Precise measurements of the proton electromagnetic form factor ratio R = µpG p E /G p M using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of R with momentum transfer Q 2 for Q 2 1 GeV 2 , in strong disagreement with previous extractions of R from cross section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Lab's Hall A measured R at four Q 2 values in the range 3.5 GeV 2 ≤ Q 2 ≤ 5.6 GeV 2 . A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q 2 motivated a new analysis of the GEp-II data. This article presents the final results of the GEp-II experiment, including details of the new analysis, an expanded description of the apparatus and an overview of theoretical progress since the original publication. The key result of the final analysis is a systematic increase in the results for R, improving the consistency of the polarization transfer data in the high-Q 2 region. This increase is the result of an improved selection of elastic events which largely removes the systematic effect of the inelastic contamination, underestimated by the original analysis. * Corresponding author: puckett@jlab.org 2

The issue of modeling the Earth's lower ionosphere in calm and disturbed conditions remains one of the most urgent issues in atmospheric research. The difficulty of obtaining experimental data at heights of the D-region (50-90 km) hinders the construction of good quality empirical models of ionospheric parameters; therefore, the dynamics of the component concentrations under conditions of disturbances (e.g., X-ray flares) are typically described by theoretical models of varying complexity. Considering the dynamics of a large number of charged and small neutral components allows, a more detailed and interconnected description of the photochemistry of the medium (

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It is demonstrated that it is required to create probabilistic statistical models of the ionosphere for calculating radio propagation in a wide frequency range. This, in fact, presents a new type of ionospheric modeling. These models are classified into pure statistical and deterministic stochastic. We describe the key principles of building such models, present some examples of their construction, and discuss some difficulties arising from them.