| 1. |
- Boberg, Fredrik, et al.
(författare)
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Solar mean magnetic field variability: A wavelet approach to Wilcox Solar Observatory and SOHO/Michelson Doppler Imager observations
- 2002
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Ingår i: Journal of Geophysical Research. - 2156-2202. ; 107:A10: 1318
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Solar mean magnetic field (SMMF) measurements from the Wilcox Solar Observatory and with the SOHO/MDI instrument are described and analyzed. Even though two completely different methods of observation are used, the two data sets obtained show a strong similarity. Using continuous wavelet transforms, SMMF variability is found at a number of temporal scales. Detected SMMF signals with a 1–2 year period are considered to be linked to variations in the internal rotation of the Sun. Intermediate SMMF oscillations with a period of 80–200 days are probably connected to the evolution of large active regions. We also find evidence for 90 min variations with coronal mass ejections as a suggested origin.
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| 2. |
- Lihavainen, Heikki, et al.
(författare)
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Observational signature of the direct radiative effect by natural boreal forest aerosols and its relation to the corresponding first indirect effect
- 2009
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union. - 0148-0227 .- 2156-2202. ; 114
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- By using a screened set of long-term aerosol measurement data, the contribution of natural boreal forest aerosols to the direct radiative effect (DRE) was observed at a remote continental site in northern Finland. Averaged over the summer season, the magnitude of this effect at the top of the atmosphere was estimated to be in the range -(0.37-0.74) W m(-2) in our study region and possibly somewhat higher over the whole boreal forest region. Globally, the DRE owing to boreal forest aerosols is much smaller than that owing to natural sea salt or dust aerosols, as well as direct radiative forcing by anthropogenic aerosols. We also updated the earlier estimates of the first indirect radiative effect (IRE) by natural boreal forest aerosols. We found that this IRE is likely to be substantially higher, perhaps more than an order of magnitude, than the corresponding DRE
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| 3. |
- Sadeghi, Soheil, et al.
(författare)
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Cluster Observations of Quasi-Static Potential Structures Overlapping with Alfvénic Regions
- 2012
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Results are presented from an equatorward crossing of the Cluster spacecraft through the high-altitude auroral acceleration region, over a system of East-West aligned auroral arcs in the Southern hemisphere auroral oval. The event occurred during quiet geomagnetic conditions during the expansion phase of a weak substorm. Acceleration potential profiles of the quasi-static structures are determined from the particle and field data. The observations reveal a dynamically developing system of small-scale and large-scale quasi-static structures overlapping with Alfvénic regions. Such overlaps are found within the PSBL and inside the Region 2 of downward currents. No density cavities are seen in the overlap regions. Growths of small-scale potential structures were observed in the PSBL and in the middle of Region 2, during the ~1.5 minutes between the Cluster 4 and Cluster 3 passages. During this period, the Alfvénic regions retreated both at the poleward and equatorward oval boundaries, and the large-scale quasi-static potentials intensified.
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