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Instabilities Generated by Thermal Sources

A mechanism that is based on a thermal energy source due to collisional current dissipation in the F-region has been described by Das and Das [DD83] and Lee [Lee84]. The mechanism produces highly field-aligned irregularities (striations) in the absence of steep gradients. Large electric fields of 25-50 mV/m that are perpendicular to the magnetic field are required however, so these irregularities should occur primarily in the auroral zone where large electric fields are common even during quiet conditions. The inherent motion of the irregularities is zero, but there exists a drift velocity due to the electric field. Since the irregularities are almost field-aligned, they can move with this drift velocity. Wavelengths of the order of 1000 m and velocities of the order of 100 m/s have been ascribed to these irregularities by Das and Das [DD83, p. 316,], while Lee [Lee84] identifies two regimes, one from 10 m to 100 m and the other from 100 m to 10000 m.

Andreas Schiffler
Wed Oct 9 10:05:17 CST 1996