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Oscillations of cometary tails : a vortex shedding phenomenon?
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Nisticò, G., Vladimirov, V., Nakariakov, V. M. (Valery M.), Battams, K. and Bothmer, V. (2018) Oscillations of cometary tails : a vortex shedding phenomenon? Astronomy & Astrophysics, 615 . A143. doi:10.1051/0004-6361/201732474 ISSN 0004-6361.
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WRAP-oscillations-cometary-tails-shedding-phenomenon-Nakaviakov-2018.pdf - Accepted Version - Requires a PDF viewer. Download (10Mb) | Preview |
Official URL: http://dx.doi.org/10.1051/0004-6361/201732474
Abstract
Context
During their journey to perihelion, comets may appear in the field of view of space-borne optical instruments, showing in some cases a nicely developed plasma tail extending from their coma and exhibiting an oscillatory behaviour.
Aims
The oscillations of cometary tails may be explained in terms of vortex shedding because of the interaction of the comet with the solar wind streams. Therefore, it is possible to exploit these oscillations in order to infer the value of the Strouhal number S t, which quantifies the vortex shedding phenomenon, and the physical properties of the local medium.
Methods
We used the Heliospheric Imager (HI) data of the Solar TErrestrial Relations Observatory (STEREO) mission to study the oscillations of the tails of comets 2P/Encke and C/2012 S1 (ISON) during their perihelion in Nov 2013. We determined the corresponding Strouhal numbers from the estimates of the halo size, the relative speed of the solar wind flow, and the period of the oscillations.
Results
We found that the estimated Strouhal numbers are very small, and the typical value of S t ~ 0.2 would be extrapolated for size of the halo larger than ~106 km.
Conclusions
Although the vortex shedding phenomenon has not been unambiguously revealed, the findings suggest that some kind of magnetohydrodynamic (MHD) instability process is responsible for the observed behaviour of cometary tails, which can be exploited for probing the physical conditions of the near-Sun region.
| Item Type: | Journal Article | |||||||||||||||
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| Subjects: | Q Science > QB Astronomy | |||||||||||||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | |||||||||||||||
| Library of Congress Subject Headings (LCSH): | Solar wind, Comets | |||||||||||||||
| Journal or Publication Title: | Astronomy & Astrophysics | |||||||||||||||
| Publisher: | EDP Sciences | |||||||||||||||
| ISSN: | 0004-6361 | |||||||||||||||
| Official Date: | July 2018 | |||||||||||||||
| Dates: |
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| Volume: | 615 | |||||||||||||||
| Article Number: | A143 | |||||||||||||||
| DOI: | 10.1051/0004-6361/201732474 | |||||||||||||||
| Status: | Peer Reviewed | |||||||||||||||
| Publication Status: | Published | |||||||||||||||
| Reuse Statement (publisher, data, author rights): | Reproduced with permission from Astronomy & Astrophysics, © ESO | |||||||||||||||
| Access rights to Published version: | Restricted or Subscription Access | |||||||||||||||
| Copyright Holders: | ESO | |||||||||||||||
| Date of first compliant deposit: | 9 August 2018 | |||||||||||||||
| Date of first compliant Open Access: | 9 August 2018 | |||||||||||||||
| RIOXX Funder/Project Grant: |
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