Abstract
Ellerman bombs (EBs) are transient brightenings on the outer wings of the H Balmer α line observed in emerging active regions. They are observable manifestations of small-scale magnetic reconnection events in the solar photosphere. We aim to develop a method for automatic detection and tracking of EBs, in order to characterize their properties and investigate the local magnetic field configuration at their locations.
For the thesis, we use high-resolution Hα observations aligned with Fe I 6173 Å magnetic field maps (BLOS) from the Swedish 1-m Solar Telescope (SST) on La Palma. EBs are identified using a four-level intensity threshold applied to the Hα wings and subsequently tracked in time. We required a lifetime above 74 s and a maximum area of at least 0.035 arcsec2. We detected a total of 51 EBs. They have a median maximum area of 0.275 arcsec2, a median lifetime of 3 min and are predominantly circular in shape.
18 EBs show a simple dipole configuration where flux cancellation is clearly observed, while 26 EBs occur in unipolar regions. The remaining 7 EBs have insufficient magnetic signal. We note that for unipolar EBs, a polarity inversion line (PIL) is located between 0.′′044 to 0.′′295 away. We identify a subset of unipolar EBs associated with more complex fan-spine topologies with a 3D magnetic null point.
Our results indicate that Hα and BLOS observations alone are insufficient to accurately describe the unipolar EBs produced by fan-spine topologies.
Supervisors:
- Luc Rouppe van der Voort, Professor at Institute of Theoretical Astrophysics, UiO
- Ignasi Josep Soler Poquet, PhD student at Institute of Theoretical Astrophysics, UiO
Intern. assessor: Øystein Elgarøy, Professor at Institute of Theoretical Astrophysics, UiO
Extern. assessor: Jaime de la Cruz Rodriguez, Professor at Stockholm University