Earth's magnetic field

 Earth's magnetic field

 , Geographic magnetism, terrestrial magnetism

  

 

  Geographical field, the magnetic field attached to the earth.  It is basically bipolar at the surface of the earth (that is, it has two poles, the geographic north and south).  Dupole distorts off the surface.

  The magnetic field of a bar magnet

 

   Polar polar orbital magnetic storm electro jet chapman ferro current system

 

  Understand the geographical area of ​​the earth through the principle of dynamo effect.

  The currents in the center of the earth create a magnetic field according to a principle called the dynamo effect.

 

  In the 1830's, the German mathematician and astronomer Carl Friedrich Gass studied the Earth's magnetic field and concluded that the principal Doppler component is inside the Earth rather than outside.  It showed that the doppler component was a decreasing function inversely proportional to the square of the Earth's radius, a result that led scientists to speculate on the origin of the Earth's magnetic field in terms of ferromagnetism (such as a huge bar).  In the magnet), different rotation theories, and different dynamo theories.  Theories of ferromagnetism and rotation are generally discredited - ferromagnetism because the curry point (the temperature at which ferromagnetism is destroyed) reaches only 20 kilometers or more (approximately 12 miles) below the surface.  There is, and is, a theory of rotation because there seems to be no fundamental relationship between mass.  Movement and its associated magnetic field.  Most geomagnetists find themselves dealing with various dynamo theories, according to which a source of energy in the center of the earth causes a self-sustaining magnetic field.

  Earth's stable magnetic field is created by sources both above and below the surface of the planet.  Outside the cover, these include geomagnetic dynamos, crystal magnetization, ion spherical dynamos, ring currents, magnetopaz currents, tail currents, field-connected currents, and orbital or connective electro jets.  Geomagnetic dynamo is the most important resource because, without this field, there would be no other resource.  The effect of other sources, not more than the surface of the earth, is just as strong or stronger than that of a geomagnetic dynamo.  In the ensuing discussion, each of these sources is considered and the reasons given are explained.

  Earth's magnetic field is subject to change at all times.  Each of the major sources of the so-called stable field undergoes changes that cause temporary variations, or disruptions.  There are two major obstacles in the main field: cosperiodic reversals and secular transformation.  The ionospheric dynamo is concerned with seasonal and solar cycle changes, as well as solar and lunar marine effects.  The current of the ring responds to the solar wind (the ionized atmosphere of the sun which spreads outwards in space and carries with it the solar magnetic field), the strength increases when the proper conditions of the solar wind are present.  There is another phenomenon associated with the development of ring current, the magnetospheric substorm, which is most clearly seen in the aurora borealis.  A very different type of magnetic variation is caused by magnetic hydrodynamic (MHD) waves.  These waves are sinusoidal changes in the electrical and magnetic fields that are associated with changes in particle density.  These are the means by which information about changes in electromagnetism is transmitted, both inside the earth and in the atmosphere around charged particles.  Each of these sources of change is also discussed separately below.

  The position of the Earth's geographic North Pole

  A map of the Earth's Arctic region marks the known geographical locations and times of the North Pole since 1900.

  Encyclopædia Britannica, Inc./Kenny Chmielewski

  Observation of the Earth's magnetic field

  Field representation

  The electric and magnetic fields are created by the electric charge, a basic property of matter.  Electric fields are created by charges more comfortable than an observer, while magnetic fields are created by moving charges.  The two fields are different aspects of the electromagnetic field, this is the force that causes the electric charges to interact with each other.  The electric field, E, is defined as the force per unit charge at any point around the distribution of charge when a positive test charge is placed at that point.  For point charges, the electric field refers to a positive charge radically far and a negative charge.

  A magnetic field is created by moving charges.  Magnetic induction, B, can be defined as E. The force per unit is proportional to the strength of the pole when the test magnetic pole is brought close to the source of the magnet.  However, it is more common to define it with the Lorentz-force equation.  This equation states that the force felt by a charge q, moving with velocity v, is given by it.

