DETERMINE AND ANALYZE THE MAGNETIC FIELD … · Nilai pengukuran medan magnet merujuk kepada bacaan...

DETERMINE AND ANALYZE THE MAGNETIC FIELD MAGNITUDE OVER

THE UNIVERSITI TUN HUSSEIN ONN AREA USING MAGNETOMETER

NOOR SYAZANA BINTI ARSHAD

A project report submitted in partial

fulfillment of the requirement for the award of the

Master of Electrical Engineering

Faculty of Electrical and Electronic Engineering

Universiti Tun Hussein Onn Malaysia

JANUARY 2012

v

ABSTRACT

In this project, the magnitude of the magnetic field were observed and analyzed

around Universiti Tun Hussein Onn (UTHM) using Magnetometer. The

measurement of magnetic field magnitude was obtained from Overhauser

Magnetometer reading. The magnetic field data was analyzed using Surfer 10

software. Initially, the Overhauser Magnetometer was assembled and the magnetic

survey was conducted in walking mode. The magnetic field survey locations are

Wireless and Radio Science Center (WARAS), Open Field, UTHM Library and Tun

Fatimah College. The survey was conducted on 1st, 17th and 30th November 2011 also

on 9th and 12th December 2011, on three periods on each survey day, which are

morning, noon and evening. Consecutively, the results were given in the form of

contour map of magnetic field on each survey location which was later compared

with the International Geomagnetic Reference Field (IGRF-11). IGRF-11 is a

standard mathematical description of the Earth's main magnetic field. The contour

map reveals that the Earths magnetic field fluctuates unpredictably during

geomagnetic storm occasion and yet fluctuates considerably during quiet

geomagnetic days. The magnetic field survey data shows that the Earths magnetic

field varies throughout the day thus proved that IGRF-11 geomagnetic model cannot

be used to predict exact value of Earths magnetic field magnitude. It can be

concluded that the space weather disturbance greatly affect the Earths magnetic field

in equatorial region.

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ABSTRAK

Projek ini merujuk kepada kajian dan analisis magnitud medan magnet bumi di

sekitar kawasan Universiti Tun Hussein Onn (UTHM) menggunakan Magnetometer.

Nilai pengukuran medan magnet merujuk kepada bacaan Overhouser Magnetometer.

Data medan magnet di analisis menggunakan perisian Surfer 10. Pada peringkat

permulaan, Overhouser Magnetometer di pasang dan kajian medan magnet di

jalankan menggunakan mod berjalan. Lokasi-lokasi kajian medan magnet bertempat

di Wireless and Radio Science Center (WARAS), padang terbuka, perpustakaan

UTHM dan Kolej Tun Fatimah. Kajian ini telah dijalankan pada 1, 17 dan 30

November 2011 juga pada 9 dan 12 Disember 2011. Data medan magnet telah di

ambil pada tiga waktu berbeza iaitu waktu pagi, waktu tengahari dan waktu petang.

Berikutnya, hasil kajian di dalam bentuk peta kontur pada setiap lokasi kajian telah

dibandingkan dengan International Geomagnetic Reference Field (IGRF-11). IGRF-

11 ialah model piawaian matematik merujuk kepada medan magnet bumi. Peta

kontur menunjukkan medan magnet bumi berubah dengan tidak terjangka semasa

berlakunya kejadian ribut medan magnet tetapi kembali stabil sewaktu ketiadaan

kejadian ribut medan magnet. Data medan magnet yang diukur menunjukkan medan

magnet bumi berubah sepanjang hari sekaligus membuktikan bahawa IGRF-11

model tidak boleh digunakan untuk meramal nilai magnitud medan magnet bumi.

Kesimpulannya, gangguan kepada keadaan cuaca di angkasa lepas kuat

mempengaruhi medan magnet bumi di kawasan Khalutistiwa.

.

