Space physics

Space physics is the study of plasmas as they occur naturally in the Earth's upper atmosphere. As such, it encompasses a far-ranging number of topics, such as heliophysics which includes the solar physics of the sun: the solar wind, planetary magnetospheres and ionospheres, auroras, cosmic rays, and synchrotron radiation. Space physics is a fundamental part of the study of space weather and has important implications not only to understanding the universe, but also to practical everyday life, including the operation of communications and weather satellites. Space physics is distinct from other fields of astrophysics which study similar phenomena, in that space physics utilizes in situ measurements from high altitude rockets and spacecraft.

Space physics can be traced back to the ancient Chinese, who recorded sun spots. The Chinese also discovered the principle of the compass, but did not understand how it worked. During the 16th century, in De Magnete, William Gilbert gave the first description of the Earth's magnetic field, showing that the Earth itself is a great magnet, which explained why a compass needle points north. Deviations of the compass needle magnetic declination were recorded on navigation charts, and a detailed study of the declination near London by watchmaker George Graham resulted in the discovery of irregular magnetic fluctuations that we now call magnetic storms, so named by Alexander Von Humboldt. Gauss and William Weber made very careful measurements of Earth's magnetic field which showed systematic variations and random fluctuations. This suggested that the Earth was not an isolated body, but was influenced by external forces. A relationship between individual aurora and accompanying geomagnetic disturbances was noticed by Anders Celsius and Olof Peter Hiorter in 1747. In 1860, Elias Loomis (1811–1889) showed that the highest incidence of aurora is seen inside an oval of 20 - 25 degrees around the magnetic pole. In 1881, Hermann Fritz published a map of the "isochasms" or lines of constant magnetic field.

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