Earth Magnetism.docx

ST. ANTHONY’SSENIORSECOND ARYSCHOOL

AISSCE -19

Physics Project

 Topic –Earth Magnetism  Roll Number –  Class – XII (PCM)

Submitted by – Priyanshu Patel Submitted to – Sir Uttam Singh Pal

Acknowledgement I would like to sincerely and profusely thank my physics teacher Mr. Uttam Singh Pal, for his able guidance and support in completing my project.

I would also like to extend my gratitude to the principal for providing me with all the facility that was required Last but not the least,I would extend my gratitude towards all teaching and non-teaching staff of St. Anthony’s senior secondary school and towards my friends who has supported me to complete this project.

Index        

 

Earth’s Magnetism The Earth’s Magnetism:Origin The Earth’s Magnetic Field Some Important Terms Related To Earth’s Magnetic Field Importance of Earth’s Magnetic Field Intensity of Earth’s Magnetic Field Relation Between Elements of Earth’s Magnetic Field Global Variation In Earth’s Magnetic Field  Magnetic Field Revarsals  Neutral Point Mission to the core:A try to travel to the center of the Earth Mission to the core:A try to travel to the center of the Earth

“Creativity is contagious, pass it on” – Albert Einstein

EARTH MAGNETISM THE EARTH’S MAGNETISM : ORIGIN Some early theories regarding earth’s magnetism —  In 1600,Sir William Gilbert in his book ‘De Magnete’ first suggested that the earth itself is a huge magnet. Earth behaves as a powerful bar magnet and its magnetism is due to the presence of magnetic material at its centre.  Prof. Patrick Blackett suggested that the earth’s magnetism is due to rotation of earth about its own axis. Every substance is made of charged particles such as protons and electrons. As these particles rotate along with the earth, they cause circulating currents which in turn, magnetise the earth.  Cosmic rays cause the ionisation of gases in the earth’s atmosphere. As the earth rotates, strong electric currents are set up due to the movement of the charged ions. These currents may be the source of earth’s magnetism.

 The ‘modern theory’ that we currently considerwas given by WalterM. Elsasterand Sir E.Bullard, they proposed that there are large deposits of ferromagnetic materials like iron, nickel, etc. in the core of the earth. The core of the earth is very hot and molten. The circulating ions in the highly conducting liquid region of the earth’s core form current loops and hence produce a magnetic field. This is known as ‘dynamo effect’. We shall note that:  The changes in the earth’s magnetic field are so complicated and irregular that the exact cause of earth’s magnetism is yet to be known.

THE EARTH’S MAGNETIC FIELD The Earth's magnetic field is approximately a magnetic dipole, with the magnetic field South Pole near the Earth's geographic North Pole and the other magnetic field North Pole near the Earth's geographic South Pole. A magnetic field extends infinitely, though it weakens with distance from its source. The Earth's magnetic field, also called the geomagnetic field, which effectively extends several tens of thousands of kilometers into space, forms the Earth's magnetosphere. A paleomagnetic study of Australian red dacite and pillow basalt has estimated the magnetic field to be at least 3.5 billion years old.

SOME IMPORTANT TERMS RELATED TO EARTH’S MAGNETIC FIELD  Geographical pole is either of the two points on a rotating body where its axis of rotation intersects its surface. As with Earth's North and South Poles, they are usually called that body's "north pole" and "south pole", one lying 90 degrees in one direction from the body's equator and the other lying 90 degrees in the opposite direction from the equator.

Every planet has geographical poles. If, like the Earth, a body generates a magnetic field, it will also possess magnetic poles.  Magnetic pole.The magnetic poles are located where the magnetic field lines due to the dipole enter or leave the earth. The location pf the north magnetic pole is at latitude of 79.74 N and a longitude of 71.8 W and the magnetic South Pole is at 79.74 S, 108.22 E.  Magnetic field lines. Theyare a visual and intuitive realisation of the magnetic field. The magnetic field lines in a magnetic field are those imaginary lines which continuously represent the direction of the magnetic field.  Geographic axis.The straight lines passing through the geographical north and south poles of the earth is called its geographic axis. It is the axis of rotation of earth.  Magnetic axis.The straight line passing through the magnetic north and South Pole of the earth is called its magnetic axis.  Geographic equator.An equator is an imaginary line around the middle of a planet or other celestial body. It is halfway between the North Pole and the South Pole, at 0 degrees latitude. Anequator divides the planet into a Northern Hemisphere and a Southern Hemisphere. The Earth is widest at its Equator  Magnetic equator. The irregular imaginary line, passing round the earth near the equator, on which a magnetic needle has no dip.

