Date of Award
Program or Major
Doctor of Philosophy
Kristina A Lynch
In this thesis we discuss the results of the Enstrophy sounding rocket, launched from Poker Flat Research Range on the evening of February 11, 1999. The rocket flew through a very dynamic auroral region with multiple bright arcs and into the polar cap. Four Free Flying Magnetometers employing autonomous, nano-spacecraft technology and designed by JPL were deployed from the main payload during the flight and multipoint magnetic field measurements were made.
Magnetic field data reduction was performed on data obtained from the FFMs. The data reduction procedure is very complicated in the sense that it requires transformation from a spinning and precessing coordinate system (measurements are in this system) to a non-spinning, non-processing, Earth-magnetic-field aligned B-L system (z axis is along B---the Earth magnetic field, x is in the B-L plane and pointing away from L---the angular momentum vector, and y axis comprises the right-handed coordinate system) and the extraction of magnetic fluctuation on the order of 10s nanotesla (nT) from a signal on the order of 10 4 nT. Therefore, very accurate fitting of all the involved parameters is a necessity. Details of the data reduction procedure are discussed. Large magnetic field fluctuations were seen by all the FFMs when the rocket was near its apogee (about 1070 km), at the poleward edge of an auroral arc.
Field Aligned Current (FAC) density was calculated from the multipoint magnetic field measurements by Taylor series expansion to the first order. Both spatial structures and temporal variations are seen during this event and interpretations of the results are made. The delays in the magnetic fluctuations between the FFMs indicates current sheet structures were moving relative to each other, which is further supported by the fact that the results from a simple model of multiple payloads crossing through several moving current sheets could reproduce most of the delays in magnetic field measurements. But at other times, the magnetic perturbations on different FFMs did not correlate well with any time delay, which indicates the presence of localized Alfven waves and/or even more filamentary currents. The non-zero deflections in magnetic field magnitude might be considered as the presence of compressional Alfven waves. Further study of this event was done by applying wavelet transformation and correlation analysis to the FFM measurements. The motions of individual structures were deduced using this method.
Zheng, Yihua, "Multipoint measurements of field aligned current density in the auroral zone" (2001). Doctoral Dissertations. 31.