Early Evolution of the Cavity and Core of a Coronal Mass Ejection in the Inner Corona

Coronal mass ejections (CMEs) typically exhibit a three-component structure in white-light (WL) coronagraphs. Utilizing the seamless observations of the inner corona ($\le$ 3 R$_\odot$), we have revealed the early evolution of the cavity and core of a CME starting at $\sim$18:20 UT on 2014 October 14. The CME originates from a hot channel (HC), which appears as the bright core and compresses the cavity in WL images. Specifically, most of the dark cavity in WL is filled by bright loop-like structures in 174 Å. The differential emission measure (DEM) analysis indicates that the electron temperature decreases from the core ($\sim$13.4 MK) to the cavity ($\sim$1.35 MK), and the CME cavity is significantly cooler than that enshrouding a prominence ($\ge$ 2 MK). The effective temperature of the cavity increases over time in general, probably due to the compression by the HC expansion. The evolution of the CME bright core includes slow-rise, fast-rise (up to $\sim$330 km s$^{-1}$), and residual-acceleration phases. The cavity exhibits an evolution similar to the core but lags by $\sim$4 minutes, with a lower speed peaking at $\sim$220 km s$^{-1}$. Moreover, the 2D radial speed distribution exhibits the highest speeds at the core apex. The kinematical results further confirm the compression of the cavity. The present event supports the new explanation of the CME structures, i.e., the magnetic flux rope (MFR), which is proxied by the HC, is only responsible for the core, while the cavity is likely a low-density region between the CME front and the MFR.