Event DetailsEvent Dates: Monday, March 13, 2017 - 4:00pmSeminar Location: JILA AuditoriumSpeaker Name(s): Sanjiv TiwariSpeaker Affiliation(s): NASA Marshall and the University of Alabama Seminar Type/SubjectScientific Seminar Type: Astrophysical & Planetary Sciences ColloquiaEvent Details & Abstract: Similar to active regions on other Sun-like convective stars, sunspot active regions have the strongest magnetic field found on the Sun and are the brightest features in the EUV and X-ray corona (i.e., they have the strongest coronal heating). Active regions are also the source of the largest flares and CMEs often leading to severe space weather. In this talk, I will cover three parts of my recent research on solar active regions. First, I will give a brief update on the latest understanding of sunspot fine-scale structure, from Hinode (SOT/SP) data (figure above). I will also present an update on the small-scale penumbral dynamic events, e.g., penumbral jets, and bright dots. Second, I will present results from an ongoing work where, by using SDO (AIA+HMI) data and robust nonlinear force-free modeling, we find that the brightness of an active region coronal loop depends on where in the photosphere (i.e., in umbra, penumbra, or plage) each foot of the loop is rooted. I will also show microflares that result from magnetic flux cancellation and trigger nearby subflares in already braided (non-potential) magnetic loops. In the last segment, I will show how the speed of CMEs emanating from an active region is related to the active region’s magnetic non-potentiality (measured from HMI vector magnetograms), and how we will use HMI vector magnetic field data to improve prediction of severe space weather; for continuing this work we have recently won an NSF grant. I will discuss a few questions that are raised by my recent research and can be addressed using the unprecedented data to be obtained by the upcoming DKIST.