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    The interplanetary magnetic field associated with the propagation of solar relativistic particles
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    Length scales in space are so large that they are considerably greater than the skin depth for processes which are reasonably fast. Therefore, in space situations all plasmas can be assumed to have infinite conductivity and the concepts of field freezing and magnetic pressure generally apply. Using these laws we can solve a number of problems in astrophysics. For example, a plasma stream known as the solar wind is ejected from the sun and impinges on the upper atmosphere of the earth with significant effects. This stream has no magnetic field embedded in it. According to the field-free zing concept, an external magnetic field should be unable to penetrate such a plasma. There is a random interplanetary magnetic field in the solar system. The plasma stream arriving from the sun displaces this external magnetic field. It might be said that the "plasma broom" sweeps the interplanetary magnetic field from the vicinity of the sun. Magnetic belts are formed around the sun in which the magnetic field is weaker than in neighboring regions. The magnetic belts facilitate the passage to the earth of fast charged particles which are ejected from the sun (corpuscular stream). In other words, when it encounters the magnetic field of the earth, the plasma stream flows around it the way a liquid flows around a solid body.
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    Abstract. Interplanetary linear magnetic holes (LMHs) are structures in which the magnetic field magnitude decreases with little change in the field direction. They are a 10–30% subset of all interplanetary magnetic holes (MHs). Using magnetic field and plasma measurements obtained by Cluster-C1, we surveyed the LMHs in the solar wind at 1 AU. In total 567 interplanetary LMHs are identified from the magnetic field data when Cluster-C1 was in the solar wind from 2001 to 2004. We studied the relationship between the durations and the magnetic field orientations, as well as that of the scales and the field orientations of LMHs in the solar wind. It is found that the geometrical structure of the LMHs in the solar wind at 1 AU is consistent with rotational ellipsoid and the ratio of scales along and across the magnetic field is about 1.93:1. In other words, the structure is elongated along the magnetic field at 1 AU. The occurrence rate of LMHs in the solar wind at 1 AU is about 3.7 per day. It is shown that not only the occurrence rate but also the geometrical shape of interplanetary LMHs has no significant change from 0.72 AU to 1 AU in comparison with previous studies. It is thus inferred that most of interplanetary LMHs observed at 1 AU are formed and fully developed before 0.72 AU. The present results help us to study the formation mechanism of the LMHs in the solar wind.
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    The correlations between the Kp index and solar wind variables measured during the flights of Mariners 2, 4, and 5 are discussed. It is shown that during the time of these flights, Kp is highly correlated with σBT, N, a measure of the interplanetary magnetic field fluctuations. It is better correlated with this quantity than it is with either the interplanetary magnetic field strength or the plasma speed. Kp is given by the relation The typical, large-scale structure of events in the solar wind that occur in conjunction with major geomagnetic activity is also discussed.
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    The interaction of a magnetized plasma beam with a stationary dipole field, analogous to the interaction of the solar wind with the Earth's magnetosphere, is explored in a laboratory experiment. Experimental parameters are chosen to scale qualitatively similar to the parameters in the Earth's magnetosphere. We find that the magnetization of the laboratory “solar wind,” generated by injecting a plasma across a preexisting magnetic field, requires a certain minimum magnetic field strength. Differences between the resulting magnetospheres for northward and southward “solar wind” or “interplanetary” magnetic fields (IMF) are demonstrated by global pictures and by magnetic field measurements above the north polar region. These measurements show patterns of the variation of the transverse field component which are similar to those found by satellite measurements above the Earth. This indicates the presence of similar field‐aligned current systems. We demonstrate particularly the presence (for northward IMF) and absence (for southward IMF) of the pattern attributed to the “NBZ” (northward B z ) current system.
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