| 1. |
- Borälv, E., et al.
(författare)
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Correlation between ground-based observations of substorm signatures and magnetotail dynamics
- 2005
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Ingår i: Annales Geophysicae. - 0992-7689 .- 1432-0576. ; 23, s. 997-1011
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Tidskriftsartikel (refereegranskat)abstract
- We present a substorm event study combining Cluster and ground-based instrumentation. For this event ground-based magnetograms show a substorm onset and two separate substorm intensifications over Scandinavia, at the time located in the pre-midnight sector. During the substorm Cluster is located in the southern plasma sheet at a downtail distance of 18.5 Re. For all the substorm signatures seen on ground, corresponding plasma sheet drop-outs and re-entries of all or individual spacecraft of the Cluster constellation are observed. In general, plasma sheet drop-outs are assumed to be due to plasma sheet thinning/thickening and/or to magnetotail flapping. However, in the literature there has been some disagreement on both spatial and temporal characteristics of plasma sheet thinning and thickening during substorms. We therefore investigate the causes for the plasma sheet drop-outs for this event, which at first glance appears to show plasma sheet thinning at substorm onset, contradictory to the present standpoint in the literature.
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| 2. |
- Sharma, S., et al.
(författare)
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First-principles approach to noncollinear magnetism : Towards spin dynamics
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:19, s. 196405-
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Tidskriftsartikel (refereegranskat)abstract
- A description of noncollinear magnetism in the framework of spin-density functional theory is presented for the exact exchange energy functional which depends explicitly on two-component spinor orbitals. The equations for the effective Kohn-Sham scalar potential and magnetic field are derived within the optimized effective potential (OEP) framework. With the example of a magnetically frustrated Cr monolayer it is shown that the resulting magnetization density exhibits much more noncollinear structure than standard calculations. Furthermore, a time-dependent generalization of the noncollinear OEP method is well suited for an ab initio description of spin dynamics. We also show that the magnetic moments of solids Fe, Co, and Ni are well reproduced.
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| 3. |
- Bultmark, F., et al.
(författare)
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Tests of the efficiency of an augmented distorted planewave basis in electronic structure calculations
- 2008
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 20:23, s. 235241-
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Tidskriftsartikel (refereegranskat)abstract
- An augmented distorted planewave plus local orbital basis set has been developed and implemented in a simple fashion in order to test its efficiency for electronic structure calculations. It is based on the idea of using distorted planewaves (Gygi 1993 Phys. Rev. B 48 11692) as basis functions in the interstitial region instead of ordinary planewaves, as in the usual linearized augmented planewave and augmented planewave plus local orbitals methods. This is shown to lead to a significantly more rapid convergence for open structures as well as a modestly improved convergence for close packed structures.
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