Translational Tomography of the Solar Corona using Parker Solar Probe’s WISPR

We present early steps toward “translational tomography” of the solar corona: using PSP-WISPR image sequences to reconstruct coronal structure proximal to the track of Parker Solar Probe. We first apply our method to a pre-flight simulation of a WISPR flythrough and then to actual WISPR image sequences near perihelion. Our method relies on known perspective changes due to the rapid trajectory of PSP through the solar corona near perihelion. This method allows us to extract feature location and large-scale structure near the track of the spacecraft itself. To produce the inversions we neglect local proper motions and model the apparent kinematics of a stationary solar wind feature, from WISPR’s point of view. This family of analytic functions serves as a partial basis for the vector space of WISPR image sequences; a basic change-of-basis operation yields the initial “tomogram,” which constrains streamer structure location with respect to the orbital track. For initial analyses, this tomogram corresponds to the ribbon of material whose length runs along the track of the spacecraft (over a selected window of time) and whose width runs perpendicular to that track (locally horizontal). We present the basics of the method- using two different geometric models of the spacecraft trajectory, initial test results from a pre-flight model, and the first-cut results for three recent perihelion passes. Future work includes regularization of basis elements, improvement of the proof-of-concept inversions, and rigorous application to near-perihelion WISPR image sequences. The tool will grow in utility as the orbital distances decrease in future encounters.