Disconnection of open magnetic flux by reconnection is required to balance
the injection of open flux by CMEs and other eruptive events. Making use of
recent advances in heliospheric background subtraction, we have imaged many
abrupt disconnection events. These events produce dense plasma clouds whose
distinctie shape can now be traced from the corona across the inner solar
system via heliospheric imaging. The morphology of each initial event is
characteristic of magnetic reconnection across a current sheet, and the
newly-disconnected flux takes the form of a "U"-shaped loop that moves outward,
accreting coronal and solar wind material.
We analyzed one such event on 2008 December 18 as it formed and accelerated
at 20 m/s^2 to 320 km/s, expanding self-similarly until it exited our field of
view 1.2 AU from the Sun. From acceleration and photometric mass estimates we
derive the coronal magnetic field strength to be 8uT, 6 Rs above the
photosphere, and the entrained flux to be 1.6x10^11 Wb (1.6x10^19 Mx). We model
the feature's propagation by balancing inferred magnetic tension force against
accretion drag. This model is consistent with the feature's behavior and
accepted solar wind parameters.
By counting events over a 36 day window, we estimate a global event rate of
1/day and a global solar minimum unsigned flux disconnection rate of 6x10^13
Wb/y (6x10^21 Mx/y) by this mechanism. That rate corresponds to ~0.2 nT/y
change in the radial heliospheric field at 1 AU, indicating that the mechanism
is important to the heliospheric flux balance.Comment: preprint is 20 pages with 8 figures; accepted by APJ for publication
in 201