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AGU: Space Weather

 

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  • Magnetospheric Physics: Forecasting
  • Magnetospheric Physics: Magnetospheric configuration and dynamics
  • Magnetospheric Physics: Solar wind/magnetosphere interactions
  • Magnetospheric Physics: Energetic particles, trapped
Abstract
Cited By (5)
 

Abstract

SPACE WEATHER, VOL. 1, 1014, 7 PP., 2003
doi:10.1029/2003SW000023

Precursor analysis and prediction of large-amplitude relativistic electron fluxes

R. S. Weigel

Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA

A. J. Klimas

NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

D. Vassiliadis

Universities Space Research Association at NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

An analysis of large-amplitude relativistic electron fluxes, J e , is given using models that predict their appearance based on solar wind precursors. It has been noted that relativistic electron flux bursts in the magnetosphere are associated with high-speed solar wind streams. This observation is used to motivate several models that quantify the association in terms of 2 × 2 contingency tables. For each model, the minimal cost structure for which the model would be useful is computed as a function of large threshold values of J e . The first model is based on the observation that a threshold crossing in the daily averaged solar wind velocity, V SW, tends to precede large relativistic electron fluxes. The optimal ratio of correct to false alarms forecasts found using this algorithm is 18:4 for a threshold corresponding to amplitudes of J e at L = 4.4 above J c = 103 particles/str·cm2·s (corresponding to 110 total events). The second model allows for jumps in the solar wind to be an event indicator and yields slight improvements in the forecast ratio for larger values of J c . The dependence of the optimal forecast ratio on L shell is also considered. It is shown that there are L values for which a threshold crossing of the daily average of V SW from below to above 600 km/sec is a sufficient condition for the appearance of large-amplitude relativistic electron fluxes on one of the following three days. It is also shown that the condition of a threshold crossing of V SW above 600 km/s is not a necessary condition, because ≃80% of events were not preceded by this condition.

Received 18 August 2003; accepted 24 September 2003; published 12 December 2003.

Citation: Weigel, R. S., A. J. Klimas, and D. Vassiliadis (2003), Precursor analysis and prediction of large-amplitude relativistic electron fluxes, Space Weather, 1(3), 1014, doi:10.1029/2003SW000023.

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