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PSP/WISPR Observations of Dust Density Depletion near the Sun. II. New Insights from within the Depletion Zone
| Author | Stenborg, Guillermo; Howard, Russell; Vourlidas, Angelos; Gallagher, Brendan; |
| Keywords | Parker Data Used; Circumstellar dust; Solar F corona; 236; 1991 |
| Abstract | Visible light observations from the Wide-field Imager for Solar PRobe (WISPR) aboard the Parker Solar Probe (PSP) mission offer a unique opportunity to study the dust environment near the Sun. The existence of a dust-free zone (DFZ) around stars was postulated almost a century ago. Despite numerous attempts to detect it from as close as 0.3 au, observational evidence of a circumsolar DFZ has remained elusive. Analysis of WISPR images obtained from heliocentric distances between 13.3-53.7 R $_\ensuremath\odot$ over multiple PSP orbits shows a gradually decreasing brightness gradient along the symmetry axis of the F-corona for coronal heights between 19 and 9 R $_\ensuremath\odot$. Below 9 R $_\ensuremath\odot$, the gradient reverses its trend, approaching the radial dependence exhibited at heights above 19 R $_\ensuremath\odot$. After taking into account the effects of both the electron corona background and the nonresolved starlight, the WISPR observations down to 4 R $_\ensuremath\odot$ are consistent with forward-modeling simulations of the F-corona brightness within [-6, 5]\% if a circumsolar region of depleted dust density between 19 and 5 R $_\ensuremath\odot$ enclosing a DFZ is considered. In addition, we show, for the first time, that the F-corona brightness inward of about 15 R $_\ensuremath\odot$ depends on the observer s location for observing distances below 35 R $_\ensuremath\odot$. |
| Year of Publication | 2022 |
| Journal | \apj |
| Volume | 932 |
| Number of Pages | 75 |
| Section | |
| Date Published | jun |
| ISBN | |
| URL | |
| DOI | 10.3847/1538-4357/ac6b36 |
