Seasonal Variation of High-Latitude Geomagnetic Activity in Individual Years

Research output: Contribution to journalArticleScientificpeer-review

Standard

Seasonal Variation of High-Latitude Geomagnetic Activity in Individual Years. / Tanskanen, E. I.; Hynönen, R.; Mursula, K.

In: Journal of geophysical research: Space physics, Vol. 122, No. 10, 21.11.2017, p. 10,058–10,071.

Research output: Contribution to journalArticleScientificpeer-review

Harvard

APA

Vancouver

Author

Bibtex - Download

@article{9327c08b1ca34259af8fa830d27f87ea,
title = "Seasonal Variation of High-Latitude Geomagnetic Activity in Individual Years",
abstract = "We study the seasonal variation of high-latitude geomagnetic activity in individual years in 1966-2014 (solar cycles 20-24) by identifying the most active and the second most active season based on westward electrojet indices AL (1966-2014) and IL (1995-2014). The annual maximum is found at either equinox in two thirds and at either solstice in one third of the years examined. The traditional two-equinox maximum pattern is found in roughly one fourth of the years. We found that the seasonal variation of high-latitude geomagnetic activity closely follows the solar wind speed. While the mechanisms leading to the two-equinox maxima pattern are in operation, the long-term change of solar wind speed tends to mask the effect of these mechanisms for individual years. Large cycle-to-cycle variation is found in the seasonal pattern: equinox maxima are more common during cycles 21 and 22 than in cycles 23 or 24. Exceptionally long winter dominance in high-latitude activity and solar wind speed is seen in the declining phase of cycle 23, after the appearance of the long-lasting low-latitude coronal hole.",
keywords = "Decadal time scales, Geomagnetic activity, Seasonal variation, Solar cycle-to-cycle variation, Solar wind-magnetosphere coupling, Sun-Earth coupling",
author = "Tanskanen, {E. I.} and R. Hyn{\"o}nen and K. Mursula",
year = "2017",
month = "11",
day = "21",
doi = "10.1002/2017JA024276",
language = "English",
volume = "122",
pages = "10,058–10,071",
journal = "Journal of geophysical research: Space physics",
issn = "2169-9380",
number = "10",

}

RIS - Download

TY - JOUR

T1 - Seasonal Variation of High-Latitude Geomagnetic Activity in Individual Years

AU - Tanskanen, E. I.

AU - Hynönen, R.

AU - Mursula, K.

PY - 2017/11/21

Y1 - 2017/11/21

N2 - We study the seasonal variation of high-latitude geomagnetic activity in individual years in 1966-2014 (solar cycles 20-24) by identifying the most active and the second most active season based on westward electrojet indices AL (1966-2014) and IL (1995-2014). The annual maximum is found at either equinox in two thirds and at either solstice in one third of the years examined. The traditional two-equinox maximum pattern is found in roughly one fourth of the years. We found that the seasonal variation of high-latitude geomagnetic activity closely follows the solar wind speed. While the mechanisms leading to the two-equinox maxima pattern are in operation, the long-term change of solar wind speed tends to mask the effect of these mechanisms for individual years. Large cycle-to-cycle variation is found in the seasonal pattern: equinox maxima are more common during cycles 21 and 22 than in cycles 23 or 24. Exceptionally long winter dominance in high-latitude activity and solar wind speed is seen in the declining phase of cycle 23, after the appearance of the long-lasting low-latitude coronal hole.

AB - We study the seasonal variation of high-latitude geomagnetic activity in individual years in 1966-2014 (solar cycles 20-24) by identifying the most active and the second most active season based on westward electrojet indices AL (1966-2014) and IL (1995-2014). The annual maximum is found at either equinox in two thirds and at either solstice in one third of the years examined. The traditional two-equinox maximum pattern is found in roughly one fourth of the years. We found that the seasonal variation of high-latitude geomagnetic activity closely follows the solar wind speed. While the mechanisms leading to the two-equinox maxima pattern are in operation, the long-term change of solar wind speed tends to mask the effect of these mechanisms for individual years. Large cycle-to-cycle variation is found in the seasonal pattern: equinox maxima are more common during cycles 21 and 22 than in cycles 23 or 24. Exceptionally long winter dominance in high-latitude activity and solar wind speed is seen in the declining phase of cycle 23, after the appearance of the long-lasting low-latitude coronal hole.

KW - Decadal time scales

KW - Geomagnetic activity

KW - Seasonal variation

KW - Solar cycle-to-cycle variation

KW - Solar wind-magnetosphere coupling

KW - Sun-Earth coupling

UR - http://www.scopus.com/inward/record.url?scp=85031319852&partnerID=8YFLogxK

U2 - 10.1002/2017JA024276

DO - 10.1002/2017JA024276

M3 - Article

VL - 122

SP - 10,058–10,071

JO - Journal of geophysical research: Space physics

JF - Journal of geophysical research: Space physics

SN - 2169-9380

IS - 10

ER -

ID: 15871011