Engineering Papers⌕ Search

Engineering topics

Hovestadt, D.

Publications and source records attributed to Hovestadt, D..

153 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Direct observations of the charge states of low energy solar particles

The charge states of carbon and oxygen of solar origin have been measured directly in interplanetary space. At 100 keV per nucleon the C(+5)/C(+6) and O(+7)/O(+8) ratios are 1.8 and 1.6, respectively. Abundance ratios of low energy heavy nuclei to He are found which are significantly larger than the corresponding photospheric values. The enhancement of O/He is 35, and both Si/He and Fe/He are overabundant by a factor of 100. To explain these observations a mechanism is proposed which first preferentially accelerates heavy ions and is followed by either storage of these ions in the coronal regions or strong adiabatic deceleration.

Gloeckler, G.↗
NASA NTRS1974

Measurement of elemental abundance of very low energy solar cosmic rays

Heavy interplanetary particles (Z from 3 to 30) have been observed during a solar flare period between October 29 and November 4, 1972. The nuclear abundance has been determined by a two parameter analysis of a thin window proportional counter - solid state detector device aboard the Explorer 47 (IMP-7) satellite. Energy spectra are given for C, O and Fe. The elemental abundance relative to oxygen is determined for carbon, neon, magnesium, silicon and the iron group in the energy range 0.62 to 6.9 MeV/nucleon. For the Fe/O ratio no energy dependence could be observed within the error limits.

Hovestadt, D.↗
NASA NTRS1974

Nuclear composition of solar cosmic rays

Experimental observations of the elemental and isotopic composition of solar flare particles are discussed. Sources and characteristics of particle-emitting solar flare events are reviewed, and techniques for separating particle species are briefly described. Data are presented for the elemental composition of the solar atmosphere, and the possibility of determining the solar helium abundance from solar cosmic-ray observations is explored. The main experimental determinations of heavy element abundances at energies greater and less than 10 MeV/nucleon are summarized, and techniques for measuring the ionic charge composition of solar cosmic rays are outlined. Models explaining heavy element enhancements are described along with processes leading to gamma-ray emission during solar flare events. Observations of the rare isotopes of hydrogen and helium during solar flare events are noted, and a lower atmospheric limit is derived for nuclear reactions leading to positron decay. The possibility of investigating low-energy solar cosmic rays by measuring the relative abundances of different elements is evaluated.

Hovestadt, D.↗
NASA NTRS1973

Direct Observations of the Charge States of Low Energy Solar Particles

The charge states of carbon and oxygen of solar origin were measured directly in interplanetary space. At 100 keV per nucleon the C(+5)/C(+6) and O(+7)/O(+8) ratios are 1.8 and 1.6 respectively. It was found that the abundance ratios of low energy heavy nuclei to He is significantly larger than corresponding photospheric values: the enhancement of O/He is 35 and both Si/He and Fe/He are overabundant by a factor of 100. To explain these observations a mechanism is proposed which first preferentially accelerates heavy ions and is followed by either storage of these ions in the coronal regions or strong adiabatic deceleration.

Gloeckler, G.↗
NASA NTRS1973

Intensity Oscillation of Low Energy Solar Particles Observed on the IMP 7 Satellite

Solar flare particles in the energy range from 125 to 160 KeV per charge were detected and analyzed by an electrostatic deflection vs. energy instrument on board the Explorer 47 (IMP 7) satellite. A harmonic analysis of the counting rates shows that frequently, the fluctuation of the particle flux can be approximately represented by N(t) = f(t)sin 2 pi nu t where f(t) is a smoothly varying function of t. The oscillation frequency nu varies from flare to flare and is of the order of 2 x .001/sec. The physical implications of the finding are discussed.

Fan, C. Y.↗
NASA NTRS1973

Measurement of Elemental Abundance of Very Low Energy Solar Cosmic Rays

Heavy interplanetary particles were observed during a solar flare period between October 29 and November 4, 1972. The nuclear abundance was determined by a two parameter analysis (dE/dx vs E technique) of a thin window proportional counter - solid state detector device aboard the Explorer 47 (IMP-7) satellite. Energy spectra are given for C, O and Fe. The elemental abundance relative to oxygen is determined for carbon, neon, magnesium, silicon and the iron group in the energy range 0.62 to 6.9 MeV/nucleon. For the Fe/O ratio no energy dependence could be observed within the error limits.

Hovestadt, D.↗
NASA NTRS1973

Differential energy spectra of low energy (less than 8.5 MeV per nucleon) heavy cosmic rays during solar quiet times

Explorer 47 satellite observations of carbon, oxygen, and heavier nuclei differential energy spectra below 8.5 MeV/nucleon are presented for solar quiet time periods. A dE/dx vs E method for particle identification and energy determination was used. The instrumentation telescope included an isobutane proportional counter, a surface barrier Si detector, and a cylindrical plastic scintillator anticoincidence shield. The observations were performed outside the bow-shock and in the ecliptic plane. Results show an anisotropy of about 25% at 22 degrees west of the sun with a C/O ratio of 0.5 supporting a solar origin. The low energy portions of the C and O spectra have steep negative slopes, and the corresponding power law is given. Peculiarities in the O spectrum are discussed.

Hovestadt, D.↗