Glossary term: Magnetic Field

Description: Electric currents produce a surrounding zone of influence called a magnetic field. In turn, electrically charged particles moving through a magnetic field will experience a force unless they are travelling parallel to the field.

In astronomy, there are many situations where matter is ionized, its atoms split into charged particles (for hydrogen, protons, and electrons). The resulting plasma can produce, and interact with, magnetic fields.

In the interior of stars, moving plasma streams create a magnetic field through what is known as the dynamo effect. Near the star's surface, that magnetic field can lead to stellar activity, such as star spots or flares. A star's magnetic field can cause spots or flares at the stellar surface, and streams of charged particles known as stellar winds flow outward from the star along magnetic field lines. In the case of the Sun, some of the charged particles that constitute the solar wind reach Earth, where they are deflected by Earth's magnetic field towards Earth's North and South Poles. Where these particles make Earth's atmosphere glow, they produce the aurorae.

There are a variety of additional astrophysical situations where magnetic fields play important roles, from the ultra-strong magnetic fields of neutron stars or in the vicinity of black holes, to interstellar magnetic fields that influence the large-scale motion of gas and plasma in a galaxy.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".