Response of the polar magnetic field intensity to the exceptionally high solar wind streams in 2003

Lukianova, Renata; Мурсула, К.; Kozlovsky, Alexander

doi:10.1029/2011gl050420

Cited by 10 publications

(13 citation statements)

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“…Even at monthly time scale we find high correlations between the two parameters for all months, giving evidence that other factors in solar wind, especially the intensity of the interplanetary magnetic fields which is enhanced during CMEs [Richardson and Cane, 2012], have a significantly smaller effect for the monthly averages of ΔH at Sodankylä. This supports the earlier studies which have shown the importance of the SW speed for substorm occurrence [Tanskanen et al, 2005] and high-latitude geomagnetic activity [Finch et al, 2008;Lukianova et al, 2012;Holappa et al, 2014].…”

Section: Discussionsupporting

confidence: 92%

Centennial evolution of monthly solar wind speeds: Fastest monthly solar wind speeds from long‐duration coronal holes

2017

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High‐speed solar wind streams (HSSs) are very efficient drivers of geomagnetic activity at high latitudes. In this paper we use a recently developed ΔH parameter of geomagnetic activity, calculated from the nightside hourly magnetic field measurements of the Sodankylä observatory, as a proxy for solar wind (SW) speed at monthly time resolution in 1914–2014 (solar cycles 15–24). The seasonal variation in the relation between monthly ΔH and solar wind speed is taken into account by calculating separate regressions between ΔH and SW speed for each month. Thereby, we obtain a homogeneous series of proxy values for monthly solar wind speed for the last 100 years. We find that the strongest HSS‐active months of each solar cycle occur in the declining phase, in years 1919, 1930, 1941, 1952, 1959, 1973, 1982, 1994, and 2003. Practically all these years are the same or adjacent to the years of annual maximum solar wind speeds. This implies that the most persistent coronal holes, lasting for several solar rotations and leading to the highest annual SW speeds, are also the sources of the highest monthly SW speeds. Accordingly, during the last 100 years, there were no coronal holes of short duration (of about one solar rotation) that would produce faster monthly (or solar rotation) averaged solar wind than the most long‐living coronal holes in each solar cycle produce.

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Section: Discussionsupporting

confidence: 92%

Centennial evolution of monthly solar wind speeds: Fastest monthly solar wind speeds from long‐duration coronal holes

2017

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“…Previous studies have shown that solar wind speed is an important driver of long‐term (e.g., monthly and yearly) geomagnetic activity at low latitudes and midlatitude (Akasofu, ; Crooker, Feynman, & Gosling, ; Richardson, Cane, & Cliver, ; Richardson, Cliver, & Cane, ) and, especially, at high latitudes (Finch et al, ; Holappa, Mursula, & Asikainen, ; Holappa, Mursula, Asikainen, & Richardson, ; Lukianova, Mursula, & Kozlovsky, ; Mursula, Holappa, & Lukianova, ; Mursula, Lukianova, & Holappa, ) and of substorm activity (Tanskanen et al, ). Here we study to what extent the solar wind speed controls the seasonal variation of high‐latitude geomagnetic activity.…”

Section: Seasonal Variation Of Solar Wind Speed In 1995–2014mentioning

confidence: 99%

Seasonal Variation of High‐Latitude Geomagnetic Activity in Individual Years

2017

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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.

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“…So far, the temporal resolution of 1 min, or at most 10 s, has been the international standard for decades (e.g., in International Real‐time Magnetic Observatory Network). The instrumentation in Greenland has recently been upgraded, and the 1‐s resolution measurements are available from a few stations since 2010 and from several stations since 2011, while the earlier, lower frequency measurements and the geomagnetic activity indices derived from them have been widely utilized (Lukianova et al, ; Mursula et al, ; Tavares et al, ). This high‐frequency data (1‐s) have been so far left unanalyzed to full detail.…”

Section: Introductionmentioning

confidence: 99%

High‐Frequency Geomagnetic Fluctuations at Auroral Oval and Polar Cap

et al. 2018

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Rapid magnetic fluctuations are known to be closely linked to the high-latitude geomagnetic activity, in particular, to geomagnetic pulsations and subtorms. Increasing amount of commercial activity in the arctic regions requires better monitoring capability and improved understanding on the effects of geomagnetic hazards to infrastructure. In this study, we analyze rapid, 1-s fluctuations in Greenland. To measure high-frequency geomagnetic fluctuations in the auroral oval and polar cap, we use high time resolution data of 1 s from 12 stations covering a large latitudinal range of 64 to 84 quasi-dipole geomagnetic latitude (QDGMlat). We found out that the large magnetic field fluctuations exceeding 0.2 nT/s are observed 10-30% of the time in auroral oval latitudes, depending on the solar cycle phase and station location. The latitudinal differences are much larger in fluctuation coverage (fractional derivative rate, FDR) than in fluctuations amplitude (dH∕dt). The highest |dH∕dt| and FDRs at noon are observed at the northern stations from 72 to 84 QDGMlat, while in south Greenland from 72 to 65 QDGMlat, the highest |dH∕dt| and FDRs are recorded at midnight. The largest differences in seasonal variation between noon and midnight are observed in the polar cap, where a summer increase is seen at noon and almost flat seasonal profile at midnight. Plain Language SummaryWe analyze Earth's magnetic field measurements from Greenland in 2011-2013. We use high time resolution measurements obtained from 12 stations, covering a large geographic area. We use the rate of change of the magnetic field as the basis of our analysis, and we have developed a new method called the fractional derivative rate for this purpose. Differences between the years, time of day, and geographic location along the north-south axis are studied separately. We found out that there are significant differences between the stations, with the northernmost stations being more magnetically active during noon and the southernmost stations more active during midnight. The largest differences in these activity patterns are seen in the northernmost area, the polar cap. Understanding these variations in activity between the geographic locations will help us prepare more accurate and better targeted space weather forecasts in the future.

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Response of the polar magnetic field intensity to the exceptionally high solar wind streams in 2003

Cited by 10 publications

References 12 publications

Centennial evolution of monthly solar wind speeds: Fastest monthly solar wind speeds from long‐duration coronal holes

Centennial evolution of monthly solar wind speeds: Fastest monthly solar wind speeds from long‐duration coronal holes

Seasonal Variation of High‐Latitude Geomagnetic Activity in Individual Years

High‐Frequency Geomagnetic Fluctuations at Auroral Oval and Polar Cap

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