The velocity of the dust near the Sun during the Solar Eclipse of March 29, 2006 and sungrazing comets

TL;DR

This study measures the velocity of dust near the Sun during the 2006 solar eclipse using Doppler shifts, revealing a retrograde orbit likely originating from sungrazing comets and indicating dust grain sizes below 0.1 microns.

Contribution

First direct velocity measurements of solar corona dust during an eclipse, linking dust motion to cometary origins and providing size estimates of dust grains.

Findings

Dust grains exhibited retrograde motion near the Sun.

Sungrazing comets contributed significantly to dust content.

Most dust grains were smaller than 0.1 microns.

Abstract

The measurements of the Doppler shifts of the Fraunhofer lines, scattered by the dust grains in the solar F-corona, provides the insight on the velocity field of the dust and hence on its origin. We report on such measurements obtained during the total eclipse of March 29, 2006. We used a Fabry-P\'erot interferometer with the FOV of 5.9 degrees and the spectral resolution of about 5000 to record Fraunhofer spectral lines scattered by the dust of the F-Corona. The spectral region was centered on the MgI 5172.69 A line. The measured line-on-sight velocities with the amplitude in the range from -10 to 10 km/s show that during our observations the dust grains were on the orbit with a retrograde motion in a plane nearly perpendicular to the ecliptics. This indicates their cometary origin. Indeed, at the end of March, 2006, SOHO recorded several sungrazing comets with the orbital elements close to what was deduced from our measurements. We conclude that the contribution of comets to the dust content in the region close to the Sun can be more important albeit variable in time. We also deduce that the size of the most of the dust grains during our observations was less than 0.1 microns.