Energy distribution of electrons with E < 800 eV in the areomagnetosphere

The electron distribution functions measured in the neighborhood of Mars by means of the Hyperbolic Retarding Potential Analyzer (HARP) carried aboard the Phobos 2 spacecraft are presented. The measurements were carried out over an energy/charge (E/q) from ~0.3 eV to ~800 eV in eight independent angular sectors ~ 20[deg] x 10[deg] covering the FOV ~ 180[deg] in the X-Z plane in the antisolar directions.The total intensity and energy distribution function of electrons downstream of the bow shock clearly differ from those in the undisturbed solar wind. The electron fluxes are significantly increased and the energy distribution of electrons in the magnetosheath was found to be characterized by the double-peaked structure. The high energy fluxes often exceed the flux values for the low energy peak.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29560/1/0000648.pd

Multispacecraft observations of the terrestrial bow shock and magnetopause during extreme solar wind disturbances

Three events are discussed from the declining phase of the last solar cycle when the magnetopause and/or the bow shock were observed unusually close to the Earth due to major interplanetary disturbances. The observed extreme locations of the discontinuities are compared with the predictions of three magnetopause and four bow shock models which describe them in considerably different ways using statistical methods based on observations. A new 2-D magnetopause model is introduced (based on Verigin et al., 2009) which takes into account the pressure of the compressed magnetosheath field raised by the interplanetary magnetic field (IMF) component transverse to the solar wind flow. The observed magnetopause crossings could be predicted with a reasonable accuracy (0.1–0.2 <I>R</I>_E) by one of the presented models at least. For geosynchronous magnetopause crossings observed by the GOES satellites, (1) the new model provided the best predictions when the IMF was extremely large having a large negative <I>B</I>_z component, and (2) the predictions of the model of Shue et al. (1998) agreed best with the observations when the solar wind dynamic pressure was extremely large. The magnetopause crossings close to the cusp observed by the Cluster spacecraft were best predicted by the 3-D model of Lin et al. (2010). The applied empirical bow shock models and the 3-D semi-empiric bow shock model combined with magnetohydrodynamic (MHD) solution proved to be insufficient for predicting the observed unusual bow shock locations during large interplanetary disturbances. The results of a global 3-D MHD model were in good agreement with the Cluster observations on 17 January 2005, but they did not predict the bow shock crossings on 31 October 2003

Magnetosonic Mach number effect of the position of the bow shock at Mars in comparison to Venus

[1] We study the effect of the magnetosonic Mach number on the position of the bow shock (BS) at Mars. The magnetosonic Mach number is calculated from solar wind data obtained by the ACE satellite upstream of Earth and extrapolated to Mars during two intervals, starting in 2005 and 2007, when Mars and Earth were close to opposition. An increased Mach number is observed to cause the Martian BS to move to lower altitudes and the variation in the terminator altitude is proportional to the Mach number change. When the Mach number is lowered, the BS flares more. We also compare our results to previous studies at Venus. The variation in BS altitude with magnetosonic Mach number is found to be very similar to the variation of the Venusian BS, which has previously been shown to decrease linearly in altitude with increasing Mach number