Origins of plasma sheet By

• Published in: Journal of Geophysical Research: Space Physics 2011-07, Vol.116 (A7), p.n/a
• Main Author: Petrukovich, A. A.
• Format: Article
• Language: English
• Subjects: Atmospheric sciences; Convection; Magnetism; magnetotail; Statistical models
• ISSN: 0148-0227; 2169-9380; 2156-2202; 2169-9402
• DOI: 10.1029/2010JA016386

With 11 years of Geotail measurements we analyzed sources of plasma sheet By and constructed a model, depending on IMF By, coordinates X, Y, and geodipole tilt angle. By dependence on dipole tilt due to the neutral sheet warping and hinging has an odd (antisymmetric) profile with respect to Y. In addition, a new, even with respect to Y, By component was discovered, which is positively correlated with dipole tilt with the maximal amplitude ±1–2 nT. In the postmidnight sector the dipole tilt effects in By almost cancel each other, while at the premidnight sector they are summed up and are comparable with the IMF penetration. Such season‐dependent net By creates a principal azimuthal asymmetry of the magnetotail and is consistent with some polar convection and aurora observations. Plasma sheet By is often substantially larger than the statistically expected value. This effect can be understood as “amplification” due to internal plasma sheet dynamics. As a result an asymmetric tail of the By distribution forms, causing certain overestimation of the regression coefficients in statistical models. Key Points New plasma sheet By component depending on dipole tilt Large plasma sheet By cannot be ignored Magnetotail has seasonal azimuthal asymmetry, consistent with PC convection