The data processing of MAGSAT investigator B test tapes and data tapes, and tapes of selected data on 15 magnetically quiet days is reported. The 1980 World Chart spherical model was compared with the MAGSAT (3/80) and MAGSAT vector data were used in the models. An article on modelling the geomagnetic field using satellite data is included

Barraclough, D. R.

Hide, R.

Leaton, B. R.

Lowes, F. J.

Malin, S. R. C.

Wilson, R. L.

English

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1. Introduction
Title of investigation: Spherical harmonic rqRstsentaties of the win
g-R-101tic field for world charting and
investigations of some fundamental problems at
physics and geophysics
Investigators: D.R.Barraclough. Institute of Geological Sciences
Ug	 R.Ride, Meteorological Office
R.R.Leaton, Institute of Geological Sciences
me
F.J.Lowes, University of Newcastle-upon-Tyne
Uj E 	 S.R.C.Malin, Institute of Geological Sciences
se 2,
o W c
R.L.Wilson, University of Liverpoolrz
E
Progress Report, June 1st, 1981
(z82-10203) SFhERILAL dA!%MGNlL	 S82-235710
RRPRESELNIATIUX OF THE 8A!b GkLMAGNETA.0 fiELD
FOR IWALD CHARTING AUL 1hiE511"'kTIQNS Gf
SOME FUNLANENTAI PbC8LtES OF PHYSICS AIL	 unclas
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2. Techniques
Data used: Magsat Investigator B test tapes
Nagsat Investigator 3 data tapes
Tapes of selected data on 15 aagnetically quiet days
Spherical harmonic models of the geomagnetic field produced
from Magsat data by G=
Programs used: GSFC programs for analysing selected quiet day data
Analysis program producing spherical harmonic models
of the geomagnetic field and including, besides the
usual internal poloidal field, external and toroidal
f ields
Various test programs produced by ICS and Liverpool groups
3. Accomplishments
Investigator B test tapes were read successfully. A start had been made
on a preliminary survey of the first batch of Investigat o r 3 data tapes
when it was discovered (and later verified by NASA) that these were not
error-free. It was decided to postpone further work on these tapes until
corrected versions were received. These finally arrived at the end of the
reporting period.
The selected quiet-day data are of particular interest to the Liverpool
group. They have experienced some difficulties with the GSFC analysis
program, particularly concerning the altitude correction. Tests of
Maxwell's equations against other proposed modified equations have
begun and initial results look promising.
The 1980 World Chart spherical model has been compared with the MGST
(3/80) and MGST(6/80) models. Agreement in declination is satisfactory
(to within + ON between latitudes of SOON and 500S, the region where
Magsat vector data were used in the MGST models.
6. Significant results
The investigation is at too earlier a stage for there to be any really
significant results to be announced. The agreement of the 1980 World	 =
Chart model with the Magsat data (as represented by the MGST(3/80) and
(6/80) models) is reassuring, however.
5. Publications
r
Barraclough, D.R., 1981. Geomagnetic field modelling using satellite
data, Nature, 290, 86.
6. Problems
Delays in delivery of Investigator B data tapes and errors in the first
batch of tapes have caused hold-ups in the investigation.
L Data quality and delivery.
See remarks in Section 6.
morph. As mentioned above. introduced plants 60 we suspected of in the	 hwmosdc	 w"
stitch chionotaxonotak considerations being poisonous may be fed to Backus highlighted In his uniqueness
wouldwould today fain a red flat aping sperimatal animals, n extracts. dried audio. an OWY to be relatively poody
ha	 ton. Another example k the plan% or residues. determined In an analysis of Fdau alone.
sicklepod millivetch Womealur fakous With current ptosom to arm-mine for That series (which Stern abd Droldamp
Lem.). which was introduced around I= coal. *An k mw* Interest is finding plant COW •2&*	 Ru soleal	 0 11	 of term
ad has been recommended for raw species that 
will 
grow on mine spok which 
all 
boo the must value of in. Each
plantings for ow 25 yew mognow repreduchigrap*and phividingerou" wigs starts with a nctww (n - 0) win
that am" Anmliaiw spOda contain tome control, and, if possible. razing for and succeeding Woo have valor of a
concentrations of nitro compounds led to livestock and food aad cover for wildlife. equaltom + 2.m + 4. n + 6. and soon. to
Weatilkation of sicklepod mMrfttcb a The dew need for such plants to be non- agreement with the fkdhW notad above,
poisonous, and efforts at now being poisonow Sim special urgency to the Stern and Brokkamp found, using
directed to Its eradication. Fourth. proSrammeouthoulabove. simulated data. that the terms with w a a
had the largest uncertainty for a gWen
series.
Now that data are ava&W* from
Geoniagnetic field modelling Mamt. it is passible to sts* &W efitaftusing real daw Sum et @L (G.	 t. Am
0	 0
using satellite data Lem 7, 941; IM). In an of the fidesrepom of results from Mepat. be" =6an initial at.	 apt at this. They have
/MMDMWP BodspilyJA
compared 
wo r-4th. one based on vector
data from early in the Magsat mission
AcctmATE DEwawricira of the Earth's guarantee a good description of the other (November IM) and the other bond only
magnetic field am useful for navigational field composent& In particular, large on scalar (F) data collected at about the
purpoies and form the basis for many errors in the vertical component (Z) of the saw time. Values of 2compoed from the
scientific audies.Suradescriptionsumally Feld occurred am the dipli-equator (the two models differed by up to 2JW OT at
