Dynamics of Explosive Events Observed by the Interface Region Imaging Spectrograph

In this research, we investigate Explosive Events (EEs) in the off-limb solar atmosphere, with simultaneous observations from the Si IV, Mg II k, and slit-jaw images (SJI) of the Interface Region Imaging Spectrograph (IRIS), on 17 August 2014, and 19 February. IRIS data can be investigated to observe the motion of matter, fluctuations, energy absorption, and heat transition of the solar atmosphere. Mechanisms responsible for solar large-scale structures, such as flares and coronal mass ejections, might originate from these small-scale energetic events. Therefore, the study of these events can be helpful for understanding mechanisms in mass and energy transport from the chromosphere toward the transition region and corona. We obtain intensity profiles from spectra in two altitudes, i.e., at the solar limb and 5 arcsec distance from solar limb, and then analyze the EE fluctuations at these two altitudes along the slit. We find that some spectral line profiles show enhancements in blue and red wings indicating upward and downward flows, and some profiles have opposite EEs in both wings. The amplitude of the Doppler velocity in the two data sets of different altitudes was approximated to be about 50 km s⁻¹. We calculated the phase velocity of the oscillations using a technique based on cross-correlation. The phase velocity is obtained as about 220 km s⁻¹. According to the periodic red and blue enhancements in EEs, we suggest that the fluctuations in the EEs with one side enhancement indicate a swaying motions of spicules about their axes, and those EEs observed in both wings indicate a rotational motions of spicules. The swaying and rotational motions are indicative of kink and torsional waves, respectively.