Simultaneous interplanetary scintillation and optical measurements of the acceleration of the slow solar wind

Abstract. Simultaneous observations of the slow solar wind off the southeast limb of the Sun were made in May 1999 using optical measurements from the C2 and C3 LASCO coronagraphs on board the SOHO spacecraft and radio-scattering measurements from the MERLIN and EISCAT facilities. The observations show the slow solar wind accelerating outwards from 4.5 solar radii (R), reaching a final velocity of 200-300 km s^-1 by 25-30 R. The acceleration profile indicated by these results is more gentle than the average profile seen in earlier LASCO observations of larger scale features, but is within the variation seen in these studies.

Key words: Interplanetary physics (solar wind plasma; sources of the solar wind; instruments and techniques)