Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011spd....42.1715w&link_type=abstract
American Astronomical Society, SPD meeting #42, #17.15; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
Cancellation of magnetic flux in magnetograms has been defined in observational terms as "the mutual apparent loss of magnetic flux in closely spaced features of opposite polarity." Physically, this removal of flux could correspond to one of three mechanisms: (i) the emergence of U-shaped magnetic loops, (ii) the submergence of Omega-shaped loops, or (iii) reconnection in the magnetogram layer. Evidence has been reported for all three of these mechanisms, but does one predominate? Does most canceling flux enter the outer solar atmosphere, or submerge into the interior? Answers to these questions will improve our understanding of both the solar-cycle and quiet-Sun dynamos, as well as the origins of structures that erupt in coronal mass ejections (CMEs). We can investigate cancellation mechanisms at work in an active region's magnetic fields using time-averaged Doppler shifts along polarity inversion lines (PILs) of the line-of-sight (LOS) magnetic field near disk center. Along these PILs, the LOS component of the magnetic field vanishes, so LOS flows inferred from Doppler shifts are perpendicular to the magnetic field. If the evolution is ideal, such flows imply the transport of magnetic flux across the atmospheric layer imaged in the magnetogram. As a preliminary step in our study, we present an innovative method to remove biases in the measured Doppler velocities due to offset in the line-center position, which might arise from a well-known correlation between brightness and blueshifts in the convecting photospheric plasma. In cases with significant discrepancies between flux cancellation rates separately inferred from (1) changes in LOS flux near canceling PILs and (2) combined Doppler velocities and transverse field strengths along PILs, we can characterize departures from ideal evolution in terms of an effective magnetic diffusivity, which can be evaluated from the data.
Fisher George
Sun Xiaosong
Welsch Brian
No associations
LandOfFree
Understanding the Physics of Flux Cancellation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Understanding the Physics of Flux Cancellation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Understanding the Physics of Flux Cancellation will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1204516