A Study of a Tiny Two-Ribbon Flare Driven by Emerging Flux

We present observations of the eruption of a miniature filament that occurred near NOAA Active Region 9537 on 2001 July 14. The eruption was observed by the Hida Observatory Domeless Solar Telescope, in the Hα line center and ±0.4 Å wings, the Solar and Heliospheric Observatory EUV Imaging Telescope (EIT) and Michelson Doppler Imager, and the Yohkoh Soft X-Ray Telescope (SXT). The miniature filament began to form and was clearly visible in Hα images by around 06:50 UT. It erupted about 25 minutes later, accompanied by a small two-ribbon subflare (with an area of 61 arcsec²). The two ribbons were also found to approach each other at a speed of 3.33 km s^-1. We found that this event was caused by the emergence of new magnetic flux in a quiet region. The emerging flux appeared as a bright region in the EIT and SXT images taken on the previous day. It moved southward into an area of preexisting opposite-polarity flux, where a cancelling magnetic flux region was formed. The miniature filament then appeared, and we suggest that it played some role in inhibiting the release of energy by delaying reconnection between the emerging and preexisting flux, as evidenced by the disappearance of the bright region between opposite polarities in the EUV and soft X-ray images. Consequently, magnetic energy was stored as a result of the slow converging motion of the two opposite-polarity flux regions (0.17 km s^-1). Reconnection below the filament provoked the filament eruption, and the two-ribbon flare occurred. Miniature filaments are thought to be small-scale analogs of large-scale filaments. Our observations also suggest some common properties between small-scale and large-scale flares. These results support the view that a unified magnetic reconnection model may be able to explain all scales of flares.