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A Brief History of Recurrent Solar Modulation of the Galactic Cosmic Rays (1937-1990)
Simpson, J. A.
This brief review of the pre-Ulysses era begins with the first measurements by ionization chambers in 1937 of a cosmic ray 27-day intensity variation that was believed to have its origin in recurrent variations of the geomagnetic field. However, with the introduction of neutron monitor analysis of the nucleonic component, it was shown in the 1940s…
Fractionation of SI, NE, and MG Isotopes in the Solar Wind as Measured by Soho/Celias/MTOF
Bochsler, P.; Geiss, J.; Galvin, A. B. +9 more
Using the high-resolution mass spectrometer CELIAS/MTOF on board SOHO we have measured the solar wind isotope abundance ratios of Si, Ne, and Mg and their variations in different solar wind regimes with bulk velocities ranging from 330 km/s to 650 km/s. Data indicate a small systematic depletion of the heavier isotopes in the slow solar wind on th…
The Theory of Anomalous Cosmic Rays
Giacalone, J.; Jokipii, J. R.
Anomalous cosmic rays are a heliospheric phenomenon in which interstellar neutral atoms stream into the heliosphere, are ionized by either solar radiation or the solar wind, and are subsequently accelerated to very high energies, greater than 1 GeV. Current thinking has the bulk of the acceleration to very-high energies taking place, by the mechan…
Three-dimensional Solar Modulation of Cosmic Ray and Anomalous Components in the Inner Heliosphere
McKibben, R. B.
Our picture of modulation in the inner heliosphere has been greatly affected by observations from the Ulysses mission, which since 1992 has provided the first comprehensive exploration of modulation as a function of latitude from 80 deg S to 80 deg N heliographic latitude. Among the principal findings for the inner heliosphere are: a) the cosmic r…
O5+ in High Speed Solar Wind Streams: SWICS/Ulysses Results
Wimmer-Schweingruber, Robert F.; Gloeckler, George; Geiss, Johannes +3 more
Recent observations with UVCS on SOHO of high outflow velocities of O5+ at low coronal heights have spurred much discussion about the dynamics of solar wind acceleration. On the other hand, O6+ is the most abundant oxygen charge state in the solar wind, but is not observed by UVCS or by SUMER because this helium-like ion has …
Corotating Particle Events
Simnett, G. M.; Kunow, H.; Horbury, T. +8 more
The corotating particle events give us a unique opportunity to probe the three-dimensional structures of the heliosphere. This is especially true if we have observations over a period of extreme stability of the CIRs, such as existed over the recent solar minimum. We discuss how the observations fit into the context of current heliospheric magneti…
Interstellar Matter and the Boundary Conditions of the Heliosphere
Frisch, Priscilla C.
The interstellar cloud surrounding the solar system regulates the galactic environment of the Sun, and determines the boundary conditions of the heliosphere. Both the Sun and interstellar clouds move through space, so these boundary conditions change with time. Data and theoretical models now support densities in the cloud surrounding the solar sy…
Recurrent Solar Modulation of the Galactic Cosmic Rays and the Anomalous Nuclear Component in Three Dimensions of the Heliosphere
Simpson, J. A.
Ulysses Mission investigations, extending from pole-to-pole of the Sun and inner heliosphere in the period 1993-1996, have led to discoveries that will change dramatically models to account for the physical phenomena underlying the 26-day modulation of galactic cosmic rays and anomalous nuclear components and their propagation modes. These new fin…
Solar EUV and UV Emission Line Observations Above a Polar Coronal Hole
Wilhelm, K.; Bodmer, R.
The roll manoeuvre of SOHO on September 3, 1997 provided the opportunity to study the northern coronal hole with SUMER slits in east-west orientation, so that polar plumes and inter-plume lanes could be observed simultaneously. A preliminary analysis of the observations shows that lines emitted by ions with the lowest formation temperatures (with …
Elemental Abundances in Coronal Structures
Kohl, John L.; Noci, Giancarlo; Raymond, John C. +1 more
A great deal of evidence for elemental abundance variations among different structures in the solar corona has accumulated over the years. Many of the observations show changes in the relative abundances of high- and low-First Ionization Potential elements, but relatively few show the absolute elemental abundances. Recent observations from the SOH…