The overall goal of this project is to continue the operations of the Kodiak SuperDARN Radar. The Super Dual Auroral Radar Network, or SuperDARN, is an international collaborative experiment for observations of plasma motions in Earth's upper atmosphere. By observing ionospheric plasma motions, a multitude of geophysical processes can be studied. These processes range from E-region plasma instabilities, to the relationships between auroral luminosity and electric fields, to the global-scale convective response to changes in the solar wind and interplanetary magnetic field. Each of these areas of study contributes to the overall goals of space physics: developing an understanding of the coupling of energy from the solar wind into Earth's upper atmosphere and its effects on man or manmade systems. The Kodiak radar is particularly well suited for studies of he general areas to be addressed are convection observations, substorm processes, dayside transients, reconnection features at the cusp, mesospheric winds observed in meteor scatter, gravity waves, and thermosphere-ionosphere interactions, and these will be supported by this award.
The SuperDARN network comprises nine radars in the northern hemisphere, and seven radars in the southern hemisphere, each operated independently by the member institutions, and supported by the national agencies in their countries of residence. As is the nature of such networks, data from the SuperDARN network are used in such a wide variety of studies by such a wide range of scientists that it is prohibitive to produce a comprehensive list of the topics.
Over the time period covered by this grant a number of exciting and important results were obtained. In addition, a number of students worked on the project in ways that contributed significantly to their educations. Major findings: The first major study examined average flow patterns for ten substorm intervals in an attempt to identify common features. The features that could be identified were: 1) An increase of the zonal convection speed in the pre-midnight region equatorward of the convection reversal boundary associated with a southward turning of the IMF becoming effective at the dayside magnetosphere, 2) A further enhancement of the zonal convection speed about 8 minutes prior to expansion onset, and 3) An abrupt and significant decrease of convection speed at the onset time accompanied by a rotation of the near-midnight flow from zonal to meridional out of the polar cap. These features are consistent with features identified in previous case studies of convection patterns during substorms. Another study examined the characteristics of radar scatter and optical emissions from the ionospheric volume heated by high-power RF. It was found that there was a significant change in both of these quantities when the heating frequency passed through the second gyroharmonic. Optical emissions increased while HF backscatter decreased. The observations were compared to expectations from theory and were found to agree substantially. Another study was published that reviewed a number of the developments and findings from the first decade of SuperDARN. Another study examined the altitude distribution of optical emissions generated in HF ionospheric heating. Kodiak radar observations were used in conjunction with the optical observations to indicate the presence of ionospheric irregularities. Another paper presented a methodology for the remote sensing of magnetic reconnection in the magnetosphere from the ionosphere. This method combines measurements of ionospheric plasma convection and the ionospheric footprint of the reconnection separatrix. A study was undertaken with the goals of determining the level of fluctuation due to internal magnetospheric processes, and to examine the probability of observing a significant velocity fluctuation within any given time interval. The study included 6 years of observations from periods when the interplanetary magnetic field (IMF) was moderately southward and steady. A study used SuperDARN data to study high-latitude ionospheric convection over a three hour period (starting at 22:00 UT on 2 January 2003), during which the Interplanetary Magnetic Field (IMF) flipped between two states, one with By>>|Bz| and one with Bz>0, both with negative Bx. We found that day side ionospheric convection was controlled by the IMF in both hemispheres. Another study used the Super Dual Auroral Radar Network (SuperDARN) convection database in conjunction with a list of substorm onsets determined from the IMAGE satellite to examine the relationship between substorm onset locations and features of the convection pattern. In addition to the publications a large number of conference presentations were made and data were supplied to a large number of users for studies in which nobody supported by this grant was named as co-author. Student training: Beginning in the first year of the grant three students carried out projects which ultimately led to their Master’s theses. A UAF engineering student supported under this grant wrote driver software for the digital receivers used by many of the radars. Writing the driver software constituted a portion of the student’s thesis work. A second student developed a technique for spectral estimation of the radar target. He developed a new class of pulse sequences for the radar from which the target spectrum is estimated. The new sequence was similar to the multi-pulse technique that is the standard technique used for range-spread targets, however it overcame many of the shortcomings of multi-pulse and provided a much lower variance in estimates of the target velocity. A third student wrote new software for extracting meteor-scatter data from the primary data steam. In the rewrite, we reexamined and revised the algorithms. Another student developed a multi receiver system to implement radar imaging. The system consists of seven digital receiver PCI-cards installed in a computer bus extension chassis. Each of the seven cards has three analog radio-frequency inputs. Each input connects to one of the antennas of the array. The receivers directly sample the RF signals and all mixing, filtering, and phasing is done digitally. Combining the individual data streams using high-resolution spectral techniques, images of the radar field of view can be created that give significantly greater azimuthal resolution than has ever been achieved using a scientific HF radar. Another student development project was arbitrary transmit-beam forming. This system consists of four digital synthesizers, which are also PCI-cards installed in another computer bus extension chassis. The system allows forming transmit beams of nearly arbitrary width, (greater than the minimum), which allows imaging over larger areas than would be possible using conventional beam forming.
