Reflection of Coronal Global Waves

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Nugget
Number:	217
1st Author:	Ines Kienreich
2nd Author:	Hugh Hudson
Published:	January 13, 2014
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Introduction

Flares and CMEs can excite large-scale waves in the corona, observable by many techniques with our excellent modern data. These global waves can in extreme cases produce the [chromospheric] signature that we call a [Moreton wave], but since Uchida's early interpretative workin terms of MHD wave propagation, we have understood the chromospheric wave to be a consequence of the global wave itself. Controversy has raged on and off regarding the relationships between the globalwaves and their causes (flare [blast wave]? or CME [bow wave]?). In this Nugget we do not discuss the exciters, but only the wave propagation.The particular events studied (see Ref. [1]) occurred on 27 January 2011: SOL2011-01-27T08:50 [B1.1], T12:18 [B1.9] , and T20:03 (C1.5), all from the same active region. This is already interesting, because these are minor flares.The RHESSI Browser shows them, highlighting the 12:18 event because of its association with a radio [type II] event.

This Nugget describes the subsequent propagation of the global waves and reports a new property: the apparently [specular reflection] of the wavesat a distant magnetic domain wall.

Observations

We make use of the EUV images obtained by [STEREO-A] and by [PROBA2]; this epoch put STEREO-A almost at [quadrature], i.e. with a nearly orthogonalview of the events. Thus the analysis of the wave dynamics can delve into the three-dimensional structure, something only possible with STEREO. Figure 1 shows an overview.

References

• [1] STEREO-A and PROBA2 Quadrature Observations of Reflections of Three EUV Waves from a Coronal Hole