8 research outputs found
Cometary Ionospheres: An Updated Tutorial
This chapter aims at providing the tools and knowledge to understand and model the plasma environment surrounding comets in the innermost part near the nucleus. In particular, our goal is to give an updated post-Rosetta view of this ionised environment: what we knew, what we confirmed, what we overturned, and what we still do not understand
Erratum: Evolution of the ion environment of comet 67P during the Rosetta mission as seen by RPC-ICA
Birth of a comet magnetosphere: A spring of water ions
The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (~3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (<800 electron volts), produced upstream of Rosetta, and lower energy locally produced ions; we estimate the fluxes of both ion species and energetic neutral atoms
Cometary plasma response to interplanetary corotating interaction regions during 2016 June-September: a quantitative study by the Rosetta Plasma Consortium
Four interplanetary corotating interaction regions (CIRs) were identified during 2016 JuneâSeptember by the Rosetta Plasma Consortium (RPC) monitoring in situ the plasma environment of the comet 67P/ChuryumovâGerasimenko (67P) at heliocentric distances of âŒ3â3.8 au. The CIRs, formed in the interface region between low- and high-speed solar wind streams with speeds of âŒ320â400 kmâsâ1 and âŒ580â640 kmâsâ1, respectively, are characterized by relative increases in solar wind proton density by factors of âŒ13â29, in proton temperature by âŒ7â29, and in magnetic field by âŒ1â4 with respect to the pre-CIR values. The CIR boundaries are well defined with interplanetary discontinuities. Out of 10 discontinuities, four are determined to be forward waves and five are reverse waves, propagating at âŒ5â92 perâcent of the magnetosonic speed at angles of âŒ20°â87° relative to ambient magnetic field. Only one is identified to be a quasi-parallel forward shock with magnetosonic Mach number of âŒ1.48 and shock normal angle of âŒ41°. The cometary ionosphere response was monitored by Rosetta from cometocentric distances of âŒ4â30 km. A quiet time plasma density map was developed by considering dependences on cometary latitude, longitude, and cometocentric distance of Rosetta observations before and after each of the CIR intervals. The CIRs lead to plasma density enhancements of âŒ500â1000 perâcent with respect to the quiet time reference level. Ionospheric modelling shows that increased ionization rate due to enhanced ionizing (>12â200 eV) electron impact is the prime cause of the large cometary plasma density enhancements during the CIRs. Plausible origin mechanisms of the cometary ionizing electron enhancements are discussed
Comparison of the efficacy of rabeprazole 10 mg and omeprazole 20 mg for the healing rapidity of peptic ulcer diseases
Cometary plasma science -- A white paper in response to the voyage 2050 call by the European space agency
Comets hold the key to the understanding of our solar system, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the solar system, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. Fast flybys of comets have made many new discoveries, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the solar system. This white paper reviews the present-day knowledge of cometary plasmas, discusses the many questions that remain unanswered, and outlines a multi-spacecraft ESA mission to accompany a comet that will answer these questions by combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems