Abstract
Aims. Recent insterest in flux emergence within mature active regions has led to several observational studies. Our aim is to model
such a scenario and investigate the evolution of the system.
Methods. We solve the 3D MHD equations numerically with a Lagrangian-remap scheme. The mature active region is modelled, in
the initial condition, with a potential field. The smaller emerging region is a twisted flux tube and is placed between the two polarities
of the mature region. The polarities of the new flux are aligned the same way as those of the mature region. The new flux emerges
closer to the main negative polarity than the main positive polarity. To investigate the effects of reconnection, the distribution of the
parallel electric field is calculated throughout the simulation. The topology of the magnetic field is then studied in regions of interest
indicated by the electric field distribution.
Results. The expansion of the new negative polarity is restricted due to the curvature of the overlying field and also because it is of
the same sign. Reconnection is found to be strongest at low heights (below the corona) and along the outer side of the new positive
polarity and its magnetic tongue. The effect of reconnection, in combination with the pressure between the two flux systems, is to
resist the expansion of the new flux. The system then relaxes. Large-scale eruptions, such as CMEs, are not expected from the setup
considered. At the new negative polarity, the high magnetic pressure can generate strong parallel electric fields which may lead to
localized reconnection. The results of the model are in qualitative agreement with observations.
Original language | English |
---|---|
Article number | A108 |
Number of pages | 7 |
Journal | Astronomy and Astrophysics |
Volume | 531 |
Issue number | July 2011 |
DOIs | |
Publication status | Published - Jul 2011 |
Keywords
- Magnetohydrodynamics (MHD)
- Flux emergence
- Numerical simulation
- Magnetic reconnection
- Solar atmosphere