UNITED STATES DEPARTMENT OF THE INTERIOR

APRIL 1989

GEOLOGICAL SURVEY

PRELIMINARY GEOMAGNETIC DATACOLLEGE OBSERVATORY

FAIRBANKS, ALASKA

OPEN FILE REPORT 89-Q300D

BARROW

^ o ,*> */

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 CAROL ANN VARNER AND IN COOPERATION WITH THE GEOPHYSICAL INSTITUTE OF THE UNIVERSITY OF ALASKA FAIRBANKS. THE COLLEGE OBSERVATORY IS 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)

COLLEGE 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 an 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 OOOC-0300, 0300-0600...2100-2400 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 10y 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 0< 25

25< 5050< 100

100< 200200< 350350< 600600< 10001000< 16501650< 25002500+

ak~0

3 7

15274880 140 240 400 (10Y)

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 raagnetograms 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^Bjj+h-Sjj; Z=B^r,-Szwhere D, H and Z are absolute values;Bry Bj, and Brr are base-lin<» vilues;Sp, Sj, and s£ are scale values;and d, h and z are sealings in millimeters.

NOAA FORM 76-133 U ' s - DEPARTMENT OF COMMERCE (9-72) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

MAGNETIC ACTIVITY (Greenwich civil time, counted from midnight to midnight)

DATE

1

234

5

6

7

8

9

10

11

12

13

14

15

16

1718

19

20

21

22

23

24

25

26

27

28

29

30

31

K-IN DICES

<n <o Ot IM o o o -& A & AO O O O

54753465322355465476

43232255437542332223

22151221235633334566

21114134342200013442

12232100202223112224

556655564 4 7 533454466

n e « . «- N N

A A & i N

65446534654446645433

33225763464324423211

25111111552254554522

46343522100033121222

21111112665222223675

55554454545465546322

SUM

4036294037

2235362416

1910303134

2224121020

138

251531

4238383533

OBSERVATORY

COLLEGE, ALASKAMONTH AND YEAR

April 1989

Ak

5643285250

1449471708

1604332941

2119070513

0603300741

5644493940

TIME SCALE ONMAGNETOGRAMS

20 nun/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

,

n u yK SCALE USED: ° " *

LOWER LIMIT FOR K - 9......... 675.7 322.2 (nun)

CURRENT SCALE VALUE........ 3.69 7.77 (7 /mm)

LOWER LIMIT FOR K -9 ........ 2490 2500 (to nearest 107)

SCALINGS AND COMPUTATIONS HAVE BEEN CHECKED.

APPROVED John B. Townshend, ChiefOBSERVER IN CHARGE

NOAA FORM 76-133 SUPERSEDES C&GS FORM 818 fr U.S. GOVERNMENT PRINTING OFFIC E: 1972-760-948

NQAA FORM 86-500

(11/73)

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COLLEGE OBSERVATORY, COLLEGE, ALASKA PRELIMIBARY CALIBRATIOH DATA FOR: APRIL

NORMAL MAGNETOGRAFE

COMPONENT

D

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PERIOD

FROM

oool ux } 4/1 /89ooo 1 UT. % 4/16/89

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TO

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24oo 6/r : 4/6/89Z4oo ur' 4/13/8924oo ur; 4/30/89

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SCALE VALUE

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CALIBRATION

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MOSTHLT MEAN ABSOLUTE VALUES*

04.7'£ 55 325* COMPUTED FROM FIVE QUIETEST DAIS DURING 1ONTH.

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