engleski

First Observations of a Dome-shaped Large-scale Coronal Extreme-Ultraviolet Wave

We present first observations of a dome-shaped large-scale extreme ultraviolet coronal wave, recorded by the Extreme Ultraviolet Imagerinstrument onboard STEREO-B on 2010 January 17. The main arguments that the observed structure is the wave dome(and not the coronal massejection, CME) are(1)the spherical form and sharpness of the dome’s outer edge and the erupting CME loops observed inside the dome ; (2)the low-coronal wave signatures above the limb perfectly connecting to the on-disk signatures of the wave ; (3)the lateral extent of the expanding dome which is much larger than that of the coronal dimming ; and(4)the associated high-frequency type II burst indicating shock formation low in the corona. The velocity of the upward expansion of the wave dome(v ∼650 kms−1) is larger than that of the lateral expansion of the wave(v ∼ 280kms−1), indicating that the upward domeexpansion is driven all the time, and thus depends on the CME speed, whereas in the lateral direction it is freely propagating after the CME lateral expansion stops. We also examine the evolution of the perturbation characteristics: first the perturbation profile steepens and the amplitude increases. Thereafter, the amplitude decreases with r^−2.5±0.3, the width broadens, and the integral below the perturbation remains constant. Our findings are consistent with the spherical expansion and decay of a weakly shocked fast-mode MHD wave.

Sun:corona–Sun:coronalmassejections(CMEs)–Sun:flares

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