Micropulsation data recorded at Palo Alto, California during 1963-4 and Ralston, Alberta during 1967 have been used to study "Intervals of pulsations of diminishing period" (IPDP). IPDP's are found to be generated in the dusk-midnight quadrant of the magnetosphere at an equatorial distance of about 6 earth radii. An intensive study of the Ralston data reveals that IPDP's occur during the expansive phase of magnetospheric substorms.
It is proposed that IPDP's are generated by a cyclotron instability between energetic protons and left-hand ion cyclotron waves. Their main characteristics are determined by the perturbations of the dusk-midnight sector of the magnetosphere by magnetospheric substorms. One of the main disturbances in that region is a slow decrease and then sudden increase in the magnetic field corresponding to the buildup and decay of a partial ring current. IPDP's show an increase in midfrequency due to the change in the cyclotron instability frequency produced by the increasing magnetic field. This theory is tested by a comparison of frequency increase of IPDP's observed at Ralston and magnetic field increase in the magnetosphere observed by the ATS-1 satellite.
Other conditions necessary for IPDP generation are then discussed. It is shown that different combinations of these conditions result in the generation of hm emissions and band type micropulsations. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/35433 |
Date | January 1970 |
Creators | Roxburgh, Kenneth R. |
Publisher | University of British Columbia |
Source Sets | University of British Columbia |
Language | English |
Detected Language | English |
Type | Text, Thesis/Dissertation |
Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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