UNITED STATES DEPARTMENT OF THE INTERIOR

DECEMBER 1986

GEOLOGICAL SURVEY

PRELIMINARY GEOMAGNETIC DATACOLLEGE OBSERVATORY

FAIRBANKS, ALASKA

OPEN FILE REPORT 86-0300L

BARROW

THIS REPORT WAS PREPARED UNDER THE DIRECTION OF JOHN B, TOWNSHEND, CHIEF OF THE COLLEGE OBSERVATORY, WITH THE ASSISTANCE OF THE OBSERVATORY STAFF MEMBERS: R,V, O'CONNELL AND L,Y, TORRENCE AND IN COOPERATION WITH THE GEOPHYSICAL INSTITUTE OF THE UNIVERSITY OF ALASKA, THE COLLEGE OBSERVATORY IS A PART OF THE BRANCH OF GLOBAL SEISMOLOGY AND GEOMAGNETISM OF THE U,S, GEOLOGICAL SURVEY,

Explanation of Data and Reports

Magnetic Activity Report

Principal Magnetic Storms

Preliminary Calibration Data and Monthly Mean Absolute Values

Magnetogram Hourly Scalings - Five Quietest Days

Sample Format for Normal and Storm Magnetograms

Normal Magnetograms

Storm Magnetograms (When Normal is too disturbed to read)

CQILEGE OBSERVATORY PRELIMINARY GEOMAGNETIC DATA

EXPLANATION OF DATA AND REPORTS

INTRODUCTION

The preliminary geomagnetic data included here is made available to scientific personnel and organizations as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore, it should be regarded as preliminary. Inquiries about this report or about the College Observatory should be addressed to:

Chief, College ObservatoryU.S. Geological Survey800 Yukon DriveFairbanks, Alaska 99775-5160

Requests for copies of the magnetograms except for the current month should be addressed to:

World Data Center A NOAA D63m 325 Broadway Boulder, Colorado 80303

OBSERVATORY LOCATION

The College Observatory, operated by the U.S. Geological Survey, is located at the University of Alaska, Fairbanks, Alaska. It is near the Auroral Zone and the northern limit of the world's greatest earthquake belt, the Circum-Pacific Seismic Belt. Although the observatory's basic operation is in geo­ magnetism and seismology, it cooperates with other scientists and organizations in areas where the facil­ ity and personnel can be of service.

The observatory is one of three operated by the USGS in Alaska. The others are located at Barrow and Sitka.

The position of the observatory site is: Geographic latitute........ 64° 51.6'NGeographic longitude.......147° 50.2'WGeomagnetic latitude.......+64.6°Geomagnetic longitude......+256.5°Elevation..................200 meters

GEOMAGNETIC DATA

Normal and storm magnetograms and appropriate calibration data are processed at the observatory and are available for analysis or copying. Also available are mean hourly scalings for the five quietest days for the month and K-Indices.

Magnetic Activity

The K-Index; The K-Index is a logarithmic measure­ ment of the range of the most disturbed component (D or H) of the geomagnetic field for eight intervals 0000-0300, OUUO-OfoOO...2100-24OO UT. It is~a measure of the difference between the highest and lowest deviation from a smooth curve to be expected for a component on a magnetically quiet day, within a three hour interval.

The Equivalent Daily Amplitude, AK: The K-Index is converted into an equivalent range, ak, which is near the center of the limiting gamma ranges for a given K. The average of the eight values is called equivalent daily amplitude AK. The unit lOy has been chosen so as not to give the illusion of a accuracy not justified.

The schedule for converting gamma range to K, and -K to ak is as follows:

Gamma Range K - Index ak 0<

25<50<

100<200<350<

2550

100200350600

600< 1000 1000< 1650 1650< 2500 2500+

37

15274880

140240400 (IOY)

Principal Magnetic StormsGradual and sudden commencement magnetic distur­

bances with at least one K-Index of 5 or greater, which are believed to be part of a world-wide disturbance, are classified as principal magnetic storms. The time of the storm beginning and ending; direction and amplitude of sudden commencements; period of maximum activity; and storm range are reported. Monthly reports of these data are forwarded to the World Data Center A in Boulder, Colorado.

Magnetogram Hourly ScalingsMagnetogram hourly scalings are averaged for

successive periods of one hour for the D, H, and Z elements. The Value in the column headed "01" is the average for the hour beginning .0000 and ending 0100. Note that the values on the scaling sheet are in tenths of mm with the decimal point omitted. The user of these scalings should keep in mind that the tabular values are hourly means and if one is interested in the detailed morphology of the magnetic field, refer directly to the magnetograms.

MagnetogramsThe normal magnetograms in this report are repro

duced at about one-third the size of the originals. Preliminary base-line values and scale values adopted for use with the original magnetograms are included. For days when the magnetic field is too disturbed for the Normal magnetogram to be readable, Storm magnetograms are reproduced.

Absolutes, Base-lines and Scale ValuesTo determine the absolute value of the magnetic

field from the hourly means or from point scalings the following equations should be used:

D=BD+d-SD ; H=BH+h-SH ; Z=BZ+Z.SZwhere D, H and Z are absolute values;Bp, Bj, and BZ are base-line values;SD' ^H and SZ are scale values;and d, h and z are scalings in millimeters.

NUAA FORM 76 133 U - S - DEPARTMENT OF COMMERCE (9-72) "»-'*» NATIONAL OCEANIC AN.D ATMOSPHERIC ADMINISTRATION

MAGNETIC ACTIVITY (Greenwich civil time, counted from midnight

DATE

1

2

3

4

5

6

78

9

10

11

12

13

14

15

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19

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2324

25

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to midnight)

K-INDICES

« 1C » CMo o o -& A £ Ao o o o

32461045113300141000

10010013000110011204

12230000001244661102

1125011100001-1001000

10232204222622241 ~3 2 5

234621231 00 2000200001014

Ift «B - « M N

A A A i . .. .. M

332-522331512100

001330Oil021

1011-1

0000

4221

311 00111422 34231001 0

25212110012100123411

44225621732332311211

4 2 .2 233110000-000012115200

SUM

2419161403

0310030516

1303143005

1907040510

1822271916

251603020513

OBSERVATORY

College, AlaskaMONTH AND YEAR

December 1986

AK

2118091101

0106010210

0701083302

1603020206

1222351111

220901010211

TIME SCALE ONMAGNETOGRAMS

20 min/hr

SUDDEN COMMENCEMENTS

d h m

POSSIBLE SOLAR-FLAREEFFECTS BASED ON

INSPECTION OF GRAMS ALONE (WITHOUT

REFERENCE TO DATAFROM OTHER SOURCES)

BEGIN END

d h m d h m

»

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z(mm)

(7/mm)

(to nearest 107)SC A LINGS AND COMPUTATIONS HAVE BEEN CHECKED.

/ APPROVED John B. Townshend, Chief, College ObservatoryOBSERVER IN CHARGE

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