UNITED STATES DEPARTMENT OF THE INTERIOR

JULY 1988

GEOLOGICAL SURVEY

PRELIMINARY GEOMAGNETIC DATACOLLEGE OBSERVATORY

FAIRBANKS, ALASKA

OPEN FILE REPORT 88-0300G

BARROW

COLLEGE OBSERVATORY PRELIMINARY .GEOMAGNETIC DATA

EXPLANATION OF DATA AND REPORTS

INTRODUCTION

The preliminary geomagnetic data induced here is made available to scientific personnel and i -ganizations as part of a cooperative effort and on a da^-.a exchange basis because of the early need by som« 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.......+64.6Geomagnetic longitude......+256.5°Elevation..................200 meters

GEOMAGNETIC DATA

Normal and storm magnetograms and appropriate calibration data are processed at the observatory and are nvailable 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, 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 ak 0< 2T~

25<5CX

1CXK 200< 350<

50100200350600

600< 1000 1000< 1650 1650< 2500 2500*

37

15274880

140240400 (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 SealingsMagnetogram 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 magnetogramB are included. For days when the magnetic field is too disturbed for the Normal magnetogram to be readable, Storm magnetopram 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=B1)-»-d-SD ; H=BH+h-SH : Z=B2+z-Szwhere D, H and Z are absolute values;BJJ, BJJ and BZ are base-lin^ values;Sp, S,, and £7 are scale values;and d, h and z are scalings in millimeters.

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, 0 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)

NUAA FORM 76-133 °- S- DEPARTMENT OF COMMERCE (9-72) NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION

MAGNETIC ACTIVITY (Greenwich civil time, counted from midnight

DATE

1

2

3

4

5

6

7

89

10

11

12

13

14

15

16

1718

19

20

21

2223

24

25

26

27

28

2930

31

to midnight)

K-INDICES

m « «i N o o o «-& A & Ao o o o

3334444312123-2 1 10100

34552335222510001111

34553446321033232213

33462212224521661120

13665445345423232211

2344344-32113111123201343

M «D -

£ * * !«M

.- _ .- (M

42234212322100000121

42213311622000212

1

01

542254220122021532

742342422512101

652564421122112

553421332112012222

12

2 .2211

23222

313312

SUM

2424140705

2621220110

3030111520

3118232407

3136251712

292218111119

OBSERVATORY

College AlaskaMONTH AND YEAR

July 1988

AK

1618070402

2315210004 '

2830050814

4010172903

4040200905

251610050511

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

K SCALE USED: D

LOWER LIMIT FOR K = 9......... (ffij 7

CURRENT SCALE VALUE........ 3-70

LOWER LIMIT FOR K - 9 ........ 25GOSCALINGS AND COMPUTATIONS HAVE BEEN CHECKED.

APPROVED

H Z

322.2 ("»»>7.79 (7/mm)

2510 (to nearest 107)

John B. Townshend, Chief, College ObservatoryOBSERVER IN CHARGE

NOAA FORM 76-133 SUPERSEDES C&GS FORM SIS U.S. GOVERNMENT PRINTING OFFIC E: 1873-761 -887

NOAA FOR

M 86

-500

(11/

73)

Data

from

Individual Observatoriess

PRIN

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COLLEGE GBSERVATOHI, COLLEGE, ALASKA PRELIKIKAOT CALIBRATIOH DATA FOR: July 1988

FORMAL MAGKETOGRAFE

COMPONENT

D

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PERIOD

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CAUBRATICIK

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BASELINE

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COMPONENT

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FROM

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CALIBRATION

SCALE VALUE

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CALIBRATION

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MOHTHLI MEAN ABSOLUTE VALUES*

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