We present RHESSI and TRACE observations of multiple flare activity that occurred in the active region NOAA 10656 over the period of two hours on 2004 August 18 .
Out of four successive flares , there were three events of class C while the final event was a major X1.8 solar eruptive flare .
The events during the pre-eruption phase , i.e. , before the X1.8 flare , are characterized by localized episodes of energy release occurring in the vicinity of an active region filament which produced intense heating along with non-thermal emission .
A few minutes before the eruption , the filament undergoes an activation phase during which it slowly rises with a speed of \sim 12 km s ^ { -1 } .
The filament eruption is accompanied with an X1.8 flare during which multiple HXR bursts are observed up to 100–300 keV energies .
We observe a bright and elongated coronal structure simultaneously in E ( UV ) and 50–100 keV HXR images underneath the expanding filament during the period of HXR bursts which provides strong evidence for ongoing magnetic reconnection .
This phase is accompanied with very high plasma temperatures of \sim 31 MK and followed by the detachment of the prominence from the solar source region .
From the location , timing , strength , and spectrum of HXR emission , we conclude that the prominence eruption is driven by the distinct events of magnetic reconnection occurring in a current sheet formed below the erupting filament .
These multi-wavelength observations also suggest that the localized magnetic reconnections associated with different evolutionary stages of the filament in the pre-eruption phase play a crucial role in destabilizing the filament by a tether-cutting process leading to large-scale eruption and X-class flare .