Abstract
Abstract. We have determined the locations of over 6000 individual auroral kilometric radiation (AKR) bursts between July 2002 and May 2003 using a very long baseline interferometer (VLBI) array. Burst locations were determined by triangulation using differential delays from cross-correlated Cluster WBD waveforms. Typical position uncertainties are 200-400km in the plane normal to the source-spacecraft line, but much larger along this line. The AKR bursts are generally located above the auroral zone with a strong preference for the evening sector (22:00 MLT±2h). However, a few epochs imaged during the austral summer have loci in the daytime sector, especially near 15:00 MLT. There is marginal evidence for a small N-S hemispheric asymmetry in mean MLT and invariant latitude.
Highlights
Auroral kilometric radiation (AKR) is an intense, narrowband terrestrial radio emission which occurs in shortduration bursts at frequencies between 50–800 kHz
The technique is a restricted application of the well-known, very long baseline interferometry (VLBI) technique of conventional radio astronomy in that the independent Wideband Data (WBD) receivers are phase coherent and the received electric field waveforms are cross-correlated after correction for geometrical delay on each baseline
Mutel et al.: AKR burst emission derived from Cluster WBD VLBI studies cross-correlated after correcting for propagation delays and the resulting cross-correlation function (CCF) is searched for significant peaks
Summary
Auroral kilometric radiation (AKR) is an intense, narrowband terrestrial radio emission which occurs in shortduration bursts at frequencies between 50–800 kHz. AKR emission is well correlated in intensity and frequency of occurrence with magnetospheric activity (Kurth and Gurnett, 1998; Liou et al, 2000), and with season (Kumamoto et al, 2003). We cross-correlate AKR burst waveforms from each pair of spacecraft to determine the burst time of arrival differences. By using the differential time delays on all baselines, the 3-dimensional location of individual bursts can be determined by triangulation. The technique is a restricted application of the well-known, very long baseline interferometry (VLBI) technique of conventional radio astronomy in that the independent WBD receivers are phase coherent and the received electric field waveforms are cross-correlated after correction for geometrical delay on each baseline. We utilize only the resulting differential time delays to determine source locations and not the interferometer phases. We do not Fourier invert the measured visibilities to deduce source structure (AKR bursts are coherent, and are completely unresolved (Baumback et al, 1986))
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
