Speaker
Junwei Zhao
(Stanford University)
Description
Through cross-correlating oscillation signals at different
locations, we are able to reconstruct how waves propagate
away from a virtual wave source inside a sunspot in the
photospheric level. Before helioseismic waves are visible
from the source inside the sunspot, a surprisingly
fast-moving wave is detected propagating along the sunspot's
radial direction from the inside to the outside, extending
about 15~Mm beyond the sunspot boundary. The wave has an
apparent phase velocity of 45 km/s. The observation is
consistent with a magnetoacoustic wave, excited at
approximately 5~Mm beneath the sunspot surface, sweeping
across the photosphere, although it is not clear how this
wave is excited at that depth. This wave may help open a new
window to study the internal structure and dynamics of sunspots.
Primary author
Junwei Zhao
(Stanford University)
