Detection of Three-minute Oscillations in Full-disk Ly α Emission during a Solar Flare

Journal Article · Tue Oct 10 04:00:00 EDT 2017 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8213/AA8F3A· OSTI ID:22654371

Milligan, Ryan O.; Fletcher, Lyndsay ^[1]; Fleck, Bernhard ^[2]; Ireland, Jack; Dennis, Brian R. ^[3]

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1. SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)
2. ESA Directorate of Science, Operations Department, c/o NASA/GSFC Code 671, Greenbelt, MD 20071 (United States)
3. Solar Physics Laboratory (Code 671), Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

In this Letter we report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Ly α (from GOES /EUVS) and Lyman continuum (from Solar Dynamics Observatory ( SDO )/EVE) emission from the 2011 February 15 X-class flare (SOL2011-02-15T01:56) revealed a ∼3 minute period present during the flare’s main phase. The formation temperature of this emission locates this radiation at the flare’s chromospheric footpoints, and similar behavior is found in the SDO /Atmospheric Imaging Assembly 1600 and 1700 Å channels, which are dominated by chromospheric continuum. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not found at hard X-ray (HXR) energies (50–100 keV) in Reuven Ramaty High Energy Solar Spectroscopic Imager data we can state that this 3-minute oscillation does not depend on the rate of energization of non-thermal electrons. However, a second period of 120 s found in both HXR and chromospheric lightcurves is consistent with episodic electron energization on 2-minute timescales. Our finding on the 3-minute oscillation suggests that chromospheric mechanical energy should be included in the flare energy budget, and the fluctuations in the Ly α line may influence the composition and dynamics of planetary atmospheres during periods of high activity.

• OSTI ID: 22654371
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 848; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CHROMOSPHERE
DETECTION
ELECTRONS
EMISSION
EXTREME ULTRAVIOLET RADIATION
FLUCTUATIONS
HARD X RADIATION
INJECTION
KEV RANGE
LYMAN LINES
OSCILLATIONS
PLANETARY ATMOSPHERES
RADIANT FLUX DENSITY
SOLAR FLARES
SUN
ULTRAVIOLET RADIATION