Speaker:  Dr. Jiong Qiu Big Bear Solar Observatory, NJIT

Title:  The Sun on Fire: from Microflares to Coronal Mass Ejections

Abstract:  Viewed through telescopes, the Sun is a restless star. Impulsive solar energy release events are frequently observed on a variety of scales from microflares to coronal mass ejections. Solar flares are characterized by sudden brightening on the Sun's surface. Advanced ground-based and satellite-borne telescopes have detected very small energy release events, or microflares. We have explored properties of these tiny flares. It is believed that energy release in solar flares, large or small, is governed by magnetic reconnection, when anti-parallel magnetic field lines collide and reconnect with each other, efficiently converting magnetic energy into heating plasmas and accelerating particles. We have evaluated the rate of magnetic reconnection, a key physical parameter in magnetized plasmas, by carefully analyzing its observational signatures in flares.

Often accompanied by flares, a large bundle of plasmas wrapped in magnetic fields are violently hurled out of the Sun to the interplanetary space, which may reach the Earth's magnetosphere and cause magnetic storms. This is coronal mass ejection (CME), the most spectacular energy release on the Sun. CMEs are believed to be driven magnetically, but the exact mechanism remains in heated debate. Past studies suggested a close temporal correlation between flare emissions and the rising motion of CMEs at the early stage of eruption in many events. We have furthered such studies by linking flares and CMEs with magnetic reconnection. It is shown that both acceleration of mass ejections and energetic emission of solar flares are correlated with magnetic reconnection rate inferred from observations. It is also found that the magnitude of mass acceleration is likely scaled with magnetic reconnection rate. These new findings strongly argue that magnetic reconnection is an important process during the early phase of many CMEs, when acceleration is most significant.


Host: Dana Longcope