Seasonal Variation of High-Latitude Geomagnetic Activity in Individual Years
| Autor: | Reko Hynönen, Eija Tanskanen, Kalevi Mursula |
|---|---|
| Přispěvatelé: | Department of Electronics and Nanoengineering, University of Oulu, Aalto-yliopisto, Aalto University |
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Geomagnetic activity
010504 meteorology & atmospheric sciences Decadal time scales Seasonal variation ta1171 Solar cycle 23 Electrojet Coronal hole solar cycle‐to‐cycle variation Atmospheric sciences 01 natural sciences 0103 physical sciences medicine Solstice Sun-Earth coupling 010303 astronomy & astrophysics geomagnetic activity 0105 earth and related environmental sciences seasonal variation Seasonality medicine.disease Solar maximum Sun‐Earth coupling decadal time scales solar wind‐magnetosphere coupling Solar wind Geophysics Earth's magnetic field Solar wind-magnetosphere coupling Space and Planetary Science Climatology Environmental science Solar cycle-to-cycle variation |
| Zdroj: | JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS. 122(10):10 |
| ISSN: | 2169-9380 |
| DOI: | 10.1002/2017JA024276 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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