UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY

PRELIMINARY GEOMAGNETIC DATA COLLEGE OBSERVATORY

* MARCH 1985

FAIRBANKS, ALASKA

OPEN FILE REPORT 85-O~OOC

COLLEGE

T H I S REPORT WAS PREPARED UNDER THE D I R E C T I O N OF JOHN B, TOWNSHEND, CHIEF OF THE COLLEGE OBSERVATORY; W I T H THE ASSISTANCE OF THE OBSERVATORY STAFF MEMBERS: J I E B PAPP, E , A I SAUTER, L , Y , TORRENCE, P a A , FRANKLIN AND I N COOPERATION W I T H THE GEOPHYSICAL I N S T I T U T E OF THE U N I V E R S I T Y O F ALASKA, THE COLLEGE OBSERVATORY I S A PART OF THE BRANCH OF GLOBAL SEISMOLOGY AND GEOMAGNETISM OF THE U , S , GEOLOGICAL SURVEY n

Fxplanation of Data and Reports

Magnetic Activity Report

Outstanding Magnetic Effects

Principal Magnetic Storms

Preliminary Calibration Data and Monthly Mean Absolute Values

Magnetogram Hourly Scalings

Sample Format for Normal and Storm Magnetograms

Normal Magnetograms

Storm Magnetograms (Vhen Normal is too disturbed to read )

r, V O f l A G N E T I C v DATA

m L A N A T I O N OF DATA AND REPORTS

INTRODUCTION

The preliminary geomagnetic data included here i s m d e avai lable t o s c i e n t i f i c personnel and organizations a s ?a r t of a cooperative e f f o r t and on a data exchange bas is because of the ea r ly need by some users. To ' avoid delay, a l l of the data is copied from or ig inal forms processed a t the observatory; therefore it should be regarded a s preliminary. Inquir ies a b u t t h i s report o r about the College O b s e ~ a t o r y should be adees sed to:

- Chief, College Observatory U.S. Geological Survey 800 Yukon Drive Fairbanks, Alaska 99701

Requests f o r copies of the magnetograms except f o r the current month should be addressed to:

World Data Center A NOAA D63, 325 Broadway Boulder. Colorado 80303

OBSERVATORY .LOCATION

The College Observatory, operated by the U.S. Geological Survey, i s located a t the University of Alaska, Fairbanks, Alaska. It is near the Auroral Zone and the northern l i m i t of the world's g rea t e s t earthquake b e l t , the circum-Pacific Seismic b e l t . Although the observatory's basic operation is i n geo- magnetism and seismology, it cooperates with other s c i e n t i s t s and organizations i n areas where the f a c i l - i t y and personnel can be of service.

The observatory is one of three operated by the USGS i n Alaska. The o thers a r e located a t Barrow and S i t h .

The pos i t ion of the observatory s i t e i s : Geographic l a t i t ude . . . . . . .6f? 5 1 . 6 ' ~ Geographic longitude.. . . . . l 4 p 50.2'W Geomagnetic l a t i t ude . . . . . . +64. G' Geomagnetic longitude.. . . . +256.P Elevation ................. 200 meters

Normal, Storm and Rapid Run magnetograms and appropriate ca l ib ra t ion data a r e processed da i ly a t the observatory and a r e ava i l ab l e f o r analys is o r

. copying. Also avai lable , a r e mean hourly scalings, K-Indices, selected magnetic phenomena repor ts and on a real-time bas is a r e recordings from a 3-compo- nent f luxgate magnetometer and F-component protoh nagnetoaeter.

GEOMAGNETIC DATA

Selected Phenomena & Outstanding Magnetic Effec ts W i d Run records were reviewed a t t he observatory f o r selected magnetic phenomena and the events i den t i f i ed were formrded t o the IUGG Commission on Magnetic Variations and Disturbances. This nas discontinued on January 1, 1976, but a repor t on Outstanding Magnetic Effec ts i s prepared monthly f o r this repor t .

a g n e t i c Activity The K-Index: The K-Index is a logaritkunic measure-

ment o f t h e range of the most disturbed compcnent (D or H) of the geomagnetic f i e l d f o r e igh t i n t e rva l s beginning 0000-0300, 03OS0600.. .2100-U00 UT. It is a measure of t he difference between the highest and lowest deviation from a smooth curve t o be expected f o r a component on a magnetically quie t day, within a th ree hour in terval .

