The compilation of a catalog of the MAGSAT-observed high altitude disturbances is discussed and an example of contents and format is given. The graphs allow the investigation of Birkeland current signatures which are superimposed upon the main geomagnetic field. An example of a display of the MAGSAT orbital tracks in a polar geomagnetic coordinate system with the locations, flow directions, and intensities of field aligned currents shown in color is also given. The display was generated using an interactive color graphics terminal

Potemra, T. A.

English

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https://ntrs.nasa.gov/search.jsp?R=19820015700 2020-03-21T09:25:03+00:00Z
Please Refer to:
TSSD-9336
111E JOHNS 1 OPKIHS UNIVERSITY 	 i...,+
APPLIED PHYSICS LABORA,roRy
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_-J	 Ulophonp (30)) 953 .7100 and 702.7800
"'Made available under NASA sponsorship
it !hp interest of early and wide dis'
s ration of Earth Resourcv.s Survey
;ram information and wi6iotlt liability
any use mode thereof "
November k, 1981
Original photography may be purohased
from BROS Data Center
National Aeronautics and Space Administration
	
SiouX k'alls,+, Sn ..x,7190
Goddard Space Flight Center
Greenbelt, Maryland 20771
Attention:	 Mr. Locke M. Stuart, MAGSAT Investigation Manager
Subject; Progress Report on "Investigation of MAGSAT and TRIAD Magnetom-
eter Data to Provide Corrective Information on high-Latitude
External Fields", for the Period July 1 to September 30, 1981,
T. A. Potemra, principal Investigator
Enclosures: (1) Example of MAGSAT High Latitude Disturbance Catalog
(2) Example of Color Display of MAGSAT High Latitude Dis-
turbances
(3) Abstracts of APL MAGSAT Scientific Presentations
Gentlemen:
Of the $33,000 made available from NASA to this Laboratory on
July 1, 1981 to support the subject study of MAGSAT data, $18,000 was spent
during the three-month period ending September 30, ' 1981. This funding was
used to support a Post Doctoral Associate and a portion of the time of the
Principal Investigator, Dr. T. A. Potemra. The activities of these investi-
gators included the development of computer programs for the correlative
analysis of the MAGSAT and TRIAD magnetic field data sets. A catalog of the
MAGSAT-observed high latitude disturbances is presently being prepared for the
entire data set, an example of which is shown in Enclosure (1). Of particular
interest is a display of the MAGSAT orbital tracks in a polar geomagnetic:
..00rdinate system with the locations, flow directions, and intensities of
field-aligned currents shown in color (Enclosure (2)). This color display is
made possible by an interactive color graphics terminal which will be used for
future global studies with the MAGSAT data.
The scientific results of the APL studies have been presented in
papers presented at the IAGA meeting in Edinburgh (August 3-15, 1981) and
scheduled for the Fall AGU meeting in San Francisco (December 7-11, 1981), the
abstracts for which are attached as Enclosure (3). Dr. Potemra and his col-
leagues are preparing two manuscripts for the special Geophysical Research
Letters issue on MAGSAT.
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33 Sep. 1981 (A;I.1..Li€d 	 1U p	 GJ/43 00201
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NASA/GSFC
	 TSSD-9,336
Mr, Locke M. Stuart
	 Page 2
.
The response of the international community to the unique MAGSAT
measurements was overwhelming at the IAGA meeting in Edinburgh, and we cer-
tainly hope that sufficient support For these important investigations will
continue.
If there are any questions concerning this report, please call
Dr. Potemra at r«tephone number (301) 953-7100, extension 3253.
Sincerely yours,
George C. Weiffenbach
Space Department Head
GCW :TAP :klb
External Distribution:
R. A. Langel, NASA/GSrC
M. Sugiura, NASA/GSFC
M. Settle, NASA Hqs .
E. R. Schmerling, LASA Hqs.
Enclosure (1) to
'CSSD-9336
The attached is an example of our MAGSAT catalog of hit,h latitude
magnetic activipy. The purpose of this study is to investigate Hirkeland
current signatures which are superimposed upon the main geomagnetic field . A
field-aligned current sheet will produce a magnetic field transverse (east and
south components) to the main field, as may be seen in the central portion of
the plot, These three :races are the MAGSAT data for November 6, 1979 from
which the MAGSX 4/81 magnetic field model (Langel) has been subtracted,
versus universal time and associated orbital parameters.
Further studies are being conducted in order to locate the bound-
aries and higher frequency characteristics of the Birkeland current signa-
tures The two traces at * the bottom are the standard deviations of the data
from its average for each 10 seconds. This may enable separation of magnetic
signatures due to local current densities from magnetic signatures due to
potential fields or in "curl-free" regions . The top lef t of the graph plots
the course of MAGSLT through invPriant latitude and magnetic local time. The
top right contains the Fourier transform of the Region 1-2 disturbances at
dusk (60-80) and at dawn (80-60). These transforms will allow us to determine
the scale length, time period and intensity of the lai:ge-scale features as
well as higher frequency components due to wave activity.
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Enclosure (2) to
TSSP -9336
Tat order to generate a global 24 —hr "snapshot" of Birkeland current
systems in botla the northern and southern hemispheres we have developed u
color graphic display of magnetic field clam acquired From the MAGSAT vector
araagnetometer. Because of MAGSAT's unique sun—synchronous orbit its trajectory
sweeps batik and forth across more than 50% of Lho auroral oval ill eithtsr heuai-
sphere during a single day. The resulting data set allows us to inap out a
composite picture, of the location, and :intensity of field —aligned currents froil
individual passes across the *auroral oval. Figures la and b are examples of
the composites that can be generated from co%?jcuti.ve orbits. The figures
display 
'ill computed from D x B i.e., J 11 x plotted oil MLT (mngneti,c
local. Lime) invariant latitude dial. The co°1cN bar extending, from left to
righL is a scale of relaLive intensity and direction. Zero current is black
in the center while makimum inward directed current is blue white on the right
and u>aximum outward mirrent is yellow—red on the left.
In both the northern and southern hemispheres region 1 and 2 current
systems	 are readily identified 	 near	 the dawn—civa-k meridian, The current in-
tensities and locations exhibit temporal and spatial suability ill	 this vicin-
ity.	 The confusion of Lila	 `cusp" and	 "llarang"	 regions is also readily identi-
fied	 near noon	 and	 midnight	 respectively	 and	 the	 variation of	 the current
systems (around the oval can also be observed.
This new meLhod of magnetic field dan display has the potential to
enhance our overall understanding of the spatial and temporal variability of
Birlceland current systems and their response to various interplanetary param -
eters.