take the form of mathematical models, line of zero Inclination). In terms of the the Earthessurfaceand by upto 1.30ATat
most often in tmm of an expansion in coefficients of the spherical harmonic the satellites alutude. (For comparison.
P*wrk3l hannon^ and magnetic charts model, those having equal values of m and typical mid-latitude valuesof Z we of the
cue raft be produced from the models. R were least wed determined. I new are the oraer or 4t3." nT. # The d3i;"c&u xi, %mm
A major difficulty in producing sectorial harmonics. which divide the plotted on a world map, showed a pattern
temu-netic 
field models has always been surface of a splioere into segments like thou of six foci, 
all 
positioned very near to de
the acquisition of an up-to-date and well of an orange. It was also shown that the dip-equator. When the two models ivei
distributed set of accuratcobsmvions. As large errors could be removed by using compared coefficient by coefficient. Chose
a satellite in a polar orbit can survey the small amounts of vector data (about 10 per in the Backus series described above did
entire globe in a matter of days, it was in cent of the total) covering the equatorial indeed show liner differences than the
obvious step to use such a satellite to region. coefficients not belonging to such series.
measure the geomagnetic field. Hurwitz and Knapp (qA at.) and Lowes There were suggestions that other effects
The most recent satellite survey of the (Geophys. J. R. arr. Sw. 42. 637; 1975) were present affecting the 'nowBackus'
geome8ortic field was performed by the showedthat the root of the problem lay terms and work is in progress in this area.
NASA/US Geological Survey satellite with wh. at they termed the perpendicular Thus, the doubts cast on geomagnetic
Magsat between November 1979 and June error effect. When fitting only a single field models based solely on Fdata seem to
1990. Magsat differed from previous component of a vector field. the perpo. be confirmed. Fortunately there an
pornapetic survey satellites in that it was dicular components synthesized from the relatively few such models and most of
able to measure not only the strength of the resulting model can have errors associated these have been produced for specific
field but also its direction. with them which we considerably larger purposes related to the scalar data on which
Since the geomagnetic field is derivable than the errors in the component fitted. they were based. Most producers of models
from a scalar potential which satisfies This results from the lack of constraints in for	 navigational and general scientific
Uiplace's equation, it was possible to use the perpendicular directions. In some purposes (for example. Barracloush et al
the earlier satellite observations of F to cases. for example the production of Geophys. J. R. our. Sor. 43, 645; 1975;
refine existing models of the field. models	 from	 Z	 data	 only.	 the Baker et &L Geophys. J. R. &Sir. Sm. in
Although such models fitted the input F perpendicular am effect is of minor the press) have been careful to use F
data very well (with a r.m.s. residual of importance because of the particular con- observations as only a pan of the input
about 10 nT), there was evidence that they figuration of the geomagnetic field. It turns data and char models will therefore be free
did rxit describe the vector geomagnetic out, however, the fitting F data is a from the deficiencies discussed above.
field as accurately (Ben'kova et eL Suft. particularly bad choice. The perpendicular Potential users of field models should be
int. As. Gr~g. Aemm No. 152-163; error effect leads to large errors in Z and wary in their choice of models. Field
1971; Fabiano & Peddie J. geWhys. ReL these are especWHy troublesome where Z is models based solely on Fdata can be used
76, 3816; 1971). These findiop led to striall. that is, am the dip4quator. as with some confidence if out is interested
several theoretical studies of the noted above. only in the intensity of the geomagnetic
production of field models from F Backus (Q. R Mock #AYL Matilt. 21,195; field. If vector information is needed it k
observations along. 1968: J. geop&m Rea 75, 63W. 19W, but to avoid rich models and to use
Hurwitz and Knapp (J. Seq*& Ra. Geophys. Res. Lett. 1. 21; 1974) Instead one of the models band on
79,VM; 1974) and Darraclough and Nevitt investigated whether models derived from component data as well as F date. The
(AA EBfth p6m. ImMm 13, 123; Fdataitione woo unique and showed that, International Association of Geomeg-
1976), using simulated data with noise under certain conditions, they Were not. In netism and Aeronomy. at its next scientific
added, verified that good fus to Fdid not practical field modelling Using real data assembly this	 summer.	 plans	 to
I that conditions for noit-uniquerm are recommend an International Geomagnetic
 P. BffFAk*U1h 10 A the GIFORMSMILIM not fulfilled. Sim and Bredekamp (J. Reference 
Field 
which should provide a so
Unit, Instititte of Grolooket Scirarn. 8"Phys. go. 90, 1776; 1975) have, of reliable	 models	 describing the
Edv4yrsk however. shown do certain series of terms geomagnetic field since W.	 C
OF POOR QUALITY
	 I:


Spherical harmonic representation of the main geomagnetic field for world charting and investigations of some fundamental problems of physics and geophysics

Spherical harmonic representation of the main geomagnetic field for world charting and investigations of some fundamental problems of physics and geophysics

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