Long-term decrease in the response of midlatitude stations to high-speed solar wind streams in 1914-2000
| Autor: | D. Martini, H.-J. Linthe, Kalevi Mursula, Mikko Orispää |
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| Rok vydání: | 2015 |
| Předmět: |
010504 meteorology & atmospheric sciences
Northern Hemisphere STREAMS Atmospheric sciences 01 natural sciences Term (time) Latitude Solar wind Geophysics Earth's magnetic field 13. Climate action Space and Planetary Science Climatology Middle latitudes Local time 0103 physical sciences Environmental science 010303 astronomy & astrophysics 0105 earth and related environmental sciences |
| Zdroj: | Journal of Geophysical Research: Space Physics. 120:2662-2674 |
| ISSN: | 2169-9380 |
| DOI: | 10.1002/2014ja020813 |
| Popis: | We investigate geomagnetic activity at two high-latitude, two midlatitude, and two low-latitude stations of the northern hemisphere and find that the increasing trend of geomagnetic activity in 1914–2000 is considerably lower at the two midlatitude stations (Niemegk and Fredericksburg) than at low- or high-latitude stations. As Niemegk occupies a specific position among geomagnetic stations, serving as the standard station for the K/Ak index derivation, it is crucial to understand the origin and long-term characteristics of this difference. We show here that geomagnetic activity at the studied midlatitude stations is relatively stronger in the declining phases of the 1 and 2 first solar cycles (15 and 16) than elsewhere, leading to the smaller long-term trend. We also find that the latitudinal differences in the trends are strongly dependent on local time, being considerably larger in the dawn sector. These differences can be explained by the relatively stronger contribution of high-speed streams to geomagnetic activity at the particular range of midlatitudes, compared to the stations at lower and higher latitudes. |
| Databáze: | OpenAIRE |
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