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TABLE OF CONTENTS

TITLE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF FIGURES xii

LIST OF TABLES xvii

LIST OF SYMBOL AND ABBREVIATION xviii

LIST OF APPENDICES xx

CHAPTER 1 INTRODUCTION 1

1.1 Background 1

1.2 Problem Statement 3

1.3 Objectives 4

1.4 Scope 4

1.5 Expected Result 5

1.6 Thesis Organization 6

CHAPTER 2 LITERATURE REVIEW 7

2.1 Introduction 7

2.2 Earths Magnetic Field 8

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2.2.1 Static Anomalies 9

2.2.2 Dynamic Anomalies 11

2.2.2.1 Solar Cycle 11

2.2.2.2 Solar Wind 14

2.2.2.3 Geomagnetic Storm 16

2.3 Effects of Earths Magnetic Field to Our Lives 17

2.3.1 Effects on Satellite Operation 18

2.3.2 Effects on Communication and Navigation System 18

2.3.3 Effects on Power System and Pipelines 18

2.3.4 Effects on Magnetic Surveys 19

2.4 Overhouser Magnetometer (GSM-19GW) 19

2.4.1 Overview 19

2.4.2 Standard Magnetometer Components 20

2.5 Global Positioning System (GPS) 23

2.5.1 GPS Overview 23

2.5.2 GPS Operation 23

2.5.3 GPS Signal 25

2.5.4 Sources of GPS signal errors 26

2.6 Universal Transverse Mercator (UTM) 27

2.6.1 Benefit of using UTM coordinate system 27

2.6.2 UTM Coordinate Reading 28

2.6.3 UTM Coordinate System in GPS 29

2.7 International Geomagnetic Reference Field (IGRF) 30

2.7.1 Overview 30

2.7.2 IGRF-11 Online Calculator 33

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CHAPTER 3 METHODOLOGY 35

3.1 Introduction 35

3.2 Equipment Assembly 38

3.2.1 The GSM-19GW Magnetometer Assembly 38

3.2.2 The GSM-19GW Magnetometer Setting 39

3.2.2.1 Setting the Positioning System 39

3.2.2.2 Setting the Time 41

3.2.3 Garmin GPS Navigator 42

3.3 Data Collection 43

3.3.1 Selecting Magnetic Survey Site 43

3.3.2 Data Acquisition by Magnetometer 45

3.3.3 Precaution to Conduct Magnetic Survey 46

3.4 Contour Map Design 47

3.4.1 Surfer 10 Software Overview 47

3.4.2 Contour Map 48

3.4.3 3D Surface Map 49

3.4.4 Contour Map Design Procedure 50

3.5 Contour Map Visualization 52

3.5.1 Google Earth 6 Overview 52

3.5.2 Contour Map Visualization Procedure 54

CHAPTER 4 RESULT AND ANALYSIS 55

4.1 Introduction 55

4.2 Space Weather Report 56

4.3 IGRF-11 Geomagnetic Model 61

4.4 Data Analysis 62

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4.4.1 WARAS Area 63

4.4.2 Open Field Area 65

4.4.3 Tun Fatimah College Area 67

4.4.4 UTHM Library Area 69

4.4.5 Earths Magnetic Field Variation at Different

Places in UTHM 72

4.4.6 Comparison of Actual Data and IGRF-11

Data at Different Places in UTHM 74

4.4.7 Analysis Discussion 76

4.4.8 Analysis Summary 79

4.5 Contour Map Design 82

4.5.1 The Earths magnetic field fluctuations are

unpredictable during geomagnetic storm occasion 82

4.5.2 The Earths magnetic field fluctuations are stable

during quiet geomagnetic days 86

4.5.3 The daily Earths magnetic field variation during

quiet geomagnetic days begin with lowest value

at morning and slowly increases until reach its

peak at local noon and gradually reduces at evening 90

4.5.4 Earths magnetic field magnitude higher at high

interference area than low interference area 94

4.5.5 Wi-Fi hotspot areas are exposed wireless

communication disturbance due to Type II Radio

Emission which occurs due to solar burst 100

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4.6 Contour Map Visualization 102

4.6.1 Earths magnetic field magnitude higher at high

interference area than low interference area 102

4.6.2 Wi-Fi hotspot areas are exposed wireless

communication disturbance due to Type II Radio

Emission which occurs due to solar burst 103

CHAPTER 5: CONCLUSION AND RECOMMENDATION 104

5.1 Conclusion 104

5.2 Recommendation 106

REFERENCES 107

APPENDICES 111

xii

LIST OF FIGURES

2.1 The total intensity of the earths magnetic field 9

2.2 Vertical distribution of the total field lines of flux 10

2.3 The magnetic susceptibility of Earth mineral 10

2.4 Sunspot polarity 12

2.5 Sunspot during solar maximum 12

2.6 Sunspot during solar minimum 13

2.7 Solar flares 13

2.8 Distortion of magnetosphere by solar wind 14

2.9 Van Allen Radiation Belt 15

2.10 Charged particles ejected from the Sun distort

Earth's magnetic field 16

2.11 Space weather effects on technology 17

2.12 Standard magnetometer components 20

2.13 Magnetometer sensor 21

2.14 Magnetometer console 21

2.15 Sectional staff rods 22

2.16 Magnetometer backpack 22

2.17 GPS Satellite 24

2.18 24 satellite constellation orientation 24

2.19 UTM grid zones of the world 29

http://astronomy.swin.edu.au/cosmos/S/Sun

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2.20 Components of Earths geomagnetic field 32

