UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY

PRELIMINARY GEOMAGNETIC DATA COLLEGE OBSERVATORY

FAIRBANKS, ALASKA

"NOVEMBER 1991 OPEN FILE REPORT 91-030gK

COLLEGE a

THIS REFORT WAS PREP.ARFJl UNDER THE DIRECTION OF JOHN B TOWNSWEND, CHIEF OF THE COLLEGE OBSERVATORY, WITH THE ASSISTANCE OF THE OBSERVATORY STAFF MEMBERS: R . V . OTONNELL AND CAROL ANN VARNER AND IN COOPERATION WITH THE GEOPHYSICAL INSTITUTE OF THE UNLVF,RSLTY OF ALASKA FAIRBANKS. THE C O Z U G E 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 Stoms

Preliminary Calibrat ion 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

INTRQDUCTIO?l OBSERVATORY LOCATION

The preliminary geoma~nstic data included here is The College Observatory, operated by the U.S.

made available to scientific personnel and Geological Survey, i~ located at the Univer~ity of

argaaizatiana aa part of a cooperative effort and on a Alaska, Fairbanks, Alaska, It is near the auroral

data exchange baais because OF the early need by some Zone and the northern limit of the world's greatest

users. Tha data is copied from original forma earthquake belt, the Circum-Pacific Seismic Belt.

processed at Zha observatorp; therefore, it should be Although the observatory% haaic operation ia in

regarded as preliminary. Inquiries about this report geomagnetism and seismology, it cooperates with the

or about the College Observabory ahould be addressed other scientists and organizations in axeaB where the

to: facility and personnel can be of newice.

Chief, College Observatory U.S. Geological Survey 800 Yukon Drive Fairbanks, Alaska 99775-5160

Requests for copies of the magnetograma except for

the cuxrent month ~hould be addressed to:

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

Gamna Range K-Index & Qc 25 0 0

The observatory is one of three operatsd by the

USGS in Alaska. The othera axe located at Barrow and

Sitka . The position of the obaenratory site is:

MPLANATIOH OF DATA 6 REPORTS

Geographic Latitude., .... 64' 51.6'N Geographic longitude.,.,.l47' 50.2'W Geomagnetic latitude. . . . .+64.6' ~eoma~netl= longitude . . . . +256.5' Elevation.., .....,.......200 meters

Available Data b Reports

Normal and storm magnetograms and appropriate

calibration data are processed at the observatory and

are available for analysis or copying. Magnetic

Activity Report (K-Indices 6 AK values), Principal

Magnetic Storms Report, and Magnetogram Hourly

Scalings for tha five quietest days of the month are

also available.

Mametic Activity

The K-Index: The K-Index is a logarithmic

measurement o f the range of tho moat disturbed

component (D or HI of the geomagnetic field for eight intesvals 0000-0300, 0300-0600 ... 2100-2400 UT. It ia

a measure of the difference between the highest and

lowesb deviation from a smooth curve to be expected

for a component on a magnetically quiet day, within a

three hour interval.

The Eauivalent Daily Amplitude. AK: The K-Index is

converted into an equivalent range, ak, which ia near

the center of the limiting gamna ranges for a given K.

The average of the eight values is called equivalent p daily amplitude dK. The unit 107 has been chosen so

as not to give the illusion of an accuracy net

justified.

Tho schedule for converting g a m a range to K, and K to ak i~ as follows:

Principal Mametic Storms Gradual and sudden commencement magnetic

disturbances with at least one K-Index af 5 or greater, which are believd to be part of a warld-wide disturbance, are classified as principal magnetic

storms. The time of the storm beginning and ending; direction and amplitude of sudden conmencement; period

of maximum activity; and storm range are reported.

Monthly reports of these data are Eorwarded to the

World Data Center A In Boulder, Colorado. Ma~neto~ram Hourly Scalizl~s

Magnetogram hourly scalings are averaged for aucceasire periods of ono hour for the D, H, and 2 elements. The Value in the column headed "01" is the

average for the hour begizmim 0000 and ending 0100. Note that the values on the s e a l i n g sheet are in tenths of ma with the decimal point omitted. The user of these sealings should keep in mind that the tabular

values are hourly means and if one is intere~ted in

the detailed morphology of the magnetic field, refar

directly to the magnetogram.

Magneto~rams

The normal magnetograms in this report are

reproduced at about one-third the size of the

originals. Preliminary base-line values and scale values adopted for use w i t h the original magnetograms are included. For daya when the magnetic field is too disturbed fox the lormal magnetogram to be readabla,

Storm magnetograma axe reproduced.

Absolutes. Base-lines and Scale Values

To determine the absolute value of the magnetic

fisld from the hourly means ar from point scalings the

follo~lriag equations should be used:

D-BD+d SD; &=BH+h S*; Z=BZ+2 SZ where D, H and Z are absolute values; B D A H and BZ are baar-line values; SD, S and SZ are acala values; B and d, h and z are sealings in millimeters.

Un 5, DEPARTMENT OF COMMERCE NOAA 76a'U NATIONAL QCEANlC AND ATMOSPHERIC ADMINISTRATION (9-721

MAGNETIC ACTIVITY

I (Greenwie k c iv i I time, countsd frnm midnig hi to midnight)

QHSERYATORY

College, Alaska MONTH AND Y E A R

NOVEiVLBER, 19 9 1

I K S C A L E USED:

LOWER LIMIT FOR K = 9.. ... . .. .