IMPORTANCE OF EARTH’S MAGNETIC FIELD The Earth's magnetic field serves to deflect most of the solar wind, whose charged particles would otherwise strip away the ozone layer that protects the Earth from harmful ultraviolet radiation.

Compasses are mainly used in navigation to find direction on the earth. This works because the Earth itself has a magnetic field which is similar to that of a bar magnet. The compass needle aligns with the Earth's magnetic field direction and points north-south. Animals including birds and turtles can detect the Earth's magnetic field, and use the field to navigate during migration. Cows and wild deer tend to align their bodies north-south while relaxing, but not when the animals are under high voltage power lines, leading researchers to believe magnetism is responsible. Note - To produce this bipolar field, it is necessary to suppose that the Earth Core is traveled, in a perpendicular plan in the polar axis, by a buckle of constant current between 2 and 6 billion amperes.

INTENSITY OF EARTH’S MAGNETIC FIELD The intensity of the field is often measured in gauss (G), but is generally reported in nanoteslas (nT), with 1 G = 100,000 nT. A nanotesla is also referred to as a gamma (γ).[13] The tesla is the SI unit Of themagnetic field, B. The Earth's field ranges between approximately 25,000 and 65,000 nT (0.25–0.65 G). By comparison, a strong refrigerator magnet has a field of about 10,000,000 nanoteslas (100 G). A map of intensity contours is called an isodynamic chart. As the World Magnetic Model shows, the intensity tends to decrease from the poles to the equator. A minimum intensity occurs in the South Atlantic Anomaly over South America while there are maxima over northern Canada, Siberia, and the coast of Antarctica south of Australia EXPERIMENTAL EVIDENCES IN SUPPORT OF EARTH ’S MAGNETIC FIELD

 A freely suspended magnetic needle comes to rest roughly in NorthSouth direction. This suggests that the earth behaves as a huge magnet with its south pole lying somewhere near the geographic north pole and its south pole lying somewhere near the geographic south pole.

 An iron bar buried in the earth becomes weak magnet after some time. The magnetism is induced by earth’s magnetic field.  Existence of neutral points near a bar magnet indicates the presence of earth’s magnetic field. At these points, magnetic field of the magnet is cancelled by the earth’s magnetic field.

ELEMENTS OF EARTH’S MAGNETIC FIELD The earth’s magnetic field at a place can be completely described by three parameters which are called elements of earth’s magnetic field. They are declination, dip and horizontal component of earth’s magnetic field.

 Magnetic declination. The angle between the geographical meridian and the magnetic north meridian at a place is called the magnetic declination (α) at that place. Magnetic declination arises because the magnetic axis of the earth does not coincide with its geographical axis. To determine magnetic declination at a place set up a compass needle that is free to rotate in a horizontal plane about a vertical axis. The Angle (α)that this needle makes with the geographic north-south (Ng-Ns) direction is the magnetic declination. By knowing declination, we can determine the vertical plane in which the earth’s magnetic field lies. In India, the value of α is small. It is 041 E for Delhi and 058 W for Mumbai. This means that the N-pole of a compass almost points the direction of geographic north. The declination is greater at higher altitudes and smaller near the equator.  Angle of Dip or magnetic inclination. The angle made by earth’s total magnetic field B with the horizontal direction in the magnetic meridian is called angle of dip () at any place. The angle of dip is different at different places on the surface of the earth. Consider a dip needle, which is just another compass needle but pivoted horizontally so that it is free to rotate in a vertical plane coinciding with the magnetic meridian. It orients itself so that its Npole finally points exactly in the direction of the earth’s total magnetic

field B. The angle between the horizontal and the final direction of the dip needle gives the angle of dip at the given location. At the magnetic equator the dip needle rests horizontally so that the angle of dip is zero at the magnetic equator. The dip needle rests vertically at the magnetic poles so that the angle of dip is 90 at the magnetic poles. At all other places, the dip angle lies between 0 and 90.  Horizontalcomponent of earth’s magnetic field. It is the component of the earth’s total magnetic field B in the horizontal direction in the magnetic meridian. If  is the angle of dip at any place, then the horizontal component of earth’s field B at that place is given by BH = Bcos At the magnetic equator, =0 , At the magnetic poles, =90 ,

BH= Bcos0 = B BH=Bcos90 = 0

Thus the value of BH is different at different places on the surface of the earth.

