An explanation of the solar transition region

Abstract

Prompted by high resolution observations, I propose an explanation for the 40+ year old problem of structure and energy balance in the solar transition region. The ingredients are simply cross-field diffusion of neutral atoms from cool threads extending into the corona, and the subsequent excitation, radiation and ionization of these atoms via electron impact. The processes occur whenever chromospheric plasma is adjacent to coronal plasma, and are efficient even when ion gyro-frequencies exceed collision frequencies. Cool threads - fibrils and spicules perhaps - grow slowly in thickness as a neutral, ionizing front expands across the magnetic field into coronal plasma. Radiative intensities estimated for H L$\alpha$ are within an order of magnitude of those observed, with no ad-hoc parameters - only thermal parameters and geometric considerations are needed. I speculate that the subsequent dynamics of the diffused material might also explain observed properties of trace elements.

ApJ letters, in press

References in corpus (2)

• Energy Balance in the Solar Transition Region. IV. Hydrogen and Helium Mass Flows With Diffusion
• Observations Supporting the Role of Magnetoconvection in Energy Supply to the Quiescent Solar Atmosphere

Cited by in corpus (17)

• Heating of the magnetized solar chromosphere by partial ionization effects
• Fluid description of multi-component solar partially ionized plasma
• Ubiquitous High Speed Transition Region and Coronal Upflows in the Quiet Sun
• Three-dimensional simulations of solar magneto-convection including effects of partial ionization
• Heating of the partially ionized solar chromosphere by waves in magnetic structures
• The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations
• Thermal fine structure and magnetic fields in the solar atmosphere: spicules and fibrils
• Axion Searches with Helioscopes and astrophysical signatures for axion(-like) particles
• Signatures of impulsive localized heating in the temperature distribution of multi-stranded coronal loops
• On the effects of ion-neutral interactions in solar plasmas
• The solar chromosphere observed at 1 Hz and 0."2 resolution
• On the magnetic structure of the solar transition region
• Comparison of Nonlinear Force-free Field and Potential Field in the Quiet Sun
• Solar low-lying cool loops and their contribution to the transition region EUV output
• Magnetic connections across the chromosphere-corona transition region
• Dynamic Ly alpha jets
• MHD waves in the partially ionized plasma: from single to multi-fluid approach