Magnetic dipole

Introduction
A dipole is an idealized system that is used for an approximate description of a field created by more complex systems of charges. There are three main types of dipoles, which are electric, magnetic and current dipoles. Magnetic dipole is an analogue of an electric dipole which can be represented as a system of two «magnetic charges». In fact, this analogy is debatable, as from the perspective of modern electrodynamics, magnetic charges (or magnetic monopoles) do not exist. Nonetheless, a basic magnetic dipole can be refferred to as a tiny magnet composed of adjacent positive and negative charges. Considering that a closed circuit is believed to be the original source of magnetism, a typical example of a magnetic dipole would be a wire loop with constant current passing through it.

Definition
Magnetic dipole moment, or simply magnetic moment is the main value that is used to characterize magnetic properties of some matter. The best way to define it would be to think of a maximum amount of torque that can be caused by magnetic force on a dipole arising per unit value of surrounding magnetic field in vacuum. According to right-hand rule, the magnetic dipole moment points through the loop. The magnitude is current in the loop times the area of the loop. The unit for measuring magnetic dipole moment is not a base unit in the International System of Units (SI), so it is measured in A*m2or J/T. Elementary particles, atomic nuclei, as well as electric shells of atoms and molecules all have some magnetic moment. In elementary particles, according to quantum mechanics, the dipole moment is caused by their own mechanical moment, which is called spin.

Importance in clinical medicine
Due to the fact that the phenomenon of a magnetic dipole is directly connected with magnets that are commonly used in medicine, the concept of a magnetic dipole is widely present in many medical spheres. One of the most important scientific breakthroughs in the field of medical use of magnets that changed the course of hisory was the invention of nuclear magnetic resonance spectroscopy (NMR-spectroscopy). Understanding of a basic dipole-dipole principle, when two nuclei that have a magnetic moment can interact with each other even being separated by some space, as well as an ability to calculate the vector of this dipole-dipole interaction, resulted in an appearance of a brand-new way of structural medical examination of compounds in the late 1940s'. With the development of NMR-spectroscopy over the years, it became one of the dominant ways of determining structure of proteins, as well as studying dynamics of biomolecules, and even creation of biologically active substances, which emphasizes it's importance in the sphere of medical pharmacology.

Tn addition, the study of NMR tomography is widely used in magnetic resonance imaging (MRI), as an essential part of it is analyzing the NMR of protons and nuclei of hydrogen, which are present in almost every tissue in a human body. MRI tomography allows for qualitative and non-invasive visualization of brain, spinal cord and other internal organs.

The power of magnetic dipole interaction is alsoappliedlso used in altermative medicine, for instance, in magnotherapy. Some practitioners state that body tissues, when being exposed to a magnetic field with a steady current (magnetostatic field), are capable of changing physicochemical properties of aqueous systems, as well as changing orientation of big ionized biological molecules (such as enzymes), which leads to acceleration of biochemical and biophysical processes in our body. However, the metholodogy used in magnetic therapy is being strongly critisized by various institutons, including the American National Science Foundation (NSF), which questions rationality and effectiveness of this type of medical practice.