ULF magnetic fluctuations in the plasma sheet as recorded by the Explorer 34 satellite
Garrett, Henry B.
Dessler, A. J.
Master of Science
From 1967 to 1969, the Explorer 34 satellite made approximately 2 passes (6 were used in this study) through the earth's plasma sheet at a distance of 2 to 34 R. On board was a tri-axial, fluxgate magnetometer which made possible the observation of the magnetic field vector every 2.556 seconds. This provided a platform for studying ULF (ultra-low-frequency) magnetic waves in the .1 to .2 Hz band. The signal was anlayzed by calculating the power spectral density function. This function was proportional to the inverse square of the frequency in the plasma sheet and exhibited few, if any, significant spectral peaks. Further, the plasma sheet was characterized by higher power spectral density values than the high-latitude tail. The coordinate component exhibited the greatest power spectral density levels in comparison to the other two components. The most significant result, however, was that the power spectral density, calculated from the frequency range .12 to .1 Hz in the plasma sheet, increased from minimal levels during quiet times to maximum levels during the later stages of the substorm. It is shown that this result is of importance in testing substorm theories.