THE HELIUM ABUNDANCE IN POLAR CORONAL HOLES AND THE FAST SOLAR WIND

Journal Article · Sat Sep 10 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/738/2/172; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21584850

I have studied the helium abundance in polar coronal holes and the fast solar wind using a time-dependent numerical model for the hydrogen-helium solar wind that spans the mid-to-upper chromosphere, transition region, corona, and solar wind. The model calculates the particle density, flow velocity, parallel and perpendicular temperature, and heat flux for all particle species simultaneously. The focus is on (1) the coronal/solar wind helium abundance as a function of the total magnetic field expansion and (2) the coronal abundance enhancements resulting from low helium heating rates. It is shown that the magnetic field expansion factor may be important in the determination of the solar wind helium abundance and that this can be understood in terms of gravitational settling in the chromosphere. I find that a total magnetic field expansion factor of about 20 is consistent with the observed helium abundance in the solar wind. Furthermore, it is demonstrated that existing observations, both spectroscopic observations of the corona and in situ observations in the solar wind, are compatible with helium abundance enhancements in the corona. For proton-electron plasma properties in accordance with observations, the coronal helium abundance enhancements occur in the region 1.2-2 R{sub sun}.

• OSTI ID: 21584850
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 738; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
ATMOSPHERES
CHROMOSPHERE
DENSITY
ELEMENT ABUNDANCE
ELEMENTS
FLUIDS
GASES
HEAT FLUX
HEATING RATE
HELIOSPHERE
HELIUM
MAGNETIC FIELDS
NONMETALS
PHYSICAL PROPERTIES
RARE GASES
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR CORONA
SOLAR WIND
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR WINDS
VELOCITY