Relations between elements of earth’s magnetic field. Figure____shows the three elements of earth’s magnetic field. If  is the angle of dip at any place, then the horizontal and vertical components of earth’s magnetic field B at that place will be BH = Bcos and BV=Bsin 𝐵𝑣 𝐵ℎ

=

Or

𝐵𝑠𝑖𝑛𝛿 𝐵𝑐𝑜𝑠𝛿

𝑩𝒗 𝑩𝒉

= tan……… (2)

Also BH2+ BV2 = B2(cos2 + sin2) = B2 Or

B=√𝑩𝒉𝟐 + 𝑩𝒗𝟐 …….(3)

……… (1)

Equation (1), (2) and (3) are the different relations between the elements of earth’s magnetic field. By knowing the three elements, we can determine the magnitude and direction of the earth’s magnetic field at any place.

 Magnetic maps These are the detailed charts which indicate on the world map the lines passing through all such places where one of the three magnetic elements has same value. Three types of lines are drawn on such maps. These are— i. Isogonic lines. The lines joining the places of equal declination are called isogonic lines. The line of zero declination is called agonic line. ii. Isoclinical lines.The lines joining the places of equal dip or inclination are called Isoclinical lines. The line of zero dip is called Aclinic line or magnetic equator. The points of 90 dip are called magnetic poles. The magnetic equator crosses the geographic equator twice once in Atlantic and then in Pacific Ocean. iii.

Isodynamic lines. The lines joining the places having the same value of horizontal component of earth’s magnetic field are called isodynamic lines. The horizontal component is zero at poles and maximum at the magnetic equator.

Global variations in the earth’s magnetic field Earth’s magnetic field changes both in magnitude and direction from place to place. Some of the noticeable global variations are as follows:  The magnitude of the magnetic field on earth’s surface is small, nearly 410-5 T.  Still smaller is the background field of our galaxy, the Milky Way, being about 2pT i.e., 210-12 T.  If we assume that the earth’s field is due to dipole of 8.01022 Am2 located at its centre, then the earth’s magnetic field will be less than

1T(10-6T) at a distance of 5 times the radius of the Earth i.e., at about 32,000 km. Up to this distance, the magnetic field is entirely governed by the Earth.  At distance greater than 32,000 km, the pattern of the earth’s magnetic field gets severely distorted by solar wind.  Solar wind causes ionisation of atmosphere near the magnetic poles of the earth. This in turn causes beautiful displays of colours high up in the sky and is known as Aurora.

Solar wind The solar wind is a steam of hot charged ions, composed of equal numbers of protons and electrons continuously flowing rapidly radially outward from the sun with a speed of approximately 400km/s. A long magneto tail stretches out for several thousand earth diameters in a direction away from the sun. At distances greater than 32,000 km the dipole field pattern of the earth’s magnetic field gets severely distorted by the solar wind.Solar wind is more than 4000 times as strong as the wind speed recorded on Barrow Island. Additionally, it reaches temperatures of around 1 million degrees Celsius, almost 15,000 times the hottest recorded temperature on Earth.The solar wind escapes from coronal holes, which are generally found at the Sun's poles. A coronal hole is an area in the corona that is thinner and less dense than the surrounding areas. It appears as a dark spot on the Sun's surface since it is also a cooler temperature than the surrounding corona

Aurora borealis and aurora Australis This is a spectacular display of light seen in the night sky at high altitudes, occurring most frequently near the earth’s magnetic poles. The displays of aurora appear as giant curtains high up in the atmosphere. The aurora is caused when the charged particles of the solar wind get attracted by the magnetic poles of the earth and there they ionise the atmosphere atoms or molecules. The aurora in the northern hemisphere is called aurora borealis or northern lights and the aurora in southern hemisphere is called as aurora australis or southern lights.Satellites can take pictures of the aurora from Earth's orbit and

the images they get are pretty striking. In fact, auroras are bright enough that they show up strongly on the night side of the Earth even if one were looking at them from another planet.

