Auroral zone dayside precipitation during magnetic storm initial phases

Citation
Bt. Tsurutani et al., Auroral zone dayside precipitation during magnetic storm initial phases, J ATMOS S-P, 63(5), 2001, pp. 513-522
Citations number
45
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS
ISSN journal
1364-6826 → ACNP
Volume
63
Issue
5
Year of publication
2001
Pages
513 - 522
Database
ISI
SICI code
1364-6826(200103)63:5<513:AZDPDM>2.0.ZU;2-#
Abstract
Significant charged-particle precipitation occurs in the dayside auroral zo ne during and after interplanetary shock impingements on the Earth's magnet osphere. The precipitation intensities and spatial and temporal evolution a re discussed. Although the post-shock energy flux (1020 erg cm(-2) s(-1)) i s lower than that of substorms, the total energy deposition rate may be con siderably greater (similar to an order of magnitude) than nightside energy rates due to the greater area of the dayside portion of the auroral oval (d efined as extending from 03 MLT through noon to 21 MLT). This dayside preci pitation represents direct solar wind energy input into the magnetosphere, ionosphere system. The exact mechanisms for particle energization and preci pitation into the ionosphere are not known at this time. Different mechanis ms are probably occurring during different portions of the storm initial ph ase. immediately after shock compression of the magnetosphere. possible pre cipitation-related mechanisms are: (1) betatron compression of preexisting outer zone magnetospheric particles. The anisotropic plasma is unstable to loss-cone instabilities, leading to plasma wave growth, resonant particle p itch-angle scattering and electron and proton losses into the upper ionosph ere. (2) The compression of the magnetosphere can also lead to enhanced fie ld-aligned currents and the formation of dayside double-layers. Finally (3) in the latter stages of the storm initial phase. there is evidence for a l ong-lasting viscous-like interaction occurring on the Ranks of the magnetop ause. Ground-based observations identifying the types of dayside auroral fo rms would be extremely useful in identifying the specific solar wind energy transfer mechanisms. (C) 2001 Elsevier Science Ltd. All rights reserved.