PSP/WISPR Observations of Dust Density Depletion near the Sun. II. New Insights from within the Depletion Zone

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 ⊙ 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 ⊙. Below 9 R ⊙, the gradient reverses its trend, approaching the radial dependence exhibited at heights above 19 R ⊙. After taking into account the effects of both the electron corona background and the nonresolved starlight, the WISPR observations down to 4 R ⊙ 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 ⊙ enclosing a DFZ is considered. In addition, we show, for the first time, that the F-corona brightness inward of about 15 R ⊙ depends on the observer’s location for observing distances below 35 R ⊙.

[1]  A. Vourlidas,et al.  In-flight Calibration and Data Reduction for the WISPR Instrument On Board the PSP Mission , 2021, Solar Physics.

[2]  N. Raouafi,et al.  Pristine PSP/WISPR Observations of the Circumsolar Dust Ring near Venus's Orbit , 2021, The Astrophysical Journal.

[3]  S. Habbal,et al.  The Color and Brightness of the F-corona Inferred from the 2019 July 2 Total Solar Eclipse , 2021, The Astrophysical Journal.

[4]  A. Vourlidas,et al.  PSP/WISPR Observations of Dust Density Depletion near the Sun. II. New Insights from within the Depletion Zone , 2020, Astronomy & Astrophysics.

[5]  M. Kelley,et al.  Parker Solar Probe Observations of a Dust Trail in the Orbit of (3200) Phaethon , 2019, The Astrophysical Journal Supplement Series.

[6]  N. Raouafi,et al.  Near-Sun observations of an F-corona decrease and K-corona fine structure , 2019, Nature.

[7]  A. Fitzsimmons,et al.  Properties of the Bare Nucleus of Comet 96P/Machholz 1 , 2019, Astronomical Journal.

[8]  J. Stauffer,et al.  Evidence for a Circumsolar Dust Ring Near Mercury’s Orbit , 2018, The Astrophysical Journal.

[9]  J. Stauffer,et al.  Characterization of the White-light Brightness of the F-corona between 5° and 24° Elongation , 2018, The Astrophysical Journal.

[10]  J. Hormaechea,et al.  Formation and past evolution of the showers of 96P/Machholz complex , 2018 .

[11]  D. Bewsher,et al.  Mapping the circumsolar dust ring near the orbit of Venus , 2017 .

[12]  M. Lockwood,et al.  The Solar Probe Plus Mission: Humanity’s First Visit to Our Star , 2016 .

[13]  Jens Rodmann,et al.  The Wide-Field Imager for Solar Probe Plus (WISPR) , 2014 .

[14]  M. H. Jones,et al.  Imaging of a Circumsolar Dust Ring Near the Orbit of Venus , 2013, Science.

[15]  Dennis Ping-Cheng Wang,et al.  Development and test of an active pixel sensor detector for heliospheric imager on solar orbiter and solar probe plus , 2013, Optics & Photonics - Optical Engineering + Applications.

[16]  A. Buffington,et al.  A Heliospheric Imager for Deep Space: Lessons Learned from Helios, SMEI, and STEREO , 2010 .

[17]  Sei‐ichiro Watanabe,et al.  Dust ring formation due to sublimation of dust grains drifting radially inward by the Poynting–Robertson drag: An analytical model , 2009 .

[18]  J. Davies,et al.  The Heliospheric Imagers Onboard the STEREO Mission , 2009 .

[19]  E. Christian,et al.  The STEREO Mission: An Introduction , 2008 .

[20]  C. Leinert,et al.  Evidence for dust accumulation just outside the orbit of Venus , 2007, 0708.0912.

[21]  R. Howard,et al.  Electron Density Modeling of a Streamer Using LASCO Data of 2004 January and February , 2006 .

[22]  A. Vourlidas,et al.  Deriving the Electron Density of the Solar Corona from the Inversion of Total Brightness Measurements , 2001 .

[23]  C. J. Wolfson,et al.  Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) , 2000, SPIE Optics + Photonics.

[24]  E. L. Wright,et al.  Observational confirmation of a circumsolar dust ring by the COBE satellite , 1995, Nature.

[25]  Faculteit der Wiskunde en Natuurwetenschappen,et al.  Zodiacal Light in the Solar Corona. , 1947 .

[26]  H. N. Russell On Meteoric Matter Near the Stars , 1929 .