HELIOSPHERIC MAGNETIC-FIELD STRENGTH OUT TO 66 AU - VOYAGER-1, 1978-1996

We discuss Voyager 1 (V1) observations of the heliospheric magnetic fi eld strength from 1978 through 1996. During this period the distance o f V1 from the Sun increased from approximate to 3 AU to 66 AU and its heliographic latitude increased from approximate to 5 degrees S to 33 degrees N. The magnetic field strength profile observed by V1 is consi stent with Parker's spiral field model when one considers (1) the sola r cycle variation of the observed magnetic field strength at 1 AU, B-1 (t) (which is a measure of the source field strength) and (2) the lati tudinal and solar cycle variations of the solar wind speed, V(t, theta ), Both B-1(t) and V(t, theta) make significant contributions to the v ariation of the magnetic field strength variations observed by V1. The re is no evidence for a ''magnetic flux deficit'' increasing with dist ance from the Sun. There is a solar cycle variation of the magnetic fi eld strength in the outer heliosphere, which will affect the modulatio n of cosmic rays.