NASA Langley Research Center
Hampton, Virginia

Experiments

	Langley Home Page
	Space Environments &Technology Archive System Home Page
	Space Environments &Effects Home Page
	NASA Home Page

Experiment Title: Heavy Ions in Space

Original Principal Investigator(s): Silberberg, Rein - Invest. Role: Original, Tsao, C.H. - Invest. Role: Original, Adams, Dr. James H. - Invest. Role: Original, Adams, Dr. James H. - Invest. Role: Present,

Since 1972, an anomalous flux of N, O, and Ne relative to carbon has been observed in the energy region from 3 to 100 MeV/u. Between 30 and 100 MeV/u, the abundance and energy spectrum of this flux are poorly known, and above 100 MeV/u they are completely unknown. A low-inclination orbit would be particularly suitable for studying this component because the geomagnetic field screens out the fully stripped cosmic-ray nuclei below 2250 MeV/u. Therefore, the present experiment permits a study of the newly observed nuclei in the unexplored region above 100 MeV/u, which were obscured by cosmic-ray nuclei in previous experiments. The source of this component is unknown but is believed to be of extrasolar origin because of the lack of a gradient away from the sun, anticorrelation with the sunspot cycle, anticorrelation with solar (1 MeV) proton flux, and a C/O ratio that is not typical of the solar abundances. It has been proposed that if the origin of this component is extrasolar, the most likely source is neutral interstellar gas that is first singly ionized by the solar wind and/or solar ultraviolet radiation and then accelerated by the interplanetary solar plasma. Any knowledge of the mechanism by which this component interacts with the solar wind gives important insight into these processes and the nature of the solar plasma. A question to be explored is whether the solar plasma beyond the Earth's orbit can accelerate particles to energies greater than or equivalent to 100 MeV/u. If on the other hand, the component is of solar origin, it would be most important to understand the production and acceleration mechanisms that are responsible.

The heavy nuclei provide a sensitive probe to test the origin of radiation belt particles. Two processes contribute to the radiation belt particles: neutron decay, and injection and local acceleration of solar-wind particles. Heavy nuclei provide a pure sample of the second type. Hence, they permit us to determine to which energies solar-wind particles can be accelerated in the Earth's field and the magneto tail, and to what extent this contributes to the radiation belt. The previous experiment on Skylab concerning heavy radiation belt nuclei did not permit a clear separation from the anomalous component. The high geomagnetic cutoff of a low-inclination orbit would provide a clear separation of these components.

The importance of ultraheavy (UH) nuclei measurements lies in the fact that these nuclei can by synthesized only in special astrophysical settings. Thus, the charge spectrum in the UH region reveals the character of the sources more directly than is possible from the charge spectrum of the lighter nuclei. In addition, the UH nuclei provide sensitive indicators of the amount of interstellar propagation and the time of travel of the galactic radiation. The problem in studying UH nuclei has been their extremely low flux. This is aggravated by their short interaction length, which lead to rapid absorption in even a few grams per square centimeter of atmosphere. They are best observed above the atmosphere with detectors of prodigious collecting power.

Existing data on heavy ions in space have mostly come from relatively small, electronic detectors exposed in satellites and short-duration rocket flights. This experiment will use a relatively new, independent technique (sensitive plastics) on a recoverable, long-duration exposure. This represents the first opportunity for an experiment of such large collecting power.

Photograph Classification: Postflight

Associated Photograph(s):
LaRC - L90-01797
KSC - None
JSC - None
LaRC - L90-10356
KSC - None
JSC - S32-75-043
LaRC - L92-21185
KSC - None
JSC - S32-S-278
LaRC - L84-07187
KSC - KSC-384C-331.06
JSC - None
LaRC - L90-01796
KSC - None
JSC - None
LaRC - L92-21190
KSC - None
JSC - S32-S-283
LaRC - L89-04397
KSC - KSC-384C-318.01
JSC - None
LaRC - L90-10373
KSC - None
JSC - S32-75-067

Back to Experiments Page

LDEF Archive System Home Page