Radio Observation of Electron Acceleration at Solar Flare Reconnection Outflow Termination Shocks

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Using meter-wave solar radio spectral observations of the 2001 September 28 flare, we discuss simultaneously appearing type II-like bursts observed at 40-80 MHz and ≈300 MHz as radio signatures of the upper and lower reconnection outflow termination shock (TS). The features are identified during the impulsive phase but well after the regular traveling-shock type II burst and during the rise of a coronal mass ejection. The upper and lower TS features reveal a tendency for flux anticorrelation over time. We use radio imaging data (Nancay Radio Heliograph) and Yohkoh soft X-ray images to support the TS hypothesis. Assuming shock drift acceleration, we compute the flux of accelerated electrons for lower TS conditions that lead to an electron population with energies of ≈15 keV.