Statistics
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsm23a0467y&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #SM23A-0467
Statistics
2407 Auroral Ionosphere (2704)
Scientific paper
In December 2002, a Versatile Electromagnetic Wave Receiver (VIEW) was deployed at South Pole station. This system records HF waveforms continuously for up to 6 hours/day. Summary files are examined weekly by Dartmouth personnel, and interesting time intervals are saved to CD-rom. This interactive experimental method provides extremely high time- and frequency-resolution measurements of auroral radio emissions, while discarding data from times when no events occur. The motivation was to measure three types of auroral radio emissions: Auroral Roar, a relatively narrowband (δf/f <0.1) emission near 2 and 3 times the F region ionospheric electron cyclotron frequency (fce); Auroral Hiss, a whistler mode wave emission with frequencies lower than 1MHz. ; and Auroral medium frequency (MF) burst, broadband impulsive radio emissions observed at ground level during the breakup phase of auroral substorms. In the year of 2003, we recorded about 80 minutes of auroral roar emission, consisting of 40 different events, at South Pole station. Hughes and LaBelle [2001] observed the first flickering auroral roar, with a ~10 Hz pulsation in emission strength, in Greenland. They proposed that these pulsations are related to the electron flux modulations similar to those which cause flickering aurora. By examining all 80 minutes (40 events) of auroral roar captured in 2003, we found more than 10 cases of flickering auroral roar from 10 different days. However, most instances were brief, sometimes only a few seconds. The total time of flickering auroral roar was a few minutes (a few percent of the total time of occurrence of auroral roar emissions). We also observed the first ever example of higher frequency flickering auroral roar, with a modulation frequency around 100 Hz. We investigate these events by taking time series of the strength of the auroral roar emissions, taking Fourier transforms to determine the frequencies of the flickering. In this poster, we show statistics of the auroral roar flickering frequency and compare these to optical flickering aurora statistics in the published literature. We also show examples of variations of the flickering frequency during flickering auroral roar events. Hughes, J.M., and J. LaBelle, First observations of flickering auroral roar, Geophys. Res. Lett., 28, 123-126, 2001.
LaBelle James
Weatherwax A.
Ye Shuzhen
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