TY - JOUR A1 - Louis, Rohan E. A1 - Kliem, Bernhard A1 - Ravindra, B. A1 - Chintzoglou, Georgios T1 - Triggering an Eruptive Flare by Emerging Flux in a Solar Active-Region Complex JF - Solar physics : a journal for solar and solar-stellar research and the study of solar terrestrial physics N2 - A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on 2012 July 1 (SOL2012-07-01) in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade (). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted the arcade between the two active regions, weakening its downward tension force and thus destabilizing the considerably sheared flux under the arcade. The complex event was also associated with supporting precursor activity in an enhanced network near the active regions, acting on the large-scale overlying flux, and with two simultaneous confined flares within the active regions. KW - Flares, dynamics KW - Sunspots, magnetic fields KW - Chromosphere, active KW - Corona KW - Prominences, active Y1 - 2015 U6 - https://doi.org/10.1007/s11207-015-0726-8 SN - 0038-0938 SN - 1573-093X VL - 290 IS - 12 SP - 3641 EP - 3662 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Louis, Rohan E. A1 - Puschmann, Klaus G. A1 - Kliem, Bernhard A1 - Balthasar, Horst A1 - Denker, Carsten T1 - Sunspot splitting triggering an eruptive flare JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. We investigate how the splitting of the leading sunspot and associated flux emergence and cancellation in active region NOAA 11515 caused an eruptive M5.6 flare on 2012 July 2. Methods. Continuum intensity, line-of-sight magnetogram, and dopplergram data of the Helioseismic and Magnetic Imager were employed to analyse the photospheric evolution. Filtergrams in H alpha and He I 10830 angstrom of the Chromospheric Telescope at the Observatorio del Teide, Tenerife, track the evolution of the flare. The corresponding coronal conditions were derived from 171 angstrom and 304 angstrom images of the Atmospheric Imaging Assembly. Local correlation tracking was utilized to determine shear flows. Results. Emerging flux formed a neutral line ahead of the leading sunspot and new satellite spots. The sunspot splitting caused a long-lasting flow towards this neutral line, where a filament formed. Further flux emergence, partly of mixed polarity, as well as episodes of flux cancellation occurred repeatedly at the neutral line. Following a nearby C-class precursor flare with signs of interaction with the filament, the filament erupted nearly simultaneously with the onset of the M5.6 flare and evolved into a coronal mass ejection. The sunspot stretched without forming a light bridge, splitting unusually fast (within about a day, complete approximate to 6 h after the eruption) in two nearly equal parts. The front part separated strongly from the active region to approach the neighbouring active region where all its coronal magnetic connections were rooted. It also rotated rapidly (by 4.9 degrees h(-1)) and caused significant shear flows at its edge. Conclusions. The eruption resulted from a complex sequence of processes in the (sub-)photosphere and corona. The persistent flows towards the neutral line likely caused the formation of a flux rope that held the filament. These flows, their associated flux cancellation, the emerging flux, and the precursor flare all contributed to the destabilization of the flux rope. We interpret the sunspot splitting as the separation of two flux bundles differently rooted in the convection zone and only temporarily joined in the spot. This explains the rotation as the continued rise of the separating flux, and it implies that at least this part of the sunspot was still connected to its roots deep in the convection zone. KW - Sun: flares KW - sunspots KW - Sun: photosphere KW - Sun: chromosphere KW - techniques: photometric Y1 - 2014 U6 - https://doi.org/10.1051/0004-6361/201321106 SN - 0004-6361 SN - 1432-0746 VL - 562 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Denker, Carsten A1 - Kuckein, Christoph A1 - Verma, Meetu A1 - Manrique Gonzalez, Sergio Javier Gonzalez A1 - Diercke, Andrea A1 - Enke, Harry A1 - Klar, Jochen A1 - Balthasar, Horst A1 - Louis, Rohan E. A1 - Dineva, Ekaterina Ivanova T1 - High-cadence Imaging and Imaging Spectroscopy at the GREGOR Solar Telescope-A Collaborative Research Environment for High-resolution Solar Physics JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series N2 - In high-resolution solar physics, the volume and complexity of photometric, spectroscopic, and polarimetric ground-based data significantly increased in the last decade, reaching data acquisition rates of terabytes per hour. This is driven by the desire to capture fast processes on the Sun and the necessity for short exposure times "freezing" the atmospheric seeing, thus enabling ex post facto image restoration. Consequently, large-format and high-cadence detectors are nowadays used in solar observations to facilitate image restoration. Based on our experience during the "early science" phase with the 1.5 m GREGOR solar telescope (2014–2015) and the subsequent transition to routine observations in 2016, we describe data collection and data management tailored toward image restoration and imaging spectroscopy. We outline our approaches regarding data processing, analysis, and archiving for two of GREGOR's post-focus instruments (see http://gregor.aip.de), i.e., the GREGOR Fabry–Pérot Interferometer (GFPI) and the newly installed High-Resolution Fast Imager (HiFI). The heterogeneous and complex nature of multidimensional data arising from high-resolution solar observations provides an intriguing but also a challenging example for "big data" in astronomy. The big data challenge has two aspects: (1) establishing a workflow for publishing the data for the whole community and beyond and (2) creating a collaborative research environment (CRE), where computationally intense data and postprocessing tools are colocated and collaborative work is enabled for scientists of multiple institutes. This requires either collaboration with a data center or frameworks and databases capable of dealing with huge data sets based on virtual observatory (VO) and other community standards and procedures. KW - astronomical databases KW - methods: data analysis KW - Sun: chromosphere KW - Sun: photosphere KW - techniques: image processing KW - techniques: spectroscopic Y1 - 2018 U6 - https://doi.org/10.3847/1538-4365/aab773 SN - 0067-0049 SN - 1538-4365 VL - 236 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER -