We have observed the fine temporal and spatial structure of a filament eruption on 2002 May 27 following an M2-class flare. Our observations at Big Bear Solar Observatory were made at the wavelength of Ha 1.3 Å , with a cadence of 40 ms. The event was also observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) at X-ray energies from 3 to 50 keV and by the Transition Region and Coronal Explorer (TRACE) in poFe xii 195 Å . The event appears to be a "failed eruption," as the filament material, seen in absorption by TRACE, first accelerated then decelerated as it approached its peak height of ∼ km while 4 8 # 10 the filament threads drained back to the Sun. The fact that the eruption did not lead to a coronal mass ejection indicates that the coronal magnetic field near ∼ km did not open during the flare. The height-time curve 4 8 # 10 obtained from the TRACE 195 Å images during the deceleration phase shows that the deceleration of the filament exceeded the gravitational deceleration by more than a factor of 10, which suggests that the filament material was pulled back by magnetic tension. Also of importance are three sequential but cospatial features-brightenings in EUV, a loop-top hard X-ray emission, and "rupturing" of the Ha filament-that point to a release of energy (and probably magnetic reconnection) above the initial filament's location but well below its terminal height. Reconnection above a filament does not appear in most models, with the notable exception of quadrupolar and "breakout" models. These observations provide evidence that at least two conditions are required for a successful eruption: a reconnection very low in the corona (possibly above the filament) and open or opening fields above that point.

Summary 1.Stability is an important property of ecological systems, many of which are experiencing increasing levels of anthropogenic environmental changes. However, how these environmental changes influence ecosystem stability remains poorly understood. 2. We conducted an 8-year field experiment in a semi-arid natural grassland to explore the effects of two common environmental changes, precipitation and nitrogen enrichment, on the temporal stability of plant above-ground biomass. A split-plot design, with precipitation as the main plot factor and nitrogen as the subplot factor, was used. Temporal stability was related to potential explanatory abiotic and biotic variables using regressions and structural equation modelling. 3. Increase in growing season precipitation enhanced plant species richness and promoted temporal stability of plant above-ground biomass. Nitrogen fertilization, however, reduced both plant species richness and temporal stability of plant above-ground biomass. Contrary to expectations, species richness was not an important driver of stability. Instead, community temporal stability was mainly driven by water and nitrogen availability that modulated the degree of species asynchrony and, to a lesser extent, by the stability of dominant plant species. 4. Synthesis. Our results highlight the importance of limiting resources for regulating community biomass stability and suggest that the projected increase in growing season precipitation may potentially offset negative effects of increased atmospheric nitrogen deposition on species diversity and community stability in semi-arid grasslands.

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