Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-08-24
Astrophys.J.638:1140-1153,2006
Astronomy and Astrophysics
Astrophysics
32 pages, 14 figures, submitted to ApJ
Scientific paper
10.1086/498863
We present a study of the spatial and spectral evolution of the loop-top (LT) sources in a sample of 6 flares near the solar limb observed by {\it RHESSI}. A distinct coronal source, which we identify as the LT source, was seen in each of these flares from the early ``pre-heating'' phase through the late decay phase. Spectral analyses reveal an evident steep power-law component in the pre-heating and impulsive phases, suggesting that the particle acceleration starts upon the onset of the flares. In the late decay phase the LT source has a thermal spectrum and appears to be confined within a small region near the top of the flare loop, and does not spread throughout the loop, as is observed at lower energies. The total energy of this source decreases usually faster than expected from the radiative cooling but much slower than that due to the classical Spitzer conductive cooling along the flare loop. These results indicate the presence of a distinct LT region, where the thermal conductivity is suppressed significantly and/or there is a continuous energy input. We suggest that plasma wave turbulence could play important roles in both heating the plasma and suppressing the conduction during the decay phase of solar flares. With a simple quasi-steady loop model we show that the energy input in the gradual phase can be comparable to that in the impulsive phase and demonstrate how the observed cooling and confinement of the LT source can be used to constrain the wave-particle interaction.
Jiang Yan Wei
Liu Siming
Liu Wei
Petrosian Vahe
No associations
LandOfFree
Evolution of the Loop-Top Source of Solar Flares--Heating and Cooling Processes does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Evolution of the Loop-Top Source of Solar Flares--Heating and Cooling Processes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evolution of the Loop-Top Source of Solar Flares--Heating and Cooling Processes will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-262743