Two-fluid Numerical Simulations of Solar Spicules

Abstract

We aim to study the formation and evolution of solar spicules by means of numerical simulations of the solar atmosphere. With the use of newly developed JOANNA code, we numerically solve two-fluid (for ions + electrons and neutrals) equations in 2D Cartesian geometry. We follow the evolution of a spicule triggered by the time-dependent signal in ion and neutral components of gas pressure launched in the upper chromosphere. We use the potential magnetic field, which evolves self-consistently, but mainly plays a passive role in the dynamics. Our numerical results reveal that the signal is steepened into a shock that propagates upward into the corona. The chromospheric cold and dense plasma lags behind this shock and rises into the corona with a mean speed of 20-25 km s −1 . The formed spicule exhibits the upflow/downfall of plasma during its total lifetime of around 3-4 minutes, and it follows the typical characteristics of a classical spicule, which is modeled by magnetohydrodynamics. The simulated spicule consists of a dense and cold core that is dominated by neutrals. The general dynamics of ion and neutral spicules are very similar to each other. Minor differences in those dynamics result in different widths of both spicules with increasing rarefaction of the ion spicule in time.

Heating of a Quiet Region of the Solar Chromosphere by Ion and Neutral Acoustic Waves

“…For P d = 300 s cooling events discernible in Fig. 4 are related to the fluctuations of perturbed ion temperature associated with acoustic waves; rarefactions that follow shock-fronts lead to pressure decrease (e.g., Kuźma et al 2017;Kuźma et al 2018) and consequently act contrary to plasma heating. Energy dissipated by these waves in the chromosphere is sufficient to heat up the plasma up to 10 4 K on a time-scale of 10 3 s.…”

“…These two-fluid equations were derived by a number of authors (e.g., Smith & Sakai 2008;Zaqarashvili et al 2011;Meier & Shumlak 2012;Soler et al 2013;Ballester et al 2018, and references therein). They were implemented into the JOANNA code (Wójcik 2017) which was recently used by Kuźma et al (2017) and Srivastava et al (2018) to simulate twofluid jets and by to study two-fluid acoustic cut-off periods. In our model we assume initial thermal balance between ion and neutral components of plasma, T i = T n = T 0 (Oliver et al 2016) and neglect all electron-components due to the small mass of electrons in relation to ions and neutrals.…”

Two-fluid Numerical Simulations of the Origin of the Fast Solar Wind

“…Some of the injected plasma subsides rapidly after reaching its maximum phase (e.g. Kuźma et al 2017;Srivastava et al 2018). This entire process is driven by ongoing granulation in the photosphere.…”

Chromospheric Heating by Magnetohydrodynamic Waves and Instabilities

“…How do these contribute to the fast component of the solar wind at higher altitudes? Despite significant observational and theoretical developments over two decades on magnetic waves, shocks, instabilities, and formation of the jets/flows, their respective roles or inter-relationships in a variety of chromospheric magnetic structures are not yet fully understood (e.g., Kudoh and Shibata 1999;De Pontieu et al 2004;Shibata et al 2007;Nishizuka et al 2011;Iijima and Yokoyama 2015;Zhelyazkov et al 2015;Brady and Arber 2016;Kuźma et al 2017;Kayshap et al 2018b;Mishra and Srivastava 2019;Wójcik et al 2019;Wang and Yokoyama 2020;Zaqarashvili et al 2020).…”