Effect of areal expansion and coronal heating on the solar wind

1994 ◽  
Vol 70 (1-2) ◽  
pp. 387-390
Author(s):  
Y. -M. Wang
Keyword(s):  
Solar Wind ◽  
Coronal Heating

scholarly journals Numerical Study of Divergence Cleaning and Coronal Heating/Acceleration Methods in the 3D COIN-TVD MHD Model

2021 ◽  
Vol 9 ◽  
Author(s):  
Chang Liu ◽  
Fang Shen ◽  
Yousheng Liu ◽  
Man Zhang ◽  
Xiaojing Liu
Keyword(s):  
Solar Wind ◽  
Numerical Study ◽  
Three Dimensional ◽  
Coronal Heating ◽  
Solar Wind Structure ◽  
Wind Simulation ◽  
Simulation Results ◽  
Mhd Model ◽  
Cleaning Methods ◽  
Powell Method

In the solar coronal numerical simulation, the coronal heating/acceleration and the magnetic divergence cleaning techniques are very important. The coronal–interplanetary total variation diminishing (COIN-TVD) magnetohydrodynamic (MHD) model is developed in recent years that can effectively realize the coronal–interplanetary three-dimensional (3D) solar wind simulation. In this study, we focus on the 3D coronal solar wind simulation by using the COIN-TVD MHD model. In order to simulate the heating and acceleration of solar wind in the coronal region, the volume heating term in the model is improved efficiently. Then, the influence of the different methods to reduce the ∇⋅B constraint error on the coronal solar wind structure is discussed. Here, we choose Carrington Rotation (CR) 2199 as a study case and try to make a comparison of the simulation results among the different magnetic divergence cleaning methods, including the diffusive method, the Powell method, and the composite diffusive/Powell method, by using the 3D COIN-TVD MHD model. Our simulation results show that with the different magnetic divergence cleaning methods, the ∇⋅B error can be reduced in different levels during the solar wind simulation. Among the three divergence cleaning methods we used, the composite diffusive/Powell method can maintain the divergence cleaning constraint better to a certain extent, and the relative magnetic field divergence error can be controlled in the order of 10−9. Although these numerical simulations are performed for the background solar corona, these methods are also suitable for the simulation of CME initiation and propagation.

scholarly journals Coronal heating and wind acceleration by nonlinear Alfvén waves – global simulations with gravity, radiation, and conduction

2008 ◽  
Vol 15 (2) ◽  
pp. 295-304 ◽  
Author(s):  
T. K. Suzuki
Keyword(s):  
Solar Wind ◽  
Alfven Waves ◽  
Coronal Heating ◽  
Alfvén Waves ◽  
Flux Tubes ◽  
Giant Stars ◽  
Solar Winds ◽  
Dynamical Simulations ◽  
Consistent Manner ◽  
Red Giant

Abstract. We review our recent results of global one-dimensional (1-D) MHD simulations for the acceleration of solar and stellar winds. We impose transverse photospheric motions corresponding to the granulations, which generate outgoing Alfvén waves. We treat the propagation and dissipation of the Alfvén waves and consequent heating from the photosphere by dynamical simulations in a self-consistent manner. Nonlinear dissipation of Alfven waves becomes quite effective owing to the stratification of the atmosphere (the outward decrease of the density). We show that the coronal heating and the solar wind acceleration in the open magnetic field regions are natural consequence of the footpoint fluctuations of the magnetic fields at the surface (photosphere). We find that the properties of the solar wind sensitively depend on the fluctuation amplitudes at the solar surface because of the nonlinearity of the Alfvén waves, and that the wind speed at 1 AU is mainly controlled by the field strength and geometry of flux tubes. Based on these results, we point out that both fast and slow solar winds can be explained by the dissipation of nonlinear Alfvén waves in a unified manner. We also discuss winds from red giant stars driven by Alfvén waves, focusing on different aspects from the solar wind.

