ACE Scientific Goals

The observations from ACE instruments allow the investigation of a wide range of fundamental problems in the following major areas:

  1. The Elemental and Isotopic Composition of Matter
    A major objective is the accurate and comprehensive determination of the elemental and isotopic composition of the various samples of "source material" from which nuclei are accelerated. Thus, ACE measurements will:

  2. Origin of the Elements and Subsequent Evolutionary Processing
    Isotopic "anomalies" in meteorites indicate that the solar system was not homogeneous when formed, while other data suggest that the solar composition continues to evolve. Similarly, the galaxy is neither uniform in space nor constant in time due to continuous stellar nucleosynthesis. ACE measurements will:

  3. Formation of the Solar Corona and Acceleration of the Solar Wind
    Solar energetic particles, solar wind, and spectroscopic observations show that the elemental composition of the corona is differentiated from that of the photosphere, although the processes by which this occurs, and by which the solar wind is subsequently accelerated, are poorly understood. The detailed composition and charge-state data provided by ACE will:

  4. Particle Acceleration and Transport in Nature
    Particle acceleration is ubiquitous in nature and is one of the fundamental problems of space plasma astrophysics. The unique data set that will be obtained by ACE measurements will:

Oxygen Spectrum
Typical energy spectrum of energetic Oxygen-16 nuclei resulting from the various particle populations that will be observed by ACE. The solid curves represent "steady-state" components, while the dotted curves are for "transient" phenomena. Also shown is a postulated quiet-time flux of supra-thermal solar particles (dashed curve). The energy ranges of the ACE instruments are indicated for resolution of isotopes (blank), elements only (cross-hatched), and ionic charge-states (stipled). Other nuclear species generally tend to have spectra that are similarly shaped to that of oxygen (but of varying intensity) when plotted as a function of energy/nucleon.

Author: Eric R. Christian -
Curators: ACE Science Center -

Last Updated: February 5, 2000

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