@article{9bac9b2a6ca3471c97e3a726cff86759,
title = "Solar Orbiter's encounter with the tail of comet C/2019 Y4 (ATLAS): Magnetic field draping and cometary pick-up ion waves",
abstract = "Context. Solar Orbiter is expected to have flown close to the tail of comet C/2019 Y4 (ATLAS) during the spacecraft's first perihelion in June 2020. Models predict a possible crossing of the comet tails by the spacecraft at a distance from the Sun of approximately 0.5 AU. Aims. This study is aimed at identifying possible signatures of the interaction of the solar wind plasma with material released by comet ATLAS, including the detection of draped magnetic field as well as the presence of cometary pick-up ions and of ion-scale waves excited by associated instabilities. This encounter provides us with the first opportunity of addressing such dynamics in the inner Heliosphere and improving our understanding of the plasma interaction between comets and the solar wind. Methods. We analysed data from all in situ instruments on board Solar Orbiter and compared their independent measurements in order to identify and characterize the nature of structures and waves observed in the plasma when the encounter was predicted. Results. We identified a magnetic field structure observed at the start of 4 June, associated with a full magnetic reversal, a local deceleration of the flow and large plasma density, and enhanced dust and energetic ions events. The cross-comparison of all these observations support a possible cometary origin for this structure and suggests the presence of magnetic field draping around some low-field and high-density object. Inside and around this large scale structure, several ion-scale wave-forms are detected that are consistent with small-scale waves and structures generated by cometary pick-up ion instabilities. Conclusions. Solar Orbiter measurements are consistent with the crossing through a magnetic and plasma structure of cometary origin embedded in the ambient solar wind. We suggest that this corresponds to the magnetotail of one of the fragments of comet ATLAS or to a portion of the tail that was previously disconnected and advected past the spacecraft by the solar wind. ",
keywords = "Comets: individual: C/2019 Y4 ATLAS, Instabilities, Plasmas, Solar wind, Waves",
author = "L. Matteini and R. Laker and T. Horbury and L. Woodham and Bale, {S. D.} and Stawarz, {J. E.} and T. Woolley and K. Steinvall and Jones, {G. H.} and Grant, {S. R.} and Q. Afghan and M. Galand and H. O'brien and V. Evans and V. Angelini and M. Maksimovic and T. Chust and Y. Khotyaintsev and V. Krasnoselskikh and M. Kretzschmar and E. Lorf{\`e}vre and D. Plettemeier and J. Sou{\v c}ek and M. Steller and {\v S}tver{\'a}k and P. Tr{\'a}vn{\'i}{\v c}ek and A. Vaivads and A. Vecchio and Wimmer-Schweingruber, {R. F.} and Ho, {G. C.} and R. G{\'o}mez-Herrero and J. Rodr{\'i}guez-Pacheco and P. Louarn and A. Fedorov and Owen, {C. J.} and R. Bruno and S. Livi and I. Zouganelis and D. M{\"u}ller",
note = "Funding Information: Acknowledgements. Solar Orbiter is a mission of international cooperation between ESA and NASA, operated by ESA. Solar Orbiter magnetometer operations are funded by the UK Space Agency (grant ST/T001062/1). TH and LW are supported by STFC grant ST/S000364/1, TW was supported by STFC grant ST/T506151/10 and RL by an Imperial College President{\textquoteright}s scholarship. JES is funded by the Royal Society University Research Fellowship URF/R1/201286. SRG and QA are supported by STFC PhD studentships. SDB acknowledges the support of the Leverhulme Trust Visiting Professor programme. The RPW instrument has been designed and funded by CNES, CNRS, the Paris Observatory, The Swedish National Space Agency, ESA-PRODEX and all the participating institutes. EPD/STEP was built at CAU and funded by the German Space Agency (DLR) under grant numbers 50OT0901, 50OT1202, 50OT1702 and 50OT2002. JRP and RGH acknowledge the financial support of the Spanish MICIU/AEI under projects ESP2017-88436-R and PID2019-104863RBI00/AEI/10.13039/501100011033. Solar Orbiter Solar Wind Analyser (SWA) data are derived from scientific sensors which have been designed and created, and are operated under funding provided in numerous contracts from the UK Space Agency (UKSA), the UK Science and Technology Facilities Council (STFC), the Agenzia Spaziale Italiana (ASI), the Centre National d{\textquoteright}Etudes Spa-tiales (CNES, France), the Centre National de la Recherche Scientifique (CNRS, France), the Czech contribution to the ESA PRODEX programme and NASA. Solar Orbiter SWA work at UCL/MSSL is currently funded under STFC grants ST/T001356/1 and ST/S000240/1.",
year = "2021",
month = dec,
day = "14",
doi = "10.1051/0004-6361/202141229",
language = "English",
volume = "656",
journal = "Astronomy & Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
}