Evidence for a Circumsolar Dust Ring Near Mercury’s Orbit

Abstract

To test a technique to be used on the white-light imager onboard the recently launched Parker Solar Probe mission, we performed a numerical differentiation of the brightness profiles along the photometric axis of the F-corona models that are derived from STEREO Ahead Sun Earth Connection Heliospheric Investigation observations recorded with the HI-1 instrument between 2007 December and 2014 March. We found a consistent pattern in the derivatives that can be observed from any S/C longitude between about 18° and 23° elongation with a maximum at about 21°. These findings indicate the presence of a circumsolar dust density enhancement that peaks at about 23° elongation. A straightforward integration of the excess signal in the derivative space indicates that the brightness increase over the background F-corona is on the order of 1.5%–2.5%, which implies an excess dust density of about 3%–5% at the center of the ring. This study has also revealed (1) a large-scale azimuthal modulation of the inner boundary of the pattern, which is in clear association with Mercury’s orbit; and (2) a localized modulation of the inner boundary that is attributable to the dust trail of Comet 2P/Encke, which occurs near ecliptic longitudes corresponding to the crossing of Encke’s and Mercury’s orbital paths. Moreover, evidence of dust near the S/C in two restricted ranges of ecliptic longitudes has also been revealed by this technique, which is attributable to the dust trails of (1) comet 73P/Schwassmann–Wachmann 3, and (2) 169P/NEAT.

Predicting the Time of Arrival of Coronal Mass Ejections at Earth From Heliospheric Imaging Observations

“…Stenborg and Howard (2017) showed that at the larger elongations covered by the HI‐1 instruments, the use of background models obtained considering extended periods of time leads to the introduction of artifacts. This occurs due to the subtle changes resulting from different viewpoints (Stenborg et al., 2018). Therefore, to remove the background contribution from the F‐corona from each individual HI‐1 observation, we created its respective background model following Stenborg and Howard (2017).…”

The Solar Orbiter Heliospheric Imager (SoloHI)

“…The initial, perhaps tentative, Helios result of a 2% increase in the dust density just outside the orbit of Venus (Leinert & Moster 2007) was confirmed by the analyses of SECCHI/HI data (Jones et al 2013(Jones et al , 2017. Stenborg et al (2018b) found a similar 3-5% increase in the orbit of Mercury also using SECCHI/HI. Finally, the SoloHI F-corona observations during the maximum of cycle 25 from high latitudes and within 0.5 AU provide an unprecedented and probably unique possibility to investigate whether CMEs interact in any significant way with the interplanetary dust and whether we can use this interaction to probe the CME magnetic fields.…”

Effects of neighbouring planets on the formation of resonant dust rings in the inner Solar System

“…At larger particle sizes, however, it produced a weak apsidal alignment pattern similar in appearance to that of Mars. We included Mercury in this study due to the recent findings by Stenborg et al (2018), that indicate the existence of a circumsolar dust ring near Mercury's orbit. Using optical data obtained by the Parker Solar Probe, Stenborg et al (2018) derive a maximum excess of dust density of 3-5%.…”