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Investigating Alfvénic wave propagation in coronal open-field regions.

Morton RJ, Tomczyk S, Pinto R - Nat Commun (2015)

Bottom Line: The existence of Alfvén waves far from the Sun has been known since the 1970s, and recently the presence of ubiquitous Alfvénic waves throughout the solar atmosphere has been confirmed.However, the presence of atmospheric Alfvénic waves does not, alone, provide sufficient support for wave-based models; the existence of counter-propagating Alfvénic waves is crucial for the development of turbulence.The results enhance our knowledge of Alfvénic wave propagation in the solar atmosphere, providing support and constraints for some of the recent Alfvén wave turbulence models.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Mathematics and Information Sciences, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK. [2] High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307-3000, USA.

ABSTRACT
The physical mechanisms behind accelerating solar and stellar winds are a long-standing astrophysical mystery, although recent breakthroughs have come from models invoking the turbulent dissipation of Alfvén waves. The existence of Alfvén waves far from the Sun has been known since the 1970s, and recently the presence of ubiquitous Alfvénic waves throughout the solar atmosphere has been confirmed. However, the presence of atmospheric Alfvénic waves does not, alone, provide sufficient support for wave-based models; the existence of counter-propagating Alfvénic waves is crucial for the development of turbulence. Here, we demonstrate that counter-propagating Alfvénic waves exist in open coronal magnetic fields and reveal key observational insights into the details of their generation, reflection in the upper atmosphere and outward propagation into the solar wind. The results enhance our knowledge of Alfvénic wave propagation in the solar atmosphere, providing support and constraints for some of the recent Alfvén wave turbulence models.

No MeSH data available.


Related in: MedlinePlus

Physical properties of the open-field region.Multiple complementary techniques are used to estimate the physical properties of the magnetized plasma. (a) The measured outward propagation speed (solid line), averaged over the boxed region in Fig. 4a, is compared with the estimated propagation speed calculated from the analytic density profile (dashed line in b) and PFSS magnetic field (dashed line in c). (b) The electron density estimates from CoMP (stars) is shown and is compared with the density profiles obtained from magneto-seismology of solar atmosphere (red diamonds) and an analytic density profile (dashed line—ref. 7). (c) The magnetic field strength profile from the magneto-seismology (red diamonds) is compared with the magnetic field strength estimated from the PFSS potential field extrapolation (dashed line). The error bars in all plots are the s.d. of the respective quantities.
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f5: Physical properties of the open-field region.Multiple complementary techniques are used to estimate the physical properties of the magnetized plasma. (a) The measured outward propagation speed (solid line), averaged over the boxed region in Fig. 4a, is compared with the estimated propagation speed calculated from the analytic density profile (dashed line in b) and PFSS magnetic field (dashed line in c). (b) The electron density estimates from CoMP (stars) is shown and is compared with the density profiles obtained from magneto-seismology of solar atmosphere (red diamonds) and an analytic density profile (dashed line—ref. 7). (c) The magnetic field strength profile from the magneto-seismology (red diamonds) is compared with the magnetic field strength estimated from the PFSS potential field extrapolation (dashed line). The error bars in all plots are the s.d. of the respective quantities.

Mentions: The measured properties of the Alfvénic waves, that is, amplitude and propagation speed, are further exploited to gain estimates for the gradients of magnetic field strength and density in the open-field region (see Methods). These gradients are shown in combination with electron density measurements available from CoMP, an analytic model of electron densities in an open magnetic field region from measurements in white light7 and the magnetic field estimated from the PFSS extrapolation model (Fig. 5a–c).


Investigating Alfvénic wave propagation in coronal open-field regions.

Morton RJ, Tomczyk S, Pinto R - Nat Commun (2015)

Physical properties of the open-field region.Multiple complementary techniques are used to estimate the physical properties of the magnetized plasma. (a) The measured outward propagation speed (solid line), averaged over the boxed region in Fig. 4a, is compared with the estimated propagation speed calculated from the analytic density profile (dashed line in b) and PFSS magnetic field (dashed line in c). (b) The electron density estimates from CoMP (stars) is shown and is compared with the density profiles obtained from magneto-seismology of solar atmosphere (red diamonds) and an analytic density profile (dashed line—ref. 7). (c) The magnetic field strength profile from the magneto-seismology (red diamonds) is compared with the magnetic field strength estimated from the PFSS potential field extrapolation (dashed line). The error bars in all plots are the s.d. of the respective quantities.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525157&req=5

f5: Physical properties of the open-field region.Multiple complementary techniques are used to estimate the physical properties of the magnetized plasma. (a) The measured outward propagation speed (solid line), averaged over the boxed region in Fig. 4a, is compared with the estimated propagation speed calculated from the analytic density profile (dashed line in b) and PFSS magnetic field (dashed line in c). (b) The electron density estimates from CoMP (stars) is shown and is compared with the density profiles obtained from magneto-seismology of solar atmosphere (red diamonds) and an analytic density profile (dashed line—ref. 7). (c) The magnetic field strength profile from the magneto-seismology (red diamonds) is compared with the magnetic field strength estimated from the PFSS potential field extrapolation (dashed line). The error bars in all plots are the s.d. of the respective quantities.
Mentions: The measured properties of the Alfvénic waves, that is, amplitude and propagation speed, are further exploited to gain estimates for the gradients of magnetic field strength and density in the open-field region (see Methods). These gradients are shown in combination with electron density measurements available from CoMP, an analytic model of electron densities in an open magnetic field region from measurements in white light7 and the magnetic field estimated from the PFSS extrapolation model (Fig. 5a–c).

Bottom Line: The existence of Alfvén waves far from the Sun has been known since the 1970s, and recently the presence of ubiquitous Alfvénic waves throughout the solar atmosphere has been confirmed.However, the presence of atmospheric Alfvénic waves does not, alone, provide sufficient support for wave-based models; the existence of counter-propagating Alfvénic waves is crucial for the development of turbulence.The results enhance our knowledge of Alfvénic wave propagation in the solar atmosphere, providing support and constraints for some of the recent Alfvén wave turbulence models.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Mathematics and Information Sciences, Northumbria University, Newcastle Upon Tyne NE1 8ST, UK. [2] High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307-3000, USA.

ABSTRACT
The physical mechanisms behind accelerating solar and stellar winds are a long-standing astrophysical mystery, although recent breakthroughs have come from models invoking the turbulent dissipation of Alfvén waves. The existence of Alfvén waves far from the Sun has been known since the 1970s, and recently the presence of ubiquitous Alfvénic waves throughout the solar atmosphere has been confirmed. However, the presence of atmospheric Alfvénic waves does not, alone, provide sufficient support for wave-based models; the existence of counter-propagating Alfvénic waves is crucial for the development of turbulence. Here, we demonstrate that counter-propagating Alfvénic waves exist in open coronal magnetic fields and reveal key observational insights into the details of their generation, reflection in the upper atmosphere and outward propagation into the solar wind. The results enhance our knowledge of Alfvénic wave propagation in the solar atmosphere, providing support and constraints for some of the recent Alfvén wave turbulence models.

No MeSH data available.


Related in: MedlinePlus