  The binary T Tauri system JW 566 in the Orion Molecular Cloud underwent an
energetic, short-lived flare observed at submillimetre wavelengths by the
SCUBA-2 instrument on 26 November 2016 (UT). The emission faded by nearly 50%
during the 31 minute integration. The simultaneous source fluxes averaged over
the observation are 500 +/- 107 mJy/beam at 450 microns and 466 +/- 47 mJy/beam
at 850 microns. The 850 micron flux corresponds to a radio luminosity of
$L_{\nu}=8\times10^{19}$ erg/s/Hz, approximately one order of magnitude
brighter (in terms of $\nu L_{\nu}$) than that of a flare of the young star
GMR-A, detected in Orion in 2003 at 3mm. The event may be the most luminous
known flare associated with a young stellar object and is also the first
coronal flare discovered at sub-mm wavelengths. The spectral index between 450
microns and 850 microns of $\alpha = 0.11$ is broadly consistent with
non-thermal emission. The brightness temperature was in excess of
$6\times10^{4}$ K. We interpret this event to be a magnetic reconnection that
energised charged particles to emit gyrosynchrotron/synchrotron radiation.
