Eos, Transactions American Geophysical Union

The Heliosphere Through the Solar Activity Cycle



Ulysses, the joint European Space Agency/NASA mission, has been providing unique contributions to our understanding of the heliosphere since its launch in 1990. The in situ measurements made by the magnetic field and particle instruments on Ulysses have led to a fully three-dimensional view of the heliosphere between 1.3 and 5.4 astronomical units from Earth, owing to the spacecraft's particular orbit that extends to 80° latitude. Also, these instruments have been operational for more than a complete 11-year solar cycle (cycle 23), making it possible to examine variations in the field and particle data with varying solar activity. In this sense, Ulysses adds a fourth dimension—time—to the heliospheric picture.