Publications
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A model of geomagnetic secular variation for 1980-1983 A model of geomagnetic secular variation for 1980-1983
We developed an updated model of the secular variation of the main geomagnetic field during 1980 through 1983 based on annual mean values for that interval from 148 worldwide magnetic observatories. The model consists of a series of 80 spherical harmonics, up to and including those of degree and order 8. We used it to form a proposal for the 1985 revision of the International Geomagnetic...
Authors
N.W. Peddie, A.K. Zunde
Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, June 1987 Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, June 1987
No abstract available.
Authors
John B. Townshend, R. V. O’Connell, L.Y. Torrence
The geomagnetic jerk of 1969 and the DGRFs The geomagnetic jerk of 1969 and the DGRFs
Cubic spline fits to the DGRF/IGRF series indicate agreement with other analyses showing the 1969-1970 magnetic jerk in the h ??12 and g ??02 secular change coefficients, and agreement that the h ??11 term showed no sharp change. The variation of the g ??01 term is out of phase with other analyses indicating a likely error in its representation in the 1965-1975 interval. We recommend...
Authors
D. Thompson, J.C. Cain
Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, July 1987 Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, July 1987
No abstract available.
Authors
John B. Townshend, R. V. O’Connell, L.Y. Torrence
Rainfall, ground-water flow, and seasonal movement at Minor Creek landslide, northwestern California: Physical interpretation of empirical relations Rainfall, ground-water flow, and seasonal movement at Minor Creek landslide, northwestern California: Physical interpretation of empirical relations
Simple ground-water flow analyses can clarify complex empirical relations between rainfall and landslide motion. Here we present detailed data on rainfall, ground-water flow, and repetitive seasonal motion that occurred from 1982 to 1985 at Minor Creek landslide in northwestern California, and we interpret these data in the context of physically based theories. We find that landslide...
Authors
R.M. Iverson, J. J. Major
Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, April 1987 Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, April 1987
No abstract available.
Authors
John B. Townshend, R. V. O’Connell, L.Y. Torrence
Landslides of Eastern North America Landslides of Eastern North America
No abstract available.
Authors
Arthur P. Schultz, C.S. Southworth
Current loops fitted to geomagnetic model spherical harmonic coefficients. Current loops fitted to geomagnetic model spherical harmonic coefficients.
One hundred-sixty circular current loops with radial axes were fitted by least squares to the 899 spherical harmonic coefficients of a 29th degree model. In the first case, the parameters that were fitted for each loop were the normalized magnetic moment, the distance from the center of the Earth to the current element, the colatitude and E. longitude of the loop axis, and one-half of...
Authors
L.R. Alldredge
On predicting changes in the geomagnetic field On predicting changes in the geomagnetic field
The present method of using constant secular variation rates to forecast magnetic components at a given site or to forecast spherical harmonic coefficients is known to be inaccurate. A new predictive method using trend and trigonometric functions fitted to known past values is used to extrapolate for a few years into the future. This provides an improvement over the usual linear...
Authors
L.R. Alldredge
On regional geomagnetic charts On regional geomagnetic charts
When regional geomagnetic charts for areas roughly the size of the United States were compiled by hand, some large local anomalies were displayed in the isomagnetic lines. Since the late nineteen sixties, when the compilation of charts using computers and mathematical models was started, most of the details available in the hand drawn regional charts have been lost. One exception to this...
Authors
L.R. Alldredge
On the interpretation of the geomagnetic energy spectrum On the interpretation of the geomagnetic energy spectrum
Two recent high-degree magnetic energy spectra, based mostly on MAGSAT data, are compared and found to agree very well out to order and degree n = 15, but the spectrum remains somewhat uncertain for higher degrees. The hypothesis that a primary break in the slope of the spectrum, plotted semi-logarithmically, is due to a transition from dominance by core sources to dominance by crustal
Authors
E.R. Benton, L.R. Alldredge
Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, November 1987 Preliminary geomagnetic data, College Observatory, Fairbanks, Alaska, November 1987
No abstract available.
Authors
John B. Townshend, R. V. O’Connell, L.Y. Torrence