Temporal variations in the earth’s magnetic field The earth’s magnetic field changes both in magnitude and direction as time passes. These changes ae of two types

Short term changes The geomagnetic field changes on time scales from milliseconds to millions of years. Shorter time scales mostly arise from currents in the ionosphere (ionospheric dynamo region) and magnetosphere, and some changes can be traced to geomagnetic storms or daily variations in currents. Changes over time scales of a year or more mostly reflect changes in the Earth's interior, particularly the iron-rich core. Frequently, the Earth's magnetosphere is hit by solar flares causing geomagnetic storms, provoking displays of aurorae. The short-term instability of the magnetic field is measured with the K-index. Data from THEMIS (Time History of Events and Macroscale Interactions during Substorms) show that the magnetic field, which interacts with the solar wind, is reduced when the magnetic orientation is aligned between Sun and Earth – opposite to the previous hypothesis. During forthcoming solar storms, this could result in blackouts and disruptions in artificial satellites.

Long term changes Changes in Earth's magnetic field on a time scale of a year or more are referred to as secular variation. Over hundreds of years, magnetic declination is observed to vary over tens of degrees. The direction and intensity of the dipole change over time. Over the last two centuries the dipole strength has been decreasing at a rate of about 6.3% per century. At this rate of decrease, the field would be negligible in about 1600 years. However, this strength is about average for the last 7 thousand years, and the current rate of change is not unusual. A

prominent feature in the non-dipolar part of the secular variation is a westward drift at a rate of about 0.2 degrees per year. This drift is not the same everywhere and has varied over time. The globally averaged drift has been westward since about 1400 AD but eastward between about 1000 AD and 1400 AD. Changes that predate magnetic observatories are recorded in archaeological and geological materials. Such changes are referred to as paleomagnetic secular variation or paleosecular variation (PSV). The records typically include long periods of small change with occasional large changes reflecting geomagnetic excursions and reversals.

MAGNETIC FIELD REVERSALS The Earth has a magnetic field, as can be seen by using a magnetic compass. It is mainly generated in the very hot molten core of the planet and has probably existed throughout most of the Earth's lifetime. The magnetic field is largely that of a dipole, by which we mean that it has one North Pole and one South Pole. At these places, a compass needle will point straight down, or up, respectively. It is often described as being similar in nature to the field of a bar (e.g. fridge) magnet. However there is much small-scale variation in the Earth's field, which is quite different from that of a bar magnet. In any event, we can say that there are currently two poles observed on the surface of the Earth, one in the Northern hemisphere and one in the Southern hemisphere. By magnetic reversal, or 'flip', we mean the process by which the North Pole is transformed into a South Pole and the South Pole becomes a North Pole. Interestingly, the magnetic field may sometimes only undergo an 'excursion', rather than a reversal. Here, it suffers a large decrease in its overall strength, that is, the force that moves the compass needle. During an excursion the field does not reverse, but later regenerates itself with the same polarity, that is, North remains North and South remains South.

 How often do reversals occur?

As a matter of geological record, the Earth's magnetic field has undergone numerous reversals of polarity. We can see this in the magnetic patterns found in volcanic rocks, especially those recovered from the ocean floors. In the last 10 million years, there have been, on Average, 4 or 5 reversals per million years. At other times in Earth's History, for example during the Cretaceous era, there have been much longer periods when no reversals occurred. Reversals are not predictable and are certainly not periodic in nature.Reversals occur nearly randomly in time, with intervals between reversals ranging from less than 0.1 million years to as much as 50 million years. The most recent geomagnetic reversal, called the Brunhes–Matuyama reversal, occurred about 780,000 years ago. A related phenomenon, a geomagnetic excursion, amounts to an incomplete reversal, with no change in polarity. The Laschamp event is an example of an excursion, it having occurred during the last ice age (41,000 years ago). Hence we can only speak about the average reversal interval.

