Pressure correction procedure

The corrected index SymH* was calculated using a simple formula SymH*= 0.8·SymH - 13.0·√Pdyn , whose purpose was to minimize contributions (1) from the magnetopause current and (2) from the induction currents that flow in the mantle and partially shield the Earth's interior from penetration of the external magnetic field. The adopted values of the coefficients in the above equation [Tsyganenko, 1996] are based on simple model estimates and are close to those chosen by Kozyra and Liemohn [2003] (0.77 and 11.9, respectively), with the only difference that their formula (1) included an additive constant, irrelevant in our treatment.