Pulsations Of Precipitating Energetic Electrons : Active Satellite Data

We present the patterns of high frequency energetic electron (∼ 20 to ∼ 300 keV) pulsations in middle latitudes, in subauroral and auroral regions, based on low altitude nearly polar orbiting satellite (Intercosmos-24, project ACTIVE) measurements. Two detectors with different orientations allowed the fluxes within and outside the loss cone to be compared. The trapped electrons do not exhibit the strong pulsations observed within the bounce loss cone. The pitch angle diffusion coefficient changes significantly on time scales comparable to or even shorter than the bounce period of electrons. The same is valid for changes of precipitating electron energy spectra. There are indications that both pitch angle and energy diffusion are in operation. VLF emissions at f < 3.5 kHz with a complicated structure are observed simultaneously with the electron pulsations, but there is no clear correlation between waves and particles. If the characteristics of the electron pulsations and VLF emissions are of a temporal character, they are qualitatively consistent with the models of nonlinear wave particle interactions, or with the concept of a flowing cyclotron maser. However, the pulsations may originate from fine spatial structure. Variability of the precipitation flux implies short time and/or small scale changes of ionization at altitudes down to 70 km. © 1998 Elsevier Science Ltd. All rights reserved.606643653Baker, D.N., Blake, J.B., Gorney, D.J., Higbie, P.R., Klebesadel, R.W., King, J.H., Highly relativistic magnetospheric electrons: A role in coupling to the middle atmosphere? (1987) Geophys. Res. Lett., 14, pp. 1027-1030Bryant, D.A., Courtier, G.M., Bennet, G., Equatorial modulation of electrons in a pulsating aurora (1971) J. Atmos. Terr. Phys., 33, pp. 849-858Coroniti, F.V., Kennel, C.F., Electron precipitation pulsations (1970) J. Geophys. 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In Situ Observations of Ionospheric Heating Effects: First Results from a Joint SURA and NorSat-1 Experiment

©2020. American Geophysical Union. All Rights Reserved. This work presents the first results of measurements of artificial plasma disturbance characteristics using the low-orbit NorSat-1 satellite, which are excited when the ionospheric F2 layer is modified by powerful high-frequency (HF) waves emitted by the SURA heating facility. NorSat-1 carries the multineedle Langmuir probe instrument, which is capable of sampling the electron density at a nominal rate up to 1 kHz. The uniqueness of this experiment lies in the fact that the satellite passes very close to the center of the HF-perturbed magnetic flux tube and in situ observations are first carried out in winter when the absorption is still small in the morning as the Sun is low above the horizon. There are HF-induced plasma temperature and density variations at satellite altitudes of about 580 km. Plasma irregularities are detected by in situ measurements down to 200 m at the southern border of the SURA heating region