Rotating fluids and the outer core - Earth Dynamics: Deformations and Oscillations of the Rotating Earth - page 398

C Find next Coriolis frequency.
19 CONTINUE
SIG=(SIG1*ERR2-SIG2*ERR1)/(ERR2-ERR1)
C Calculate new sidereal period.
TS=12.D0/SIG
C Find new period.
T=HSSD/SIG
Z=SIG*DSQRT((1.D0-ESQD)/(1.D0-ESQD*SIG*SIG))
C Find error for new iterate.
ERRI=ERR(Z,M,N,SIG)
WRITE(6,17)SIG,TS,ERRI,T
C Decide whether to do new search, do another iterate, or end.
WRITE(6,20)
20 FORMAT(1X,'Enter -1 for new search, 0 for another iterate,',1X,
1 'or 1 for new harmonic')
READ(5,*)IBR
IF(IBR.LT.0) GO TO 21
IF(IBR.GT.0) GO TO 23
C Prepare for another iteration.
SIG1=SIG2
ERR1=ERR2
SIG2=SIG
ERR2=ERRI
GO TO 19
C Decide to search new harmonic or go to end.
23

CONTINUE
WRITE(6,22)

22 FORMAT(1X,'Enter -1 for new M and N, 0 for end')

READ(5,*)ISW
IF(ISW.LT.0) GO TO 10
END

C

DOUBLE PRECISION FUNCTION ERR(Z,M,N,SIG)
C Calculates root function for Poincare inertial wave equation
C in a spheroid.
IMPLICIT DOUBLE PRECISION(A-H,O-Z)
AM=DFLOAT(M)
AN=DFLOAT(N)
ERR=(AN+1.D0)*(AN+AM)*PMN(Z,M,N-1)-AN*(AN-AM+1.D0)*PMN(Z,M,N+1)
1 -(2.D0*AN+1.D0)*AM*Z*PMN(Z,M,N)/SIG
RETURN
END

Eigenperiods, computed by the foregoing codes for a core-mantle boundary with
hydrostatic flattening f 1/394.03 (corresponding to that for Earth model Cal8),

for some of the shorter period modes, are given in Table 6.1.

=

6.2 Dynamics of the fluid outer core

The solutions of the Poincare inertial wave equation show that a contained, rotating
fluid is capable of a great variety of free oscillations with periods greater than
12 sidereal hours.