In this Letter, we present radio diagnostics for the magnetic field and the density distribution of nonthermal electrons in the microwave source of the Ml.l flare of 2004 November 1. We calculate the nonthermal gyro-synchrotron radiation using observations made at the Nobeyama Radio Observatory to get the longitudinal magnetic field and the magnitude of the transverse magnetic field. The computed longitudinal magnetic field at two hard X-ray footpoints has opposite polarities, which basically agrees with SOHO MDI observations. The main finding is that the magnitude of the transverse magnetic field summed around the magnetic neutral line of the SOHO MDI magnetogram has a short-term impulsive increase during the rising phase of the flare. We propose that the increase of the transverse magnetic field may be considered evidence of the magnetic reconnection process in this flare. The computed mean angle between the magnetic field and line of sight decreases steadily during the flare, clearly indicating the reconfiguration of the magnetic field, presumably the relaxation of the sheared magnetic field. Moreover, the calculated density of nonthermal electrons increases from footpoints to looptop, while the spectral index calculated by the Nobeyama Radio Heliograph at 17 and 34 GHz decreases from footpoints (soft) to looptop (hard), which may confirm that the reconnection site is close to the looptop source.
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机译：在这封信中，我们介绍了2004年11月1日Ml.1火炬微波源中磁场和非热电子密度分布的无线电诊断。我们使用在野部山无线电天文台进行的观测来计算非热陀螺同步辐射以获得纵向磁场和横向磁场的大小。在两个硬X射线脚点处计算出的纵向磁场具有相反的极性，这基本上与SOHO MDI观测结果一致。主要发现是，在火炬的上升阶段，SOHO MDI磁图的磁性中性线周围的横向磁场的总和具有短期脉冲增加。我们建议，横向磁场的增加可被视为该耀斑中磁重连过程的证据。在耀斑期间，磁场和视线之间的计算出的平均角度稳步减小，这清楚地表明了磁场的重新配置，大概是剪切磁场的松弛。而且，计算出的非热电子密度从脚点到环顶增加，而由Nobeyama Radio Heliograph在17和34 GHz处计算出的光谱指数从脚点（软）到环顶（硬）减小，这可以确认重新连接的地点很近到looptop源。
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