NOTE: Text is contributed by the analyst (Pine); scans are from log sheets (Korgan).
October 7, 2007 1100UT
10/06/2007 0500 MDT 1100 UT
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| First minute of session. |
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Session features dense sferics and tweeks. Note the dark band (horizontal white box) at about
2 kHz. This is the frequency of the tweek “hooks”, or cutoff frequency. Whistlers of low to medium intensity are audible, but are not easy to find in the spectrogram. |
Whistlers logged at :03, :10, :36 and :59. Whistlers at :36 and :59 are visible in lulls in the background (boxes
October 7, 2007 1200UT
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The first 2 minutes of this session were characterized by dense sferics. Note the absence of the tweek hook band. Almost no tweeks an hour after tweeks were common. Four whistlers logged in the two minutes.
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Whistler (W1) logged at 120650 UT is shown followed by a fainter whistler (W2) logged at 120655. |
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Whistler (W1) logged at 121100 UT followed by a second whistler (W2) at 121115 UT.
Each whistler is preceded by a strong sferic burst (B1 and B2) indicating that these are two-hop whistlers originating from local sferics and bouncing off the ionosphere at the magnetic conjugate point and returning as a whistler. Since the sferic density is less than earlier in the day, it makes it easier to recognize the originating bursts. It is probable that most or all of the whistlers observed this day were two-hop whistlers. |
October 7, 2007 1311UT
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Sferics are lower intensity and density. Whistlers logged at 1311:02, :05, :16, :35, 1312:01, :38, :46, :52 and :56.
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Close-up of first 20 seconds of spectrogram showing first 3 whistlers.
Log entries starting at 1313 UT:
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Sferics now low density |
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Whistler at 1406 UT |
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We finish this report with a strong 2-hop whistler followed by a faint, breathy echo logged at 140931 UT. |
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Spectrogram of 30 seconds starting at 1313 UT. Several strong whistler are visible |
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Another whistler sampler. |
October 7, 2007 1400UT
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