Conditions for Chromospheric Plasma Acceleration or Trigger of Chromospheric Mass Ejections by Magnetic-field-aligned Electric Fields

Abstract

Abstract Backward-propagating or reverse fluctuations in Alfvénic turbulence were recently found to produce magnetic-field-aligned (MFA) electric fields that can easily transfer their energy to the plasma, either in the form of heat (or electron beams that quickly dissipate their energy as heat) if electrons absorb most of the MFA energy, or in the form of translational motion of the plasma if the ions absorb most of the MFA energy. Conditions for the direct proton acceleration (jet formation) in the quiet chromosphere included a temperature ≤104 K and a magnetic field between about 10 and 100 G, conditions very similar to those under which chromospheric plasma jets or dynamic jet-like spicules are observed with the Interface Region Imaging Spectrograph. Here the conditions for direct ion acceleration by MFA electric fields are determined for a much broader range of electron densities and plasma temperatures, to include both quiet and flaring conditions of the chromospheric plasma. For the higher chromospheric electron densities of solar flaring conditions, direct ion and therefore plasma acceleration by MFA electric fields is found to be possible in the much stronger (kG) magnetic fields of active regions, provided the plasma temperature remains less than about 105 K. Under flaring conditions, the MFA electric fields may cause the acceleration or at least trigger the upward motion of dense (>1012–1013 cm−3) chromospheric plasma. It is also suggested that chromospheric nonresonant MFA acceleration, by producing local electron beams, may eliminate the need for electron beams to propagate from the flaring corona down to the denser chromosphere.