UNITED STATES DEPARTMENT OF THE INTERIOR

SEPTEMBER 1986

GEOLOGICAL SURVEY

PRELIMINARY GEOMAGNETIC DATACOLLEGE OBSERVATORY

FAIRBANKS, ALASKA

OPEN FILE REPORT 86-03001

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: H.K, REX AND L,Y, TORRENCE AND IN COOPERATION WITH THE GEOPHYSICAL INSTITUTE OF THE UNIVERSITY OF ALASKA, 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 to disturbed to read)

COLLEGE OBSERVATORY PRELIMINARY GEOMAGNETIC DATA

EXPLANATION OF DATA AND REPORTS

INTRODUCTION OBSERVATORY LOCATION

The preliminary geomagnetic data included here is raade 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 Observatory U.S. Geological Survey SOO Yukon Drive Fairbanks, Alaska 99701

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

World Data Center A N'OAA D63, 325 Broadway Boulder, Colorado 80303

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 latitude.......64°51.6'NGeographic longitude..... .147° 50.2'WGeomagnetic latitude......+64.6°Geomagnetic longitude... ..+256. 5°Elevation.................200 meters

GEOMAGNETIC DATA

Normal, Storm and Rapid Run magnetograms and appropriate calibration data are processed daily at the observatory and are available for analysis or copying. Also available, are mean hourly scalings, K-Indices, selected magnetic phenomena reports and on a real-time basis are recordings from a 3-compo- nent fluxgate magnetometer and F-component proton magnetometer.

'.fagnetic Activity The K-Index: The K-Index is a logarithmic measure­

ment of the range of the most disturbed component (D or K) of tne geomagnetic field for eight intervals beginning 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 an accuracy not justified.

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

Gamma Range K - Index C< 25 0

25 <50 <

100 <200 <350 <600 <1000

1000 <1650 1650 < 2500 25CX>

50100200350600

ak C 3

15274880 UC 240 400 (10y)

The Magnetic Daily Character Figure, C: To each Universal day a. character is assigned on the basis C=0, if it is quiet; C=l, if it is moderately disturbed; C=2, if it is greatly disturbed. The method used to assign characters at the College Observatory is based on AK as follows:

AK Range £ 0»I1 011«*50 150+ 2

Routine assignment of C was discontinued at College on January 1, 1976.

Selected Phenomena & Outstanding ?fegnetic EffectsPrior to January 1, 1976, the Normal and Rapid

Run records were reviewed at the observatory for selected magnetic phenomena and the events identified were forwarded to the IUGG Commission on Magnetic Variations and Disturbances. This was discontinued on January 1, 1976, but a report on Outstanding Magnetic Effects is prepared monthly for this report.

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 averages 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 sheets are in tenths of mm with the decimal point omittei. The user of these scalings should keep in mind that the tabular values are hourly means and if he is interested in the detailed morphology of the magnetic field, he should 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=B£+d-&v H=BH+h-SH ; Z=B-7+z-S2where D,~H and"2 are' absolute values;Bp, B^ and &% are base-line values;Sp, Sj, and S£ 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 AND ATMOSPHERIC ADMINISTRATION

MAGNETIC ACTIVITY (Greenwich civil time, counted from midnight

DATE

1

2

3

4

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

SI

to midnight)

K-INDICES

r> ic Ot <M0 6 0 -A A & A0 0 O O

32252545221032102214

31142113104413241111

11014767346642231236

1101244234443344 3253

43120112245534653336

45673246324431332114

in a> »- CM

»IM

A J> £ i_ _ _ eg

111

531121211322

310300101200000

1024534222216 5 3

112121334362 322

2111025646436 5 3

6425 3 3211222300

21222

11100

43311

2331 3

12333

2 >* >

230

SUM

1726111218

1411121204

1039301727

091928

~ 26 23

1509343432

3629191911

OBSERVATORY

College, AlaskaMONTH AND YEAR

September 1986

AK

1225050610

0906080702

0662321031

04122124 16

0904383835

5228121007

TIME SCALE ONMAGNETOGRAMS

20 mm/hr

SUDDEN COMMENCEMENTS

d h m

POSSIBLE SOLAR-FLAREEFFECTS BASED ON

INSPECTION OF GRAMS ALONE (WITHOUT

REFERENCE TO DATAFROM OTHER SOU«CES)

BEGIN END

d h m d h m

K SCALE USED: D

LOW ER LIMIT FOR K = 9. ....... 675.7CURRENT SCALE VALUE........ 3-71

LOWER LIMIT FOR K - 9 ........ <c21U

SCALINGS AND COMPUTATIONS HAVE BEEN CHECKED.

APPROVED

H Z

322.2 ^ mm ^7.81 (7/mm)

2520 (to nearest 107)

John B. Townshend, Chief, College ObservatoryOBSERVER IN CHARGE

NOAA FORM 76-133 SUPERSEDES C&GS FORM 6lE U.S. GOVERNMENT PRINTING OF F I C E : 1973-761-857

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