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The Confined X-class Flares of Solar Active Region 2192
Temmer, M.; Veronig, A. M.; Su, Y. +1 more
The unusually large active region (AR) NOAA 2192, observed in 2014 October, was outstanding in its productivity of major two-ribbon flares without coronal mass ejections. On a large scale, a predominantly north-south oriented magnetic system of arcade fields served as a strong top and lateral confinement for a series of large two-ribbon flares ori…
Global Trends of CME Deflections Based on CME and Solar Parameters
Kay, C.; Opher, M.; Evans, R. M.
Accurate space weather forecasting requires knowledge of the trajectory of coronal mass ejections (CMEs), including any deflections close to the Sun or through interplanetary space. Kay et al. introduced ForeCAT, a model of CME deflection resulting from the background solar magnetic field. For a magnetic field solution corresponding to Carrington …
Circumsolar Energetic Particle Distribution on 2011 November 3
Lario, D.; Rodríguez-Pacheco, J.; Gómez-Herrero, R. +7 more
Late on 2011 November 3, STEREO-A, STEREO-B, MESSENGER, and near-Earth spacecraft observed an energetic particle flux enhancement. Based on the analysis of in situ plasma and particle observations, their correlation with remote sensing observations, and an interplanetary transport model, we conclude that the particle increases observed at multiple…
The Cause of the Weak Solar Cycle 24
Schüssler, M.; Jiang, J.; Cameron, R. H.
The ongoing 11 year cycle of solar activity is considerably less vigorous than the three cycles before. It was preceded by a very deep activity minimum with a low polar magnetic flux, the source of the toroidal field responsible for solar magnetic activity in the subsequent cycle. Simulation of the evolution of the solar surface field shows that t…
Plasma and Magnetic Field Characteristics of Solar Coronal Mass Ejections in Relation to Geomagnetic Storm Intensity and Variability
Wang, Rui; Yang, Zhongwei; Liu, Ying D. +5 more
The largest geomagnetic storms of solar cycle 24 so far occurred on 2015 March 17 and June 22 with {D}{st} minima of -223 and -195 nT, respectively. Both of the geomagnetic storms show a multi-step development. We examine the plasma and magnetic field characteristics of the driving coronal mass ejections (CMEs) in connection with the de…
The Influence of Spatial resolution on Nonlinear Force-free Modeling
Sun, X.; Schrijver, C. J.; Canou, A. +11 more
The nonlinear force-free field (NLFFF) model is often used to describe the solar coronal magnetic field, however a series of earlier studies revealed difficulties in the numerical solution of the model in application to photospheric boundary data. We investigate the sensitivity of the modeling to the spatial resolution of the boundary data, by app…
The Peculiar Behavior of Halo Coronal Mass Ejections in Solar Cycle 24
Gopalswamy, N.; Michalek, G.; Yashiro, S. +3 more
We report on the remarkable finding that the halo coronal mass ejections (CMEs) in cycle 24 are more abundant than in cycle 23, although the sunspot number in cycle 24 has dropped by ∼40%. We also find that the distribution of halo-CME source locations is different in cycle 24: the longitude distribution of halos is much flatter with the number of…
Large Solar Energetic Particle Events Associated with Filament Eruptions Outside of Active Regions
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +4 more
We report on four large filament eruptions (FEs) from solar cycles 23 and 24 that were associated with large solar energetic particle (SEP) events and interplanetary type II radio bursts. The post-eruption arcades corresponded mostly to C-class soft X-ray enhancements, but an M1.0 flare was associated with one event. However, the associated corona…
Magnetic Structure and Dynamics of the Erupting Solar Polar Crown Prominence on 2012 March 12
Reeves, Katharine K.; van Ballegooijen, Adriaan; DeLuca, Edward E. +3 more
We present an investigation of the polar crown prominence that erupted on 2012 March 12. This prominence is observed at the southeast limb by the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA; end-on view) and displays a quasi-vertical thread structure. A bright U-shaped or horn-like structure is observed surrounding the upper…
Multiwavelength Observations of a Partially Eruptive Filament on 2011 September 8
Feng, L.; Cheng, X.; Guo, Y. +5 more
In this paper, we report our multiwavelength observations of a partial filament eruption event in NOAA active region (AR) 11283 on 8 September 2011. A magnetic null point and the corresponding spine and separatrix surface are found in the AR. Beneath the null point, a sheared arcade supports the filament along the highly complex and fragmented pol…