Geology Reference
In-Depth Information
25
20
15
10
5
0
20
22
24
26
28
30
32
Frequency in cycles per day x 10 -4
Figure 4.16 Prograde free core nutation (PFCN) spectral resonance.
140
120
100
80
60
40
20
0
-32
-30
-28
-26
-24
-22
-20
-18
Frequency in cycles per day x 10 -4
Figure 4.17 Retrograde free core nutation (RFCN) spectral resonance.
The estimate of the PFCN amplitude, A , is found to be 89.5723 microarcseconds
(μas).
For the RFCN, a peak power of a 2
123.51 milliarcseconds squared (mas 2 )was
=
10 3 cycles per day,
equivalent to a period of 417.427 days. The fitted resonance curve is shown plotted
over the local power spectrum in Figure 4.17.
As for the PFCN, the fitted resonance curve (4.111) is integrated between its
half-power points to get an estimate of the square of the amplitude as
found with Q =
6.6747 and central frequency f 0 =−
2.39563
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