Magnetic Field of Earth
Category: Earth Science
Planet earth has a magnetic field that extends from the earths inner core to where it meats the solar winds.
The solar wind is released from the upper atmosphere. It is a charged particles, also known as plasma, which varies in speed, density and temperature over time and longitude. The charged particles or plasma have energies usually consisting between 1.5-10 KeV.. The magnetic fields ranges from 25-65 tesla units in magnitude. The only time the solar wind is observable on the earth is when it is strong enough to produce phenomena such as the aurora. Auroras heat the ionosphere, causing its plasma to expand into the magnetosphere, increasing the size of the plasma geosphere, and causing escape of atmospheric matter into the solar wind. The overall shape of the earths magnetosphere has the solar wind to thank, fluctuations in its speed, density, and entrained magnetic field strangle effects space local environment.
The magnetic field of earth largely deflects most of the charged particles emanating from the sun. If these particles are are not protected then they would strip away at the ozone layer, which is how we are protected from harmful ultraviolet rays.
Above the ionosphere is the magnetosphere, this extends several tens of thousands of kilometers into space. This region protects the earth from cosmic rays. If it wasn't for the magnetosphere the upper atmosphere of earth would be striped away along with the ozone layer which protects the earth from the ultraviolet rays. Some of the charged particles from the solar wind are trapped in the Van Allen radiation belt. A smaller number of particles from the solar wind manage to travel, as though on an electromagnetic energy transmission line, to the Earth's upper atmosphere and ionosphere in the auroral zones
The magnetic field is generated by the motion of molten iron alloys in the earths outer core which leads it to change over time. The scientific term (nomenclature) for the earth's outer core is geodynamo. Geodynamo comes form a theory in geophysics called dynamo theory which proposes a mechanism by which a celestial body like earth or a star generates a magnetic field. Dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. Induction or creation of magnetic field is described by the induction equation:
where u is velocity, B is magnetic field, t is time, and is the magnetic diffusivity with electrical conductivity and permeability. The ratio of the second term on the right hand side to the first term gives the magnetic Reynolds number, a dimensionless ratio of advection of magnetic field to diffusion. the magnetic field that is generated also aligned with the earths access of rotation.
The magnetic north pole is constantly changing and moving slowly . 100 years ago the magnetic north pole was located in northern Canada almost 2000 KM south of the geographic north pole. The magnetic north pole is constantly changing and is now located 450 km south of the geographic north pole. The magnetic south pole is interestingly enough not on the exact opposite side of the world as the magnetic north but currently sits 20* closer to the equator then the northern.
The geographic north pole is the north pole that is at the direct top of the world with the geographic south which sits at the exact bottom. geographic north and south unlike the magnetic north which is determined by the earths molten iron outer core's motion and movement. The reason it is called the geographical is because it is geographically at the exact top and does not move.
The geo magnetic north and south is like a bipolar bar magnet, if you could imagine, having two ends although they are exactly across from each other like the geographic north/south they do not sit at the exact top and bottom of the earth rather their positions are dependent on the general overall flow of earths magnetic field. It is currently located in Canada. This does not help a compass to work but id does heavily influence the paths of solar wind particles that causes the aura, also known as the northern lights.
To sum it all up: the earth spins like a top around the geographic north pole, compasses point to the magnetic north pole which is a magnetic south at the same time, the northern lights are strongest around the geo magnetic north pole. All three poles move. The magnetic and geo magnetic poles change rapidly while the geographic north pole changes 10 meters a year as the earth wobbles on its axis due to seasonal air pressure differences across the globe.
The intensity of the magnetic field is greatest near the poles and is weakest near the equator, this is usually measured in G-gauss, but is generally reported in nT-nanotesla, with 1G = 100,000 nT. nT also refers to Y-gamma. The field rest between 25,000 - 65,000 nT or 0.25 - 0.65 G.