K-IN DICES TIME SCALE ON

Ak M A G N E T O G R A M S

DATE - g r n U) z C t

1 - N

% A : 0 0 0 (s - A - z - A S U M CT

20 mmlhr

4 3 6 7 7 7 7 5 SUDDEN COMMENCEMENTS

5 4 2 4 4 4 3 2 2 2 3 6 5 3 4 3 2 4 3 5 3 5 5 5 5 4 6 . 4 5 5 4 2

2 5 5 4 3 4 4 2 3 2 2 4 2 3 2 2 1 2 5 4 7 7 7 5 5 6 8 7 7 6 7 3 2 2 3 6 3 4 4 2

2 3 3 5 4 4 4 4 2 2 4 2 1 2 2 1 0 1 3 3 6 5 2 2 2 3 5 5 4 1 2 2 2 3 5 6 , 6 5 5 2

3 3 5 6 6 3 3 3 2 2 3 6 6 5 4 2 3 3 4 6 6 5 6 3 3 5 5 6 6 7 6 3 POSSIBLE S O L A R - F L A R E

2 2 3 5 5 5 4 4 EFFECTS B A S E D O N

INSPECTION O F GRAMS A L O N E (WITHOUT

REFERENCE TO D A T A

3 3 5 7 7 8 6 7 FROM O T H E R SOURCES!

5 5 7 6 7 4 5 3 3 3 6 7 6 5 4 4 2 3 3 3 5 5 2 3 2 2 3 2 3 3 2 1

1 2 3 5 3 3 1 0 0 1 0 2 4 5 2 1 2 0 1 4 5 2 2 2 3 2 1 4 5 5 2 3 3 4 3 4 3 1 2 3

I CURRENT SCALE VALUE... . .,..

John 8. mmshd, Chief

D

675.7

LOWER LIMIT FOR K = 9 ........ 1 2 4 7 0 I 2 4 9 0

.-

1 OBSERVER 1N C H A R G E

N O A A F O R M 76-133 SUPERSEDES C & G S FORM 8 f 5 Q U.S. G O V E R N M E N T P R I N T I N G O F F I C E : ~ 9 f z - - 6 @ . ~ j a

3 .66 I (to nearest IOY)

H

322.2

S C A L I N GS AND COMPUTATIONS HAVE BEEN CHECKED.

7 . 7 3

2

(Y/rnm)

tmm3

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& k

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a * m a - m

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d N c n N N

I

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CALIBRATION

I I I I

I I 1 The Cot Lege Observatory has used awerat absolute i n s t r m t s and different observing piers since i t began

operations in 1968. To avoid a r t i f i c ia l secutar shf f t s in the absotute values prbl ished when ins trmnts were changed, corrections were applied to provide continuity i n the data f r o m the time the abservatory began operating,

For mny years the instrunmts r rsd fo r observing absolute rat- have had zero correction. Effective with the May

I989 Pret imina~y Oata Report, i n accordawe with a directive issued by the USGS Branch of GLobaL Seismology and Geamagnetism arralysis persmmL, these tongstanding corrections are discontinued ami st1 data l isted I D , H & 2) are

for the position a t absolute pier l a and without any corrections applied. The net effect of these changes is as follows:

Declination (01: Mo Change Horizontal intensity (H): -54 i .e., H absolute and baseline values are 5 6 Less than previously reported.

Verticat Intensity (21: +336; i.e., Z akolute and baseline vatues are 33dhigher than previously reported.

I

MONTHLY MEAN ABSOLUTE VALUES*

0 t i I 26" 3 ? d E 12744 d 55 3;2 d

+ C ~ P U T E D F R ~ FIVE QUIETEST DAYS DURING MONTH. ONLY JtJo PAYS OF THIS

DRYSUSED: 1 2 , 25. , , - MoKTH HAVING Al: 5 10 t

SCALE VALUE

operations i n 1948. To avoid a r t i f i e i a l secular shif ts in the absolute vatues p b l i s h d whm instrunents were changed, correct ions were appl id t o provide continuity in the data f ran the t i m e the Observatory began o p r a t ing. For mny years the instrunents used for observing absolute walvbs have had zero correction. E f fec t ive with the May

1989 Preliminary Data Reprt , in accordanee with a directive issued by the USGS Branch of Global Seismology and Geomagnetism analysis personnel, these Lmgstanding c o r r e c t i m are discontinued a& a l l data Listed (D, H & 2) a r e

for the p i t i m at absolute pier l a and without any correctiorrs applied, The net effect of these changes i s as

Dee1 inat im (D): No Change ~ o r i z m t a l Intensity (HI : -5% i.e., H absolute a d baseline values are 5 b less than previously reperted,

vertical Intensity (2): +33< i .e., Z absolute and baseline values are 33 h i g h e r than previous ly reported.

October 1991 Preliminary Cal ibra t ion Data Sheet w a s not available when O c t r epc r t was maiied.

I NAMETOGRAN IMMMY SCALINGS - FIVE QUlElESV DAYS I

October 1991 Yliurly Scalings Sheet was not available when October Report was mailed. It is included in the November report.

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