Yuan, Ding (Researcher in physics), Pascoe, D. J. (David J.), Nakariakov, V. M. (Valery M.), Li, B. and Keppens, Rony (2015) Evolution of fast magnetoacoustic pulses in randomly structured coronal plasmas. Astronomy & Astrophysics, 799 (2). doi:10.1088/0004-637X/799/2/221 ISSN 0004-6361.

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Abstract

Magnetohydrodynamic waves interact with structured plasmas and reveal the internal magnetic and thermal structures therein, thereby having seismological applications in the solar atmosphere. We investigate the evolution of fast magnetoacoustic pulses in randomly structured plasmas, in the context of large-scale propagating waves in the solar atmosphere. We perform one dimensional numerical simulations of fast wave pulses propagating perpendicular to a constant magnetic field in a low-β plasma with a random density profile across the field. Both linear and nonlinear regimes are considered. We study how the evolution of the pulse amplitude and width depends on their initial values and the parameters of the random structuring. A randomly structured plasma acts as a dispersive medium for a fast magnetoacoustic pulse, causing amplitude attenuation and broadening of the pulse width. After the passage of the main pulse, secondary propagating and standing fast waves appear in the plasma. Width evolution of both linear and nonlinear pulses can be well approximated by linear functions; however, narrow pulses may have zero or negative broadening. This arises because a narrow pulse is prone to splitting, while a broad pulse usually deviates less from their initial Gaussian shape and form ripple structures on top of the main pulse. A linear pulse decays at almost a constant rate, while a nonlinear pulse decays exponentially. A pulse interacts most efficiently with a random medium which has a correlation length of about half of its initial pulse width. The development of a detailed model of a fast MHD pulse propa
gating in highly structured medium substantiates the interpretation of EIT waves as fast magnetoacoustic waves. Evolution of a fast pulse provides us with a novel method to diagnose the sub-resolution filamentation of the solar atmosphere.

Item Type:	Journal Article
Alternative Title:
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science, Engineering and Medicine > Science > Physics
Library of Congress Subject Headings (LCSH):	Solar wind, Magnetohydrodynamic waves
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Official Date:	30 January 2015
Dates:	Date Event 30 January 2015 Published
Volume:	799
Number:	2
DOI:	10.1088/0004-637X/799/2/221
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Date of first compliant deposit:	28 December 2015
Date of first compliant Open Access:	28 December 2015
Funder:	China. Guo jia ke xue ji shu bu [Ministry of Science and Technology] (CMST), Fonds Wetenschappelijk Onderzoek (FWO), European Commission (EC), European Research Council (ERC), Guo jia tian wen tai (China) [National Astronomical Observatories of China], Science and Technology Facilities Council (Great Britain) (STFC), National Research Foundation of Korea (NRF), Guo jia zi ran ke xue ji jin wei yuan hui (China) [National Natural Science Foundation of China] (NSFC), Provincial Natural Science Foundation of Shandong
Grant number:	2012CB825601 (CMST), PIRSESGA-2011-295272 (EC), 321141 (ERC), KLSA201312 (NAOC), ST/L000733/1 (STFC), 40904047 (NSFC), 41174154 (NSFC), 41274176 (NSFC), JQ201212 (PNSFS)

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