We study the properties of the He I 10830 line in nine selected solar flares,using spectral data obtained with the Multi-channel Infrared Solar Spectrograph(MISS) at Purple Mountain Observatory(PMO) and photospheric images from the Michelson Doppler Imager(MDI) onboard the Solar and Heliospheric Observatory(SOHO).Our results indicate that,over an area of 3-8,the He I 10830 line shows emission exceeding the continuum in nearby quiet region when the Geostationary Operations Environmental Satellite(GOES) X-ray class of the flare reaches a threshold value(C4.5).The He I 10830 line emission is detected only in the kernels of the Hα brightenings,but is not associated with the size of the flare.It is found that,whenever the He I 10830 line shows excess emission over the nearby continuum both the Hα and the Ca II 8542 lines display enhanced intensities exceeding their preflare intensities.The He I 10830 line emission can occasionally extend into the umbra of the involved sunspot,which is inconsistent with previous studies.The weak com-ponent of He I 10830 line changes from emission to absorption earlier than does the main component.Our results favor the photoionization-reconnection mechanism for the excitation of the He I 10830 line.
