Effects of Coronal Structures on the Dynamics of the Global Coronal Wave of SOL2017-09-10

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	associations with coronal mass ejections		associations with coronal mass ejections
	[https://en.wikipedia.org/wiki/Coronal_mass_ejection (CMEs)].		[https://en.wikipedia.org/wiki/Coronal_mass_ejection (CMEs)].
-	We interpret them as fast-mode magnetohydrodynamic shocks driven by the	+	We interpret them as fast-mode magnetohydrodynamic shocks.
-	expanding CME.	+	This "bow shock" will probably decouple from the driving CME and take the form of a
-	This "bow shock" will probably decouple from the driving CME, then	+
-	propagating in the form of a	+
	[https://en.wikipedia.org/wiki/Blast_wave blast wave]		[https://en.wikipedia.org/wiki/Blast_wave blast wave]
	after the expansion ceases in the lower corona.		after the expansion ceases in the lower corona.
-	{which is supposed to be the low-corona footprint
	Previous observations show EUV wave motion		Previous observations show EUV wave motion
	in directions seemingly opposite to the initial		in directions seemingly opposite to the initial
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	Multiple coronal magnetic structures can affect the propagation of a		Multiple coronal magnetic structures can affect the propagation of a
-	global wave.	+	global coronal wave.
	A [https://en.wikipedia.org/wiki/Coronal_hole coronal-hole] boundary		A [https://en.wikipedia.org/wiki/Coronal_hole coronal-hole] boundary
	can in principle reflect and also transmit wave		can in principle reflect and also transmit wave
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	This remarkable event showed interactions between its global wave		This remarkable event showed interactions between its global wave
	and multiple coronal structures.		and multiple coronal structures.
-	The global wave resulted from a huge CME observed by spacecraft on opposite	+	The global wave resulted from a huge CME in one hemisphere, and the wave propagated into
-	sides of the Sun.	+	the opposite hemisphere.
	It impinged upon both north and south polar coronal holes		It impinged upon both north and south polar coronal holes
-	and extended to the unprecedented full 180&\deg; range of latitudes	+	and extended to the unprecedented full range of latitudes (Ref. [3] and
-	\citep[see][and \href{run:animation1.mp4}{Animation 1}]{HuHuidong2019ApJ}.	+	[https://youtu.be/Q91jr92z64M Animation 1]).
	The transmitted secondary wave probably pushes streamers to collide		The transmitted secondary wave probably pushes streamers to collide
	on the opposite side of the Sun.		on the opposite side of the Sun.
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	it curves towards the photosphere while still		it curves towards the photosphere while still
	connected with the wave transmitted by the  coronal hole.		connected with the wave transmitted by the  coronal hole.
-	A collision between two streamers is observed (see Animation 2 and	+	A collision between two streamers is observed (see [https://youtu.be/p6W1aTPkp4Q  Animation 2]  and
	Figure 1c), which suggests that the lateral parts of the shock		Figure 1c), which suggests that the lateral parts of the shock
	probably also collide on the opposite side.		probably also collide on the opposite side.

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Revision as of 11:48, 1 November 2022

Nugget
Number:	438
1st Author:	Huidong HU
2nd Author:
Published:	October 17, 2022
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Previous Nugget:	KW-Sun: The Konus-Wind Solar Flare Database in Hard X-Ray and Soft Gamma-Ray Ranges
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Contents 1 Introduction 2 Propagation on the opposite side of the Sun 3 Interactions with Dim Regions and a Small Bipolar Structure 4 Conclusions 5 Acknowledgements 6 References

Introduction

A "solar extreme ultraviolet (EUV) wave" reveals a large-scale disturbance propagating in the corona and thus observable by SDO/AIA, for example. Observations and simulations suggest that such global waves have close associations with coronal mass ejections (CMEs). We interpret them as fast-mode magnetohydrodynamic shocks. This "bow shock" will probably decouple from the driving CME and take the form of a blast wave after the expansion ceases in the lower corona. Previous observations show EUV wave motion in directions seemingly opposite to the initial motion of the CME, spreading globally even onto the solar hemisphere opposite to that of the eruption itself (e.g Ref. [1]).

Multiple coronal magnetic structures can affect the propagation of a global coronal wave. A coronal-hole boundary can in principle reflect and also transmit wave energy, and this has been observed previously (Ref. [2]). Diffraction, refraction and reflection may similarly occur occur when the wave interacts with the magnetic field of a remote active region. The propagation speed of the wave can be elevated inside a coronal cavity. So far, it is still unclear how large and persistent such a wave can be, and what contributes to its global nature and remarkable persistence.

In this Nugget we describe the global wave structures associated with the flare SOL2017-09-10. This remarkable event showed interactions between its global wave and multiple coronal structures. The global wave resulted from a huge CME in one hemisphere, and the wave propagated into the opposite hemisphere. It impinged upon both north and south polar coronal holes and extended to the unprecedented full range of latitudes (Ref. [3] and Animation 1). The transmitted secondary wave probably pushes streamers to collide on the opposite side of the Sun. The EUV wave shows different behavior when it encounters a small bright point with a bipolar structure and on-disk dim regions. The EUV wave also interacts with multiple active regions on both sides of the Sun

Propagation on the opposite side of the Sun

After the CME-driven shock has propagated beyond the limb, as seen from the direction of the eruption, it curves towards the photosphere while still connected with the wave transmitted by the coronal hole. A collision between two streamers is observed (see Animation 2 and Figure 1c), which suggests that the lateral parts of the shock probably also collide on the opposite side. Including the transmission within the polar coronal holes, the wave eventually has extended to all latitudes, both north and south.

Interactions with Dim Regions and a Small Bipolar Structure

The EUV wave also reflects from both polar coronal holes, and this secondary wave then propagates roughly across all meridians. Figure 2 shows that the speed of the wavefront drops noticeably after it has left the south-polar coronal hole, and is elevated when it enters an on-disk coronal cavity. Part of the primary EUV wavefront bends around a small bright bipolar magnetic structure when the wavefront approaches a filament channel near the bipolar structure. As shown in Figure 3, the bright bipolar structure halts part of the primary wave, and the low-density filament channel, with a high characteristic wave speed, accelerates the wave.

Conclusions

Global waves excited by flare/CME events can have global scales. We have discussed the EUV wave associated with SOL2017-09-10. In this remarkable event the disturbance traversed all longitudes and entered both polar coronal holes; these interactions and others altered the structure of the disturbance.

Acknowledgements

Ying D. LIU, and Bei ZHU share the authorship of this Nugget and of Ref. [3].

References

[1] "New Insights into the Physical Nature of Coronal Mass Ejections and Associated Shock Waves within the Framework of the Three-dimensional Structure"

[2] "Secondary Waves and/or the ``Reflection from and ``Transmission through a Coronal Hole of an Extreme Ultraviolet Wave Associated with the 2011 February 15 X2.2 Flare Observed with SDO/AIA and STEREO/EUVI"

[3] "Effects of Coronal Density and Magnetic Field Distributions on a Global Solar EUV Wave"