BASE GEOPHYSICS

Magnetometers are devices which consist of sensors that measure Magnetic field intensity and direction. There are different types of these devices for such purpose, However when it comes to magnetic data acquisition in geophysics they can be categorized into two groups depending on type of the field (direction) measured, which are Vertical field  such as Fluxgates and Total field such as Proton Precessing and Alkali vapor magnetometers. Here down I have written to you  this post about the basics of these devices, so that you can understand their operation principles.  Flux - Gate Magnetometer It applies Electromagnetic induction concepts.  In the Fluxgate method a high susceptibility alloy rod (fluxgate) is used which responds parabolically to an applied magnetic field strength. The fluxgate is excited with a sinusoidally varying magnetic field using a coil around it. The resultant field within the fluxgate becomes H = H 0 + psinωt A secondary coil is used to measur...

Don't you know that  there are some rocks that have magnetic properties? This may be related either to the fact that rocks contain some magnetic minerals such as Iron Oxides or rock forming minerals such as olivine, pyroxene, which may be magnetized by external fields and result to overall rock magnetism. That's why I have tried to write to you this post, so that you can get an idea on how rock magnetism is induced. Okay ! Without waste the time let's look how this is related as described below. Around a bar, magnetic flux exists indicated by the lines of forces converges at ends. Magnetic poles always exists in pairs of opposite polarity hence DIPOLE .                         Figure: A Bar with lines of magnetic flux. Force between two magnetic poles F = Mm/4πUr 2 Where, U is the magnetic permiability of the medium separating the poles. Magnetic Flux density, B: ...

Have you realized that, on some  days in the night sky near the poles, it looks like shining  or even mixed brighten lights?  Yes! Those bright lights are called Aurora. They are due to interaction of external magnetic fields with very fast and energetic radiation from the sun. This gives us an idea that there are some magnetic fields far out there around Earth that cause all these to happen! Here down I have tried to explain in brief to you about these external magnetic fields, Just keep reading. Magnetic field of External origin is strongly affected by solar wind. Solar wind is a stream of electrically charged particles (consisting mainly of e-, P & He) that is constantly emitted by the sun. Solar wind is a plasma considered as conducting fluid. Plasma : Is a physical term for ionized gas of low particle density with equal +ve and -ve charges. Interaction of charged particles can be expressed from F = BeV where F - Lorentz force Also  Fc = mv 2 /r Then,  m...