  F = q (vxB).

  In this equation, bold letters indicate vectors (quantities that have both intensity and direction) and non-bold letters indicate scalar quantities such as B, length of vector B.  x represents a cross product (ie, a vector at right angles to both v and B, along the length vB ​​sin θ).  Theta vectors is the angle between v and b.  (B is commonly referred to as a magnetic field despite the fact that the name H is specific to quantities, which is also used in the study of magnetic fields.) For a simple line current, the field is cylindrical around the current.  The sense of field depends on the direction of current, which is defined as the direction of movement of positive charges.  The principle of the right hand defines the direction of B by stating that when the thumb points in the direction of the current, it points in the direction of the fingers of the right hand.

  In the International System of Units (SI), the electric field is measured in terms of potential conversion rate, volts per meter (V / m).  Magnetic fields are measured in Tesla (T) units.  Tesla is a large unit for geophysical observations, and a smaller unit, nanotesla (nT; one nanotesla equals 10−9 Tesla), is commonly used.  A nanotisella is the equivalent of a gamma, a unit originally defined as 10−5 gas, which is a unit of magnetic field in a centimeter second system.  Both Goss and Gamma are still widely used in the literature on geo-magnetism, although they are no longer standard units.

  Both the electric and magnetic fields are represented by vectors, which can be represented in different coordinate systems, such as Cartesian, polar, and spherical.  In the Cartesian system the vector is divided into three components which are approximated by the vector on three mutual orthogonal axes which are usually labeled x, y, z.  The vector at polar points is usually expressed by the length of the vector in the x-y plane, its angle of inclination in the plane relative to the x-axis, and the third Cartesian z component.  In spherical points, the field is defined as the total field vector length, the polar angle of the vector from the z axis, and the azimuth angle of the projection of the vector in the x-y plane.  All three systems are widely used in the study of the Earth's magnetic field.

  The names used in the study of geomagnetism for the various components of the vector field are summarized as follows.  B is the vector magnetic field, and F is the intensity or length of B.  X, Y, and Z are the three Cartesian components of the field, usually measured with reference to the geographical coordinate system.  X is to the north, Y is to the east, and, completing the right-hand system, Z is to the center of the earth vertically.  The magnitude of the field presented in the horizontal plane is called H.  This projection forms an angle D (for fall) from north to east.  Dip angle, I (for tilt) is the angle formed by the total field vector with respect to the horizontal plane and is positive for the vector below the plane.  This completes the normal polar angle of spherical points.  (Geographic and magnetic north meet the "Egonic Line".)

  Components of magnetic induction vectors

  The components of the magnetic induction vector, B, are shown in three integrated systems: Cartesian, Polar, and Spherical.

  Encyclopedia Britannica, Inc.

  Field measurement

  Magnetic fields can be measured in different ways.  The simplest measurement technique still used today involves the use of a compass, a device consisting of a permanent magnetic needle that is balanced to the axis in a horizontal plane.  In the presence of a magnetic field and in the absence of gravity, a magnetic needle aligns itself perfectly with the magnetic field vector.  When it is balanced on the axis in the presence of gravity, it attaches to a component of the field.  In the traditional compass, it is a horizontal component.  A magnetic needle can also be axial and balanced on a horizontal axis.  If this instrument, called a deep meter, is first pointed in the direction of a magnetic meridian by a compass, then the needle lines up with the total field vector and measures the angle of inclination I.  Finally, it is possible to measure the intensity.  Horizontal field through the doubles of the compass needle.  It can be shown that the duration of such oscillation depends on the characteristics of the needle and the strength of the field.