2.21 Geomagnetic model of IGRF-11 in UTM coordinates 34

3.1 Methodology flow chart 37

3.2 Magnetometer and backpack assembly 38

3.3 A magnetometer console screen with highlighted

position option 39

3.4 X/Y Positioning system menu 40

3.5 A magnetometer console screen with highlighted time

option 41

3.6 A magnetometer console screen with highlighted time

inserting option 41

3.7 Garmin GPS Navigator attached to the GSM-19GW

Console 42

3.8 WARAS survey area 43

3.9 Tun Fatimah College Survey Area 44

3.10 Open Field Survey Area 44

3.11 UTHM Library Survey Area 44

3.12 a) Data acquisition method 45

b) Magnetic field survey grid 45

3.13 X/Y Positioning system menu with waypoint 1 coordinate 46

3.14 A contour map with color scale bar 48

3.15 A 3D surface map 49

3.16 Contour map in Surfer 10 in UTM coordinates 51

3.17 Google Earth virtual globe 52

3.18 KLCC Petronas Twin Tower viewed in Google Earth

with 3D buildings layer 53

xiv

3.19 Mount Everest viewed in Google Earth with 3D terrain layer 53

3.10 The contour map in correct location on Google Earth 54

4.1 Space Weather Alerts and Warnings Timeline from

1st November 2011 until 15th November 2011 57


16th November 2011 until 30th November 2011 57


1st December 2011 until 15th December 2011 58

4.4 Comparison between Actual Magnetic Field Data and

IGRF 11 Magnetic Field Data at WARAS 63


IGRF 11 Magnetic Field Data at Open Field 65


IGRF 11 Magnetic Field Data at Tun Fatimah College 67


IGRF 11 Magnetic Field Data at UTHM Library 69

4.8 Earths Magnetic Field Variation at different places in UTHM 72

4.9 Comparison of Actual Magnetic Field Data and IGRF 11

Magnetic Field Data at different places in UTHM 74

4.10 Effect of solar Ultra-Violet and X-Ray radiation on ionospheric

conductivity throughout the day 76

4.11 Solar wind and the Earth's magnetosphere 77

4.12 Solar flare eruption 78

4.13 Contour map at Open Field during morning (top left),

noon (top right) and evening (below) on 1st November 2011 82

4.14 3D Surface map at Open Field during morning (top left),

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4.15 Contour map at WARAS during morning (top left),


