Solar Wind Protons Forming Partial Ring Distributions at Comet 67P

Abstract

Comets are a highly diverse group of solar system bodies that are mainly comprised of ice and organic material (Filacchione et al., 2019). They are known for their vast tails resulting from the ices on their surface sublimating when the comets approach the sun. Cometary activity can be defined by the amount of volatiles that a comet releases into space. An example of a high-activity comet is 1P/Halley, which has been the target of several space missions, for example, ESA's Giotto mission (Reinhard, 1987). The atmosphere of such high-activity comets, especially at perihelion, can extend millions of kilometres from the nucleus. Low-activity comets (Hansen et al., 2016), such as 67P/Churyumov-Gerasimenko (hereafter 67P), only have a tenuous atmosphere that might span no more than a few thousand kilometres. The cometary activity is driven by the strength of the solar radiation and strongly varies over time due to the comet's highly elliptical orbit. The significant change in activity also changes the plasma environment around the comet with different plasma boundaries forming at certain heliocentric distances (Mandt et al., 2016).The Rosetta mission has so far been the only mission to orbit a comet. It accompanied comet 67P for 2 years and observed large variations in its cometary activity as the heliocentric distance changed from about 3.6 AU to 1.24

Indirect Observations of Electric Fields at Comet 67P

“…More information on this visualization method and a discussion of the solar wind protons can be found in Moeslinger et al. (2023).…”

“…Another estimate for the average electric field direction is available from the solar wind proton distributions (see Moeslinger et al., 2023). Because of the larger velocities and therefore larger gyroradii, these estimates are representative of an even larger spatial scale in the upstream region of the nucleus.…”

“…This procedure is presented in Moeslinger et al. (2023), but in this study we apply it to the data set of cometary pickup ions. We will outline the main algorithm and its limitations below.…”

“…More information can be found in Moeslinger et al. (2023). The fitting is done individually for each ICA scan.…”

“…In both steps we use a weighted non-linear least squares fitting algorithm. More information can be found in Moeslinger et al (2023). The fitting is done individually for each ICA scan.…”