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Measuring solar wind speeds with WISPR via apparent motion

Presentation #103.05 in the session The Corona and Solar Wind Speed.

Published onSep 18, 2023
Measuring solar wind speeds with WISPR via apparent motion

The WISPR camera on Parker Solar Probe offers the first up-close view of the young solar wind, with a rapidly-changing field of view caused by the high velocity of the spacecraft and its close proximity to the structures being imaged. This unique vantage enables new types of analysis. We are developing a new technique, using the apparent motion of the wind as a tool to measure its speed near the spacecraft at heliocentric distances comparable to PSP’s own position, with the goal of using WISPR’s wide field of view to make speed measurements at latitudes outside the orbital plane. Amid the outflowing plasma visible in WISPR image sequences, we detect the “stationary point,” a position in the field of view where plasma features do not move in the image plane. This indicates plasma which will collide with or pass near the spacecraft, as that plasma is on an inward trajectory in the spacecraft frame. The angular position of this stationary point is a function of the known spacecraft velocity and the unknown plasma velocity, allowing the plasma velocity to be determined in neighborhoods of varying size near the spacecraft and at a range of latitudes, all complementary to in-situ measurements at the spacecraft itself. This will help answer open questions regarding the nature and early evolution of the young solar wind. In this presentation, we will discuss the development of our technique and necessary background-removal and alignment steps, and show current progress.

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