MAPPING THE DISTRIBUTION OF ELECTRON TEMPERATURE AND Fe CHARGE STATES IN THE CORONA WITH TOTAL SOLAR ECLIPSE OBSERVATIONS

Journal Article · Sun Jan 10 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/708/2/1650· OSTI ID:21392399

Habbal, S Rifai; Morgan, H; Scholl, I ^[1]; Druckmueller, M ^[2]; Daw, A ^[3]; Johnson, J ^[4]; Ding, A ^[5]; Arndt, M ^[6]; Esser, R ^[7]; Rusin, V ^[8]

---

1. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
2. Faculty of Mechanical Engineering, Brno University of Technology, 616 69 Brno (Czech Republic)
3. Appalachian State University, Boone, NC 28608 (United States)
4. Electricon, Boulder, CO 80204 (United States)
5. Institute of Optics and Atomic Physics, Technische Universitaet Berlin and Institute of Technical Physics, Berlin (Germany)
6. Bridgewater State College, Bridgewater, MA 02325 (United States)
7. University of Tromsoe (Norway)
8. Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranska Lomnica (Slovakia)

The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the heliocentric distance where the transition from a collision-dominated to a collisionless plasma occurs, the charge states of different elements are established, or frozen-in. These are the charge states which are subsequently measured in interplanetary space. We show in this study how the 2006 March 29 and 2008 August 1 eclipse observations of a number of Fe emission lines yield an empirical value for a distance, which we call R{sub t} , where the emission changes from being collisionally to radiatively dominated. R{sub t} ranges from 1.1 to 2.0 R{sub sun}, depending on the charge state and the underlying coronal density structures. Beyond that distance, the intensity of the emission reflects the distribution of the corresponding Fe ion charge states. These observations thus yield the two-dimensional distribution of electron temperature and charge state measurements in the corona for the first time. The presence of the Fe X 637.4 nm and Fe XI 789.2 nm emission in open magnetic field regions below R{sub t} , such as in coronal holes and the boundaries of streamers, and the absence of Fe XIII 1074.7 nm and Fe XIV 530.3 nm emission there indicate that the sources of the solar wind lie in regions where the electron temperature is less than 1.2 x 10{sup 6} K. Beyond R{sub t} , the extent of the Fe X [Fe{sup 9+}] and Fe XI emission [Fe{sup 10+}], in comparison with Fe XIII [Fe{sup 12+}] and Fe XIV [Fe{sup 13+}], matches the dominance of the Fe{sup 10+} charge states measured by the Solar Wind Ion Composition Spectrometer, SWICS, on Ulysses, at -43{sup 0} latitude at 4 AU, in March-April 2006, and Fe{sup 9+} and Fe{sup 10+} charge states measured by SWICS on the Advanced Composition Explorer, ACE, in the ecliptic plane at 1 AU, at the time of both eclipses. The remarkable correspondence between these two measurements establishes the first direct link between the distribution of charge states in the corona and in interplanetary space.

• OSTI ID: 21392399
• Journal Information: Astrophysical Journal, Vol. 708, Issue 2; Other Information: DOI: 10.1088/0004-637X/708/2/1650; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CHARGE STATES
COLLISIONLESS PLASMA
ECLIPSE
ELECTRON TEMPERATURE
INTERPLANETARY MAGNETIC FIELDS
INTERPLANETARY SPACE
ION EMISSION
IONIZATION
IRON IONS
SOLAR CORONA
SOLAR WIND
SPECTROMETERS
SUN
ATMOSPHERES
CHARGED PARTICLES
EMISSION
IONS
MAGNETIC FIELDS
MAIN SEQUENCE STARS
MEASURING INSTRUMENTS
PLASMA
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SPACE
STARS
STELLAR ACTIVITY
STELLAR ATMOSPHERES
STELLAR CORONAE
STELLAR WINDS