Abstract
AbstractThe boundary between the solar wind and the Earth's magnetosphere, the magnetopause (MP), is highly dynamic. Its location and shape depend on SW dynamic pressure and interplanetary magnetic field (IMF) orientation. We use a 3D kinetic Particle‐In‐Cell code (IAPIC) to simulate an event observed by THEMIS spacecraft on July 16, 2007. We investigate the impact of radial ( = ) and non‐radial ( = ) IMF on the shape and size of Earth's MP for a dipole tilt of using maximum density gradient and pressure balance methods. Using the model as a reference (MP at 10.3 ), we find that for non‐radial IMF the MP expands by 1.4 and 1.7 along the Sun‐Earth (OX) and tilted magnetic equatorial (Tilt) axes, respectively, and it expands by 0.5 and 1.6 for radial IMF along the same respective axes. When the effect of backstreaming ions is removed from the bulk flow, the expansion ranges are 1.0 and 1.3 and 0.2, and 1.2, respectively. It is found that the percentage of backstreaming to bulk flow ions are 16.5% and 20% for radial and non‐radial IMF. We also show that when the backstreaming ions are not identified, up to 40% of the observed expansion that is due to backstreaming particles can be inadvertently attributed to a change in the SW upstream properties. Finally, we quantified the temperature anisotropy in the magnetosheath, and observe a strong dawn‐dusk asymmetry in the MP location, being more extended on the duskside than on the dawnside.
Highlights
The magnetic fields of planets such as Mercury, Earth, and the giant planets present an obstacle to the supersonic solar wind (SW)
The nonradial interplanetary magnetic field (IMF) event on July, 16th, 2007 observed by the THEMIS probes was chosen because it has been the subject of several detailed studies (Jelınek et al, 2010; Suvorova et al, 2010; Samsonov et al, 2017)
We discuss in detail the plasma properties at the time step 3700∆t of our simulation for both purely radial and nonradial IMF (IMF orientation corresponding to the threshold cone angle value 50◦ used by Samsonov et al (2017) as described in the introduction)
Summary
The magnetic fields of planets such as Mercury, Earth, and the giant planets present an obstacle to the supersonic solar wind (SW). A shock forms and the solar wind is redirected around the obstacle producing a cavity which is called the magnetosphere (e.g., Parks, 1991). The boundary between the shocked SW and the plasma in the magnetosphere is the magnetopause (MP). Plasma boundary layers form on either side of the magnetopause with the magnetosheath boundary layer (MSBL). On the sunward side and the low-latitude boundary layer (LLBL) on the magnetosphere side. Both layers play an important role in plasma exchange across the magnetopause (e.g., Pi et al, 2018)
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