Solar energetic particles

Figure 2.15 Ne three-isotope plot for a grain-size suite of plagioclase separates from lunar high land soil that were treated by the CSSE treatment (see text). The best fitted line through the data from all etched samples (line p) passes close to the data point GCR (galactic cosmic ray) of cosmogenic Ne. On the left side, the path of mass fractionation of SWC (solar wind composition)-Ne intersects line p at a 20Ne/22Ne ratio of -11.3, which is interpreted to represent SEP (solar energetic particle) Ne (cf. Section 2.8). Open symbols unetched sample. Solid symbols etched samples. SF Solar flare Ne. Reproduced from Signer et al. (1993).

Brenemann, H. H., Stone, E. C. (1985) Solar coronal and photospheric abundances from solar energetic particle measurements. Astrophys. J., 299, L57-61. 

Stone, E. C. (1989) Solar abundances as derived from solar energetic particles. AIP Conf. Proc., 183, 72-90. 

Wieler, R., Baur, H. (1994) Krypton and xenon from the solar wind and solar energetic particles in two lunar ilmenites of different antiquity. Meteoritics, 29, 570-80. 

Wieler, R., Baur, H., Signer, R (1986) Noble gases from solar energetic particles revealed by closed system stepwise etching of lunar soil minerals. Geochim. Cosmochim. Acta, 50, 1997-2017. 

This radioactive nucleus is also found alive in meteorites and inferred to have been alive in the early solar system. It is also produced by solar-energetic particles in the Sun s flares and carried to Earth in the solar wind (see below). 

Emission spectroscopy of the solar corona, solar energetic particles (SEP) and the composition of the solar wind yield information on the composition of the Sun. Solar wind data were used for isotopic decomposition of rare gases. Coronal abundances are fractionated relative to photo-spheric abundances. Elements with high first ionization potential are depleted relative to the rest (see Anders and Grevesse, 1989 for details). 

Reames D. V. (1998) Solar energetic particles samphng coronal abundances. Space Sd. Rev. 85, 327—340. 

Goswami J. N., Marhas K. K., and Sahijpal S. (2001) Did solar energetic particles produce the short-lived nuclides present in the early solar systeml Astrophys. J. 549, 1151-1159. 

Figure 2 A three-isotope diagram illustrating compositional variations in lunar samples and meteorites, as observed in stepwise in vacuo etching and pyrolysis. Since the observed isotopic compositions do not lie on a single straight line, at least three isotopically distinct components must contribute in variable proportions. These data are interpreted as superposition of solar wind (SW), solar energetic particles (SEP), and galactic cosmic ray, i.e., spallation (GCR)...

Pepin R. O., Palma R. L., and Schlutter D. J. (2000) Noble gases in interplanetary dust particles I. The excess helium-3 problem and estimates of the relative fluxes of solar wind and solar energetic particles in interplanetary space. Meteoritics 35, 495-504. 

Benkert J.-P., Baur H., Signer P., and Wieler R. (1993) He, Ne, and Ar from solar wind and solar energetic particles in lunar ilmenites and pyroxenes. J. Geophys. Res. 98, 13147-13162. 

The relative abundance of chemical elements in cosmic ray sources is in general similar to the solar and to the local galactic abundance but show some significant deviations. The elements that appear underabundant by a factor of about 5 are those elements that are difficult to ionize. The critical ionization potential is approximately 10 eV that corresponds to ionization at an equilibrium temperature 104 K (characteristic e.g. of the solar photosphere). The correlation of abundance with the first ionization potential is also known for solar energetic particles. Thus, it is possible that the outer layers of relatively cool stars serve as injectors of the seed particles required for the subsequent acceleration [17]. For most elements the volatility is correlated with the first ionization potential, so that volatility is also considered as a possible selection factor for the cosmic ray population. Then predominant acceleration and breakup of grains that is natural for the diffusive shock acceleration could explain the situation [18]. 

The sun has the most mass (>99%) of the solar system objects and therefore it is the prime target for studying solar system abundances. Most elements can be measured in the sun s photosphere, but data from the solar chromosphere and corona, solar energetic particles, solar wind, and solar cosmic rays (from solar flares), help to evaluate abundances of elements that have weak absorption lines (because these elements are low in abundance or only have blended absorption lines in the photospheric spectrum). 

This Ne value compares relatively well to the Ne abundance adopted in older compilations by [8] (8.09) or [11](8.08). However, the Ne values in more recent compilations (A(Ne) = 7.87 0.1 in L03, and A(Ne) = 7.84 0.06 in A05) are lower by 26% (0.10 dex). The Ne abundance in previous compilations was mainly based on the characteristic Ne/O ratio of 0.15 for the local ISM and solar energetic particles. The Ne abundance was then calculated from the adopted O abundances. Since the adopted O abundances have changed to lower values in these compilations, the Ne abundances dropped as well. Using Ne/O = 0.15 and our selected O abundance from above, the Ne... 

Table 1 summarizes the techniques used to measure noble gases. By far the most important is mass spectrometry. Mass spectrometers in space are used, e.g., for solar wind and solar energetic particle measurements or atmospheric analyses on Venus, Moon, Mars and Jupiter, while mass spectrometers in the laboratory allow us to analyze extraterrestrial samples available on Earth, i.e., lunar samples, meteorites, interplanetary dust or solar corpuscular radiation trapped by foils exposed in space. Of course. 

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