The Earth’s Magnetic Field - Ultra and Extremely Low Frequency Electromagnetic Fields - page 31

Fig. 1.12 Dungey model for the reconnection between magnetotail field lines and interplanetary
magnetic field frozen in solar wind (Dungey 1961 ). The reconnection is assumed to occur at sunlit
magnetopause during magnetic storms and substorms. Lines 0-7 illustrate convection of magnetic
field lines in antisunward direction
The energy transfer caused by the magnetic reconnection is predominant at the
boundary of the magnetosphere while the dissipation of the transmitted energy
prevails at the magnetotail due to reconnection of the antiparallel magnetic fields
in North and South portions of the tail.
For the solar-quiet time the magnetotail field lines are closed through the
equatorial plane. The magnetic storm and substorms are accompanied by recon-
nection between the solar wind field and the Earth magnetic field at the sunlit
magnetopause. For example, Fig. 1.12 shows a schematic plot of Dungey model
(Dungey 1961 ) for the reconnection process under the requirement that the inter-
planetary magnetic field is directed from the North to the South. At first the
undisturbed interplanetary field shown with line 0 interacts with the magnetosphere
providing the North and the South portions of the opened field line shown with
line 1. The high conducting plasma of the solar wind drags that part of the opened
field line which is frozen in the solar wind. The result is that this part of the field
line moves in the antisunward direction towards the magnetotail whereas the bottom
of the line is fixed at the non-conducting atmosphere. As is seen from Fig. 1.12 ,
the Northern and Southern portions of the “frozen in” field lines slide over the
lower boundary of the ionospheric current layer, as shown with lines 1-5, until their
interception at the point Q of the magnetotail. The upper portions of the field line
joins the lower one at this point thereby producing the reverse convection of the
fields lines and plasma towards the neutral point P as shown in Fig. 1.12 with field
lines 6 and 7. So the reconnection mechanism generates plasma convective motion
in the antisunward direction in outer part of the magnetotail whereas the reverse
convection arises in inner part of the magnetotail.
Additionally, the similar effect of plasma convection at the magnetotail builds
up as a result of the quasiviscous interaction between the solar wind and the
magnetosphere although this mechanism is assumed to be not so intensive as
compared to the reconnection mechanism.