4.16 3D Surface map at WARAS during morning (top left),


4.17 Contour map at Open Field during morning (top left),

noon (top right) and evening (below) on 12th December 2011 86

4.18 3D Surface map at Open Field during morning (top left),










4.23 Contour map at UTHM Library during morning (top left),


4.24 3D Surface map at UTHM Library during morning (top left),


4.25 Contour map and 3D surface map at UTHM Library(left) and

Open Field (right) during morning on 30th November 2011 94

4.26 Contour map and 3D surface map at UTHM Library (left) and

Open Field (right) during noon on 30th November 2011 95

xvi

4.27 Contour map and 3D surface map at UTHM Library(left) and

Open Field (right) during evening on 30th November 2011 96


Open Field (right) during morning on 9th December 2011 97

4.29 Contour map and 3D Surface map at UTHM library (left) and

Open Field (right) during noon on 9th December 2011 98


Open Field (right) during evening on 9th December 2011 99

4.31 Contour map and 3D surface map at UTHM Library during

noon (left) and evening (right) on 17th November 2011 100

4.32 Contour map and 3D surface map at Tun Fatimah College

during morning (left) and noon (right) on 17th November 2011 101

4.33 Contour map at UTHM during morning on 30th November 2011 102

4.34 Contour map at UTHM during noon on 9th December 2011 102

4.35 Contour map at UTHM during morning on 17th November 2011 103

4.36 Contour map at UTHM during noon on 17th November 2011 103

xvii

LIST OF TABLES

2.1 The abbreviated format for the UTM coordinates 28

2.2 Definitive and International Geomagnetic Reference

Field Values 31

2.3 Characteristics of magnetic field in Parit Raja

based on IGRF-11 33

4.1 Space Weather Alert Description 59

4.2 IGRF-11 magnetic field value at different places in

UTHM 60


IGRF 11 Magnetic Field Data at WARAS 61


IGRF 11 Magnetic Field Data at Open Field 66


IGRF 11 Magnetic Field Data at Tun Fatimah College 68


IGRF 11 Magnetic Field Data at UTHM Library 70

4.7 Earth Magnetic Field Variation at different places in UTHM 73

4.8 Comparison value of Actual Magnetic Field Data and

xviii

IGRF 11 Magnetic Field Data at different places in UTHM 75

LIST OF SYMBOLS AND ABBREVIATIONS

B Magnetic Flux Density

F Total Magnetic Field Magnitude

mng the expansions Gauss coefficients at time t

mnh the expansions Gauss coefficients at time t

H Magnetic Field Strength

nT nano Tesla

mnP the Schmidt semi-normalized associated Legendre function of

degree n and order m

R Earth reference radius

r distance from the center of the Earth

sv secular variation

colatitudes from the center of the Earth

longitude from the center of the Earth

AC Alternating Current

DC Direct Current

GPS Global Positioning System

HF High Frequency

IAGA International Association of Geomagnetism and Aeronomy

xix

IGRF International Geomagnetic Reference Field

KML Keyhole Markup Language

NOAA National Oceanic and Atmospheric Administration

UHF Ultra High Frequency

UTHM Universiti Tun Hessein Onn Malaysia

UTM Universal Transverse Mercator

WARAS Wireless and Radio Science Centre

WGS 84 World Geodetic System 1984

xx

LIST OF APPENDICES

APPENDIX TITLE PAGE

A GANTT Chart 111

B Data Statistics for WARAS area 114

C Data Statistic for Open Field area 116

D Data Statistic for Tun Fatimah College area 118

E Data Statistic for UTHM Library area 120

F NOAA Space Weather Scale 122

G GSM-19GW Overhouser Magnetometer

Technical Paper 123

1

CHAPTER 1

INTRODUCTION

1.1 Background

According to Wallace (2003), Earths magnetic field or geomagnetic field is

approximately a magnetic dipole. It consists of N pole which is located near Earths

geographic South Pole and S pole which is located near Earths geographic North Pole.

A magnetic field strength weakens if it is far from its source. The strongest magnetic

field located at the poles, and the weakest field located near the equatorial region. The

Earth's magnetic field is measure in "nano Tesla" (nT). On the Earth's surface, the

magnitude of magnetic field varies from about 30 000 nT near the equator to about 60

000 nT near the poles (Lowes.F.J, 2010).

The magnitude of magnetic field varies on different values daily. A study by

Hrvoic & Hollyer (2007) shows that the Earths magnetic field varies due to either

dynamic or static effects. Dynamic anomalies are related to solar activity and storms

from outer space. Static anomalies are related to different materials present in the Earth's

crust.

Magnetic field plays a very important part in our lives. It protects the Earth from

radiation penetration of solar wind. Extreme geomagnetic field would cause significant

damage to transformers and generators, disconnections of electric stations, power grid

blackouts, explosions on oil and gas pipelines, failures in work of computers and board

system and degradation of satellite navigation (Thompson,2007).

2

Magnetic field variations can be measured by a magnetometer. Magnetometer is

an electronic device that can measure the properties of the magnetic field near the

surface. As referred to GEM System (2008), an Overhouser Magnetometer (GSM-19) is

a superior magnetic measuring device with high sensitivity, high cycling speed, low

noise, and very low power consumption over a wide temperature range. In addition, it

can be easily configured for high sensitivity readings in low magnetic fields (for

equatorial survey) which are suitable for magnetic survey conducted in University Tun

Hussein Onn, Parit Raja, Johor.

In this project, the main aim is to observe Earths magnetic field magnitude

variation on different day, time and location. Thus, the magnetic field survey has been

conducted at four different locations in University Tun Hussein Onn Malaysia (UTHM)

namely, Wireless and Radio Science Centre (WARAS), Open Field, UTHM Library and

Tun Fatimah College. The magnetic field data has been taken on 1st, 17th and 30th

November 2011 also on 9th and 12th December 2011. For each survey day, there are

three magnetic field survey periods which are morning, noon and evening.

The magnetic survey was conducted as an attempt to provide a general overview

of Earths magnetic field magnitude anomalies during morning, noon and evening.

These magnetic field anomalies pattern can be illustrated in a contour map as well as

surface map using Surfer 10 software.

On the other hand, the International Geomagnetic Reference Field (IGRF-11)

geomagnetic model was used to provide initial approximation of Earths magnetic field

magnitude at the survey area. The primary analysis involved on comparison of actual

magnetic field magnitude and IGRF-11 magnetic field magnitude at four locations in

UTHM.

3

1.2 Problem Statement

Nowadays, people are totally relying on technological systems to do daily routine. These

systems improve the quality of our lives and make our lives easier. However, these

facilities can be affected by magnetic field variation and are used in various areas mainly

in power grid supply, fuel supply, computer operation, communication and navigation.

According to Space Weather Canada (2009), extreme variations of geomagnetic

field can be caused by extreme magnetic storm that can affect power systems, spacecraft

operations and other systems. For example, surge currents are induced in power lines

that could lead to the failure of power grids. In addition, currents in long pipelines can

cause increase corrosion. Furthermore, HF radio propagation may be impossible in many

areas for one to two days and satellite navigation may be degraded for days.

Moreover, power system experience widespread voltage control problems,

damaging transformers, and could lead to worst situation where some grid systems may

experience complete collapse or blackouts. Additionally, spacecraft operation may

experience extensive surface charging, problems with orientation, uplink/downlink and

tracking satellites.

This research is significant as it provides a fundamental information and

overview of magnetic field variation in equatorial region specifically in UTHM area. It

is essential to investigate the magnetic field as its variation can affect our daily lives

routine. A significant changes of magnetic field in a specific area can be detected and

observed by identifying and comparing with the local magnetic field variation pattern

during quiet geomagnetic day and geomagnetic storm. The variation pattern can be

observed in a contour map of Earth magnetic field.

