Data of Core Angular Momentum
Changes
Author(s): Sergei
Petrov & Véronique Dehant
Affiliation: Royal Observatorium of Belgium
Sampling
time interval:
5.0 years
Time span from 1900.0 to
2000.0
Data
unit: Excess
length of day in milliseconds
over standard day of 86400 seconds
Modelling
hypotheses:
column '1'
The zonal toroidal t_1^0
and t_3^0 components of a geostrophic flow are used to estimate the LOD from
core angular momentum. This flow is computed from the IGRF surface magnetic
field extrapolated downward and the induction equation.
The hypothesis used to get the CMB flow are the classical frozen
flux approximation.
column '2'
Quasi-steady
flow
The zonal toroidal t_1^0
and t_3^0 components of a geostrophic flow are used to estimate the LOD from
core angular momentum. This flow is computed from the IGRF surface magnetic
field extrapolated downward and the induction equation.
The
hypothesis used to get the CMB flow are the classical frozen flux approximation
and tangential geostrophy near the CMB.
column '3'
The zonal toroidal t_1^0
and t_3^0 components of a geostrophic flow are used to estimate core angular
momentum. The CMB flow is related to the magnetic field at the CMB by the
induction equation and the frozen flux approximation as well as tangential
geostrophy.
The flow is computed with a collocation method (least squares
adjustment) starting from both the IGRF surface magnetic field and the observed
LOD.
Description of the data used for model computation?
column '1'
The
IGRF surface magnetic field at 5 years intervals
column '2'
The
IGRF surface magnetic field at 5 years intervals
column '3'
The
IGRF surface magnetic field at 5 years intervals and IERS LOD data at 5 years
intervals
References
to be mentioned when data are used:
Petrov S. & Dehant V., 2001
|
|
1 |
2 |
3 |
|
1900.0 |
0.80 |
0.85 |
1.20 |
|
1905.0 |
0.98 |
1.20 |
1.61 |
|
1910.0 |
1.23 |
1.41 |
1.73 |
|
1915.0 |
1.50 |
1.00 |
0.91 |
|
1920.0 |
0.14 |
0.01 |
-0.42 |
|
1925.0 |
-0.20 |
-0.80 |
-1.35 |
|
1930.0 |
-1.32 |
-1.59 |
-2.16 |
|
1935.0 |
-1.52 |
-1.90 |
-1.75 |
|
1940.0 |
-1.46 |
-1.49 |
-0.84 |
|
1945.0 |
-1.35 |
-1.20 |
-0.43 |
|
1950.0 |
-1.15 |
-1.01 |
-0.49 |
|
1955.0 |
-0.93 |
-0.93 |
-0.80 |
|
1960.0 |
-0.30 |
-0.38 |
-0.54 |
|
1965.0 |
0.40 |
0.11 |
0.16 |
|
1970.0 |
0.63 |
0.73 |
0.99 |
|
1975.0 |
0.42 |
0.91 |
1.29 |
|
1980.0 |
0.31 |
1.02 |
0.91 |
|
1985.0 |
0.24 |
0.45 |
0.14 |
|
1990.0 |
0.32 |
0.39 |
0.12 |
|
1995.0 |
0.35 |
0.32 |
0.50 |
|
2000.0 |
0.40 |
-0.11 |
-0.33 |