CONSTRAINTS ON THE HEATING OF HIGH-TEMPERATURE ACTIVE REGION LOOPS: OBSERVATIONS FROM HINODE AND THE SOLAR DYNAMICS OBSERVATORY

Journal Article · Mon Jun 20 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/734/2/90· OSTI ID:21576613

Warren, Harry P ^[1]; Brooks, David H ^[2]; Winebarger, Amy R ^[3]

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1. Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)
2. College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)
3. NASA Marshall Space Flight Center, VP 62, Huntsville, AL 35812 (United States)

We present observations of high-temperature emission in the core of a solar active region using instruments on Hinode and the Solar Dynamics Observatory (SDO). These multi-instrument observations allow us to determine the distribution of plasma temperatures and follow the evolution of emission at different temperatures. We find that at the apex of the high-temperature loops the emission measure distribution is strongly peaked near 4 MK and falls off sharply at both higher and lower temperatures. Perhaps most significantly, the emission measure at 0.5 MK is reduced by more than two orders of magnitude from the peak at 4 MK. We also find that the temporal evolution in broadband soft X-ray images is relatively constant over about 6 hr of observing. Observations in the cooler SDO/Atmospheric Imaging Assembly (AIA) bandpasses generally do not show cooling loops in the core of the active region, consistent with the steady emission observed at high temperatures. These observations suggest that the high-temperature loops observed in the core of an active region are close to equilibrium. We find that it is possible to reproduce the relative intensities of high-temperature emission lines with a simple, high-frequency heating scenario where heating events occur on timescales much less than a characteristic cooling time. In contrast, low-frequency heating scenarios, which are commonly invoked to describe nanoflare models of coronal heating, do not reproduce the relative intensities of high-temperature emission lines and predict low-temperature emission that is approximately an order of magnitude too large. We also present an initial look at images from the SDO/AIA 94 A channel, which is sensitive to Fe XVIII.

• OSTI ID: 21576613
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 734; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ATMOSPHERES
DISTRIBUTION
ELECTRON TEMPERATURE
EMISSION
EVOLUTION
HEATING
HIGH-FREQUENCY HEATING
IMAGES
ION TEMPERATURE
PLASMA HEATING
SOLAR ATMOSPHERE
SOLAR CORONA
STELLAR ATMOSPHERES
STELLAR CORONAE