  Young stellar objects are known to exhibit strong radio variability on
timescales of weeks to months, and a few reports have documented extreme radio
flares, with at least an order of magnitude change in flux density on
timescales of hours to days. However, there have been few constraints on the
occurrence rate of such radio flares or on the correlation with pre-main
sequence X-ray flares, although such correlations are known for the Sun and
nearby active stars. Here we report simultaneous deep VLA radio and Chandra
X-ray observations of the Orion Nebula Cluster, targeting hundreds of sources
to look for the occurrence rate of extreme radio variability and potential
correlation with the most extreme X-ray variability. We identify 13 radio
sources with extreme radio variability, with some showing an order of magnitude
change in flux density in less than 30 minutes. All of these sources show X-ray
emission and variability, but only on timescales <1h do we find clear
correlations with extreme radio flaring. Strong X-ray variability does not
predict the extreme radio sources and vice versa. Radio flares thus provide us
with a new perspective on high-energy processes in YSOs and the irradiation of
their protoplanetary disks. Finally, our results highlight implications for
interferometric imaging of sources violating the constant-sky assumption.
