H alpha proxies for EIT crinkles: Further evidence for preflare "breakout"-type activity in an ejective solar eruption

We present H alpha observations from Big Bear Solar Observatory of an erupt ive flare in NOAA Active Region 8210, occurring near 22:30 UT on 1998 May 1 . Previously, using the EUV Imaging Telescope (EIT) on the SOHO spacecraft, we found that a pattern of transient, localized brightenings, which we cal l "EIT crinkles," appears in the neighborhood of the eruption near the time of flare onset. These EIT crinkles occur at a location in the active regio n well separated from the sheared core magnetic fields, which is where the most intense features of the eruption are concentrated. We also previously found that high-cadence images from the Soft X-ray Telescope (SXT) on Yohko h indicate that soft X-ray intensity enhancements in the core begin after t he start of the EIT crinkles. With the H alpha data, we find remote flare b rightening counterparts to the EIT crinkles. Light curves as functions of t ime of various areas of the active region show that several of the remote f lare brightenings undergo intensity increases prior to the onset of princip al brightenings in the core region, consistent with our earlier findings fr om EIT and SXT data. These timing relationships are consistent with the eru ption onset mechanism known as the breakout model, introduced by Antiochos and colleagues, which proposes that eruptions begin with reconnection at a magnetic null high above the core region. Our observations are also consist ent with other proposed mechanisms that do not involve early reconnection i n the core region. As a corollary, our observations are not consistent with the so-called tether-cutting models, which say that the eruption begins wi th reconnection in the core. The H alpha data further show that a filament in the core region becomes activated near the time of EIT crinkle onset, bu t little if any of the filament actually erupts, despite the presence of a halo coronal mass ejection (CME) associated with this event.