Investigating `dark’ energy in the solar corona using forward modeling of MHD waves. (arXiv:1906.10941v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Pant_V/0/1/0/all/0/1">Vaibhav Pant</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Magyar_N/0/1/0/all/0/1">Norbert Magyar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Doorsselaere_T/0/1/0/all/0/1">Tom Van Doorsselaere</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Morton_R/0/1/0/all/0/1">Richard J. Morton</a>
It is now well established that the Alfv’enic waves are ubiquitous in the
solar corona. However, the Alfv’enic wave energy estimated from the Doppler
velocity measurements in the corona was found to be four orders of magnitude
less than that estimated from non-thermal line widths. McIntosh & De Pontieu
(2012) suggested that this discrepancy in energy might be due to the
line-of-sight (LOS) superposition of the several oscillating structures, which
can lead to an underestimation of the Alfv’enic wave amplitudes and energies.
McIntosh & De Pontieu (2012) termed this coronal `dark’ or `hidden’ energy.
However, their simulations required the use of an additional, unknown source of
Alfv’enic wave energy to provide agreement with measurements of the coronal
non-thermal line widths. In this study, we investigate the requirement of this
unknown source of additional `dark’ energy in the solar corona using
gravitationally stratified 3D magnetohydrodynamic (MHD) simulations of
propagating waves. We excite the transverse MHD waves and generate synthetic
observations for the Fe XIII emission line. We establish that the LOS
superposition greatly reduces the Doppler velocity amplitudes and increases the
non-thermal line widths. Importantly, our model generates the observed
wedge-shaped correlation between Doppler velocities and non-thermal line
widths. We find that the observed wave energy is only 0.2-1% of the true wave
energy which explains 2-3 orders of magnitude of the energy discrepancy. We
conclusively establish that the true wave energies are hidden in the
non-thermal line widths. Hence, our results rule out the requirement for an
additional `dark’ energy in the solar corona.
It is now well established that the Alfv’enic waves are ubiquitous in the
solar corona. However, the Alfv’enic wave energy estimated from the Doppler
velocity measurements in the corona was found to be four orders of magnitude
less than that estimated from non-thermal line widths. McIntosh & De Pontieu
(2012) suggested that this discrepancy in energy might be due to the
line-of-sight (LOS) superposition of the several oscillating structures, which
can lead to an underestimation of the Alfv’enic wave amplitudes and energies.
McIntosh & De Pontieu (2012) termed this coronal `dark’ or `hidden’ energy.
However, their simulations required the use of an additional, unknown source of
Alfv’enic wave energy to provide agreement with measurements of the coronal
non-thermal line widths. In this study, we investigate the requirement of this
unknown source of additional `dark’ energy in the solar corona using
gravitationally stratified 3D magnetohydrodynamic (MHD) simulations of
propagating waves. We excite the transverse MHD waves and generate synthetic
observations for the Fe XIII emission line. We establish that the LOS
superposition greatly reduces the Doppler velocity amplitudes and increases the
non-thermal line widths. Importantly, our model generates the observed
wedge-shaped correlation between Doppler velocities and non-thermal line
widths. We find that the observed wave energy is only 0.2-1% of the true wave
energy which explains 2-3 orders of magnitude of the energy discrepancy. We
conclusively establish that the true wave energies are hidden in the
non-thermal line widths. Hence, our results rule out the requirement for an
additional `dark’ energy in the solar corona.
http://arxiv.org/icons/sfx.gif
