COMPARISON OF DAMPED OSCILLATIONS IN SOLAR AND STELLAR X-RAY FLARES

ABSTRACT We explore the similarity and difference of the quasi-periodic pulsations (QPPs) observed in the decay phase of solar and stellar flares at X-rays. We identified 42 solar flares with pronounced QPPs, observed with RHESSI, and 36 stellar flares with QPPs, observed with XMM-Newton. The empiri...

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Bibliographic Details
Published in:The Astrophysical journal 2016-10, Vol.830 (2), p.110
Main Authors: Cho, I.-H., Cho, K.-S., Nakariakov, V. M., Kim, S., Kumar, P.
Format: Article
Language:English
Subjects:
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
Coronal loops
Damping
DECAY
Fluid flow
LEAST SQUARE FIT
MAGNETOACOUSTICS
MAGNETOHYDRODYNAMICS
MASS
methods: observational
OSCILLATIONS
PERIODICITY
Power law
PULSATIONS
Solar corona
SOLAR FLARES
Solar oscillations
Solar power
STARS
stars: low-mass
STELLAR FLARES
Stellar oscillations
Sun: flares
Sun: oscillations
Trigonometric functions
X RADIATION
XMM (spacecraft)
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Summary:ABSTRACT We explore the similarity and difference of the quasi-periodic pulsations (QPPs) observed in the decay phase of solar and stellar flares at X-rays. We identified 42 solar flares with pronounced QPPs, observed with RHESSI, and 36 stellar flares with QPPs, observed with XMM-Newton. The empirical mode decomposition (EMD) method and least-squares fit by a damped sine function were applied to obtain the periods (P) and damping times (τ) of the QPPs. We found that (1) the periods and damping times of the stellar QPPs are 16.21 15.86 minutes and 27.21 28.73 minutes, while those of the solar QPPs are 0.90 0.56 and 1.53 1.10 minutes, respectively; (2) the ratios of the damping times to the periods ( ) observed in the stellar QPPs (1.69 0.56) are statistically identical to those of solar QPPs (1.74 0.77); and (3) the scalings of the QPP damping time with the period are well described by the power law in both solar and stellar cases. The power indices of the solar and stellar QPPs are 0.96 0.10 and , respectively. This scaling is consistent with the scalings found for standing slow magnetoacoustic and kink modes in solar coronal loops. Thus, we propose that the underlying mechanism responsible for the stellar QPPs is the natural magnetohydrodynamic oscillation in the flaring or adjacent coronal loops, as in the case of solar flares.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/830/2/110