Doppler Velocities Measured in Coronal Emission Lines from a Bright Point Observed with the EUNIS Sounding Rocket

Abstract

Spectroscopic measurements of a coronal bright point obtained with the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument on 2006 April 12 show both upflows and downflows in all five of the best observed emission lines. Relative velocities on opposite sides of the feature were found to be +/-15 km s^-1 in the line of He II 303.8 Å (formed at T~5×10⁴ K), +/-14 km s^-1 in Mg IX 368.1 Å (T~9.5×10⁵ K), +/-26 km s^-1 in Fe XIV 334.2 Å (T~2.0×10⁶ K), and +/-35 km s^-1 in both Fe XVI 335.4 and 360.8 Å (T~2.5×10⁶ K). The latter are the hottest lines for which Doppler velocities have been reported in a bright point. Photospheric longitudinal magnetograms reveal that the photospheric magnetic fields underlying the bright point were canceling during the EUNIS observation. Based on existing bright point models, this suggests that the observed hot flows were associated with magnetic reconnection.