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Analysis of characteristic parameters of large-scale coronal waves observed by STEREO/EUVI  

Nicole Muhr   Submitted: 2011-08-04 02:42

The kinematical evolution of four EUV waves, well observed by the Extreme UltraViolet Imager (EUVI) onboard the Solar-Terrestrial Relations Observatory (STEREO), is studied by visually tracking the wave fronts as well as by a semiautomatized perturbation profile method leading to results matching each other within the error limits. The derived mean velocities of the events under study lie in the range of 220-350 km s-1. The fastest of the events (May 19, 2007) reveals a significant deceleration of approx -190 m s-2 while the others are consistent with a constant velocity during the wave propagation. The evolution of the maximum intensity values reveals initial intensification by 20 up to 70%, and decays to original levels within 40-60 min, while the width at half maximum and full maximum of the perturbation profiles are broadening by a factor of 2 - 4. The integral below the perturbation profile remains basically constant in two cases, while it shows a decrease by a factor of 3 - 4 in the other two cases. From the peak perturbation amplitudes we estimate the corresponding magnetosonic Mach numbers Mms which are in the range of 1.08-1.21. The perturbation profiles reveal three distinct features behind the propagating wave fronts: coronal dimmings, stationary brightenings and rarefaction regions. All of them appear after the wave passage and are only slowly fading away. Our findings indicate that the events under study are weak shock fast-mode MHD waves initiated by the CME lateral expansion.

Authors: N. Muhr, A.M. Veronig, I.W. Kienreich, M. Temmer, B. Vrsnak
Projects: STEREO

Publication Status: Accepted by ApJ
Last Modified: 2011-08-04 08:32
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Analysis of a global Moreton wave observed on October 28, 2003  

Nicole Muhr   Submitted: 2009-11-24 04:29

We study the well pronounced Moreton wave that occurred in association with the X17.2 flare/CME event of October 28, 2003. This Moreton wave is striking for its global propagation and two separate wave centers, which implies that two waves were launched simultaneously. The mean velocity of the Moreton wave, tracked within different sectors of propagation direction, lies in the range of v ~ 900 - 1100 km s-1 with two sectors showing wave deceleration. The perturbation profile analysis of the wave indicates amplitude growth followed by amplitude weakening and broadening of the perturbation profile, which is consistent with a disturbance first driven and then evolving into a freely propagating wave. The EIT wavefront is found to lie on the same kinematical curve as the Moreton wavefronts indicating that both are different signatures of the same physical process. Bipolar coronal dimmings are observed on the same opposite East-West edges of the active region as the Moreton wave ignition centers. The radio type II source, which is co-spatially located with the first wave front, indicates that the wave was launched from an extended source region (~ 60 Mm). These findings suggest that the Moreton wave is initiated by the CME expanding flanks.

Authors: N. Muhr, B. Vrsnak, M. Temmer, A. M. Veronig, J. Magdalenic

Publication Status: accepted for ApJ
Last Modified: 2009-11-24 12:36
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Analysis of characteristic parameters of large-scale coronal waves observed by STEREO/EUVI
Analysis of a global Moreton wave observed on October 28, 2003

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