PROBING THE SOLAR WIND ACCELERATION REGION WITH THE SUN-GRAZING COMET C/2002 S2

Journal Article · Thu Jan 01 04:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/798/1/47· OSTI ID:22364732

Giordano, S. ^[1]; Raymond, J. C. ^[2]; Lamy, P. ^[3]; Uzzo, M. ^[4]; Dobrzycka, D. ^[5]

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1. INAF-Osservatorio Astrofisico di Torino, via Osservatorio 20, I-10025 Pino Torinese (Italy)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
3. Laboratoire d'Astrophysique de Marseille, 38 rue Frédéric Joliot-Curie, F-13388 Marseille cedex 13 (France)
4. Computer Science Corporation, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
5. European Southern Observatory, Karl Schwarzschild Strasse 2, D-85748 Garching (Germany)

Comet C/2002 S2, a member of the Kreutz family of sungrazing comets, was discovered in white-light images of the Large Angle and Spectromeric Coronagraph Experiment coronagraph on the Solar and Heliospheric Observatory (SOHO) on 2002 September 18 and observed in H I Lyα emission by the SOHO Ultraviolet Coronagraph Spectrometer (UVCS) instrument at four different heights as it approached the Sun. The H I Lyα line profiles detected by UVCS are analyzed to determine the spectral parameters: line intensity, width, and Doppler shift with respect to the coronal background. Two-dimensional comet images of these parameters are reconstructed at the different heights. A novel aspect of the observations of this sungrazing comet data is that, whereas the emission from most of the tail is blueshifted, that along one edge of the tail is redshifted. We attribute these shifts to a combination of solar wind speed and interaction with the magnetic field. In order to use the comet to probe the density, temperature, and speed of the corona and solar wind through which it passes, as well as to determine the outgassing rate of the comet, we develop a Monte Carlo simulation of the H I Lyα emission of a comet moving through a coronal plasma. From the outgassing rate, we estimate a nucleus diameter of about 9 m. This rate steadily increases as the comet approaches the Sun, while the optical brightness decreases by more than a factor of 10 and suddenly recovers. This indicates that the optical brightness is determined by the lifetimes of the grains, sodium atoms, and molecules produced by the comet.

• OSTI ID: 22364732
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 798; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
BRIGHTNESS
COMETS
COMPUTERIZED SIMULATION
DOPPLER EFFECT
LIFETIME
MAGNETIC FIELDS
MOLECULES
MONTE CARLO METHOD
PLASMA
PROBES
SODIUM
SOLAR CORONA
SOLAR WIND
SUN
TWO-DIMENSIONAL CALCULATIONS
ULTRAVIOLET RADIATION
VISIBLE RADIATION