Solar Cycle Occurrence of Alfvénic Fluctuations and Related Geo-Efficiency

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Solar Cycle Occurrence of Alfvénic Fluctuations and Related Geo-Efficiency. / Tanskanen, Eija; Snekvik, K.; Slavin, J. A.; Pérez-Suárez, D.; Viljanen, A.; Goldstein, M. L. ; Käpylä, M.J.; Hynönen, Reko; Häkkinen, L. V. T.; Mursula, K.

In: Journal of geophysical research: Space physics, Vol. 122, No. 10, 2017, p. 9848-9857.

Research output: Contribution to journalArticleScientificpeer-review

Harvard

Tanskanen, E, Snekvik, K, Slavin, JA, Pérez-Suárez, D, Viljanen, A, Goldstein, ML, Käpylä, MJ, Hynönen, R, Häkkinen, LVT & Mursula, K 2017, 'Solar Cycle Occurrence of Alfvénic Fluctuations and Related Geo-Efficiency' Journal of geophysical research: Space physics, vol. 122, no. 10, pp. 9848-9857. https://doi.org/10.1002/2017JA024385

APA

Tanskanen, E., Snekvik, K., Slavin, J. A., Pérez-Suárez, D., Viljanen, A., Goldstein, M. L., ... Mursula, K. (2017). Solar Cycle Occurrence of Alfvénic Fluctuations and Related Geo-Efficiency. Journal of geophysical research: Space physics, 122(10), 9848-9857. https://doi.org/10.1002/2017JA024385

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Author

Tanskanen, Eija ; Snekvik, K. ; Slavin, J. A. ; Pérez-Suárez, D. ; Viljanen, A. ; Goldstein, M. L. ; Käpylä, M.J. ; Hynönen, Reko ; Häkkinen, L. V. T. ; Mursula, K. / Solar Cycle Occurrence of Alfvénic Fluctuations and Related Geo-Efficiency. In: Journal of geophysical research: Space physics. 2017 ; Vol. 122, No. 10. pp. 9848-9857.

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@article{9235407aa070457ea239d3a78301bf14,
title = "Solar Cycle Occurrence of Alfv{\'e}nic Fluctuations and Related Geo-Efficiency",
abstract = "We examine solar wind intervals with Alfv{\'e}nic fluctuations (ALFs) in 1995–2011. The annual number, the total annual duration, and the average length of ALFs vary over the solar cycle, having a maximum in 2003 and a minimum in 2009. ALFs are most frequent in the declining phase of solar cycle, when the number of high-speed streams at the Earth's vicinity is increased. There is a rapid transition after the maximum of solar cycle 23 from ALFs being mainly embedded in slow solar wind (<400 km/s) until 2002 to ALFs being dominantly in fast solar wind (>600 km/s) since 2003. Cross helicity increased by 30{\%} from 2002 to 2003 and maximized typically 4–6 h before solar wind speed maximum. Cross helicity remained elevated for several days for highly Alfv{\'e}nic non-ICME streams, but only for a few hours for ICMEs. The number of substorms increased by about 40{\%} from 2002 to 2003, and the annual number of substorms closely follows the annual cross helicity. This further emphasizes the role of Alfv{\'e}nic fluctuations in modulating substorm activity. The predictability of substorm frequency and size would be greatly improved by monitoring solar wind Alfv{\'e}nic fluctuations in addition to the mean values of the important solar wind parameters.",
keywords = "Solar wind plasma, Plasma waves and turbulence, Solar cycle variations, Substorms, Magnetic fields and magnetism, Alfv{\'e}nic fluctuations, Space climate, Geomagnetic activity, Solar cycle time scales, High-speed streams",
author = "Eija Tanskanen and K. Snekvik and Slavin, {J. A.} and D. P{\'e}rez-Su{\'a}rez and A. Viljanen and Goldstein, {M. L.} and M.J. K{\"a}pyl{\"a} and Reko Hyn{\"o}nen and H{\"a}kkinen, {L. V. T.} and K. Mursula",
year = "2017",
doi = "10.1002/2017JA024385",
language = "English",
volume = "122",
pages = "9848--9857",
journal = "Journal of geophysical research: Space physics",
issn = "2169-9380",
number = "10",

}

RIS - Download

TY - JOUR

T1 - Solar Cycle Occurrence of Alfvénic Fluctuations and Related Geo-Efficiency

AU - Tanskanen, Eija

AU - Snekvik, K.

AU - Slavin, J. A.

AU - Pérez-Suárez, D.

AU - Viljanen, A.

AU - Goldstein, M. L.

AU - Käpylä, M.J.

AU - Hynönen, Reko

AU - Häkkinen, L. V. T.

AU - Mursula, K.

PY - 2017

Y1 - 2017

N2 - We examine solar wind intervals with Alfvénic fluctuations (ALFs) in 1995–2011. The annual number, the total annual duration, and the average length of ALFs vary over the solar cycle, having a maximum in 2003 and a minimum in 2009. ALFs are most frequent in the declining phase of solar cycle, when the number of high-speed streams at the Earth's vicinity is increased. There is a rapid transition after the maximum of solar cycle 23 from ALFs being mainly embedded in slow solar wind (<400 km/s) until 2002 to ALFs being dominantly in fast solar wind (>600 km/s) since 2003. Cross helicity increased by 30% from 2002 to 2003 and maximized typically 4–6 h before solar wind speed maximum. Cross helicity remained elevated for several days for highly Alfvénic non-ICME streams, but only for a few hours for ICMEs. The number of substorms increased by about 40% from 2002 to 2003, and the annual number of substorms closely follows the annual cross helicity. This further emphasizes the role of Alfvénic fluctuations in modulating substorm activity. The predictability of substorm frequency and size would be greatly improved by monitoring solar wind Alfvénic fluctuations in addition to the mean values of the important solar wind parameters.

AB - We examine solar wind intervals with Alfvénic fluctuations (ALFs) in 1995–2011. The annual number, the total annual duration, and the average length of ALFs vary over the solar cycle, having a maximum in 2003 and a minimum in 2009. ALFs are most frequent in the declining phase of solar cycle, when the number of high-speed streams at the Earth's vicinity is increased. There is a rapid transition after the maximum of solar cycle 23 from ALFs being mainly embedded in slow solar wind (<400 km/s) until 2002 to ALFs being dominantly in fast solar wind (>600 km/s) since 2003. Cross helicity increased by 30% from 2002 to 2003 and maximized typically 4–6 h before solar wind speed maximum. Cross helicity remained elevated for several days for highly Alfvénic non-ICME streams, but only for a few hours for ICMEs. The number of substorms increased by about 40% from 2002 to 2003, and the annual number of substorms closely follows the annual cross helicity. This further emphasizes the role of Alfvénic fluctuations in modulating substorm activity. The predictability of substorm frequency and size would be greatly improved by monitoring solar wind Alfvénic fluctuations in addition to the mean values of the important solar wind parameters.

KW - Solar wind plasma

KW - Plasma waves and turbulence

KW - Solar cycle variations

KW - Substorms

KW - Magnetic fields and magnetism

KW - Alfvénic fluctuations

KW - Space climate

KW - Geomagnetic activity

KW - Solar cycle time scales

KW - High-speed streams

U2 - 10.1002/2017JA024385

DO - 10.1002/2017JA024385

M3 - Article

VL - 122

SP - 9848

EP - 9857

JO - Journal of geophysical research: Space physics

JF - Journal of geophysical research: Space physics

SN - 2169-9380

IS - 10

ER -

ID: 15805640