4

1.3 Objectives

The objectives of this project are:

1. To acquire and observe the magnetic field magnitude variations using magnetometer

in UTHM area.

2. To produce a contour map of Earth magnetic field magnitude specifically in UTHM

area.

3. To compare the contour map of magnetic field magnitude in UTHM area with IGRF-

11 magnetic model.

1.4 Scope

This project is focused on certain aspects which are:

i. The magnetic field magnitude variation will be determined in UTHM area only.

ii. The magnetic field survey will be conducted by Overhouser Magnetometer

(GSM-19GW) in walking mode.

iii. A magnetic field contour map will be designed in Surfer 10 software.

5

1.5 Expected Result

The magnetic field of Earths surface varies from about 40,000 nT near the equator and

about 60,000 nT near the poles. The Universal Transverse Mercator (UTM) coordinates

for Parit Raja is 290496E 206438N. The latitude and longitude of Parit Raja is 1.867

and 103.117 which are in equatorial area. Therefore, it is expected that the total field is

approximately above 40,000 nT at the magnetic field survey area in UTHM.

For comparison, the magnetic model of IGRF-11 shows that the total field is

42,026.9 nT at Parit Raja location. However, the value is not accurate due to the

contribution of various interferences such as fixed interference, man-made interference

and natural interference(Lowes,2010).

Lowes(2010) states that fixed interference such buildings and parked cars are

typically contribute of magnitude 200 nT. There are also a large variety of time-varying

fields, both man-made (traffic) and natural (from electric currents in the ionosphere and

magnetosphere). The ionosphere and magnetosphere minimum contribution is about 20

nT but can be increased significantly up to 1000 nT and more during a geomagnetic

storm.

6

1.6 Report Organization

There are five chapters in this report.

Chapter 1 :

First chapter introduces the project report. Project background such as objectives and the

project scope was clearly explained in this chapter.

Chapter 2 :

The second chapter covers literature reviews regarding to this project. This chapter

provides reader key information on Earths magnetic field variation as well as the

interaction between Sun and Earth.

Chapter 3 :

Chapter three provide reader the methodology to complete this report. It also focuses on

explanations concerning method of conducting magnetic field survey. The procedure to

design contour map are also displayed in this chapter.

Chapter 4 :

Chapter four consists of analysis data in term of several aspects such as location, time

and weather condition. The results of each survey were discussed and analyzed in detail

in this chapter.

Chapter 5 :

Chapter five concludes the overall project works and provides some suggestions for

further study and improvement.

7

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapter is a crucial part of this thesis. A literature review is a body of text that aims

to review the critical points of current knowledge on a research topic. Its ultimate goal is

to keep the reader update with current literature on a topic that could be useful for future

research.

This part consists of general knowledge of all section in this thesis such as

Earths magnetic field, the effect of Earths magnetic field to our lives, Magnetometer,

Global Positioning System (GPS), Universal Transverse Mercator (UTM) and

International Geomagnetic Reference Field (IGRF).

In first section, the explanations on Earths magnetic field intensity are stated.

The factors that contribute to Earths magnetic field intensity are Static Anomalies and

Dynamic Anomalies. It is important to identify the relationship between solar cycle,

solar wind and geomagnetic storm which contributes to Dynamic Anomalies.

8

In next section, the Earths magnetic field major roles to our lives are

enlightened. It is vital to clarify the effects of Earths magnetic field disturbance to our

technology such as satellite, power system and pipeline, communication and navigation,

and magnetic survey.

On the other hand, the overview of magnetometer has been described. This section

provides the description on magnetometer benefits and application. It is essential to

identify the magnetometer components and how to assemble it.

Besides that, a section has been allocated to provide the overview of GPS. A

brief explanations regarding GPS operation, GPS signal and sources of GPS signal errors

are provided. Moreover, the benefits of using UTM coordinates system in magnetic

survey are clarified. It is essential to know how to apply UTM coordinates in GPS in

order to conduct magnetic survey.

Lastly, brief explanations on theory of constructing IGRF geomagnetic model

have been depicted. The IGRF 11 model provides the magnetic field characteristics of

Parit Raja.

2.2 Earths Magnetic Field

According to Wallace (2003), the magnetic field is produced by a single dipole. It

consists of N pole which is located near Earths geographic South Pole and S pole which

is located near Earths geographic North Pole. The magnetic field has no distinct

boundary. It simply decreases in intensity until it is no longer detectable. The Earths

magnetic field varies from about 30 000 nT near the equator region to about 60 000 nT

near the polar region (Lowes, 2010).

9

Figure 2.1: The total intensity of the Earths magnetic field (Smekalova,Voss & Smekalov,2008)

The magnitude of magnetic field varies on different values daily. Hrvoic &

Hollyer (2007) states that the magnetic field variation pattern can be due to either

dynamic or static effects. Static anomalies are related to different materials present in the

Earth's crust. Dynamic anomalies are related to solar activity and storms from outer

space.

