New loss-process for accelerated electrons around the flare loop-top?

Nonthermal emissions - hard X-rays, gamma-rays and microwave - from loop-top sources of solar flares are related to acceleration/transportation processes of electrons under the magnetic reconnection point. So in order to understand these processes, it is important to study temporal and spatial variations of loop-top sources by using data of multiwavelength observation. We studied an M3.7 class flare which occurred on Jul. 27, 2005. This flare took place behind the limb. So we can see only loop-top source itself without any effects of emissions from the footpoints. We used two frequency data of Nobeyama Radio Heliograph (NoRH; 17GHz and 34GHz, both of them are emitted by MeV electrons). According to a simulation (Minoshima et al. 2011), we expected that loop-top microwave source of 34GHz is located lower than that of 17GHz, because higher energy electrons which emit 34GHz microwave can reach to a lower altitude with less collisions during the transportation. But we got a result that the loop-top source of 34GHz was located higher than that of 17GHz during the whole period of the flare. This result might suggest that additional loss process selectively works for the higher-energy electrons emitting 34GHz. To know whether such a process really exists, we investigated decay time-scale of light curve in some emission regions. At a low-altitude region, the decay time-scale is explainable in terms of Coulomb scattering. But at a high-altitude region, higher-energy electrons which emit 34GHz microwave decrease faster than expected by Coulomb scattering. So this suggests that there are some different scattering processes at a high-altitude region. However, still the decay time-scale of 34GHz is a little longer than that of 17GHz, we cannot explain the height difference between the 17GHz and 34GHz loop-top sources in only scattering processes. We need to consider the spectral variation of accelerated /injected electrons like so-called soft-hard-soft variation.