[16] Prominences show very complicated structures and dynamics. It is because many driving forces in a broad range of space-time scales are involved in their formation and evolution. Different physical regimes with absolutely different scaling of governing dimensionless parameters could be involved. It is quite clear that there is no hope to have one unified theory or universal scenario for all of them. They are too different, though they demonstrate some common features: cool and dense material surrounded by more diluted and hot coronal plasma in the quiescent and eruptive prominences. A similar situation holds for other solar phenomena, CMEs and flares are among them. Numerous attempts to construct "universal scenario" for them neglected this situation and failed. It is, namely, because of not justified and too restrictive preassumptions, which could be valid only for limited classes of events of structures at the best and in reality cannot be considered as general ones.
[17] Early ideas to consider the solar radiation as a driver of eruptive prominences were first suggested and developed about 80 years ago. They were later used in attempts to explain the existence of the solar wind from the first principles. Now these ideas out of fashion, but they were never forgotten or disproved in a convincing manner. Radiation transfer in the moving medium is too complicated a problem. In addition to this possible candidate with still not known quantitative role, radiation pressure and absorption, we are facing other forces, which are involved without any doubts: gravity, thermal, and magnetic stresses, as well dynamical pressure and inertia of the viscous flows. The relative role of all these terms in the momentum balance vary from case to case in different proportions in solar protuberances, which makes their motions so peculiar, turbulent, and unpredictable. The same can be said about the relative role of physically different contributions in the energy transport [Akasofu and Kamide, 2005; Tsurutani et al., 2005].
[18] It was well understood long ago that prominences generally represent not magnetostatic but magnetohydrodynamic configurations. They are essentially open physical systems with mass, momentum and energy flows through them even in the quiescent shapes. Let us remember some of their basic observational properties, which were firmly established by numerous spectroscopic observations in the past and now partially forgotten in the current literature on this topic [Veselovsky, 1996, 2001, 2005, 2007]. The list of references is far from being complete and indicates only examples including several important observations of E. Pettit, who described the evolution of eruptive prominences. He concluded from observations that quiescent prominences exchange their mass in the way that inflow is approximately equal to outflow. This balance can be shifted for growing or disappearing prominences. The openness degree against mass flows through the prominences forming surges and eruptions is large and variable. It can be expressed by corresponding sets of dimensionless Trieste numbers, which are ratios of mass (energy or momentum) fluxes inside, outside and through the volume of the interest [Akasofu and Kamide, 2005; Tsurutani et al., 2005; Veselovsky, 2006]. Practically all prominences show different spiral structures, rotations, and internal motions.
[19] Classical observations of the big eruptive prominence were performed in 1919 [Veselovsky, 1996, 2001, 2007]. They showed siphon flow directed from one leg to another with the velocity increasing along the loop-like prominence body up to ~ 100 km s -1 before the falling of the material in the photosphere at the end of the loop. The evolution was observed continuously during ~7 hours. It was clearly seen that the topside part of the prominence lifted with acceleration and attained even higher velocity as a whole. Changes in the corona were also observed at that time, which coincided with the total solar eclipse on 29 May 1919 [Pettit, 1919]. (The general relativity test was the main problem, which was attacked during this eclipse observed in points with the time difference about 2 hours along the Moon's shadow.) The conclusion was also attained that observed disturbances probably emanate from the solar interiors.
[20] It is curious that when discussing the lifting and supporting forces, electrostatic and gravity forces were discussed by E. Pettit as usually at that time. Magnetic forces were known, but they did not attract attention. The suspension in the propelling vertical flow is mentioned as one of "fanciful suppositions." The existence of the permanent solar wind was not known and was not anticipated at that time. The combination with the internal siphon flow is sufficient to explain numerous eruptive cases of loop-like, one-leg shapes and "whips" without invoking "magnetic reconnection" and any topological changes of the magnetic fields. First impressions, nearly forgotten now, probably indicate the key. All in all, a "fanciful supposition" appears to be the true idea.
[21] The superposition of the external nearly vertical velocity flow with the internal siphon flow from one leg to another along the vertical arch of the prominence naturally results in the whip and the topological discontinuity of the total velocity field (and not obligatory magnetic discontinuity!). It is because of the appearance of zero point of the velocity field at some altitude. Topologically bound loop with the up and down flow inside it and the neighboring whip with the vertical up-flow diverge around this point. The lower part falls with the acceleration back on the Sun and quickly disappears, when the upper part lifts up being drained by the vertical outflow of the invisible hot coronal plasma forming later and higher the supermagnetosonic solar wind. Prominences are the important part of the dynamical turbosphere around the Sun. Magnetic forces play important role. Field-aligned electric currents and magnetic fields inside prominences make their spiral shapes, which is a common phenomenon. The balance of different forces needs quantitative evaluation of many physical parameters, which are poorly known.
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