Observing and Modeling the Sun-Earth System

A balloon-borne instrument called HIWIND was launched from New Zealand to observe thermospheric winds in the mid-latitudes. The observed winds were compared with TIEGCM model simulation and were found to be much larger than the simulated results.

D. Afonso Delgado addresses the need to model the effects of radiation anisotropy and atomic coherence on the Stokes profiles
of magnetically-sensitive lines formed in the solar chromosphere. Accounting for the physics of scattering polarization associated with these effects, and how they map to the strength and direction of weak magnetic fields on the Sun is a formidable computational task when done fully self-consistently. This has hindered the broad heliophysics community from gaining prompt access to reliable data products from solar facility spectro-polarimeters concerning quiet-Sun magnetism.

Authors R. Casini, D. Harrington, and A. de Wijn review the algebraic definition of the efficiency of a polarization modulation scheme, which is commonly adopted for solar and stellar spectro-polarimetry applications, and generalize it to allow distinct states of the modulation cycle to have arbitrary throughput and different photon-noise statistics for each state.