  Magnetic observatories constantly measure and record the Earth's magnetic field at various locations.  In such an observatory, magnetic needles are suspended by quartz fibers with a reflecting mirror.  Photographs mounted on the drum are photographed negatively as the rays of light reflected from the mirror rotate.  Variations in the field cause a relative deviation from the negative.  Typical scale factors for such observatories are 2–10 nanotypes per millimeter vertically and 20 millimeters per hour horizontally.  The printed negative print is called a magnetogram.

  Magnetic observatories have recorded data in this way for over 100 years.  Their magnetograms are photographed on microfilm and submitted to global data centers, where they are available for scientific or practical use.  Such applications include the creation of magnetic maps of the world for navigation and surveys.  Correction of data obtained from air, land and sea surveys for mineral and oil reserves;  And the scientific study of the sun's interaction with the earth.

  Other methods of measuring magnetic fields have become more convenient in recent years, and older instruments are slowly being replaced.  One such method involves a proton-precision magnetometer, which utilizes the magnetic and gyroscopic properties of protons in liquids such as gasoline.  In this method, the magnetic moment of the proton is first connected to a strong magnetic field produced by the outer coil.  Then the magnetic field suddenly stops, and the protons try to align themselves with the earth's field.  However, since protons are magnetic as well as rotating, they move with a frequency around the Earth's field, depending on the intensity of the latter.  The outer coil senses the weak voltage generated by this gear.  The duration of gyration is determined electronically with sufficient accuracy to produce sensitivity between 0.1 and 1.0 nanotesla.

  One device that complements the proton-precision magnetometer is the Flexgate magnetometer.  Unlike a proton-precision magnetometer, the FluxGate device measures the three components of a field vector rather than its amplitude.  It has three sensors, each connected to one of the three components of a field vector.  Each sensor is made of a high permeability material (e.g., mu-metal) wound from a transformer wound around the core.  The main winding of the transformer is excited with a high frequency (approximately 5 kHz) sine wave.  In the absence of any field along the axis of the transformer, the output signal in the secondary winding consists of only odd harmonics (component frequencies) of the drive frequency.  If, however, a field exists, it biases the hysteresis loop in one direction to the core.  As a result, one half of the drive cycle covers more quickly than the other.  As a result, the secondary voltage incorporates all the coordinates as well as the oddity.  The amplitude and phase of the avon harmonics are linearly proportional to the field component along the axis of the transformer.

  Most modern magnetic observatories have both proton-precision magnetometers and flux gate magnetometers mounted on granite columns in non-magnetic, temperature-controlled rooms.  The output from the devices is electrical signals, and they are digitized and recorded on magnetic media.  Many observatories also transfer their data to central facilities immediately after acquisition, where they are stored in a large computer database with data from other locations.

  Magnetic measurements are often made at locations far from designated observatories.  Such measurements are usually part of a survey designed to better describe the Earth's central field or to detect anomalies in it.  Such surveys are usually carried out on foot, by plane, by air and by space.  The proton-precision magnetometer is almost always used for surveys near the surface of the earth because it does not need to be attached.  The central field above ground level is rapidly declining, and the need for precise alignment is less acute.  Thus, flex gate magnetometers are typically mounted on a spacecraft.  Knowledge of the location and direction of a spacecraft is required to calculate the components of a vector field in a ground coordinate system.

  Characteristics of Earth's Magnetic Field

  The magnetic field observed on the surface of the earth is like a magnet attached to the planet's rotating axis.  Statistics show such a field for a bar magnet located in the center of a sphere.  If the Earth is taken along the North Geographic Pole at the top of the diagram, then the direction of the magnet along its North Magnetic Pole should be downwards towards the South Geographic Pole.  Then, as shown in the diagram, the lines of the magnetic field leave the north pole of the magnet and rotate until they cross the Earth's equator, pointing north geographically.  ۔  They orbit the earth further in the northern latitudes, eventually returning to the south pole of the magnet.  At present, the North Pole equals the bar equal to the South Pole of the magnet.  This has not always been the case.  Many times in the history of the earth the direction of the equivalent magnet has been pointed in the opposite direction