PROBING THE SHALLOW CONVECTION ZONE: RISING MOTION OF SUBSURFACE MAGNETIC FIELDS IN THE SOLAR ACTIVE REGION

Journal Article · Mon Jun 10 04:00:00 EDT 2013 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/770/1/L11· OSTI ID:22118788

Toriumi, Shin; Yokoyama, Takaaki ^[1]; Ilonidis, Stathis ^[2]; Sekii, Takashi ^[3]

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1. Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
2. W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305-4085 (United States)
3. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

In this Letter, we present a seismological detection of a rising motion of magnetic flux in the shallow convection zone of the Sun, and show estimates of the emerging speed and its decelerating nature. In order to evaluate the speed of subsurface flux that creates an active region, we apply six Fourier filters to the Doppler data of NOAA AR 10488, observed with the Solar and Heliospheric Observatory/Michelson Doppler Imager, to detect the reduction of acoustic power at six different depths from -15 to -2 Mm. All the filtered acoustic powers show reductions, up to 2 hr before the magnetic flux first appears at the visible surface. The start times of these reductions show a rising trend with a gradual deceleration. The obtained velocity is first several km s{sup -1} in a depth range of 15-10 Mm, then {approx}1.5 km s{sup -1} at 10-5 Mm, and finally {approx}0.5 km s{sup -1} at 5-2 Mm. If we assume that the power reduction is actually caused by the magnetic field, the velocity of the order of 1 km s{sup -1} is well in accordance with previous observations and numerical studies. Moreover, the gradual deceleration strongly supports the theoretical model that the emerging flux slows down in the uppermost convection zone before it expands into the atmosphere to build an active region.

• OSTI ID: 22118788
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 770; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCELERATION
ASTRONOMY
ASTROPHYSICS
CONVECTION
DETECTION
IMAGES
MAGNETIC FIELDS
MAGNETIC FLUX
NUMERICAL ANALYSIS
OPTICAL FILTERS
OSCILLATIONS
PHOTOSPHERE
PROBES
SEISMICITY
SUN
SUNSPOTS
VELOCITY
ZONES