Abstract
Recent studies of NOAA active region 10953, by Okamoto et al. (Astrophys. J.
Lett. 673, 215, 2008; Astrophys. J. 697, 913, 2009), have interpreted photospheric observations
of changing widths of the polarities and reversal of the horizontal magnetic field
component as signatures of the emergence of a twisted flux tube within the active region
and along its internal polarity inversion line (PIL). A filament is observed along the PIL and
the active region is assumed to have an arcade structure. To investigate this scenario, Mac-
Taggart and Hood (Astrophys. J. Lett. 716, 219, 2010) constructed a dynamic flux emergence
model of a twisted cylinder emerging into an overlying arcade. The photospheric signatures
observed by Okamoto et al. (2008, 2009) are present in the model although their underlying
physical mechanisms differ. The model also produces two additional signatures that can be
verified by the observations. The first is an increase in the unsigned magnetic flux in the photosphere
at either side of the PIL. The second is the behaviour of characteristic photospheric flow profiles associated with twisted flux tube emergence. We look for these two signatures
in AR 10953 and find negative results for the emergence of a twisted flux tube along
the PIL. Instead, we interpret the photospheric behaviour along the PIL to be indicative of
photospheric magnetic cancellation driven by flows from the dominant sunspot. Although
we argue against flux emergence within this particular region, the work demonstrates the
important relationship between theory and observations for the successful discovery and
interpretation of signatures of flux emergence.
Original language | English |
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Pages (from-to) | 33–45 |
Number of pages | 13 |
Journal | Solar Physics |
Volume | 278 |
Issue number | 1 |
DOIs | |
Publication status | Published - 2012 |
Externally published | Yes |
Keywords
- Flux emergence
- Photosphere