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In this Letter we present a seismological detection of a rising motion ofmagnetic flux in the shallow convection zone of the Sun, and show estimates ofthe emerging speed and its decelerating nature. In order to evaluate the speedof subsurface flux that creates an active region, we apply six Fourier filtersto the Doppler data of NOAA AR 10488, observed with SOHO/MDI, to detect thereduction of acoustic power at six different depths from -15 to -2 Mm. All thefiltered acoustic powers show reductions, up to 2 hours before the magneticflux first appears at the visible surface. The start times of these reductionsshow a rising trend with a gradual deceleration. The obtained velocity is firstseveral km s^-1 in a depth range of 15--10 Mm, then ~1.5 km s^-1 at 10-5 Mm,finally ~0.5 km s^-1 at 5-2 Mm. If we assume that the power reduction isactually caused by the magnetic field, the velocity of order of 1 km s^-1 iswell in accordance with previous observations and numerical studies. Moreover,the gradual deceleration strongly supports the theoretical model that theemerging flux slows down in the uppermost convection zone before it expandsinto the atmosphere to build an active region.

Probing the Shallow Convection Zone: Rising Motion of Subsurface Magnetic Fields in the Solar Active Region