The Sun is depicted as a dot in the center of the figure, and the Earth, a blue dot on it's orbit around the Sun. The view is from 30 degrees above the heliographic equator. The scintillation intensity level is calibrated in terms of density by comparison with IMP spacecraft densities at Earth.
Observations are least-squares fit over the period of one solar rotation.
Because of this limitation, only the corotating component of the heliospheric plasma density can be reconstructed from the data. Clearly seen is the three-dimensional Archimedean spiral structure of the dense heliospheric components of the solar wind during this solar minimum period.