 Present situation of earth’s magnetic field At present, the overall geomagnetic field is becoming weaker; the present strong deterioration corresponds to a 10–15% decline over the last 150 years and has accelerated in the past several years; Geomagnetic intensity has declined almost continuously from a maximum 35% above the modern value achieved approximately 2,000 years ago. The rate of decrease and the current strength are within the normal range of variation, as shown by the record of past magnetic fields recorded in rocks. The nature of Earth's magnetic field is one of heteroscedastic fluctuation. An instantaneous measurement of it, or several measurements of it across the span of decades or centuries, is not sufficient to extrapolate an overall trend in the field strength. It has gone up and down in the past for unknown reasons. Also, noting the local intensity of the dipole field (or its fluctuation) is insufficient to characterize Earth's magnetic field as a whole, as it is not strictly a

dipole field. The dipole component of Earth's field can diminish even while the total magnetic field remains the same or increases. The Earth's magnetic north pole is drifting from northern Canada towards Siberia with a presently accelerating rate—10 kilometers (6.2 mi) per year at the beginning of the 20th century, up to 40 kilometers (25 mi) per year in 2003, and since then has only accelerated.

NEUTRAL POINT It is the point where the magnetic field due to a magnet is equal and opposite to the horizontal component of earth’s magnetic field. The resultant magnetic field at the neutral point is zero. If a compass needle is placed at such a point, it can stay in any position.  Case 1 — magnet placed in the magnetic meridian with its north pole pointing north Figure __ shows the magnetic lines of force of a bar magnet placed in the magnetic meridian with its north-pole pointing towards the geographic north of the earth. The fields due to the magnet and the Earth are in same directions at points on the axial line and are in same directions at points on the equatorial line. So the resultant field is stronger at axial points and weaker at equatorial points. The two neutral points P and Q lie on the equatorial line.

Let r = distance of each neutral point from the centre of the magnet. 2l = length of the magnet m = dipole moment of the magnet North Then magnetic field strength at each neutral point is Bequa =

𝝁 𝟒𝝅



𝒎 𝟑

(𝒓𝟐 +𝒍𝟐 )𝟐

For a short magnet, l << r, therefore, Bequa =

𝝁



𝒎

𝟒𝝅 𝒓𝟑

At the neutral point, the field of the magnet is balanced by the horizontal component BH of the earth’s magnetic field so that BH =

𝝁



𝒎

𝟒𝝅 𝒓𝟑

Knowing r and BH, the value of the magnetic dipole moment ‘m’ can be determined.  Case 2 — magnet placed in the magnetic meridian with its southpole pointing north Figure __ shows the magnetic lines of force of a bar magnet placed in the magnetic meridian with its south-pole pointing towards the geographic north of the earth. Here the fields due to the magnet and the earth are in the same direction at points on the equatorial line and are in opposite directions at points on the axial line of the magnet. So the resultant field is weaker at axial points and is stronger at equatorial points. In this case the two neutral points P and Q lie on the axial line near the ends of the magnet. Suppose ‘r’ be the distance of each neutral point from the centre of the magnet. Let 2l be the length of the magnet. Then magnitude of the magnetic field at either of the neutral points will be Baxial =

𝝁

𝟐𝒎𝒓



𝟒𝝅 (𝒓𝟐 −𝒍𝟐 )𝟐

For a short magnet, l << r, therefore, Baxial =

𝝁

𝟐𝒎



𝟒𝝅 𝒓𝟑

Again, at the neutral point, the field of the magnetic is balanced by the horizontal component BH of the earth’s magnetic field, so we have BH =

𝝁

𝟐𝒎



𝟒𝝅 𝒓𝟑

Knowing the values of ‘r’ and BH, the magnetic dipole moment ‘m’ of the magnet can be determined.



WHAT NASA THINKS ABOUT MAGNETIC POLE REVERSAL For a period of time there will be no magnetic field around the earth. As we know that oncein a million years or so, the currents in earth’s core cool down, come to a halt and then pick up speed in the opposite direction.

