The importance of solar illumination for discrete and diffuse aurora
We present a comprehensive overview of the occurrence of discrete and diffuse aurora in the nightside Northern Hemisphere at invariant latitudes 55°-75°. Twenty-one months of Freja observations (1 January 1993 to 30 September 1994) from the Northern Hemi...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2005-12-01
|
| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/23/3481/2005/angeo-23-3481-2005.pdf |
| _version_ | 1818310308881498112 |
|---|---|
| author | M. Hamrin P. Norqvist K. Rönnmark D. Fellgård |
| author_facet | M. Hamrin P. Norqvist K. Rönnmark D. Fellgård |
| author_sort | M. Hamrin |
| collection | DOAJ |
| description | We present a comprehensive overview of the occurrence of discrete
and diffuse aurora in the nightside Northern Hemisphere at invariant
latitudes 55°-75°. Twenty-one months
of Freja observations (1 January 1993 to 30 September 1994) from
the Northern Hemisphere, obtained at altitude, are
included in this investigation. We investigate the importance of
seasonal effects, solar illumination and geomagnetic activity for
the auroral precipitation. The seasonal variations in the occurrence
of discrete aurora are separated from the dependence on solar
illumination of the ionosphere. When the effects of sunlight are
eliminated, aurora is found to be more common during the summer.
The occurrence of diffuse, as well as discrete aurora, is suppressed
by solar illumination of the ionosphere. This dependence of diffuse
auroral precipitation on ionospheric conditions is not predicted by
theories that attribute diffuse aurora to equatorial pitch-angle
diffusion of hot magnetospheric electrons. |
| first_indexed | 2024-12-13T07:44:00Z |
| format | Article |
| id | doaj.art-4c493f29abf047cbb7c24bd745cb11e9 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-13T07:44:00Z |
| publishDate | 2005-12-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-4c493f29abf047cbb7c24bd745cb11e92022-12-21T23:54:53ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762005-12-01233481348610.5194/angeo-23-3481-2005The importance of solar illumination for discrete and diffuse auroraM. Hamrin0P. Norqvist1K. Rönnmark2D. Fellgård3Department of Physics, Umeå university, Umeå, SwedenDepartment of Physics, Umeå university, Umeå, SwedenDepartment of Physics, Umeå university, Umeå, SwedenDepartment of Physics, Umeå university, Umeå, SwedenWe present a comprehensive overview of the occurrence of discrete and diffuse aurora in the nightside Northern Hemisphere at invariant latitudes 55°-75°. Twenty-one months of Freja observations (1 January 1993 to 30 September 1994) from the Northern Hemisphere, obtained at altitude, are included in this investigation. We investigate the importance of seasonal effects, solar illumination and geomagnetic activity for the auroral precipitation. The seasonal variations in the occurrence of discrete aurora are separated from the dependence on solar illumination of the ionosphere. When the effects of sunlight are eliminated, aurora is found to be more common during the summer. The occurrence of diffuse, as well as discrete aurora, is suppressed by solar illumination of the ionosphere. This dependence of diffuse auroral precipitation on ionospheric conditions is not predicted by theories that attribute diffuse aurora to equatorial pitch-angle diffusion of hot magnetospheric electrons.https://www.ann-geophys.net/23/3481/2005/angeo-23-3481-2005.pdf |
| spellingShingle | M. Hamrin P. Norqvist K. Rönnmark D. Fellgård The importance of solar illumination for discrete and diffuse aurora Annales Geophysicae |
| title | The importance of solar illumination for discrete and diffuse aurora |
| title_full | The importance of solar illumination for discrete and diffuse aurora |
| title_fullStr | The importance of solar illumination for discrete and diffuse aurora |
| title_full_unstemmed | The importance of solar illumination for discrete and diffuse aurora |
| title_short | The importance of solar illumination for discrete and diffuse aurora |
| title_sort | importance of solar illumination for discrete and diffuse aurora |
| url | https://www.ann-geophys.net/23/3481/2005/angeo-23-3481-2005.pdf |
| work_keys_str_mv | AT mhamrin theimportanceofsolarilluminationfordiscreteanddiffuseaurora AT pnorqvist theimportanceofsolarilluminationfordiscreteanddiffuseaurora AT kronnmark theimportanceofsolarilluminationfordiscreteanddiffuseaurora AT dfellgard theimportanceofsolarilluminationfordiscreteanddiffuseaurora AT mhamrin importanceofsolarilluminationfordiscreteanddiffuseaurora AT pnorqvist importanceofsolarilluminationfordiscreteanddiffuseaurora AT kronnmark importanceofsolarilluminationfordiscreteanddiffuseaurora AT dfellgard importanceofsolarilluminationfordiscreteanddiffuseaurora |