In this paper , we report our multiwavelength imaging observations of chromospheric evaporation in a C5.5 circular-ribbon flare ( CRF ) on 2014 August 24 .
The flare was observed by the Atmospheric Imaging Assembly ( AIA ) on board the Solar Dynamics Observatory ( SDO ) , X-ray Telescope ( XRT ) on board the Hinode spacecraft , and ground-based Nobeyama Radioheliograph ( NoRH ) .
The CRF consisted of a discrete circular ribbon with a diameter of \sim 1 \arcmin and a short inner ribbon observed in ultraviolet ( UV ) , extreme-ultraviolet ( EUV ) , soft X-ray ( SXR ) , and especially in 17 GHz .
The peak time ( \sim 04:58 UT ) of the flare in 17 GHz coincided with that in UV 1600 Å and SXR derivative as a hard X-ray proxy , implying the peak time of impulsive energy deposition in the lower atmosphere .
Shortly after the peak time , converging motion and filling process in the flare loop were revealed in AIA 131 Å and two XRT filters ( Be_thin and Be_med ) , which are clear evidence for chromospheric evaporation upflows .
The chromospheric evaporation lasted for \sim 6 minutes until \sim 05:04 UT .
The temperature , density , and apparent velocities of the upflows are \sim 10 ^ { 7 } K , \sim 1.8 \times 10 ^ { 10 } cm ^ { -3 } , and 50 - 630 km s ^ { -1 } with a mean value of \sim 170 km s ^ { -1 } .
By comparison with previous models , we are able to estimate that energies above 5 \times 10 ^ { 10 } erg cm ^ { -2 } s ^ { -1 } are likely needed to explain the observational results .
Since heating by thermal conduction does not seem to provide enough energy , alternative mechanisms such as nonthermal electrons or Alfvénic waves might need to be invoked .