Aurora Borealis The Physics of Aurora Borealis

The solar wind consists of highly ionized electrons and protons emitted from our sun.[footnoteRef:2] When these charged subatomic particles interact with the Earth's magnetic field, it creates a spectacular light display called the Aurora Borealis in the northern hemisphere and Aurora Australis in the southern hemisphere. These displays of light are best understood using particle physics. The force on a charged particle (F) is equal to the charge (q) times velocity (v) times magnetic field strength (B), according to Lorentz force law, as long as the particle is moving parallel to the magnetic field. If the perpendicular and parallel components of the velocity vector are considered separately, the sine of the angle between the magnetic field strength and parallel component equal zero, therefore, the force acting on a charged particle is equal to q*vperp*B. The path of the particle, if it were visible to the naked eye, would be similar to a slinky toy pulled apart. In other words, the particle will move in the direction of the magnetic field but in a circular pattern due to vperp.[footnoteRef:3] The radius (r) of this circular pattern is equal to (m*vperp)/(q*B), where m is mass. [2: Walter Lewin. "Lecture 19: How do magicians levitate women?" Massachusetts Institute of Technology, Spring 2002, http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/video-lectures/lecture-19-how-do-magicians-levitate-women/,...

] [3: Lewin, Lecture 19, time 22:15.]
When the solar winds reach the Earth's atmosphere the ionized particles become aligned with the magnetic lines of force surrounding the planet.[footnoteRef:4] The magnetic lines of force enter and exit the magnetic poles, which would bring the highly charged electrons and protons closest to the atmosphere near the poles. When these charge particles come into contract with the molecules forming the atmosphere, mainly oxygen and nitrogen, they become electronically excited. A return to the ground state results in the release of energy in the form of photons. The resulting spectacular light shows are mainly the product of oxygen returning to ground state, which appears green or red at lower or higher altitudes, respectively. By comparison, nitrogen returning to ground state will appear pink and red at lower altitudes. [4: R. Nave. "Aurora" Department of Physics and Astronomy, Georgia State University, n.d., http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/aurora.html. ]

The scientific advances required to reach this understanding of the Aurorae occurred at the beginning of the 20th century.[footnoteRef:5] Within the fields of astronomy and physics, significant progress had been made in developing spectrophotometers and spectroscopes capable of studying…