Interaction between an interplanetary magnetic cloud and the Earth's magnetosphere: Motions of the bow shock

Abstract

Abstract. An interplanetary magnetic cloud (IMC) is an important solar-terrestrial connection event. It is an ideal object for the study of solar-terrestrial relations and space weather because the Earth's space environment can be affected considerably during an IMC passage. An IMC was observed to pass the Earth during October 18-20, 1995. Wind recorded its interplanetary characteristics at • 175 RE upstream of the Earth's bow shock, and • 45 rain later, Geotail, being near the nominal location of the dawn bow shock, detected IMC-related multiple bow shock crossings. Using simultaneous measurements from Wind and Geotail, we analyzed, with a semiempirical bow shock model with two parameters, the bow shock motion caused by the interaction of the IMC with the magnetosphere during the passage. We also compared the bow shock motion predicted by the model, and hence the predicted Geotail bow shock crossings, with Geotail observations of the actual crossings. The results showed that the observed multiple bow shock crossings, which were obviously due to temporal variations of the upstream solar wind, can be Well explained by the model-predicted bow shock motion.

A comparison of bow shock models with Cluster observations during low Alfvén Mach number magnetic clouds

“…In Wu00, CC03 and J05 models, we also notice that the lower the Mach number is, the larger the fluctuations of the BS position are. This is in agreement with the Wu et al (2000) observation that the BS position depends more sensitively on small changes in M A when its values are very low because of the 1/M 2 A or 1/(M 2 A − 1) dependence of the BS stand-off distance.…”

“…The models not only depend on the M A , but also on the dynamic pressure, and in the case of the Wu et al (2000) and the Jeřáb et al (2005) models on the IMF B z component and strength, respectively. Low M A solar wind outside MCs corresponds to different solar wind conditions, which may lead to different conclusions on the models' predictive capabilities.…”

Magnetic-reconnection exhausts in the sheath of magnetic clouds

“…Clearly there is a preceding shock produced by the MC at 10:56 UT on 18 October 1995. There is a distinct directional discontinuity (DD) at 18:58 UT, which was identified as the front boundary of the MC by many authors (e.g., Wu et al 2000;Wei et al, 2003;Feng et al 2006). The leading shock and the front boundary are denoted by two vertical solid lines in Fig.…”

“…From top to bottom the panels show the magnitude of the total magnetic field (B t ), the x, y, z components of the magnetic field (B x , B y , B z ), the solar wind velocity along the Sun-Earth direction (V x ), the proton thermal speed (V th ) and density (N), and the proton beta, respectively. The MC has been discussed by many authors (e.g., Lepping et al 1997;Wu et al 2000;Wei et al 2003;Feng et al 2006). Clearly there is a preceding shock produced by the MC at 10:56 UT on 18 October 1995.…”

The evidence for the evolution of interplanetary small flux ropes: Boundary layers

“…A MC was originally defined empirically in terms of in situ spacecraft measurements of magnetic fields and particles in the interplanetary medium at ∼1 AU, viz., it has the following necessary properties: (1) the magnetic field direction rotates smoothly through a large angle during an interval of the order of 1 day; (2) the magnetic field strength is higher than average; and (3) low proton temperature compared to the ambient proton temperature [7]. MCs have received considerable attention and have been intensively investigated by many *Corresponding author (email: fenghq9921@163.com) people in the last decade with a focus on the magnetic and plasma structures, its solar origins, and relevant geomagnetic activities [8][9][10][11][12][13][14][15]. In addition to large-scale MCs, only a few studies have been conducted on small interplanetary magnetic flux ropes (SIMFRs), and their origin still remains disputed [2,3, [16][17][18].…”