SOLAR DYNAMICS OBSERVATORY/ATMOSPHERIC IMAGING ASSEMBLY OBSERVATIONS OF A REFLECTING LONGITUDINAL WAVE IN A CORONAL LOOP

Abstract

We report high resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) of intensity oscillations in a hot, T ∼8-10 MK, loop. The AIA images show a large coronal loop that was rapidly heated following plasma ejection from one of the loop's footpoints. A wave-like intensity enhancement, seen very clearly in the 131 and 94Å channel images, propagated ahead of the ejecta along the loop, and was reflected at the opposite footpoint. The wave reflected four times before fading. It was only seen in the hot, 131 and 94Å channels. The characteristic period and the decay time of the oscillation was ∼630 and ∼440 s, respectively. The phase speed was about 460-510 km s −1 which roughly matches the sound speed of the loop (430-480 km s −1 ). The observed properties of the oscillation are consistent with the observations of Doppler shift oscillations discovered by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation (SUMER) and with their interpretation as slow magnetoacoustic waves. We suggest that the impulsive injection of plasma, following reconnection at one of the loop footpoints, led to rapid heating and the propagation of a longitudinal compressive wave along the loop. The wave bounces back and forth a couple of times before fading.

Quasi-periodic Pulsations in Solar and Stellar Flares: An Overview of Recent Results (Invited Review)

“…In numerical experiments, Fang et al (2015) found that these flows result in periodic emission in the footpoints, and can be directly observed in the flare loop body (confirming the interpretation of the observations of Kumar, Innes, and Inhester, 2013;Kumar, Nakariakov, and Cho, 2015). Moreover, such a mechanism may be responsible for the standing slow waves observed in hot flare loops with SUMER (Wang, 2011;Yuan et al, 2015).…”

Determination of Transport Coefficients by Coronal Seismology of Flare-induced Slow-mode Waves: Numerical Parametric Study of a 1D Loop Model

“…In contrast, in the other case with the classical thermal conduction and viscosity coefficients, the scaling relation between the decay time and the period is linear, and a timescale of several reflections is required for the initial propagating disturbance to form the standing wave pattern. This latter loop model may explain the reflected propagating feature of a longitudinal wave event reported in Kumar et al (2013).…”

“…Like the SUMER oscillation events (e.g. Wang et al 2005), the initiation of the AIA longitudinal waves is also associated with small flares (GOES B or C-class) at the loop footpoint (Kumar et al 2013(Kumar et al , 2015Wang et al 2015;Nisticó et al 2017). Magnetic extrapolation and emission features suggest that the confined flares are produced by reconnections at a coronal null point in a fan-spine magnetic topology Kumar et al 2015).…”

A Compact Source for Quasi-periodic Pulsation in an M-class Solar Flare

“…If one suggests the modulation by MHD waves, a plausible step is to correlate the timestamps in integrated light curves and periodic waves. A series of studies was done on modulation by standing and reflective slow mode waves (Wang et al 2003a,b;Wang 2011;Kumar et al 2013Kumar et al , 2015Yuan et al 2015;Fang et al 2015;Mandal et al 2016). Most previous studies focus on a good match of periodicity and phase difference.…”