National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Energetic Ion Onset Fronts: Spatial/Temporal Variations In and Near Earth's Magnetosphere

ROSES ID: NRA-01-OSS-01      Selection Year: 2002      

Program Element: Independent Investigation: Geospace LWS

Principal Investigator: Stephen P. Christon


The ISTP spacecraft constellation permits unprecedented detailed and multipoint examination of Solar Energetic Particles (SEPs) resulting from the large number of solar particle events produced in the recent Solar Cycle maximum as they approach and interact with Earth's magnetosphere. Abrupt SEP onset fronts can be used to test current understanding of interplanetary ion and electron propagation because they are initiated in localized solar events and have a simple transport history. Some SEP ions enter the magnetosphere and interact with communcation satellites, interrupt communications, and/or disable those spacecraft. Other SEP ions precipitate in polar regions, ionize neutral atoms causing aurorae and ion outflow, and, at high flux levels, contribute to surface communication disruptions. We propose a multicase/multpoint study of ~0.4-45 MeV SEPs using instruments on the ACE (at L1 ~230 Earth radii, Re) and nearer-Earth (~6.6-44 Re) Geotail, IMP-8, and GOES spacecraft, to examine spatial/temporal variability of SEP ion onsets observed near Earth since 1997 (ACE launch). The study organizes into Tasks to: evaluate the spaceweather monitoring effectiveness of a single spacecraft at L1; test whether the more abundant energetic ~0.4-5 MeV SEP ions have similar access to the inner magnetosphere (<=6.6 Re) as tens of MeV SEP ions; determine how often either nonuniform field-aligned particle streaming or assumption of an expanding spherically symmetric uniform onset front convecting with the solar wind is supported by observations; establish the range of flux level variability at SEP onset fronts; and compile/post a public list of SEP onsets from the four spacecraft. This study's results will: improve understanding of spatial/temporal variability of SEP onsets near Earth; enhance understanding of geospace interaction with SEP particles; supplement ongoing LWS studies of MeV-energy SEP ions; and be helpful in defining future LWS spacecraft mission constraints. Data Sets: -- GOES, Geotail, IMP-8, ACE


Performance YearReferenceActions
1Eastman, T. E.; Christon, S. P.; Decker, R. B.; Roe...
1Christon, S. P.; Eastman, T. E.; Decker, R. B.; Roe...
1Eastman, T. E.; Christon, S. P.; Decker, R. B.; Roe...

Export to PDF