The original objectives of this thesis were to use the new PolarDARN radars to study the convection patterns at high latitudes and to attempt to explain them in terms of reconnection. Because the IMF is important in reconnection, studies of the Interplanetary Magnetic Field (IMF) components Bx, By and Bz were done. The study showed that <|Bz|> was lower by 21.5% than <|By|> from Jan. 2006 to Dec. 2008, so By was expected to play an important role in reconnection. The IMF, spiral angle, and the amount of warping of the solar magnetic field in interplanetary space decreased slightly during this 36-month period. The decrease in IMF was a more sensitive indicator of the solar minimum than the decrease in the 10.7 cm solar microwave flux.<p>
A solar magnetic sector boundary study from the Jan 1, 2007 Dec 31, 2008 interval showed the occurrence of four or two sectors in a synodic solar rotation cycle. A sector boundary crossing frequently takes place in less than 3 hours. The transition from four sectors to two sectors is surprisingly smooth, in that no interruption in the 27-day synodic period occurs. A superposed epoch analysis of solar wind speed near sector boundary crossings showed a speed minimum about half a day before the crossing, and a maximum about two days after the crossing. The standard deviation reached a minimum at about the same time as the velocity. The sector boundary study also showed that, since Dec. 2007, there were six roughly 27-day synodic solar rotation cycles near spring equinox when away field dominated, and that the following seven 27-day cycles close to the autumnal equinox were dominated by toward field. This is consistent with the quasi-sinusoidal annual magnetic sector polarity oscillations that occur for about three years during solar minimum. These oscillations are due to the mainly dipolar magnetic field which is roughly aligned with the Suns axis, tilted 7.25° from the normal to the ecliptic plane. The three-year oscillation for the present minimum between Solar Cycles 23 and 24 appeared to begin in Dec. 2007. For the past four solar minima, an El Nino event has occurred during the last of the three oscillations, and the El Nino and sinusoidal magnetic oscillation ended together. The new solar cycle began about 6 months before that.
During the past eight years, a new 3D topological null-separator formulation of magnetic reconnection and its effect on convection has been led by Dr. M. Watanabe in ISAS at the University of Saskatchewan. This formulation includes two types of interchange reconnection (Russell and Tanaka) as well as the traditional Dungey reconnection. For conditions when the IMF clock angle was within 30° of a Bz+ dominant convection, the new reconnection model shows that the convection can be driven strictly by the two types of interchange reconnection. The model predicts the existence of a reciprocal cell on closed field lines and an interchange merging cell surrounding an interior lobe cell. The construction of the PolarDARN radars at Rankin Inlet and Inuvik, completed in December, 2007, allowed polar cap convection to be measured for predominantly Bz+ conditions. The existence of the two predicted features was confirmed. This also required that satellite data be analyzed to determine the location of the open-closed-field-line-boundary (OCFLB). Several PolarDARN studies are represented to show convection for different IMF clock angles and seasons.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-03262010-235811 |
| Date | 01 April 2010 |
| Creators | Yan, Xi |
| Contributors | Sofko, George, McWilliams, Kathryn, Xiao, Chijin, Hussey, Glenn, Bourassa, Adam, Merriam, James |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-03262010-235811/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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