Flux cancellation rates and converging speeds of canceling magnetic features

Canceling magnetic features are commonly believed to result from magnetic reconnection in the low atmosphere. According to the Sweet-Parker type reconnection model, the rate of flux cancellation in a canceling magnetic feature is related to the converging speed of each pole. To test this prediction observationally, we have analyzed the time variation of two canceling magnetic features in detail using the high-resolution magnetograms taken by the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). As a result, we have obtained the rate and converging speed of flux cancellation in each feature: 1.3 × 10¹⁸ Mx hr ^-1 (or 1.1 × 10⁶ G cm s^-1 per unit contact length) and 0.35 km s^-1 in the smaller one, and 3.5 × 10¹⁸ Mx hr^-1 (1.2×10⁶ G cms ^-1) and 0.27 km s^-1 in the bigger one. The observed speeds are found to be significantly bigger than the theoretically expected ones, but this discrepancy can be resolved if uncertainty factors such as low area filling factor of magnetic flux and low electric conductivity are taken into account.