That field range implies that the local magnetic pressure inside the structures is generally larger than the local gas pressure. Wu, eds., Nature of Prominences and Their Role in Space Weather, Cambridge U. By comparison, the magnetic fields in filaments and prominences are typically in the range of 5–30 G (see B. The average magnetic field on Earth’s surface is 0.5 gauss (10 000 G = 1 tesla). The interrelated handedness or chirality of filaments, channels, and coronal arcades 13 13. Thus the channel field lines and associated filaments are generally flat and run horizontally along the channel direction. Channel fields are nonpotential, which means that some factor-here, the overlying coronal arcade-prevents the field lines from taking on the familiar arc shape. Magnetic fields provide support against gravity and thermal shielding from the surrounding hot coronal plasma. The magnetic environments of solar filaments and prominences influence their birth, existence, and disappearance. Only a fraction of the total length contains observable filaments.

Magnetic data of the solar disk show that PILs and the associated channels circle over long stretches of the solar surface, much like seams on tennis balls. In a nonideal plasma with finite electrical resistance, ion acoustic waves-sound waves that interact with the electromagnetic fields present-and other types of waves are possible. Because they combine longitudinal compression of the plasma and the transverse displacement of the lines of force, they propagate at an angle to the field lines. Magnetosonic waves are hybrids of sound waves and Alfvén waves. Alfvén waves travel at a speed that increases as the local plasma density decreases and as the magnetic field strength increases. The surrounding plasma wiggles along with field lines but it is not compressed as happens with sound waves. Alfvén waves are periodic transverse displacements of the lines of force. They are just sound waves, albeit in a gas of charged particles.

Longitudinal plasma-density waves propagate at the local speed of sound in the direction of the field. Three types of waves are possible in an ideal plasma that has zero electrical resistance.

When shaken by external forces, a bundle of magnetic field lines and the plasma filling them can develop traveling waves.

Properties of sun corona