Detailed Regression Model of Plasma Sheet By

• Published in: Journal of geophysical research. Space physics 2018-04, Vol.123 (4), p.2872-2883
• Main Authors: Petrukovich, A. A., Lukin, A. S.
• Format: Article
• Language: English
• Subjects: Coordinate transformations; Correlation; Deformation; IMF penetration; Interplanetary magnetic field; Magnetic fields; Optimization; Orbital mechanics; Penetration; plasma sheet; Regression coefficients; Regression models; Spacecraft; Spacecraft orbits; Statistical analysis; Statistical models; Warp
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2017JA024993

In a statistical model plasma sheet By primarily depends on interplanetary magnetic field (IMF) Byi and geodipole tilt τ. With 11 years of Geotail measurements we investigate a role of several other parameters with a linear regression model. Optimal averaging window of IMF input, maximizing correlation and regression coefficients, is found to be 2.25 hr. Influence of IMF Bzi and local Bz on IMF penetration (regression with regard to Byi) and the deviations from the predefined warp deformation are at the level 5–10% relative to the primary model coefficients. The IMF penetration beyond 25 RE is somewhat larger for northward IMF, while closer to the Earth it becomes somewhat larger for southward IMF. These smaller effects turned out to be rather uneven across the tail, making reliable quantification and physical interpretation not always possible. The major reasons of difficulties are uneven coverage and internal correlations in the input space ( Byi–τ– Bzi) due to combination of spacecraft orbit and neutral sheet dynamics, effects of coordinate transformations, etc. In particular, origins of extremely large IMF Byi penetration (order of 30–50% above the average one) for some years and tail locations remain not fully clear. A larger multispacecraft data set covering all seasons in all spatial zones is necessary to further advance in this study. Key Points Plasma sheet By statistical model is designed including IMF By, Bz, dipole tilt, angle and local Bz Averaging of input IMF for 2.25 hr increases penetration coefficient by 20%, relative to 15‐min values The effect of IMF Bzi and local Bz on IMF penetration is at the level of 10% and varies across the tail