Paper Information

Title: 

THE STUDY OF THE GEOMAGNETIC BAYS RECORDED AT TEHRAN GEOMAGNETIC OBSERVATORY (1971-80)

Type: PAPER
Author(s): JOATA BAYRAMI A.,HUSSEIN ZADEH GUYA N.
 
 
 
Name of Seminar: CONFRANCE ZHEOFIZIKE IRAN
Type of Seminar:  CONFERENCE
Sponsor:  ANJOMANE MELI ZHEOFIZIK IRAN
Date:  2006Volume 12
 
 
Abstract: 

GEOMAGNETIC FIELD VARIES WITH TIME AND SPACE IN A COMPLICATED WAY. TIME VARIATIONS CONSIST OF SECULAR AND TRANSIENT VARIATIONS. ONE OF THE TRANSIENT VARIATIONS IS NAMED GEOMAGNETIC BAY, WHICH LOOKS LIKE A MAP OF AN INDENTATION IN A COASTLINE OR GAUSSIAN CURVE. THE DURATION OF BAY CAN BE FROM A FEW MINUTES TO A FEW HOURS. THE BAYS GENERALLY OCCUR ON SOLAR QUIET DAYS ACCOMPANY WITH PI1 AND PI2 MICROPULSATIONS. THE BAYS ARE TWO-STAGE EVENTS; THE EARLY STAGE IS TRIGGER BAY AND THE SECOND IS MAIN BAY. THIS TYPE OF VARIATION (AND ALL VARIATIONS) INDUCES ELECTRIC CURRENTS IN THE EARTH. THE INDUCED ELECTRIC CURRENTS GIVE RISE IN THEIR TURN TO AN INTERNAL COMPONENT OF THE MAGNETIC VARIATIONS OBSERVED AT THE SURFACE. THE RATIO OF THE PARTS OF THE MAGNETIC FIELD OF INTERNAL AND EXTERNAL ORIGIN IS A MEASURE OF THE RESPONSE, AND IS DEPENDENT ON BOTH THE EXTERNAL CURRENT SYSTEM AND THE DISTRIBUTION OF THE ELECTRICAL CONDUCTIVITY WITHIN THE EARTH. USING THIS METHOD, THE ELECTRICAL CONDUCTIVITY OF THE EARTH CAN BE DETERMINED FOR VARIOUS DEPTHS ACCORDING TO THE PERIOD OF THE MAGNETIC VARIATIONS. IN THIS PAPER, IT IS MADE A STATISTICAL STUDY OF BAYS RECORDED AT TEHRAN GEOMAGNETIC OBSERVATORY FOR THE PERIOD OF 1971-80 ACCORDING TO THE TIME OF THEIR OCCURRENCE, INTENSITY AND DIRECTION. WE HAVE ALSO TAKEN IN CONSIDERATION THE GEOMAGNETIC SEASONS. MAXIMUM NUMBERS OF BAYS OCCUR AT MIDNIGHT WITH MODERATE INTENSITY AND POSITIVE DIRECTION. MOST OF BAYS TAKE PLACE IN EQUINOX AND DECEMBER SOLSTICE. RETURN CURRENTS ARE PREDOMINANT CURRENT SYSTEM. THE DELAY TIME BETWEEN THE ONSETS OF TWO STAGES LIE IN RANGE 10-30 MINUTES. THE RELATION BETWEEN THE NUMBERS OF THE SUNSPOTS AND THE BAYS IS INVERSELY PROPORTIONAL.

 
Keyword(s): AURORA, ELECTROJET, GEOMAGNETIC OBSERVATORY, MICROPULSATIONS, TRANSIENT VARIATIONS, GEOMAGNETIC SEASONS, GAUSSIAN CURVE
 
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