The Equivalent h i l y Amplitude, AK: The K-Index is converted i n t o an equivalent ranpe, ak, which i s near the center of the l imi t ing gamma ranges f o r a given K. The average of the e ight values i s ca l l ed equivalent da i ly amplitude AK. The u n i t 10y has been chosen so a s not to give the i l l u s i o n of an accuracy not j u s t i f i ed .

The schedule f o r converting gannna range t o K, and K t o ak i s a s follows:

Gannna Range . K - Index ak - Oc 25 0 0

25 c 50 1 3 50< 100 2 7

loo< 200 3 1 5 200 c 350 4 n - 350 c 600 5 48 600 c 1000 6 80 1000 < 1650 7 140 1650 < 2500 8 240 2 5 m 9 400 (1W)

The Magnetic Daily Character Figure. C: To each Universal day a cha rac t e r . i s assigned on t& basis C=O, i f it is quiet; C-1, i f I t is moderately disturbed; C-2, if it is g rea t ly disturbed. The method used t o ass ign characters a t t h e College Observatory i s based on AK a s follows:

Routine assignment o f C was discontinued a t College on January 1, 1976.

Pr incipal Magnetic Storns Gradual and sudden commencement magnetic d i s tu r -

bances with a t l e a s t one K-Index of 5 or grea ter , which are believed t o be pa r t of a world-wide disturbance. are c l a s s i f i e d a s pr inc ipal magnetic storms. The time of t he storm beginning and ending; d i rec t ion aml amplitude of sudden commencements; period Of maximum ac t iv i ty ; and storm range a r e reported. Monthly r epo r t s of these data a r e forwarded t o the World Data Center A In Boulder, Colorado.

Magnetogram Hourly Sealings Magnetogram hourly sca l ings Lre averages f o r

successive periods of one hour f o r the D, H and Z elements. The Value i n the column headed "01'' is the average f o r t he hour beginning 0000 and ending 0100. Note t h a t t he values on the sca l ing sheets a r e i n tenths of m with the d e c h l point omitted. The user of these sca l ings s h u l d keep i n m i n d t h a t the tabular values are hourly means and i f he i s in teres ted in t he deta i led morphology of the magnetic f i e l d , he should r e f e r d i r e c t l y to t he magnetograms.

hgnetograms The normal magnetograms i n t h i s repor t a r e repro-

duced a t about one-third t he s i z e of the or ig inals . h e l m n a r y base-line values and sca le values adopted f o r use with t he original.magnetograms a r e included. For days when the magnetic f i e l d is too disturbed f o r the Normal magnetogram t o be readable, Storm magnetograms a r e reproduced.

Absolutes. Base-lines and Scale Values To determine the absolute value of the magnetic - f i e l d from the hourly means o r from point sca l ings t he

following equations should be used: D=BD+d.SD; H=BH+h-SH; Z=B +a-SZ where D, H and Z a r e absofute values; ED, BH and BZ a r e base-line values; SD, SH and Sz a r e sca le values; and d, h and z a r e sca l ings i n millimeters.

u. s. DEPARTMENT b~ COMMERCE 'ORM ''-la NATIONAL OCEANIC AND ATMOSPHERIC ADMINIST RATION (9-72)

MAGNETIC ACTIVITY (Greenwich c iv i l ti-, countmd from midnight to midnight)

K-INDICES

I I DATE m m -

OBSERVATORY

COLLEGE, ALASKA

MONTH AND Y E A R

MARCH 1985

T lME SCALE ON MAGNETOGRAMS

20 mfn/hr

SUDDEN COMMENCEMENTS

08

POSSIBLE SOLAR-FLARE EFFECTS B A S E D ON

INSPECTION O F GRAMS ALONE (WITHOUT

REFERENCE T O DATA FROM O f HER SOURCES)

B E G I N E N D

d h m d h m

LOWER LIMIT FOR K = 9 . .. . . . . . 1 2510 I 2520 I I (to nearest lo?) S C A L IN GS AND COMPUTATIONS HAVE BEEN CHECKED.

K S C A L E USED:

LOWER LIMIT FOR K = 9 .... . . . .. CURRENT SCALE VALUE. .......

I APPROVED JOTIN B . TOWfJSIIEND, CHIEF, COLLEGE OBSERVATORY O B S E R V E R IN C H A R G E

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