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Open flux in Saturn’s magnetosphere

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Open flux in Saturn’s magnetosphere. / Badman, Sarah V.; Jackman, Caitriona M.; Nichols, Jonathan D.; Clarke, John T.; Gérard, Jean-Claude.

In: Icarus, Vol. 231, 01.03.2014, p. 137-145.

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Harvard

Badman, SV, Jackman, CM, Nichols, JD, Clarke, JT & Gérard, J-C 2014, 'Open flux in Saturn’s magnetosphere', Icarus, vol. 231, pp. 137-145. https://doi.org/10.1016/j.icarus.2013.12.004

APA

Badman, S. V., Jackman, C. M., Nichols, J. D., Clarke, J. T., & Gérard, J-C. (2014). Open flux in Saturn’s magnetosphere. Icarus, 231, 137-145. https://doi.org/10.1016/j.icarus.2013.12.004

Vancouver

Badman SV, Jackman CM, Nichols JD, Clarke JT, Gérard J-C. Open flux in Saturn’s magnetosphere. Icarus. 2014 Mar 1;231:137-145. https://doi.org/10.1016/j.icarus.2013.12.004

Author

Badman, Sarah V. ; Jackman, Caitriona M. ; Nichols, Jonathan D. ; Clarke, John T. ; Gérard, Jean-Claude. / Open flux in Saturn’s magnetosphere. In: Icarus. 2014 ; Vol. 231. pp. 137-145.

Bibtex

@article{3f378a0d6e5c4f93bb17a7fce5695903,
title = "Open flux in Saturn{\textquoteright}s magnetosphere",
abstract = "We characterise the interaction between the solar wind and Saturn{\textquoteright}s magnetosphere by evaluating the amount of {\textquoteleft}open{\textquoteright} magnetic flux connected to the solar wind. This is deduced from a large set of Hubble Space Telescope images of the ultraviolet aurora, using the poleward boundary of the main aurora as a proxy for the open-closed field line boundary in the ionosphere. The amount of open flux is found to be 10–50 GWb, with a mean of 35 GWb. The typical change in open flux between consecutive observations separated by 10–60 h is -5 or +7 GWb. These changes are a result of imbalance between open flux creation at the dayside magnetopause and its closure in the magnetotail. The 5 GWb typical decrease in open flux is consistent with in situ measurements of the flux transported following a reconnection event. Estimates of average, net reconnection rates are found to be typically a few tens of kV, with some extreme examples of unbalanced magnetopause or tail reconnection occurring at ~300 kV. The range of values determined suggest that Saturn{\textquoteright}s magnetosphere does not generally achieve a steady state between flux opening at the magnetopause and flux closure in the magnetotail. The percentage of magnetic flux which is open in Saturn{\textquoteright}s magnetosphere is similar to that measured at the Earth (2–11%), but the typical percentage that is closed between observations is significantly lower (13% compared to 40–70%). Therefore, open flux is usually closed in smaller (few GWb) events in Saturn{\textquoteright}s magnetosphere. The exception to this behaviour is large, rapid flux closure events which are associated with solar wind compressions. While the rates of flux opening and closure should be equal over long timescales, they are evidently different on shorter (up to tens of hours) timescales. The relative independence of the magnetopause and tail reconnection rates can be attributed to the long loading timescales required to transport open field lines into the tail.",
keywords = "Saturn, magnetosphere, Aurorae, Ultraviolet observations",
author = "Badman, {Sarah V.} and Jackman, {Caitriona M.} and Nichols, {Jonathan D.} and Clarke, {John T.} and Jean-Claude G{\'e}rard",
year = "2014",
month = mar,
day = "1",
doi = "10.1016/j.icarus.2013.12.004",
language = "English",
volume = "231",
pages = "137--145",
journal = "Icarus",
issn = "0019-1035",
publisher = "ELSEVIER ACADEMIC PRESS INC",

}

RIS

TY - JOUR

T1 - Open flux in Saturn’s magnetosphere

AU - Badman, Sarah V.

