We report quadrature observations of an extreme-ultraviolet ( EUV ) wave event on 2011 January 27 obtained by the Extreme Ultraviolet Imager ( EUVI ) onboard Solar Terrestrial Relations Observatory ( STEREO ) , and the Atmospheric Imaging Assembly ( AIA ) onboard the Solar Dynamics Observatory ( SDO ) .
Two components are revealed in the EUV wave event .
A primary front is launched with an initial speed of \sim 440 km s ^ { -1 } .
It appears significant emission enhancement in the hotter channel but deep emission reduction in the cooler channel .
When the primary front encounters a large coronal loop system and slows down , a secondary much fainter front emanates from the primary front with a relatively higher starting speed of \sim 550 km s ^ { -1 } .
Afterwards the two fronts propagate independently with increasing separation .
The primary front finally stops at a magnetic separatrix , while the secondary front travels farther before it fades out .
In addition , upon the arrival of the secondary front , transverse oscillations of a prominence are triggered .
We suggest that the two components are of different natures .
The primary front belongs to a non-wave coronal mass ejection ( CME ) component , which can be reasonably explained with the field-line stretching model .
The multi-temperature behavior may be caused by considerable heating due to the nonlinear adiabatic compression on the CME frontal loop .
For the secondary front , most probably it is a linear fast-mode magnetohydrodynamic ( MHD ) wave that propagates through a medium of the typical coronal temperature .
X-ray and radio data provide us with complementary evidence in support of the above scenario .