Solar flares are energetic eruptive events closely related to space weather. This project aims directly at the flare source region and studies how the magnetic fields in the solar corona can rearrange (i.e., break and reconnect) to release energy, the impact of such reconnection on the lower solar atmosphere, and the associated acceleration of electrons. Observations from both the space-based (such as the recently launched NASA's Solar Dynamics Observatory) and ground-based (such as the renowned Big Bear Solar Observatory in California)  instruments are analyzed and jointly studied with theoretical models of coronal magnetic fields.

Our most prominent findings include that (1) we verifies, for the first time, that two oppositely oriented J-shaped loops can reconnect to form continuous, eruptive S-shaped loops (called sigmoids), which have long been regarded as an important signature in space weather forecasts. (2) We present the first unambiguous observation of the rapid and permanent changes of magnetic fields on the solar surface directly associated with the sigmoid eruption. Specifically, the surface fields must become more horizontal after flares. These help to settle a long debate in the solar physics. (3) We firstly demonstrate that while the sigmoids erupt outward, the coronal magnetic fields lying below could collapse downward toward the solar surface. This may hint that outward solar eruptions could be closely related to the downward disturbance such as sunquakes (analogous to earthquakes). (4) We obtain the clearest direct observational evidence of electron acceleration by the reconnection electric field in solar flares. (5) We originally propose in an exploratory way that flare emissions in the solar atmosphere could progress towards regions where the overlying magnetic fields provide less confinement.

Other important findings include that (6) we evidence that multiple solar eruptions can occur within a single but extended flare source region, a phenomenon similar to a "domino" effect. (7) We firstly verify that an eruption mechanism deduced from major flares, in which the removal of confining fields causes the eruption of the twisted core fields, could also apply to the very small-scale flaring activities on the Sun. (8) We reveal that coronal magnetic fields could inflate for many hours before their final eruption, which provides a critical complement to the standard theory for solar eruptions. (9) We show that even a moderate flare can have manifestation as brightenings deep down to the solar surface, which advances the classical view.

The observational outcomes resulted from this project have strong impacts on modeling of solar eruptive events in realization of the goal to mitigate the adverse effects of space weather. This project supports the education and training of a beginning postdoctoral researcher, who has been promoted to a research professor. Our research results have also been used to teach graduate and undergraduate students. A number of them have been involved in solar physics research in the Space Weather Research Laboratory of New Jersey Institute of Technology.

Last Modified: 12/30/2011
Modified by: Chang Liu