Dipolarizing Flux Bundles and Magnetic Flux Transport

An important feature intimately related to substorm process is the development of dipolarization in the near-Earth region. A common concept is that it arises from magnetic flux transported by dipolarizing flux bundles generated by magnetic reconnection in the mid-tail region. This concept is based on assuming the validity of the frozen-in-field condition for dipolarizing flux bundles. The frozen-in-field condition of this structure is critically evaluated from observations and by theoretical consideration. It is shown that this structure cannot transport sufficient magnetic flux to the near-Earth region that is required from observations for substorms. An important space disturbance is magnetospheric substorm. This process changes the magnetic configuration in the Earth's magnetotail. A common viewpoint is that the magnetic field change is a result of magnetic flux transported from the mid-tail region to the near-Earth region by dipolarizing flux bundles using the concept of frozen-in-field concept. It is shown here based on observation and theory that the above magnetic structure cannot transport sufficient magnetic flux to the near-Earth region as required by observations. Contrary to common viewpoint, dipolarizing flux bundles cannot transport sufficient magnetic flux to the near-Earth region A new viewpoint is needed to explain substorm dipolarization in the near-Earth region The key methodology is the combined use of observations and theory