Measuring Solar Wind Velocities Near PSP with WISPR Image Sequences

The WISPR camera on Parker Solar Probe is providing the first-ever close-up exploration of the young solar wind, with a viewing angle that rapidly changes due to the high spacecraft velocity and the relatively small distances to coronal structures. This viewing geometry enables unique ways to study the solar wind. We are building one such approach, in which the rapid evolution of the field of view allows us to measure the radial flow velocity of the wind in a small region in front of the spacecraft, a measurement complimentary to the in-situ velocity measurements made at the spacecraft itself. Taking great care to separate plasma density features close to the spacecraft from other signals in WISPR images, we search for the "stationary point," the angular position that separates plasma features that will pass to the sunward or anti-sunward side as they and the spacecraft move past each other. This angular position depends on the spacecraft velocity, which is known, and the plasma velocity, which allows the plasma velocity to be extracted. This additional source of wind flow speed measurements, at a spatial offset from the in-situ measurements, will help address key topics around the young solar wind, such as its driving and evolution. In this presentation, we describe our technique and show early results.