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Evidence for Widespread Cooling in an Active Region Observed with the SDO Atmospheric Imaging Assembly
Solar and Stellar Astrophysics · Submitted 17 Feb 2012
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim We find that there is a time-lag signal consistent with cooling plasma, just as is usually found for loops, throughout the active region including the diffuse emission between loops for the entire 24 hour duration.
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The abstract, sentence by sentence
A well known behavior of EUV light curves of discrete coronal loops is that the peak intensities of cooler channels or spectral lines are reached at progressively later times than hotter channels. This time lag is understood to be the result of hot coronal loop plasma cooling through these lower respective temperatures. However, loops typically comprise only a minority of the total emission in active regions. Is this cooling pattern a common property of active region coronal plasma, or does it only occur in unique circumstances, locations, and times? The new SDO/AIA data provide a wonderful opportunity to answer this question systematically for an entire active region. We measure the time lag between pairs of SDO/AIA EUV channels using 24 hours of images of AR 11082 observed on 19 June 2010. We find that there is a time-lag signal consistent with cooling plasma, just as is usually found for loops, throughout the active region including the diffuse emission between loops for the entire 24 hour duration. The pattern persists consistently for all channel pairs and choice of window length within the 24 hour time period, giving us confidence that the plasma is cooling from temperatures of greater than 3 MK, and sometimes exceeding 7 MK, down to temperatures lower than ~ 0.8 MK. This suggests that the bulk of the emitting coronal plasma in this active region is not steady; rather, it is dynamic and constantly evolving. These measurements provide crucial constraints on any model which seeks to describe coronal heating.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | A well known behavior of EUV light curves of discrete coronal loops is that the peak intensities of cooler channels or spectral lines are reached at progressively later times than hotter channels. | background 1.00 | 0.05 | 0.02 | asserted 1.00 |
| s1 | This time lag is understood to be the result of hot coronal loop plasma cooling through these lower respective temperatures. | background 0.99 | 0.05 | 0.03 | asserted 0.98 |
| s2 | However, loops typically comprise only a minority of the total emission in active regions. | background 0.58 | 0.07 | 0.02 | asserted 1.00 |
| s3 | Is this cooling pattern a common property of active region coronal plasma, or does it only occur in unique circumstances, locations, and times? | gap 0.99 | 0.04 | 0.02 | unclear 0.94 |
| s4 | The new SDO/AIA data provide a wonderful opportunity to answer this question systematically for an entire active region. | background 0.36 | 0.09 | 0.03 | asserted 0.84 |
| s5 | We measure the time lag between pairs of SDO/AIA EUV channels using 24 hours of images of AR 11082 observed on 19 June 2010. | method 0.96 | 0.98 | 0.02 | asserted 1.00 |
| s6 | We find that there is a time-lag signal consistent with cooling plasma, just as is usually found for loops, throughout the active region including the diffuse emission between loops for the entire 24 hour duration. | result 1.00 | 0.97 | 0.78 | asserted 0.69 |
| s7 | The pattern persists consistently for all channel pairs and choice of window length within the 24 hour time period, giving us confidence that the plasma is cooling from temperatures of greater than 3 MK, and sometimes exceeding 7 MK, down to temperatures lower than ~ 0.8 MK. | result 0.92 | 0.95 | 0.43 | asserted 0.96 |
| s8 | This suggests that the bulk of the emitting coronal plasma in this active region is not steady; rather, it is dynamic and constantly evolving. | interpretation 1.00 | 0.81 | 0.29 | hedged possibility 0.99 |
| s9 | These measurements provide crucial constraints on any model which seeks to describe coronal heating. | interpretation 0.98 | 0.51 | 0.09 | asserted 0.99 |
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Original abstract
A well known behavior of EUV light curves of discrete coronal loops is that the peak intensities of cooler channels or spectral lines are reached at progressively later times than hotter channels. This time lag is understood to be the result of hot coronal loop plasma cooling through these lower respective temperatures. However, loops typically comprise only a minority of the total emission in active regions. Is this cooling pattern a common property of active region coronal plasma, or does it only occur in unique circumstances, locations, and times? The new SDO/AIA data provide a wonderful opportunity to answer this question systematically for an entire active region. We measure the time lag between pairs of SDO/AIA EUV channels using 24 hours of images of AR 11082 observed on 19 June 2010. We find that there is a time-lag signal consistent with cooling plasma, just as is usually found for loops, throughout the active region including the diffuse emission between loops for the entire 24 hour duration. The pattern persists consistently for all channel pairs and choice of window length within the 24 hour time period, giving us confidence that the plasma is cooling from temperatures of greater than 3 MK, and sometimes exceeding 7 MK, down to temperatures lower than ~ 0.8 MK. This suggests that the bulk of the emitting coronal plasma in this active region is not steady; rather, it is dynamic and constantly evolving. These measurements provide crucial constraints on any model which seeks to describe coronal heating.
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5 arXiv papers cite this in 9 sentences
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Cites it as background 1 paper
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For hot core loops, there is evidence for both steady [ref] as well as impulsive heating [ref] .
Observations of Plasma Upflow in a Warm Loop with Hinode/EIS · Introduction · 0.81
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