EMVIM: An empirical model for the magnetic field configuration near Venus

Abstract:

More than 2000 orbits of Venus Express of magnetic field measurements are condensed into EMVIM, an empirical model to quantify the magnetic configuration in the Venusian magnetosphere at low altitude (<500km) as a function of the upstream solar wind magnetic field (IMF components) and solar activity index F107. Empirical Orthogonal Function (EOF) analysis is used to decompose the data and to separate different dynamics on different basis function. The most important basis function represents the magnetic draping configuration of the IMFz component, while the second important one represents the draping of the IMFy component. Solar wind-magnetosphere interactions are quantified through regression analysis of EOF amplitudes and solar wind predictor variables. Combining the basis function with regression coefficients results in a model with a determination coefficient R2 of 0.29. As an applicational example, the model is used to quantify the density of the cross-tail current sheet as \[\frac{{{J}_{z}}}{\text{A}\cdot\text{k}{{\text{m}}^{\text{-1}}}}=\frac{3.75\cdot IMFy}{\text{nT}}-\frac{\text{0}\text{.0190}\cdot IMFy\cdot F107}{\text{nT}\cdot \text{sfu}}-\frac{\text{0}\text{.0018}2\cdot F{{107}^{2}}}{\text{sf}{{\text{u}}^{\text{2}}}}+\frac{\text{13}\text{.6}}{\text{A}\cdot \text{k}{{\text{m}}^{\text{-1}}}},\] revealing the intensity decreases with increasing solar activity.