OBSERVATIONS AND MODELS OF SLOW SOLAR WIND WITH Mg{sup 9+} IONS IN QUIESCENT STREAMERS

Journal Article · Tue Jan 01 00:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/762/1/18· OSTI ID:22167358

Ofman, L. ^[1]; Abbo, L.; Giordano, S. ^[2]

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1. Department of Physics, Catholic University of America, Washington, DC 20064 (United States)
2. INAF, Astrophysical Observatory of Turin (Italy)

Quiescent streamers are characterized by a peculiar UV signature as pointed out by the results from the observations of the Ultraviolet and Coronograph Spectrometer (UVCS) on board SOHO: the intensity of heavy-ion emission lines (such as O VI) shows dimmer core relative to the edges. Previous models show that the structure of the heavy-ion streamer emission relates to the acceleration regions of the slow solar wind at streamer legs and to gravitational settling processes in the streamer core. Observations of Mg{sup 9+} ion EUV emission in coronal streamers at solar minimum were first reported by the UVCS instrument. The Mg X 625 A emission is an order of magnitude smaller than the O VI 1032 A emission, requiring longer exposures to obtain statistically significant results. Here, Mg X coronal observations are analyzed and compared, for the first time, with the solar minimum streamer structure in hydrogen and O VI emissions. We employ the 2.5D three-fluid model, developed previously to study the properties of O{sup 5+} ions in streamers, and calculate for the first time the density, temperature, and outflow structure of Mg{sup 9+} ions in the solar minimum streamer. The Mg{sup 9+} ions are heated by an empirical radial heating function constrained by observations of the kinetic ion temperature obtained from Mg X emission line profiles. The detailed structure of Mg{sup 9+} density, temperature, and outflow speed is determined by the Coulomb momentum and energy exchange as well as electromagnetic interactions with electrons and protons in the three-fluid model of the streamer. The results of the model are in good qualitative agreement with observations, and provide insights on the possible link between the magnetic structure of the streamer, slow solar wind sources, and relative abundances of heavy ions.

• OSTI ID: 22167358
• Journal Information: Astrophysical Journal, Vol. 762, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
ASTRONOMY
ASTROPHYSICS
COMPARATIVE EVALUATIONS
ELECTROMAGNETIC INTERACTIONS
ELEMENT ABUNDANCE
ENERGY TRANSFER
HYDROGEN
ION EMISSION
ION TEMPERATURE
MAGNESIUM IONS
MULTICHARGED IONS
OXYGEN IONS
SOLAR CORONA
SOLAR ELECTRONS
SOLAR PROTONS
SOLAR WIND
SUN
ULTRAVIOLET RADIATION
ULTRAVIOLET SPECTROMETERS