[P-EM14] Frontiers in solar physics

[PEM14-08] Formation mechanism for solar prominence triggered by a transient heating event

*Takero Yoshihisa¹, Takaaki Yokoyama¹, Takafumi Kaneko² (1.Kyoto University, 2.Niigata)

Keywords: Sun: filaments, prominences, Sun: corona

Cool and dense plasmas in the solar corona, such as prominences and coronal rain, have been observed for many years. Several models have been proposed to explain their formation process. In a model called as "chromospheric-evaporation condensation” model, a quasi-steady heating at footpoints of a loop drives plasma evaporation into the corona and triggers condensation by runaway cooling. Indeed, numerous numerical simulations using this model have reproduced the thermal evolution during the formation process over several hours. Though the heating distribution is a key in this model, it is not clear observationally and theoretically whether such a heating distribution is plausible not only in active regions, but also in quiet regions. In addition, condensation occurring within a few tens of minutes after a non-steady transient heating event has been observed in recent years. Such phenomena cannot be explained by this model. We therefore investigate whether condensation occurs by a non-steady transient heating localized at footpoint(s) of a coronal loop in quiet regions. For this purpose, we set a dipped loop and solve 1.5-dimensional (one dimensional and three-vector components) magnetohydrodynamic equations, including radiative cooling, thermal conduction, gravity, and phenomenological turbulence heating. The loop is heated by the injected energy from imposed velocity perturbation at the footpoints. The energy dissipates through shock waves and Alfvén turbulence cascade. Prominence formation is investigated by adding transient footpoint-localized heating. We perform a parameter survey varying the magnitude of the localized heating to investigate the mechanism for condensation by transient heating. It is found that about 10³ times larger heating rate is required to form condensations compared to the case with steady heating. Furthermore, the results show that with sufficiently strong heating, sufficient plasma is supplied to the corona to allow cooling to proceed and condensation to occur. It is essential that the loop temperature decreases, and thermal conduction becomes inefficient with respect to cooling. Using the loop length L and the Field length λ_F, the condition for condensation is expressed as λ_F<L/2 under conditions where cooling exceeds heating.