• Interplanetary magnetic field measurements and solar wind coupling to Earth's magnetosphere reveal how solar activity drives geomagnetic responses; early Imp 1 results, magnetic tail dynamics, and correlations with solar wind speed establish a space weather causality framework. [1], [3], [6], [13].

• Solar energetic particles and cosmic-ray propagation near Earth are illustrated by solar protons/alpha particles from 1960 flares, exponential rigidity spectra, primary cosmic ray protons, and large fluctuations, highlighting acceleration, transport, and magnetospheric shielding. [4], [11], [12], [15], [13].

• Upper atmosphere responds to solar activity via theoretical solar-cycle models, EUV radiation measurements, solar radio flux correlations with thermopause temperature, and polar ionospheric disturbances from solar corpuscular radiation. [14], [19], [18], [20].

• Magnetosphere structure and radiation belts are mapped by Explorer-based measurements of the outer radiation zone, magnetospheric boundary, and inner belt, revealing Sun-Earth coupling in the first years of space exploration. [7], [16], [3].