AU - Jackman, Caitriona M.

AU - Nichols, Jonathan D.

AU - Clarke, John T.

AU - Gérard, Jean-Claude

PY - 2014/3/1

Y1 - 2014/3/1

N2 - We characterise the interaction between the solar wind and Saturn’s magnetosphere by evaluating the amount of ‘open’ magnetic flux connected to the solar wind. This is deduced from a large set of Hubble Space Telescope images of the ultraviolet aurora, using the poleward boundary of the main aurora as a proxy for the open-closed field line boundary in the ionosphere. The amount of open flux is found to be 10–50 GWb, with a mean of 35 GWb. The typical change in open flux between consecutive observations separated by 10–60 h is -5 or +7 GWb. These changes are a result of imbalance between open flux creation at the dayside magnetopause and its closure in the magnetotail. The 5 GWb typical decrease in open flux is consistent with in situ measurements of the flux transported following a reconnection event. Estimates of average, net reconnection rates are found to be typically a few tens of kV, with some extreme examples of unbalanced magnetopause or tail reconnection occurring at ~300 kV. The range of values determined suggest that Saturn’s magnetosphere does not generally achieve a steady state between flux opening at the magnetopause and flux closure in the magnetotail. The percentage of magnetic flux which is open in Saturn’s magnetosphere is similar to that measured at the Earth (2–11%), but the typical percentage that is closed between observations is significantly lower (13% compared to 40–70%). Therefore, open flux is usually closed in smaller (few GWb) events in Saturn’s magnetosphere. The exception to this behaviour is large, rapid flux closure events which are associated with solar wind compressions. While the rates of flux opening and closure should be equal over long timescales, they are evidently different on shorter (up to tens of hours) timescales. The relative independence of the magnetopause and tail reconnection rates can be attributed to the long loading timescales required to transport open field lines into the tail.

AB - We characterise the interaction between the solar wind and Saturn’s magnetosphere by evaluating the amount of ‘open’ magnetic flux connected to the solar wind. This is deduced from a large set of Hubble Space Telescope images of the ultraviolet aurora, using the poleward boundary of the main aurora as a proxy for the open-closed field line boundary in the ionosphere. The amount of open flux is found to be 10–50 GWb, with a mean of 35 GWb. The typical change in open flux between consecutive observations separated by 10–60 h is -5 or +7 GWb. These changes are a result of imbalance between open flux creation at the dayside magnetopause and its closure in the magnetotail. The 5 GWb typical decrease in open flux is consistent with in situ measurements of the flux transported following a reconnection event. Estimates of average, net reconnection rates are found to be typically a few tens of kV, with some extreme examples of unbalanced magnetopause or tail reconnection occurring at ~300 kV. The range of values determined suggest that Saturn’s magnetosphere does not generally achieve a steady state between flux opening at the magnetopause and flux closure in the magnetotail. The percentage of magnetic flux which is open in Saturn’s magnetosphere is similar to that measured at the Earth (2–11%), but the typical percentage that is closed between observations is significantly lower (13% compared to 40–70%). Therefore, open flux is usually closed in smaller (few GWb) events in Saturn’s magnetosphere. The exception to this behaviour is large, rapid flux closure events which are associated with solar wind compressions. While the rates of flux opening and closure should be equal over long timescales, they are evidently different on shorter (up to tens of hours) timescales. The relative independence of the magnetopause and tail reconnection rates can be attributed to the long loading timescales required to transport open field lines into the tail.

KW - Saturn, magnetosphere

KW - Aurorae

KW - Ultraviolet observations

U2 - 10.1016/j.icarus.2013.12.004

DO - 10.1016/j.icarus.2013.12.004

M3 - Journal article

VL - 231

SP - 137

EP - 145

JO - Icarus

JF - Icarus

SN - 0019-1035

ER -