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Sökning: L773:2169 897X OR L773:2169 8996 OR L773:0148 0227 OR L773:2156 2202 > (2000-2004) > On the relation bet...

On the relation between solar wind, pseudobreakups, and substorms

Kullen, Anita (författare)
KTH,Alfvénlaboratoriet
Karlsson, Tomas (författare)
KTH,Alfvénlaboratoriet
 (creator_code:org_t)
American Geophysical Union (AGU), 2004
2004
Engelska.
Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 109:A12
  • Tidskriftsartikel (refereegranskat)
Abstract Ämnesord
Stäng  
  • A statistical study of pseudobreakups and substorms is performed using Polar UV images from a 3-month period in winter 1998-1999. Data from the ACE solar wind monitor are examined in order to determine the influence of solar wind parameters on the occurrence of different substorm and pseudobreakup types. The results confirm that the IMF clock angle and the amount of solar wind energy flux control the strength of a substorm. The majority of large substorms appear when the IMF is strongly southward and the solar wind energy flux is high. Most small substorms occur during weakly positive or zero IMF B-z and low solar wind energy flux values. Pseudobreakups are associated with even lower energy fluxes than small substorms and appear typically for weakly positive IMF B-z. These results are in agreement with the scenario that pseudobreakups essentially are very weak substorms. Pseudobreakups appear during quiet times and during the growth phase or the recovery phase of weak or medium strong substorms. Time periods of enhanced geomagnetic activity with recurrent substorms are devoid of pseudobreakups. A detailed analysis of the different pseudobreakup types reveals that quiet time pseudobreakups appear predominantly during northward IMF. At least 20 percent of these appear at the poleward oval boundary. Optically, they do not differ much from very weak substorms. Growth phase pseudobreakups develop typically at the end of a 1 to 2 hour long excursion from northward to weakly southward IMF and are followed by quite weak substorms. A large majority of recovery phase pseudobreakups occur at a strongly polewardly displaced oval boundary at the end of a very active recovery phase. A considerable decrease of the polar cap size during the preceding substorm is connected to a northward turning of the IMF.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

pseudobreakup
substorm
solar wind
IMF
interplanetary magnetic-field
image-fuv imagers
magnetospheric substorm
auroral substorm
plasma sheet
geomagnetic disturbances
pseudo-breakup
growth-phase
onset
quiet

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Kullen, Anita
Karlsson, Tomas
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NATURVETENSKAP
NATURVETENSKAP
och Fysik
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Kungliga Tekniska Högskolan

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