A cylindrical structure in a magnetic field whose sides are parallel to the local magnetic field lines along its whole length. In tenuous plasmas, such as the solar corona, plasma in a flux tube is confined within that tube, causing coronal loops. Electrical currents flow easily along magnetic flux tubes, such as along the flux tubes that link Jupiter to its moon Io and also along the geomagnetic flux tubes that link the Earth’s magnetosphere to the ionosphere, causing aurorae. These currents flowing along flux tubes generate radio waves with wavelengths of tens of meters at Jupiter and about a kilometre at Earth. A current flowing along a flux tube also twists the field lines to form a flux rope; this twist provides great stability to the structure. Examples of flux ropes are coronal mass ejections.
Subjects: Astronomy and Astrophysics.