What will happen to earth? Will it get destroyed? Will that be the doomsday? Would there be any dramatic effects? And many such questions are there between us

NASA (National Aeronautics and Space Administration) says Scientists understand that Earth's magnetic field has flipped its polarity many times over the millennia. In other words, if you were alive about 800,000 years ago, and facing what we call north with a magnetic compass in your hand, the needle would point to 'south.' This is because a magnetic compass is calibrated based on Earth's poles. The N-S markings of a compass would be 180 degrees wrong if the polarity of today's magnetic field were reversed. Many doomsday theorists have tried to take this natural geological occurrence and suggest it could lead to Earth's destruction. But would there be any dramatic effects?The answer, from the geologic and fossil records we have from hundreds of past magnetic polarity reversals, seems to be 'no.' Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal. A reversal happens over hundreds or thousands of years, and it is not exactly a clean back flip. Magnetic fields morph and push and pull at one another, with multiple poles emerging at odd latitudes throughout the process. Scientists estimate reversals have happened at least hundreds of times over the past three billion years. And while reversals have happened more frequently in "recent" years,

when dinosaurs walked Earth a reversal was more likely to happen only about every one million years. Sediment cores taken from deep ocean floors can tell scientists about magnetic polarity shifts, providing a direct link between magnetic field activity and the fossil record. The Earth's magnetic field determines the magnetization of lava as it is laid down on the ocean floor on either side of the Mid-Atlantic Rift where the North American and European continental plates are spreading apart. As the lava solidifies, it creates a record of the orientation of past magnetic fields much like a tape recorder records sound. The last time that Earth's poles flipped in a major reversal was about 780,000 years ago, in what scientists call the Brunhes-Matuyama reversal. The fossil record shows no drastic changes in plant or animal life. Deep ocean sediment cores from this period also indicate no changes in glacial activity, based on the amount of oxygen isotopes in the cores. This is also proof that a polarity reversal would not affect the rotation axis of Earth, as the planet's rotation axis tilt has a significant effect on climate and glaciation and any change would be evident in the glacial record. Another doomsday hypothesis about a geomagnetic flip plays up fears about incoming solar activity. This suggestion mistakenly assumes that a pole reversal would momentarily leave Earth without the magnetic field that protects us from solar flares and coronal mass ejections from the sun. But, while Earth's magnetic field can indeed weaken and strengthen over time, there is no indication that it has ever disappeared completely. A weaker field would certainly lead to a small increase in solar radiation on Earth – as well as a beautiful display of aurora at lower latitudes - but nothingdeadly. Moreover, even with a weakened magnetic field, Earth's thick atmosphere also offers protection against the sun's incoming particles. The science shows that magnetic pole reversal is – in terms of geologic time scales – a common occurrence that happens gradually over millennia. While the conditions that cause polarity reversals are not entirely predictable – the North Pole’s movement could subtly change direction, for instance – there is nothing in the millions of years of geologic record to suggest that any of the doomsday scenarios

connected to a pole reversal should be taken seriously. A reversal might, however, be good business for magnetic compass manufacturers.

NASA approves that there are hidden portals in Earth's Magnetic field A favorite theme of science fiction is "the portal"--an extraordinary opening in space or time that connects travelers to distant realms. A good portal is a shortcut, a guide, a door into the unknown. If only they actually existed.... It turns out that they do, sort of, and a NASA-funded researcher at the University of Iowa has figured out how to find them. "We call them X-points or electron diffusion regions," explains plasma physicist Jack Scudder of the University of Iowa. "They're places where the magnetic field of Earth connects to the magnetic field of the Sun, creating an uninterrupted path leading from our own planet to the sun's atmosphere 93 million miles away." Observations by NASA's THEMIS spacecraft and Europe's Cluster probes suggest that these magnetic portals open and close dozens of times each day. They're typically located a few tens of thousands of kilometers from Earth where the geomagnetic field meets the onrushing solar wind. Most portals are small and short-lived; others are yawning, vast, and sustained. Tons of energetic particles can flow through the openings, heating Earth's upper atmosphere, sparking geomagnetic storms, and igniting bright polar auroras. NASA is planning a mission called "MMS," short for Magnetospheric Multiscale Mission, to study the phenomenon. Bristling with energetic particle detectors and magnetic sensors, the four spacecraft of MMS will spread out in Earth's magnetosphere and surround the portals to observe how they work.

