EVIDENCE OF IMPULSIVE HEATING IN ACTIVE REGION CORE LOOPS

Journal Article · Mon Nov 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/723/1/713· OSTI ID:21471308

Tripathi, Durgesh; Mason, Helen E ^[1]

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1. Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

Using a full spectral scan of an active region from the Extreme-Ultraviolet Imaging Spectrometer (EIS) we have obtained emission measure EM(T) distributions in two different moss regions within the same active region. We have compared these with theoretical transition region EMs derived for three limiting cases, namely, static equilibrium, strong condensation, and strong evaporation from Klimchuk et al. The EM distributions in both the moss regions are strikingly similar and show a monotonically increasing trend from log T[K] = 5.15-6.3. Using photospheric abundances, we obtain a consistent EM distribution for all ions. Comparing the observed and theoretical EM distributions, we find that the observed EM distribution is best explained by the strong condensation case (EM{sub con}), suggesting that a downward enthalpy flux plays an important and possibly dominant role in powering the transition region moss emission. The downflows could be due to unresolved coronal plasma that is cooling and draining after having been impulsively heated. This supports the idea that the hot loops (with temperatures of 3-5 MK) seen in the core of active regions are heated by nanoflares.

• OSTI ID: 21471308
• Journal Information: Astrophysical Journal, Vol. 723, Issue 1; Other Information: DOI: 10.1088/0004-637X/723/1/713; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
EMISSION
ENTHALPY
EVAPORATION
EXTREME ULTRAVIOLET RADIATION
HEATING
SOLAR CORONA
SUN
ATMOSPHERES
ELECTROMAGNETIC RADIATION
MAIN SEQUENCE STARS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RADIATIONS
SOLAR ATMOSPHERE
STARS
STELLAR ATMOSPHERES
STELLAR CORONAE
THERMODYNAMIC PROPERTIES
ULTRAVIOLET RADIATION