Plasma Flows in Solar Filaments as Electromagnetically Driven Vortical Flows

Electromagnetic expulsion acts on a body suspended in a conducting fluid or plasma, which is subject to the influence of electric and magnetic fields. Physically, the effect is a magnetohydrodynamic analogue of the buoyancy (Archimedean) force, which is caused by the nonequal electric conductivities inside and outside the body. It is suggested that electromagnetic expulsion can drive the observed plasma counter-streaming flows in solar filaments. Exact analytical solutions and scaling arguments for a characteristic plasma flow speed are reviewed, and their applicability in the limit of large magnetic Reynolds numbers, relevant in the solar corona, is discussed.

Mass of prominences experiencing failed eruptions

A number of solar filaments/prominences demonstrate failed eruptions, when a filament at first suddenly starts to ascend and then decelerates and stops at some greater height in the corona. The mechanism of the termination of eruptions is not clear yet. One of the confining forces able to stop the eruption is the gravity force. Using a simple model of a partial current-carrying torus loop anchored to the photosphere and photospheric magnetic field measurements as the boundary condition for the potential magnetic field extrapolation into the corona, we estimated masses of 15 eruptive filaments. The values of the filament mass show rather wide distribution in the range of $4\times10^{15}$ – $270\times10^{16}$ g. Masses of the most of filaments, laying in the middle of the range, are in accordance with estimations made earlier on the basis of spectroscopic and white-light observations.

A HAWAII-2RG infrared camera operated under fast readout mode for solar polarimetry

Polarimetry is a crucial method to investigate solar magnetic fields. From the viewpoint of space weather, the magnetic field in solar filaments, which occasionally erupt and develop into interplanetary flux ropes, is of particular interest. To measure the magnetic field in filaments, high-performance polarimetry in the near-infrared wavelengths employing a high-speed, large-format detector is required; however, so far, this has been difficult to be realized. Thus, the development of a new infrared camera for advanced solar polarimetry has been started, employing a HAWAII-2RG (H2RG) array by Teledyne, which has $$2048~\times 2048$$ 2048 × 2048 pixels, focusing on the wavelengths in the range of $$1.0\;{-}\;1.6\;~\mu {\text{m}} $$ 1.0 - 1.6 μ m . We solved the problem of the difficult operation of the H2RGs under “fast readout mode” synchronizing with high-speed polarization modulation by introducing a “MACIE” (Markury ASIC Control and Interface Electronics) interface card and new assembly codes provided by Markury Scientific. This enables polarization measurements with high frame-rates, such as 29–117 frames per seconds, using a H2RG. We conducted experimental observations of the Sun and confirmed the high polarimetric performance of the camera.