Estimating the solar wind pressure at comet 67P from Rosetta magnetic field measurements

Aims: The solar wind pressure is an important parameter of space weather, which plays a crucial role in the interaction of the solar wind with the planetary plasma environment. Here we investigate the possibility of determining a solar wind pressure proxy from Rosetta magnetic field data, measured deep inside the induced magnetosphere of comet 67P/Churyumov-Gerasimenko. This pressure proxy would be useful not only for other Rosetta related studies but could also serve as a new, independent input database for space weather propagation to other locations in the Solar System. Method: For the induced magnetospheres of comets the magnetic pressure in the innermost part of the pile-up region is balanced by the solar wind dynamic pressure. Recent investigations of Rosetta data have revealed that the maximum magnetic field in the pile-up region can be approximated by magnetic field measurements performed in the inner regions of the cometary magnetosphere, close to the boundary of the diamagnetic cavity, from which the external solar wind pressure can be estimated. Results: We were able to determine a solar wind pressure proxy for the time interval when the Rosetta spacecraft was located near the diamagnetic cavity boundary, between late April 2015 and January 2016. We then compared our Rosetta pressure proxy to solar wind pressure extrapolated to comet 67P from near-Earth. After the exclusion of disturbances caused by transient events, we found a strong correlation between the two datasets

Understanding the structure of the fading magnetosphere around comet 67P/Churyumov-Gerasimenko using measurements from the last weeks of the Rosetta mission.

International audienceAfter accompanying comet 67P/Churyumov-Gerasimenko on its journey and observing the evolution of its induced magnetosphere throughout the comet's life-cycle, the Rosetta mission concluded at the end of September 2016 with a controlled impact on the cometary nucleus. At this time, the comet was located more than 3.8 AU from the Sun, but the data still show clear indications of a small induced magnetosphere. The observations of the nascent magnetosphere of the awakening low activity comet had to be performed under constantly changing conditions, because the orbit was varied to satisfy operational requirements. This made it difficult to examine the structure of the magnetosphere of the low activity comet at that time. In contrast, near the conclusion of the Rosetta mission the spacecraft observed the fading cometary magnetosphere through multiple similar elliptical orbits, which allow us to obtain a more precise picture of its structure. We examined the measured plasma properties through these consecutive orbits, from which we were able to determine the structure of the fading magnetosphere using a simple, latitude dependant model

Understanding the structure of the fading magnetosphere around comet 67P/Churyumov-Gerasimenko using measurements from the last weeks of the Rosetta mission.

International audienceAfter accompanying comet 67P/Churyumov-Gerasimenko on its journey and observing the evolution of its induced magnetosphere throughout the comet's life-cycle, the Rosetta mission concluded at the end of September 2016 with a controlled impact on the cometary nucleus. At this time, the comet was located more than 3.8 AU from the Sun, but the data still show clear indications of a small induced magnetosphere. The observations of the nascent magnetosphere of the awakening low activity comet had to be performed under constantly changing conditions, because the orbit was varied to satisfy operational requirements. This made it difficult to examine the structure of the magnetosphere of the low activity comet at that time. In contrast, near the conclusion of the Rosetta mission the spacecraft observed the fading cometary magnetosphere through multiple similar elliptical orbits, which allow us to obtain a more precise picture of its structure. We examined the measured plasma properties through these consecutive orbits, from which we were able to determine the structure of the fading magnetosphere using a simple, latitude dependant model

Estimating the solar wind pressure at comet 67P from Rosetta magnetic field measurements

Aims: The solar wind pressure is an important parameter of space weather, which plays a crucial role in the interaction of the solar wind with the planetary plasma environment. Here we investigate the possibility of determining a solar wind pressure proxy from Rosetta magnetic field data, measured deep inside the induced magnetosphere of comet 67P/Churyumov-Gerasimenko. This pressure proxy would be useful not only for other Rosetta related studies but could also serve as a new, independent input database for space weather propagation to other locations in the Solar System. Method: For the induced magnetospheres of comets the magnetic pressure in the innermost part of the pile-up region is balanced by the solar wind dynamic pressure. Recent investigations of Rosetta data have revealed that the maximum magnetic field in the pile-up region can be approximated by magnetic field measurements performed in the inner regions of the cometary magnetosphere, close to the boundary of the diamagnetic cavity, from which the external solar wind pressure can be estimated. Results: We were able to determine a solar wind pressure proxy for the time interval when the Rosetta spacecraft was located near the diamagnetic cavity boundary, between late April 2015 and January 2016. We then compared our Rosetta pressure proxy to solar wind pressure extrapolated to comet 67P from near-Earth. After the exclusion of disturbances caused by transient events, we found a strong correlation between the two datasets

The magnetodiscs and aurorae of giant planets

Readers will find grouped together here the most recent observations, current theoretical models and present understanding of the coupled atmosphere, magnetosphere and solar wind system. The book begins with a general discussion of mass, energy and momentum transport in magnetodiscs. The physics of partially ionized plasmas of the giant planet magnetodiscs is of general interest throughout the field of space physics, heliophysics and astrophysical plasmas; therefore, understanding the basic physical processes associated with magnetodiscs has universal applications. The second chapter characterizes the solar wind interaction and auroral responses to solar wind driven dynamics. The third chapter describes the role of magnetic reconnection and the effects on plasma transport. Finally, the last chapter characterizes the spectral and spatial properties of auroral emissions, distinguishing between solar wind drivers and internal driving mechanisms. The in-depth reviews provide an excellent reference for future research in this discipline

Venus mantle‐Mars planetosphere: What are the similarities and differences?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94881/1/grl4808.pd

Cassini plasma spectrometer measurements of Jovian bow shock structure

International audienceThe Cassini spacecraft on its way to Saturn flew by Jupiter and crossed its bow shock more than forty times on the dusk-side of the planet, whereas the early missions targeting Jupiter explored the dawnside. Here we report the first results concerning these bow shock crossings, based on the measurements of the Cassini Plasma Spectrometer (CAPS), the magnetometer, and the radio and plasma wave science (RPWS) instrument. We present data for five bow shock crossings, one at about 1920 local time (LT), the other four between 2100 and 2130 LT, 47.5°-50° beyond terminator. During the flyby the solar activity was high and variable. The measurements confirm that the Jovian bow shock is huge, extending over 700 RJ down the flank; Cassini was the first to observe such distant shock features. The bow shock was turbulent and very dynamic and magnetic fluctuations were superimposed on the shock; the downstream ion distributions exhibited bimodal structure time to time. For all bow shock crossings the onset of ion thermalization was a clear shock signature supported by an electrostatic wave signal; thermalization can be used as a signature of the shock location even in those cases when the field data are rather smeared. The strength of the shock potential weakened toward more distant regions even if the local Mach number did not decrease. Reflected protons were not detected upstream above our current sensitivity limit, but the incoming solar wind fluctuated in the foot region. We argue that the Jovian bow shock is not always in a steady state, and some of the observations might be connected with this fact