VLF wave injection experiments from Siple Station, Antarctica

• Main Author: R.A. Helliwell
• Format: Report
• Language: English
• Published: Space, Telecommunications, and Radioscience Laboratory, Stanford University 1987
• Subjects: Siple; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2178; http://id.nii.ac.jp/1291/00002178/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2178&item_no=1&attribute_id=18&file_no=1

The background of VLF wave-particle experiments from Siple Station, Antarctica, including wave-induced precipitation is briefly reviewed. Single frequency ducted signals that exceed a certain 'threshold' intensity are observed at the conjugate point (Roberval, Quebec) to be amplified 30-50dB, with temporal growth rates of 30-200dB/s. Following saturation, variable frequency emissions are triggered. When a second signal is added to the first, with a frequency spacing Df<100Hz, signal growth is reduced and sidebands are generated at frequencies separated from the carriers by integer multiples (up to seven) of Df. The sidebands are attributed to short emissions triggered by the beats between the two input carriers. Mid-latitude magnetospheric hiss is crudely simulated by a sequence of 10ms pulses whose frequencies are chosen randomly within a 400Hz band. Results show that certain combinations of 10ms pulses link together to form chorus-like elements, suggesting a common origin for hiss and chorus. Under conditions of strong echoing, emissions may form into lines; a recent example, started by the Siple Station transmitter, exhibits interline spacings of about 45Hz. These lines, called magnetospheric line radiation (MLR), vary slowly in frequency and show no simple connection to the harmonics of the Canadian power grid. Interline suppression may play a role in determining the spacing of MLR lines and the absence of discrete triggered emissions.