Just one problem: Finding them. Magnetic portals are invisible, unstable, and elusive. They open and close without warning "and there are no signposts to guide us in," notes Scudder. Actually, there are signposts, and Scudder has found them. Portals form via the process of magnetic reconnection. Mingling lines of magnetic force from the sun and Earth criss-cross and join to create the openings. "X-points" are where the criss-cross takes place. The sudden joining of magnetic fields can propel jets of charged particles from the X-point, creating an "electron diffusion region." To learn how to pinpoint these events, Scudder looked at data from a space probe that orbited Earth more than 10 years ago. "In the late 1990s, NASA's Polar spacecraft spent years in Earth's magnetosphere," explains Scudder, "and it encountered many X-points during its mission." Because Polar carried sensors similar to those of MMS, Scudder decided to see how an X-point looked to Polar. "Using Polar data, we have found five simple combinations of magnetic field and energetic particle measurements that tell us when we've come across an X-point or an electron diffusion region. A single spacecraft, properly instrumented, can make these measurements." This means that single member of the MMS constellation using the diagnostics can find a portal and alert other members of the constellation. Mission planners long thought that MMS might have to spend a year or so learning to find portals before it could study them. Scudder's work short cuts the process, allowing MMS to get to work without delay. It's a shortcut worthy of the best portals of fiction, only this time the portals are real. And with the new "signposts" we know how to find them.

Mission to the core.A try to travel to the center of the Earth

Going down has always proven rather difficult.and there are huge scientific and commercial gains to be made if we could go deeper — but, try as we might, despite millennia of developing ever more advanced tools and materials, and exploration that has taken spacecraft to the edge of the Solar System, the subterranean depths still remain firmly off-limits. We are not able to reach out to the core. The Kola Superdeep Borehole, drilling had to cease when a crust temperature of 180 Celsius (356F) was recorded at a depth of 12,262 meters (7.62 miles). The engineers think they could’ve drilled a bit farther, but they decided to quit while they were ahead since the drill bit would’ve ceased to function at 15,000 meters and a predicted crust temperature of 300C. It had taken them 19 years — from 1970 to 1989 — to drill to 12,262 meters. The Kola Superdeep Borehole is still the deepest artificial hole on Earth.To scientists, one of the more fascinating findings to emerge from this well is that no transition from granite to basalt was found at the depth of about 7 km (4.3 mi), where the velocity of seismic waves has a discontinuity. Instead the change in the seismic wave velocity is caused by a metamorphic transition in the granite rock. In addition, the rock at that depth had been thoroughly fractured and was saturated with water, which was surprising. This water, unlike surface water, must have come from deep-crust minerals and had been unable to reach the surface because of a layer of impermeable rock. Microscopic plankton fossils were found 6 kilometers (4 mi) below the surface. Another unexpected discovery was a large quantity of hydrogen gas. The mud that flowed out of the hole was described as "boiling" with hydrogen. The project ended in 1995 due to the dissolution of the Soviet Union. The site has since been abandoned, and is now an environmental hazard. The ruins of the site, however, are frequently visited by curious sightseers.

Conclusion The Earth’s magnetic field is the magnetic field that surrounds the Earth. It is sometimes called the geomagnetic field.The Earth’s magnetic field is created by the rotation of the Earth and Earth's core. It shields the Earth against harmful particles in space. The field is unstable and has changed often in the history of the Earth. As the Earth spins the two parts of the core move at different speeds and this is thought to generate the magnetic field around the Earth as though it had a large bar magnet inside it.The magnetic field creates magnetic

poles that are near the geographical poles. A compass uses the geomagnetic field to find directions. Many migratory animals also use the field when they travel long distances each spring and fall. The magnetic poles will trade places during a magnetic reversal.The intensity of the magnetic field is greatest near the magnetic poles where it is vertical. The intensity of the field is weakest near the equator where it is horizontal. The magnetic field’s intensity is measured in gauss. There is no danger to human life if magnetic reversal happened.

Bibliography      

Physics NCERT textbook for class 12 Simplified physics book by S.L Arora Wikipedia Byju’s learning app Examfear www.Nasa.gov (NASA)

 www.quora.com (Quora)

‘Theoretical physics is actual philosophy ’— Max Born