Near‐Earth magnetotail shape and size as determined from the magnetopause flaring angle

Abstract

Knowledge of the average size and shape of the near‐Earth magnetotail is an essential element for our understanding of the magnetospheric response to the influence of the solar wind. An empirical model of the near‐Earth magnetotail has been developed, which depends upon distance downtail (xGSM), the solar wind momentum flux (ρv2sw), and the zGSM component of the interplanetary magnetic field (IMF Bz). This model has been created by using the pressure balance relation to calculate a set of flare angles for the nightside magnetopause in the region −22 RE ≤ xGSM ≤ −10 RE. Observations of the magnetic field in the lobe by ISEE 2 and simultaneous observations of the magnetic field and plasma properties of the solar wind by IMP 8 were used to determine the internal and external pressure components, respectively. Examination of calculated flare angle values reveal a dependence upon downtail distance and ρv2sw. Normalized to the median downtail distance and dynamic pressure, the angle of flare of the magnetopause is found to increase linearly with decreasing Bz when the IMF is southward, but there is little variation when the IMF is northward. The empirical function derived for the flaring angle of the magnetotail is used to determine a relation for the radius of the tail. Comparisons with previous empirical models and results are also performed. In addition, values of magnetic flux within the magnetotail are calculated for times of sudden impulse events.

Response of neutral atom emissions in the low‐latitude and high‐latitude magnetosheath direction to the magnetopause motion under extreme solar wind conditions

“…[12] A large negative B z , as well as increasing of the dynamic pressure, is a controlling parameter for the reduction of the dayside magnetopause dimension [Roelof and Sibeck, 1993;Petrinec and Russell, 1996;Shue et al, 1998, and references therein]. The above connection of the LENA emission to both the solar wind dynamic pressure and IMF B z indicates that the reduction of the dayside magnetopause dimension is a major controlling parameter for the LENA emission enhancements.…”

“…[2] Dynamic features of the magnetopause have been revealed by empirical models based on large in situ data sets of magnetopause crossings [e.g., Roelof and Sibeck, 1993;Petrinec and Russell, 1996]. While these types of models have successfully predicted the motion of the magnetopause near the equatorial plane even for extreme solar wind situations [Shue et al, 1998], it is still unclear to what extent the validity of the models, which assume cylindrical symmetry around the aberrated Sun-Earth direction, can be extended to the X-Z meridian structure.…”

Effects of the interplanetary magnetic field on the twisting of the magnetotail: Global MHD results

“…Most empirical magnetopause models [e.g., Sibeck et al, 1991;Petrinec and Russell, 1996;Shue et al, 1997;Kawano et al, 1999] also adopted the hypothesis that magnetopause is rotational symmetric about the aberrated Sun-Earth line and has a rounded section at magnetotail. Lu et al [2011] developed a numerical three-dimensional magnetopause model considering the impact of IMF B z and solar wind dynamic pressure (D p ) on the shape of magnetopause.…”

Solar wind control of Earth's H+ and O+ outflow rates in the 15‐eV to 33‐keV energy range

“…As a simplified example, assuming that at time t the Wind monitor is positioned near the L1 Lagrangian point, at, say, GSE x = 230 R E , and shows a solar wind speed of v(t), pressure p(t), and magnetic field B(t). On the basis of these starting values for v, p, and B, the positions of Earth's bow shock and magnetopause are predicted from the empirical model of Petrinec and Russell [1996], followed by the calculation of the distances Dx between Wind and the subsolar bow shock and dx between the bow shock and the magnetopause and a corresponding flight time of Dt = Dx/v(t) + dx/v 0 (t), assigning a reduced speed v 0 between bow shock and magnetopause (by factor 1/4). A new set of v, p, and B is then obtained from Wind data taken at time t À Dt, and this set is used to infer a new Dt, etc.…”