2.2.1 Static Anomalies

As well cited by Smekalova,Voss & Smekalov (2008), iron constitutes about 6% of the

Earths crust. Most of it is dispersed through soils, clays and rocks as chemical

compounds which are magnetically very weak. Mans activities in the past (especially

the use of fire for heating, cooking, production and industry) have changed these

compounds into more magnetic forms, creating special patterns of anomalies in the

Earths magnetic field. These anomalies are detectable with sensitive instrument, which

is magnetometer.

10

If the Earth were composed of uniform material, the magnetic lines of force would be

evenly distributed between the poles. The magnetic lines in a small area would be

parallel. However, since various materials have different magnetic susceptibilities due to

their composition, the Earths magnetic lines of force are distorted. The local

disturbances of the global magnetic field are called magnetic anomalies.

Figure 2.2: Vertical distribution of the total field lines of flux (Smekalova,Voss &

Smekalov,2008)

The anomalies from natural rocks and minerals are due chiefly to the presence of

the most common magnetic mineral, magnetite, FeOFe2O3, or its related minerals. All

rocks contain some magnetite, ranging from very small fractions of a percent to several

percent.

Figure 2.3: The magnetic susceptibility of Earth mineral (Smekalova,Voss &

Smekalov,2008)

11

Magnetic susceptibility is the ease with which a substance is magnetized by the Earths

magnetic field. The variations in magnetic susceptibility between different kinds of

mineral affect the Earths field locally.

2.2.2 Dynamic Anomalies

Hrvoic & Hollyer (2007) briefly describe that the dynamic anomalies are related to solar

wind and geomagnetic storms from outer space. These phenomena occur due to solar

cycle.

2.2.2.1 Solar cycle

The solar cycle is manifest in many properties of the Sun but is most evident in the

appearance of sunspots on the solar disk. Sunspots are regions of stronger magnetic field

which appear darker than the surrounding surface. At certain times, sunspots are rare and

the Sun appears almost without blemish. This is known as solar minimum. Later,

sunspots become more common and it is normal for many groups of spots to be visible.

The peak of common sunspots called solar maximum as well cited by Thompson (2007).

A Suns image (magnetogram) can be taken by an instrument which can detect

the strength and location of the magnetic fields on the Sun. In a magnetogram, grey areas

indicate that there is no magnetic field, while black and white areas indicate regions

where there is a strong magnetic field.

Magnetograms can show the directions of magnetic fields travel towards Earth.

The darkest areas are regions of "south" magnetic polarity (inward directed or moving

toward the center of the Sun) and the whiter regions "north" (outward directed or moving

toward Earth) polarity.

12

Figure 2.4: Sunspot polarity (Scherrer,2008)

Figure 2.5: Sunspot during solar maximum (Scherrer,2008)

The above figure shows the surface distribution and polarity of the Sun's

magnetic fields and sunspots at a very active time during its sunspot cycle. When the

Sun is very active, the number of sunspots is at a maximum, and solar magnetism is

dominated by large bipolar sunspots within two parallel bands oriented in the east-west

direction.

As a comparison, Figure 2.6 shows some sunspot during a solar minimum or low

magnetic activity period. At times of solar minimum, there are very few large sunspots,

and only tiny magnetic fields can be seen.

13

Figure 2.6: Sunspot during solar minimum (Scherrer,2008)

According to Scherrer (2008), when the magnetic fields of sunspots become

twisted and distorted due to the differential rotation of the sun, stored energy is released.

Thus, solar flares which are huge outbursts of energy are created.

Figure 2.7: Solar flares (The Watchers, 2011)

Further discussed by Thompson (2007), along with the production of

electromagnetic radiation, the flare can be associated with the ejection of clouds of

charged particles into the solar wind. This process is called a Coronal Mass Ejection

(CME) and may occur with flares. The result of the charged particles reaching the Earth

is a geomagnetic storm.

http://thetruthbehindthescenes.files.wordpress.com/2010/09/mega-storm.jpg

14

2.2.2.2 Solar Wind

Referred to Marine Magnetics Corp (2007), the Earths magnetic field is within the

influence of the Suns which is comparatively gigantic magnetic field. The Suns larger

field interacts with the Earths, giving it a distinct boundary which can be extends up to

several tens of thousands of kilometers into space. The space within that boundary is

known as the magnetosphere.

Earths magnetosphere dominates the surface magnetic field at large distances

from the planet. The magnitude of magnetic field varies daily. These phenomena occur

due to constant stream of free ions and electrons that flows from the Sun which is called

the solar wind. The Earths magnetic field interacts with the Suns magnetic field. The

Earths magnetic field is distorted by the solar wind.

