Speaker
Joten Okamoto
(NAOJ)
Description
Fine structures of prominences, especially threads, and their dynamics provide
physical information about the magnetic configuration and property in the corona.
Here we report two events of prominence activations observed by the Hinode and IRIS
satellites. The first event taken only by Hinode showed that multiple bright threads
suddenly appeared in the pre-existing prominences without any accompanying flaring
activity or eruption. They moved upward one after another in a similar way with an
apparent speed up to 55 km/s. This speed is linearly correlated with the vertical
travel distance of each thread, indicative of a constant angular rotational speed.
After reaching some heights, most of them flowed horizontally along magnetic field
lines. A bright blob sticking with one of the appearing bright threads represented a
sinusoidal motion in a space-time plot. Moreover, one of the threads in the same
bundle clearly had a feature of wave propagation. The wave travelled with a phase
speed of 90-270 km/s toward the site on which the bright threads appeared first. In
the second event, spectral data taken by IRIS showed strong blueshifts around the
highest points with a speed of 30-40 km/s, while redshifts of similar speeds were
detected around the lowest points. Line width of the bright threads were
significantly larger than those of stationary threads. These behaviors indicate
rotational motions of the prominences. We interpreted the activations as evidence of
unwinding motions caused by magnetic reconnection between helical prominence fields
and ambient fields.
Primary author
Joten Okamoto
(NAOJ)
