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Session 36 - Solar Activity.
Display session, Tuesday, June 11
We searched for H\alpha counterparts to the C_IV explosive events observed by NRL with the HRTS rocket (Moses et al., 1994). These features do not correspond to spicules and macrospicules. At H\alpha-1.0 Åwe found a third class of features: "eruptive events" which are thick, violent, and not elongated by the magnetic field like the first two. Further, we detected these outflows in the H\alpha\pm0.65 Åspicule images analysed by Suematsu et al. (1995). Although these ejecta are situated like spicules at the edges of magnetic network elements, they are morphologically far different. They appear either as a fat eruption or as a chain of spicules rising sequentially. They truly deserve the name "chromospheric eruptions," which has unfortunately been applied to solar flares. Lifetimes also distinguish the eruptions from the spicules. While spicules are visible in the H\alpha-1.0Åimages for 2 to 3 minutes, the ejections are a complex wave of eruption moving along the network element and repeating several times over 10-12 minutes. The phenomenon may repeat, usually at the same location. Although these lifetimes are considerably longer than the 90 second C_IV lifetimes found by NRL, they appear morphologically quite similar, and repetition would not be seen in the short HRTS observing time. Moses et al. suggest that the C_IV events result from magnetic reconfiguration, and comparison of the locations of the H\alpha ejections with videomagnetograms shows that roughly half correlate with magnetic elements undergoing reconnection. The complex resultant magnetic field configuration could explain why these events are not constrained to slender flux tubes like normal spicules. The combined evidence makes the eruptive events good candidates for C_IV counterparts. Moses, D. et al., (1994) ApJ 430, 913. Suematsu, Y. et al, (1995) ApJ 450, 411.
Program listing for Tuesday