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Funding: UK STFC via PhD studentship and the Consolidated Grant SMC1/YST025 (S.L.Y.); STFC and Leverhulme trust (D.H.M.). We present observations and magnetic field models of an intermediate filament present on the Sun in August 2012, associated with a polarity inversion line that extends from AR 11541 in the east into the quiet sun at its western end. A combination of SDO/AIA, SDO/HMI, and GONG Hα data allow us to analyse the structure and evolution of the filament from 2012 August 4 23:00 UT to 2012 August 6 08:00 UT when the filament was in equilibrium. By applying the flux rope insertion method, nonlinear force-free field models of the filament are constructed using SDO/HMI line-of-sight magnetograms as the boundary condition at the two times given above. Guided by observed filament barbs, both modelled flux ropes are split into three sections each with a different value of axial flux to represent the non-uniform photospheric field distribution. The flux in the eastern section of the rope increases by 4x1020 Mx between the two models, which is in good agreement with the amount of flux cancelled along the internal PIL of AR 11541, calculated to be 3.2x1020 Mx. This suggests that flux cancellation builds flux into the filament's magnetic structure. Additionally, the number of field line dips increases between the two models in the locations where flux cancellation, the formation of new filament threads and growth of the filament is observed. This suggests that flux cancellation associated with magnetic reconnection forms concave-up magnetic field that lifts plasma into the filament. During this time, the free magnetic energy in the models increases by 0.2 x 1031 ergs. Postprint

Accepted: 2007-08-26, 資料番号: SA1000265000

Throughout the eleven year cycle of the sun, solar eruptions are constantly taking place. Thought to be caused by reconnection of magnetic field lines, coronal jets are one of several types of such eruptions. Jet formation and eruption is not well understood. In some cases, jets occur when small filaments of chromospheric material are lofted into the corona. The filaments have strong magnetic flux, and are often the site of magnetic reconnection and subsequent eruption. In order to better understand the constraints on these coronal jets, we have modeled the conditions required for stable filaments and eruptions using nonlinear force-free (NLFF) field modeling. NLFF models are 3-D topological models that are used to show the morphological evolution of magnetic fields. Using the CMS2 modeling suite, we modeled two regions with jet eruptions: a coronal jet near a larger filament, and a coronal jet near an AR sigmoid. In both cases, Solar Dynamics Observatory’s HMI magnetograms and observations from AIA images are used to constrain the input parameters of the model. In this presentation, we will present our model results and discuss how they help understand solar coronal jet eruptions., This work is supported by NSF-REU solar physics program at SAO, grant number AGS-1560313, and NASA grant number NNX15AF43G.

Jets are small explosions that occur frequently in the Sun possibly driven by the local reconfiguration of the magnetic field, or reconnection. There are two types of coronal jets: standard jets and blowout jets. The purpose of this project is to determine which mechanisms accelerate plasma in two different jets, one that occurred in January 17, 2015 at the disk of the sun and another in October 24, 2015 at the limb. Two possible acceleration mechanisms are chromospheric evaporation and magnetic acceleration. Using SDO/AIA, Hinode/XRT and IRIS data, we create height-time plots, and calculate the velocities of each wavelength for both jets. We calculate the potential magnetic field of the jet and the general region around it to gain a more detailed understanding of its structure, and determine if the jet is likely to be either a standard or blowout jet. Finally, we calculate the magnetic field strength for different heights along the jet spire, and use differential emission measures to calculate the plasma density. Once we have these two values, we calculate the Alfven speed. When analyzing our results we are looking for certain patterns in our velocities. If the plasma in a jet is accelerated by chromospheric evaporation, we expect the velocities to increase as function of temperature, which is what we observed in the October 24th jet. The magnetic models for this jet also show the Eiffel Tower shaped structure characteristic of standard jets, which tend to have plasma accelerated by this mechanism. On the other hand, if the acceleration mechanism were magnetic acceleration, we would expect the velocities to be similar regardless of temperature. For the January 17th jet, we saw that along the spire, the velocities where approximately 200 km/s in all wavelengths, but the velocities of hot plasma detected at the base were closer to the Alfven speed, which was estimated to be about 2,000 km/s. These observations suggest that the plasma in the January 17th jet is magnetically accelerated. The magnetic model for this jet needs to be studied further by using a NLFFF magnetic field model and not just the potential magnetic field.