Latitudinal and radial variation of >2 GeV/n protons and α-particles in the northern heliosphere: ulysses cospin/ket and neutron monitor network observations
Abstract
Ulysses, launched in October 1990, crossed in December 1997 the heliographic equator and completed its first out of ecliptic orbit. During the time period from February 1995 to November 1997 solar activity was low and the spacecraft scanned the latitude range from 80° N to the heliographic equator. The Kiel Electron Telescope on-board Ulysses measures protons and α-particles in the energy range from 5 MeV/n to > 2 GeV/n. To separate spatial and temporal variations of > 2 GeV/n protons and α-particles along the spacecraft trajectory we used the data set from the world wide neutron monitor network. We found negligible latitudinal gradients below ~29° N and for the radial gradient an upper limit of ≈ 0.5 %/AU for > 2 GeV/n protons and α-particles. In the latitudinal range from ≈ 25 to > 70° N the latitudinal gradient is ~0.17 %/° and ~0.12 %/° for > 2 GeV/n protons and α-particles, respectively, independent of spacecraft latitude and radial distance.
- Publication:
-
Advances in Space Research
- Pub Date:
- 1999
- DOI:
- 10.1016/S0273-1177(99)00102-7
- Bibcode:
- 1999AdSpR..23..443B