The solar wind is a stream of ionized gases that blows outward from the Sun at

about 400 km/second and that varies in intensity with the amount of sunspots on the Sun.

The Earth's magnetic field shields the ionized gases of the solar wind. When the solar

wind encounters Earth's magnetic field it is deflected like water around the bow of a

ship, as illustrated in Figure 2.8.

javascript:locscrollmenu('http://www

spof.gsfc.nasa.gov/Education/Figures/stsys.gif','magnetic',755,335)

15

Figure 2.8 : Distortion of magnetosphere by solar wind (Steigerwald,2008)

As shown in Figure 2.8, the Earths magnetic field acts as a shield against the

bombardment of particles continuously streaming from the Sun (Steigerwald,2008). The

solar particles (ions and electrons) are electrically charged and most of them are

deflected by our planet's magnetic field.

The imaginary surface at which the solar wind is first deflected is called the bow

shock. The corresponding region of space sitting behind the bow shock and surrounding

the Earth is magnetosphere. However, some high energy charged particles from the solar

wind leak into the magnetosphere. The charged particles are then trapped in the Van

Allen Radiation Belt (Stern,2001).

Figure 2.9: Van Allen Radiation Belt (Stern,2001)

As illustrated in Figure 2.9, Van Allen Radiation Belt has a magnetic field that

can trap charged particles such as electrons and protons and forced them to execute a

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spiraling motion back and forth along the field lines. The charged particles are reflected

at "mirror points" where the field lines come close together and the spirals tighten.

The solar wind changes in the speed or density distorts the Earth's magnetic field,

compressing it in the direction of the Sun and stretching it out in the anti-Sun direction.

Fluctuations in the flow of solar wind cause variations in the strength and direction of

the magnetic field measured near the surface of the Earth. Abrupt changes in solar wind

speed or density are called geomagnetic storm (Thompson,2007).

2.2.2.3 Geomagnetic Storm

As referred to Swinburne Astronomy Online (2009), geomagnetic storms are a solar-

induced electromagnetic phenomenon which occurs both in atmosphere and across the

Earth's surface. The variation flow of charged particles from solar flares through the

Earth's atmosphere is causing a fluctuating magnetic field. These fluctuating magnetic

fields will induce electrical currents across Earth surface.

Figure 2.10 : Charged particles ejected from the Sun distort Earth's magnetic field

(Swinburne Astronomy Online,2009)

http://astronomy.swin.edu.au/cosmos/S/Sun

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A geomagnetic storm could cause the Earth's ionosphere (the electrified layers of

the upper atmosphere) severely disturbed by flows of charged particles. This is important

because the ionosphere acts as a "mirror" that reflect the High Frequency (HF) signals

(Thompson, 2007).

2.3 Effects of Earths Magnetic Field to Our Lives

The Earth's magnetic field is an ever-changing phenomenon that influences human

activity and the natural world in a countless of ways. The geomagnetic field changes

from place to place and from time to time. The changes are caused by geomagnetic

storm that originates from sunspot. Sunspot activity produce solar flares that leads to

solar wind and geomagnetic storm. These space weathers can greatly affect our modern

way of life and technology.

Figure 2.11: Space weather effects on technology (Space Weather Canada,2009)

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Space weather phenomena have a variety of effects on technology. Energetic

particles thrown out from the Sun interact with the Earth's magnetic field producing

magnetic disturbances and increased ionization in the ionosphere. These space

phenomena occur at 100 to 1000 km above the Earth (Space Weather Canada,2009).

The space weather phenomena can degrade navigation and surveying techniques.

In addition, it can impede geophysical exploration, disrupt electric power utilities and

pipeline operations. Moreover, it can disturb modern communications system and

satellite operation.

2.3.1 Effects on Satellite Operation

The high energy particles affect satellites causing disoperation or equipment damage that

can put the satellite out of operation. When a satellite passed through a cloud of high-

velocity electrons, an electrostatic discharge occur that actually fired the satellites rocket

thrusters, resulting in a loss of control from ground tracking stations (Space Weather

Canada,2009).

2.3.2 Effects on Modern Communication and Navigation System

Thompson (2007), state that radio waves used for satellite communications or GPS

navigation are affected by the increased ionization with disruption of the communication

or navigation systems. Geomagnetic storm corresponds with a disturbed ionosphere

causing difficult HF communications. HF is significant in various areas including

defense, emergency services, broadcasters, and marine and aviation operators.

2.3.3 Effects on Power System and Pipelines

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According to Swinburne Astronomy Online (2009), magnetic disturbances also induce

electric currents in long conductors such as power lines and pipelines causing power

system outages or pipeline corrosion. The ground induced currents tend to flow through

power lines or man-made pipeline networks because the electricity encounters less

resistance when it flows through metal, compared to rock or water. The ground induced

currents are direct currents. In contrast, the power-grid transformer operates in

alternating current. Therefore, the combination of the Direct Currents (DC) and

Alternating Currents (AC) causing the transformers to catch on fire and breakdown.

