Pre-Eruption Magnetic Configurations in the Low Atmosphere of Solar Active Regions
Abstract
Major solar eruptions, namely flares and coronal mass ejections, rely on significant local accumulations of non-potential (free; stored in electric currents) magnetic energy and, quite likely, magnetic helicity in the solar atmosphere. Without [both of] them, eruptions cannot be powered. Simple tests can show that most free energy and helicity reside close to the lower atmospheric boundary in solar active regions, i.e. their photospheric or low chromospheric interface. Therefore, the pre-eruption configuration in this boundary should reflect these high free-energy and helicity conditions that jointly determine the degree of non-potentiality in active regions. We review the two main active-region photospheric/low-chromospheric configurations leading to major eruptions: instances of intense magnetic flux emergence in the absence of intense magnetic polarity inversion lines (PILs), and instances of strong PILs. In these configurations we discuss multiple measures that can be thought of as proxies of free magnetic energy and helicity and we outline a method to actually calculate these budgets. Combining information from different, but concerted, analyses and approaches, a new picture of eruption initiation emerges. We highlight this new insight and project on its physical plausibility and the advances that it may bring.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39..604G