Precipitation of &gt; 115 kev protons in the evening and forenoon sectors in relation to the magnetic activity

Hauge, R.; Søraas, F.

doi:10.1016/0032-0633(75)90164-6

Cited by 31 publications

(12 citation statements)

References 20 publications

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“…A remarkable feature of energetic proton precipitation is their isotropic precipitation (with¯uxes being isotropic over the loss cone) which exists at any local time in any disturbance conditions (Hauge and Soraas, 1975;Lundblad et al, 1979) and forms the oval-shaped isotropic precipitation zone (Sergeev and Gvozdevsky, 1995). Recently this precipitation attracted much attention because of its potential importance for evaluation of magnetotail magnetic con®guration.…”

Section: Introductionmentioning

confidence: 99%

Dayside isotropic precipitation of energetic protons

1997

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Abstract.Recently it has been shown that isotropic precipitation of energetic protons on the nightside is caused by a non-adiabatic eect, namely pitch-angle scattering of protons in curved magnetic ®eld lines of the tail current sheet. Here we address the origin of isotropic proton precipitation on the dayside. Computations of proton scattering regions in the magnetopheric models T87, T89 and T95 reveal two regions which contribute to the isotropic precipitation. The ®rst is the region of weak magnetic ®eld in the outer cusp which provides the 1±2°wide isotropic precipitation on closed ®eld lines in a $2±3 hour wide MLT sector centered on noon. A second zone is formed by the scattering on the closed ®eld lines which cross the nightside equatorial region near the magnetopause which provides isotropic precipitation starting %1.5±2 h MLT from noon and which joins smoothly the precipitation coming from the tail current sheet. We also analyzed the isotropic proton precipitation using observations of NOAA low altitude polar spacecraft. We ®nd that isotropic precipitation of >30 to >80 keV protons continues around noon forming the continuous oval-shaped region of isotropic precipitation. Part of this region lies on open ®eld lines in the region of cusp-like or mantle precipitation, its equatorward part is observed on closed ®eld lines. Near noon it extends $1±2°below the sharp boundary of solar electron¯uxes (proxy of the open/closed ®eld line boundary) and equatorward of the cusp-like auroral precipitation. The observed energy dispersion of its equatorward boundary (isotropic boundary) agrees with model predictions of expected particle scattering in the regions of weak and highly curved magnetic ®eld. We also found some disagreement with model computations. We did not observe the predicted split of the isotropic precipitation region into separate nightside and dayside isotropic zones. Also, the oval-like shape of the isotropic boundary has a symmetry line in 10±12 MLT sector, which with increasing activity rotates toward dawn while the latitude of isotropic boundary is decreasing. Our conclusion is that for both dayside and nightside the isotropic boundary location is basically controlled by the magnetospheric magnetic ®eld, and therefore the isotropic boundaries can be used as a tool to probe the magnetospheric con®guration in dierent external conditions and at dierent activity levels.

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Section: Introductionmentioning

confidence: 99%

Dayside isotropic precipitation of energetic protons

1997

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“…They also noted that in some theoretical RC models the wave-particle scattering process is greatly simplified and therefore does not predict the strong pitch-angle diffusion postulated by Cornwall et al (1970) and observed by others (Hauge and Soraas, 1975;Soraas et al, 1999;Walt and Voss, 2001;Yahnina et al, 2000).…”

Section: Introductionmentioning

confidence: 91%

Strong pitch-angle diffusion of ring current ions in geomagnetic storm-associated conditions

Khazanov

Gamayunov

Gallagher

et al. 2007

Journal of Atmospheric and Solar-Terrestrial Physics

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“…The steep equatorward boundary where the proton precipitation drops from 410 3 to o10 2 ðcm 2 s sr keVÞ À1 is approximately co-located with the equatorward boundary of isotropic precipitation. The IB moves to lower latitudes as the ring current and plasma sheet move earthward with increasing convection field (Sergeev et al, 1983;Gussenhoven et al, 1987;Hauge and Søraas, 1975;Hultqvist et al, 1976) thus it gives information about the temporal and spatial dynamics of the inner part of the ring current and plasma sheet. As explained in Section 2 and shown in Fig.…”

Section: Article In Pressmentioning

confidence: 99%