Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B


Where is the magnetic energy for the expansion phase of auroral substorms accumulated? The main body, not the magnetotail

Syun Akasofu



The magnetosphere tries to stabilize itself when it accumulates excess magnetic energy. It has long (50 years !!) been thought that the excess magnetic energy is located in the magnetotail. Here, it is shown that the magnetic energy is accumulated between 4 Re and 10 Re.

The main reasons are:

  1. The power flow (Poynting flux) is directed to the main body.
  2. The magnetotail does not have enough energy.
  3. The onset latitude of the expansion phase can be as low as 48° (L=2.4).
  4. Dipolarization cannot explain the expansion phase.
  5. The magnetosphere is inflated when the energy is accumulated during the growth phase and deflated during the expansion phase (unloading). During the deflation, an earthward electric field is generated, driving the expansion phase current system.
  6. Magnetic reconnection is not only the process of magnetic energy conversion (W= (1/2)J2L. Current reduction.
  7. It is known that magnetic reconnection does not occur within 9 Re.

Unsolved question: What can cause the deflation (unloading) ?



Friday, 07 October 2016

Globe Room, Elvey Building

3:45 PM