatic fields arising from the particle drifts will also produce local accelerations of particles, by tending to establish an equipartition of energy between protons and electrons. This is presumably the mechanism for the local acceleration of auroral electrons, although it will also modify, but less severely, the energy spectrum of trapped protons. Various other consequences of these macroscopic, but short4ived, electric fields are examined, with a view toward understanding auroral morphology. It is proposed that an B X B drift accounts for the statistical preference for auroral patterns to move toward the sunlit hemisphere and for the departures of auroral forms from alignment along circles of geomagnetic latitude, even in the polar cap. The B field, when transferred to the atmosphere by bombardment and by ordinary conduction, will produce a Hall current parallel to auroral motions; this current is identified with the auroral electrojet and associated magnetic disturbances. It is suggested that these considerations also have a bearing on the north-south thickness of auroral forms, on auroral breakup, and on daily variations. Publication: The Astrophysical Journal Pub Date: September 1961 DOI: 10.1086/147168 Bibcode: 1961ApJ...134..401C full text sources ADS |

Time Variation of the Intensity of Auroral Hydrogen Emission and the Magnetic Disturbance.

view Abstract Citations (13) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Time Variation of the Intensity of Auroral Hydrogen Emission and the Magnetic Disturbance. Fan, C. Y. Abstract The time variation in the intensity of auroral hydrogen emission and the magnetic disturbance were simultaneously recorded for a number of cases at the Yerkes Observatory It was found that the horixontal component of the terrestrial magnetic field increases prior to the appearance of an auroral arc and that the onset of a negative bay in the disturbance coincides with the breakup of the arc to rays and an abrupt decrease in the intensity of the hydrogen emission These observations suggest that there are two current systems <}ne responsible for the acceleration of auroral protons and electrons for the excitation of auroral arcs and the other for the acceleration of auroral electrons for the excitation of auroral displays of more active types. Publication: The Astrophysical Journal Pub Date: September 1958 DOI: 10.1086/146556 Bibcode: 1958ApJ...128..420F full text sources ADS |