2.3.4 Effects on Magnetic Surveys

The geomagnetic storm directly affects operations that use the magnetic field, such as

magnetic surveys. Magnetic storms cause considerable disruption to magnetic field due

to the unpredictable and irregular nature of the geomagnetic field fluctuations. As a

result, the temporal variations of the Earth's magnetic field causing difficulty to interpret

magnetic survey data (Marshall,2007).

2.4 Overhouser Magnetometer (GSM-19GW)

2.4.1 Overview

Overhauser magnetometers were introduced by GEM Systems, Inc. following R&D in

the 80s and 90s. It is the standard equipment for archeology activities, magnetic

observatory measurement and long term magnetic field monitoring in volcanologist and

earthquake prediction (Hrvoic, Wilson & Lopez, 2009).

A magnetometer is an instrument with a single sensor that measures magnetic

flux density B (inTesla). The Earth generates a weak magnetic field that produces flux

densities (in air) of about 30 microTesla in some parts of South America to a high of

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over 60 microTesla in the Arctic Circle and Antarctica. Since magnetic flux density in

air is directly proportional to magnetic field strength H [A/m], a magnetometer is

capable of detecting fluctuations in the Earth's magnetic field (Hrvoic & Hollyer ,2007).

Overhauser magnetometer offers several benefits that can facilitate in conducting

magnetic field survey. The benefits are:

High resolution exploration mapping

Ground portable magnetic surveying for environmental and engineering

applications

The innovative "Walking" option that enables the acquisition of nearly

continuous data on survey lines.

The system records data at discrete time intervals (up to 5 readings per second)

as the instrument is carried along the line.

It also increases survey efficiency because the operator can record data almost

continuously.

It has a built-in GPS which offers many advantages such as minimizing weight.

2.4.2 Standard Magnetometer Components

An Overhouser Magnetometer (GSM-19GW) consists of standard magnetometer

components, sectional staff rods and a backpack. Figure 2.12 displays the standard

magnetometer components.

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Figure 2.12: Standard magnetometer components

The following list is a standard parts of a GSM-19GW magnetometer:

Two sensors for gradiometer application and one sensor for magnetometer

application. Sensors are dual-coils designed to reduce noise and improve gradient

tolerance.

Figure 2.13: Magnetometer sensor

One coaxial sensor cable per channel, typically RG-58/U and 206 cm long.

Console with 16 keys keyboard, graphic display (64 x 240 pixel), sensor and

power / input / output connectors. The keyboard also serves as an ON-OFF

switch.

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Figure 2.14: Magnetometer console

6-pin console connector for RS-232, external power, battery charging or external

trigger.

Sealed connectors (i.e. keyboard and front panel mounting screws are sealed so that

the instrument can operate under rainy conditions).

Charger with 2 levels of charging (full and trickle) that switch automatically from

one to another. The power supply input is 110 250V, 50 / 60 Hz.

Aluminum staffs with 4 strong tubing sections as refer to Figure 2.15. This

construction allows for a selection of sensor elevations above ground during surveys.

Figure 2.15: Sectional staff rods

A backpack is provided for walking mode magnetometer as shown in Figure

2.16.

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Figure 2.16 : Magnetometer backpack

2.5 Global Positioning System (GPS)

2.5.1. GPS Overview

Global Positioning System (GPS) is a Satellite Navigation System which is developed

by the U.S Department of Defense. It can be accessed by users on the land, sea or in the

air. However, it is not available in underwater or underground such as in a mine (UK

Telematics Online,2009).

GPS is the best navigation system available at the present time. It can provide

immediate information regarding position on the earths surface, altitude, speed,

direction of travel and time. GPS is a revolutionary system of navigation because it

works anywhere in the world, in any weather condition, 24 hours a day and has no cost

to the user (UK Telematics Online,2009).

Nowadays, the application of GPS technology is widening in magnetic survey.

GPS have the ability to make better decisions in locating and following up on anomalies.

Thus, GPS features can improve the survey cost effectiveness and time management

(UK Telematics Online,2009).

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2.5.2 GPS Operation

GPS satellites are powered by solar energy. They have backup batteries onboard to keep

them running in the event of a solar eclipse, when there's no solar power. Small rocket

boosters on each satellite keep them flying in the correct path (Garmin,1996).

Figure 2.17 : GPS satellite (Garmin,1996)

The GPS system relies on 24 satellites orbiting the Earth about 12,000 miles

above Earth surface. They are constantly moving, making two complete orbits in less

than 24 hours. These satellites are travelling at speeds of roughly 7,000 miles an hour

(Garmin,1996).

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Figure 2.9: Van Allen Radiation Belt (Stern,2001)

DETERMINE AND ANALYZE THE MAGNETIC FIELD … · Nilai pengukuran medan magnet merujuk kepada bacaan...

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