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A80, Antarctica

Latitude/Longitude:
(80.75ordm; S, 339.6ordm; E)

Mag Coordinates:
(-66.415ordm;, Midnight MLT = 2:46 UT)

Instruments    BAS Website

Main Science

The BAS-AGO LF/MF/HF receivers make a significant contribution to determining the relation between auroral roar center frequencies and the magnitude of the local geomagnetic field, because these stations lie at latitudes for which the geomagnetic field is far weaker than at any other auroral observatories where LF/MF/HF data are available. Hence, the BAS-AGO sites provided the extreme data points which, taken together with observations from other observatories, most clearly establish that the center frequency of auroral roar varies linearly with the strength geomagnetic field, as expected if the emission is associated with the electron gyroharmonic. For more details, see Hughes and LaBelle, 1998.

The BAS-AGO LF/MF/HF receivers have provided interesting data during  solar flares. First, because these receivers cover higher frequencies, they clearly measure solar type III bursts which penetrate the ionosphere at 10-16 MHz. The dispersion of the bursts is clearly observable. Other solar flare effects such as short-wave fadeout (SWF) are also clearly observed. Most interesting is possible evidence for a broadband signal at the onset of certain intense flares, which is under investigation.

Instrument | Top

BAS AGO LF/MF/HF Receiver

The LF/MF/HF receiver uses a vertical magnetic loop antennas approximately 10 m² in area, oriented to eliminate station-generated interference. A preamplifier at the antenna provides flat response to signals up to 16 MHz; above this frequency the receiver system response drops off at approximately 35 dB/octave. The antennas are located at least 250 feet from the observatories.

The receivers measure 150-point spectra over five 3-MHz bands: 1--4 MHz, 4--7 MHz, 7--10 MHz, 10--13 MHz, and 13--16 MHz. The frequency resolution is 20 kHz and the time resolution is approximately 8 s per 150-point spectrum. However, the 3-MHz bands are not measured simultaneously.  Rather, the instrument is devoted to each band for five minutes and sequentially samples all the bands, thus requiring 25 minutes to cover all frequencies. Events lasting less than 25 minutes may be captured only over a subset of the total 1-16 MHz frequency range, and very short duration events are observed only if they produce signals in the 3-MHz band being sampled at the time of the event.  In addition to performing this complicated spectral analysis, the receivers at A-80 and A-81 sample five low- and medium-frequencies (200, 400, 600, 800, and 1000 kHz) approximately once per 8 seconds. In all cases, these receivers sweep in frequency, sampling lower frequencies first then higher frequencies, and this mode of operation must be considered when interpreting the data, especially when inferring start or end times of impulsive events. 

The data are digitized, compressed using a delta-scheme invoked in digital electronics, and digitally transferred to the BAS AGO computer for archiving. They are extracted annually by the BAS team and provided to Dartmouth on CD-rom.

Other instruments used: Flux-gate Magnetometer, ULF Search-coil Magnetometer, Photometer, Riometer, VLF Receiver