Quantifying weak non-thermal meterwave solar emission using non-imaging techniques

2018 ◽  
Vol 13 (S340) ◽  
pp. 181-182
Author(s):  
Rohit Sharma ◽  
Divya Oberoi ◽  
Akshay Suresh ◽  
Mihir Arjunwadkar
Keyword(s):  
Solar Wind ◽  
Imaging Techniques ◽  
Coronal Heating ◽  
Occurrence Rate ◽  
Plasma Emission ◽  
Study Region ◽  
Radio Emissions ◽  
X Ray ◽  
Diagnostic Probe ◽  
Nonthermal Emissions

An improved understanding of the solar corona is crucial for making progress on long-standing problems like coronal heating and the origin of the solar wind. Metrewave radio emissions arise in the coronal regions and form a unique diagnostic probe of this, otherwise hard to study region. The background radio emission at these wavelengths comes from the slowly varying thermal free-free emission and on it are superposed a variety of nonthermal emissions arising from a range of plasma emission processes. The latter are coherent in nature and hence lead to a much larger observational contrast, as compared to that in EUV or X-ray, for emissions involving similar energetics. One of the prevalent hypotheses for explaining coronal heating is based on the presence of an energetically weak population of ‘nanoflares’ (Parker 1988). A necessary requirement for nanoflares based coronal heating to be effective is that their occurrence rate slopes must be <-2 (Hudson 1991). There is hence a lot of interest in studies of weak nonthermal emissions. Existing studies in EUV and X-ray bands have detected ‘microflares’ with slopes >-2 (e.g. Hannah et al. 2011). Some of the weak meterwave emissions detected are, however, believed to correspond to energies in the ‘picoflare’ range (Ramesh et al. 2013). It is hence, very interesting to study weak nonthermal emissions at metric wavelengths.

Investigation of the coronal heating through phase relation of solar activity indexes

2020 ◽  
Vol 37 ◽  
Author(s):  
K. J. Li ◽  
J. C. Xu ◽  
Z. Q. Yin ◽  
J. L. Xie ◽  
W. Feng
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Phase Relation ◽  
Large Scale ◽  
Solar Rotation ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Coronal Heating ◽  
Small Scale

Abstract The coronal heating problem is a long-standing perplexing issue. In this study, 13 solar activity indexes are used to investigate their phase relation with the sunspot number (SSN). Only three of them are found to statistically significantly lag the SSN (large-scale magnetic activity) by about one solar rotation period; the three indexes are total solar irradiance (TSI), the modified coronal index, and the solar wind velocity; the former two indexes may represent the long-term variation of energy quantity of the heated photosphere and corona, respectively. The Mount Wilson Sunspot Index (MWSI) and the Magnetic Plage Strength Index (MPSI), which reflect the large- and small-scale magnetic field activities, respectively, are also utilised to investigate their phase relations with the three indexes. The three indexes are found to be much more intimately related to MPSI than to MWSI, and MWSI statistically significantly leads TSI by about one rotation period. The heated corona is found to pulse perfectly in step with the small-scale magnetic activity rather than the large-scale magnetic activity; furthermore, combined with observations, our statistical evidence should thus attribute coronal heating firmly to small-scale magnetic activity phenomena, such as spicules, micro-flares, nano-flares, and others. The photosphere and the corona are synchronously heated, which should seemingly prefer magnetic reconnection heating to wave heating. In the long term, such a coronal heating way is inferred effective. Statistically, it is also small-scale magnetic activity phenomena that produce TSI enhancement. Coronal heating and solar wind acceleration are found to be synchronous, as standard models require.

scholarly journals CORONAL HEATING BY SURFACE ALFVÉN WAVE DAMPING: IMPLEMENTATION IN A GLOBAL MAGNETOHYDRODYNAMICS MODEL OF THE SOLAR WIND

2012 ◽  
Vol 756 (2) ◽  
pp. 155 ◽  
Author(s):  
R. M. Evans ◽  
M. Opher ◽  
R. Oran ◽  
B. van der Holst ◽  
I. V. Sokolov ◽  
...  
Keyword(s):  
Solar Wind ◽  
Coronal Heating ◽  
Alfven Wave ◽  
Wave Damping
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