SSP seminar

Deceleration and Dispersion of Coronal Bright Fronts

David Long (CfA and Trinity College Dublin)

Monday 28th March 2011, 12:00 noon
Pratt conference room, 60 Garden Street

Coronal Bright Fronts (CBFs; commonly called "EIT Waves") are large-scale disturbances that propagate across the solar corona at hundreds of kilometers per second. Despite more than ten years of research, they remain enigmatic, with many questions regarding their temporal evolution and morphology. High cadence contemporaneous observations from both the Solar Dynamic Observatory (SDO) and Solar TErrestrial RElations Observatory (STEREO) are used here to study a CBF event from 2010 August 14. The CBF was found to have a lower initial velocity and exhibit weaker deceleration in STEREO observations compared to SDO (~370 km/s and -71 m/s2 as opposed to ~500 km/s and -295 m/s2). The CBF kinematics derived using SDO were found to be highly passband-dependent, with an initial velocity ranging from 418 +/- 15 km/s to 615 +/- 36 km/s and acceleration ranging from -132 +/- 23 m/s2 to -524 +/- 85 m/s2 in the 335A and 304A passbands respectively. Significant pulse broadening was also measured using both STEREO (~55 km/s) and SDO (~65 km/s) observations. The CBF was modeled as a linear superposition of sinusoidal waves with a Gaussian envelope, allowing the second derivative of the dispersion relation for each passband studied to be determined. These results indicate that the CBF is a fast-mode magnetoacoustic wave, and allowed the CBF velocities to be used to estimate the quiet coronal magnetic field strength of ~1-2 G.


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