Enclosure (3) to
TSSD-9336
Abstracts of All MAGSAT presentations
Prepared During period from July 1, 1981 to September 30, 1981
"Preliminary Evaluation of Distant Magnetic Field Disturbances
from nirkeland Currents Using MAGSAT Data", L. J, Zanotti,
T. A. Potemra, and td. Sugiura, Presented at the IAGA Meeting in
Edinburgh, August 3-15, 1981
"Correlated Dirkeland Current Signatures from the TRIAD and
MAGSAT Magnetic Field Data", L. J. Zanetti and T. A. Potemra,
Scheduled for presentation at the Fall AGU meeting in San
Francisco, December 7-11, 1981
.PRELIMINARY F.VAI,UATION OF DISTANT MAGNETIC FIELD DISTURBAINCES
FROM BIRKELANYD CURRENTS USING M14SAT DATA
L. J. Zanotti
T. A. Fotemra (both at
	
Applied Physics lab., The Johns Hopkins
Univ., Laurel, Md. 20510)
M. Sugiura (NtSA/GSFC, Greenbelt, Md. 20771)
A major goal of the MAGSAT program is to provide an accurate near-earth
magnetic field model. The major contribution to the geomagnetic field is from
internal sources, but ionospheric and magnetospheric current systems also provide
important contributions. The MAGSAT data acquired during possibly the most quiet
two-day period during its lifetime on November 5 and 6, 1919,  (with z Kp - 4+ and
6-, respectively, and the highest three-hour Kp to 1+) show disturbances up to a
few hundred in nT in the auroral region due 'to field-aligned Birkeland currents.
The data from this day within 1. 50° geographic latitude have been used to derive
initial MAGSAT geomagnetic field models. The purpose of this study has been to
identify and evaluate the magnitude and spatial extent of the curl-free magnetic
field disturbances due to Birkela.nd currents.
1. Applied Physics Laboratory
"he Johns Hopkins University
Johns Hopkins Road
Laurel, Maryland 20810
2. 11 Scientific results form the MAGSAT missions:
main field
3. N. Fukushima
R. A., Langel
a) oral presentation only
0CORRUATE'D UIRKELAND CURRENT SIGNATURES FROM THE
TRIAD AND KAGSA.T MAGNETIC FIELD DATA
L. J. Zanetti (Applied Physics LaboraLory, Johns
Hopkins University, Laurel, Md., 20707)
T. A. Potemra
vn November 1, 1979 the MAGSAT -o ;tellire was
successfully launched into a 400 kx;
' 
polar orbit
from which it could measure the earth's magnetic
field.  During the first part of MAGSAT 1 6 eight
monthlifetime, the orbit was nearly coplanar
with that of the TRIAD satelliLa at $00 km alti-
tude. This study has concentrated on transverse
magnetic disturbances, associated with Birkeland
currents ) measured by the two spacecraft.
The satellites were nearly coplanar from
November through the middle of December I979.
Data were compared when the satellites were over
the TRIAD/ Chatanika receiving station. Of the
approximately 150 comparisons of magnetic dis-
turbances, 75% are very sitnilar in shape and
magnitude. Better agreement in the large-scale
well defined fiald-aligned current si,,nanures
occur during periods of higher K 
ps 
even with time
separations as large as 45 minute . The discrep-
ancies in the remaining cases may be' due to
temporal, longitudiial and height effects of the
Birkeland current system.
1. Fall Meeting
2. ZAIN"=1947049
3. A'Pl,/JIIU
Johns Hopkins Rd,
Laurel, Md. 20707
(301) 953-7100
4. SPR (Magnatoopharic, Physics)
5. hone
G. None
7. 20% Vall AGV ) 1.980
8. Dr, Vernon Root
AIIL/JIIU
Johns Hopkins Rd.
Laurel, Md. 20707
9. C


Investigation of MAGSAT and TRIAD magnetometer data to provide corrective information on high-latitude external fields

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