Rosetta photoelectron emission and solar ultraviolet flux at comet 67P

Abstract

The Langmuir Probe instrument on Rosetta monitored the photoelectron emission cur- rent of the probes during the Rosetta mission at comet 67P/Churyumov-Gerasimenko, in essence acting as a photodiode monitoring the solar ultraviolet radiation at wave- lengths below 250 nm. We have used three methods of extracting the photoelectron saturation current from the Langmuir probe measurements. The resulting dataset can be used as an index of the solar far and extreme ultraviolet at the Rosetta spacecraft position, including flares, in wavelengths that are important for photoionisation of the cometary neutral gas. Comparing the photoemission current to data measurements by MAVEN/EUVM and TIMED/SEE, we find good correlation when 67P was at large heliocentric distances early and late in the mission, but up to 50 percent decrease of the expected photoelectron current at perihelion. We discuss possible reasons for the photoemission decrease, including scattering and absorption by nanograins created by disintegration of cometary dust far away from the nucleus.

arXiv comment11 pages, 8 figures, accepted for publication in MNRAS

References in corpus (10)

• Temporal aspects and frequency distributions of solar soft X-ray flares
• Aggregate dust particles at comet 67P/Churyumov-Gerasimenko
• Automated Solar Flare Statistics in Soft X-rays over 37 Years of GOES Observations - The Invariance of Self-Organized Criticality during Three Solar Cycles
• Changes in the physical environment of the inner coma of 67P/Churyumov-Gerasimenko with decreasing heliocentric distance
• Inferring the interplanetary dust properties from remote observations and simulations
• Mt. Wendelstein Imaging of the Post-Perihelion Dust Coma of 67P/Churyumov-Gerasimenko in 2015/2016
• H${}_2$O and O${}_2$ Absorption in the Coma of Comet 67P/Churyumov-Gerasimenko Measured by the Alice Far-Ultraviolet Spectrograph on Rosetta
• The perihelion activity of comet 67P/Churyumov-Gerasimenko as seen by robotic telescopes
• STEREO/EUVI Event Catalog 2006-2012
• A time dependent relation between EUV solar flare light-curves from lines with differing formation temperatures

Cited by in corpus (8)

• Dust of comet 67P/Churyumov-Gerasimenko collected by Rosetta/MIDAS: classification and extension to the nanometre scale
• Ion velocity and electron temperature inside and around the diamagnetic cavity of comet 67P
• Plasma densities, flow and Solar EUV flux at comet 67P - A cross-calibration approach
• Cometary dust analogues for physics experiments
• The evolution of the electron number density in the coma of comet 67P at the location of Rosetta from 2015 November through 2016 March
• Implications from secondary emission from neutral impact on Cassini plasma and dust measurements
• Solar flares observed by Rosetta at comet 67P
• Modeling the Plasma Composition of 67P/C-G at different Heliocentric Distances