Spatial restriction to HXR footpoint locations by reconnection site geometries

It is assumed that HXR sources map to the primary energy release site in flares where particle acceleration occurs. Strong HXR sources are mostly observed at confined regions along the reconnecting magnetic arcade. We make a general approach on how the geometry of the reconnecting current sheet (CS) may influence the strength and localization of observed HXR sources. For this we use results from an analysis on the 3B/X3.8 flare on January 17, 2005 (Temmer et al., 2007), as well as measurements from the associated CME. Due to the close match of the CME acceleration profile and the flare HXR flux, we suppose that the CME might play a certain role in modifying the geometry of the CS ('symmetric' versus 'asymmetric' vertically stretched CS). This could be the driver for 'guiding' the accelerated particles to confined areas along the flaring arcade and might explain the spatially limited occurrence of strong HXR sources in comparison to elongated ribbons as seen in H-alpha and UV.