  The Extreme-ultraviolet Variability Experiment (EVE) onboard the Solar
Dynamics Observatory (SDO) detects the solar EUV spectra with high temporal
cadence and spectral resolution. The wavelength shifts of emission lines
provide key information of the dynamics of the Sun. However, some of EVE
spectral observations are influenced by the non-uniformly distributed
irradiance on the Sun, which may prevent us from correctly understanding the
physical processes happened in the solar corona. Here, based on the only
published on-orbit calibration data of EVE He II 30.38 nm line on 27 Jan 2011
(Chamberlin, 2016), we develop a method to correct the He II 30.38 nm line by
using AIA 304 imaging data. This correction method is then applied to EVE He II
30.38 nm data from 29 Oct 2010 to 3 Mar 2011 to study the Doppler oscillations
of the solar He II 30.38 nm line, in which we show that the half-month periodic
Doppler oscillation is caused by non-uniformly distributed irradiance mainly
due to the presence of active regions. Other EVE coronal lines also present
similar Doppler oscillations, suggesting that an appropriate correction must be
implemented before interpret the oscillation phenomena appearing in these
lines.
