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Don Brownlee

Publications and source records attributed to Don Brownlee.

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Principles Of Heliophysics: a textbook on the universal processes behind planetary habitability

Heliophysics is the system science of the physical connections between the Sun and the solar system. As the physics of the local cosmos, it embraces space weather and planetary habitability. The wider view of comparative heliophysics forms a template for conditions in exoplanetary systems and provides a view over time of the aging Sun and its magnetic activity, of the heliosphere in different settings of the interstellar medium and subject to stellar impacts, of the space physics over evolving planetary dynamos, and of the long-term influence on planetary atmospheres by stellar radiation and wind. Based on a series of NASA-funded summer schools for early-career researchers, this textbook is intended for students in physical sciences in later years of their university training and for beginning graduate students in fields of solar, stellar, (exo-)planetary, and planetary-system sciences. The book emphasizes universal processes from a perspective that draws attention to what provides Earth (and similar (exo-)planets) with a relatively stable setting in which life as we know it could thrive. The text includes 200 "Activities" in the form of exercises, explorations, literature readings, "what if" challenges, and group discussion topics; many of the Activities provide additional information complementing the main text. Solutions and discussions are included in an Appendix for a selection of the exercises.

astro-ph.SR

The origin of the 3.4 micron feature in Wild 2 cometary particles and in ultracarbonaceous interplanetary dust particles

We analyzed 2 ultra-carbonaceous interplanetary dust particles and 2 cometary Wild 2 particles with infrared spectroscopy. We characterized the carrier of the 3.4 micron band in these samples and compared its profile and the CH2/CH3 ratios to the 3.4 micron band in the diffuse interstellar medium (DISM), in the insoluble organic matter (IOM) from 3 primitive meteorites, in asteroid 24 Themis and in the coma of comet 103P/Hartley 2. We found that the 3.4 micron band in both Wild 2 and IDPs is similar, but different from all the other astrophysical environments that we compared to. The 3.4 micron band in IDPs and Wild 2 particles is dominated by CH2 groups, the peaks are narrower and stronger than in the meteorites, asteroid Themis, and the DISM. Also, the presence of the carbonyl group C=O at 1700 cm-1 (5.8 micron) in most of the spectra of our samples, indicates that these aliphatic chains have O bonded to them, which is quite different from astronomical spectra of the DISM. Based on all these observations we conclude that the origin of the carrier of the 3.4 micron band in IDPs and Wild 2 samples is not interstellar, instead, we suggest that the origin lies in the outermost parts of the solar nebula.

astro-ph.EP