Magnetism plays one of the most significant roles in determining the interactions between the solar wind and Earth. \u00a0In addition to carrying solar particles away from the Sun, the solar wind blows the magnetic field of the Sun out to the rest of the solar system. The Sun’s extended magnetic field is called the interplanetary magnetic field (IMF), and it can interact with the region of space around Earth influenced by our magnetic field, called the magnetosphere. \u00a0If you have ever played with magnets, then you know the way magnets behave depends on how they are lined up to one another. Interactions between the IMF carried by the solar wind and Earth\u2019s magnetosphere are similarly dependent on how the directions of their magnetic field lines line up relative to each other.<\/p>\n
Earth\u2019s magnetic field lines \u201cpoint\u201d towards the north pole, and this direction from south to north is referred to as the z-direction. \u00a0The x-direction points from Earth towards the Sun, and the y-direction points from east to west. (see below) Magnetic field strength in general is denoted as B, and Bz refers to the strength of the magnetic field in the north-south direction. If the Bz of the Coronal Mass Ejection is northward (recorded as positive values in the red ACE data<\/a>) then the IMF lines are pointing in the same direction as Earth\u2019s magnetic field lines. \u00a0As a result, the interaction between the two sets of field lines is minimal and auroral activity is also minimal. The effect is kind of like two magnets lined up and repelling each other.<\/p>\n![\"Bxyz-Earth-Sun\"](\"https:\/\/blog.aurorasaurus.org\/wp-content\/uploads\/2015\/08\/Bxyz-Earth-Sun.gif\")
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