A filament eruption was observed on 2010 October 31 in the images recorded by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) in its Extreme Ultra-Violet (EUV) channels. The filament showed a slow-rise phase followed by a fast rise and was classified to be an asymmetric eruption. In addition, multiple localized brightenings which were spatially and temporally associated with the slow-rise phase were identified, leading us to believe that the tether-cutting mechanism initiated the eruption. An associated flux rope was detected in high-temperature channels of AIA, namely 94 and 131 Å, corresponding to 7 and 11 MK plasma respectively. In addition, these channels are also sensitive to cooler plasma corresponding to 1-2 MK. In this study, we have applied the algorithm devised by Warren et al. to remove cooler emission from the 94 Å channel to deduce only the high-temperature structure of the flux rope and to study its temporal evolution. We found that the flux rope was very clearly seen in the clean 94 Å channel image corresponding to Fe XVIII emission, which corresponds to a plasma at a temperature of 7 MK. This temperature matched well with that obtained using Differential Emission Measure analysis. This study provides important constrains in the modeling of the thermodynamic structure of the flux ropes in coronal mass ejections.

The direction of the axis of an interplanetary coronal mass ejection (ICME) plays an important role in determining if it will cause a geomagnetic disturbance in the Earth’s magnetosphere upon impact. Long period southward-pointing ICME fields are known to cause significant space weather impacts and thus geomagnetic storms. We present an extensive analysis of CME–ICME directionality using 86 halo-CMEs observed between 2007 and 2017 to compare the direction of the source filament axial magnetic field on the Sun and the direction of the interplanetary magnetic field near the Earth at the L1 Lagrangian point. Excluding 12 cases that were too ambiguous to determine, for the remaining 74 ICMEs, we find an agreement in terms of the northward/southward orientation of B z between ICMEs and their CME source regions in 85% of cases. Some of the previous studies discussed here have obtained an agreement of 77% and 55%. We therefore suggest that our method can be meaningful as a first step in efficiently predicting geoeffective ICMEs by observing and analyzing the source regions of CMEs on the Sun.

There have been a few previous studies claiming that the effects of geomagnetic storms strongly depend on the orientation of the magnetic cloud portion of coronal mass ejections (CMEs). Aparna & Martens, using halo-CME data from 2007 to 2017, showed that the magnetic field orientation of filaments at the location where CMEs originate on the Sun can be used to credibly predict the geoeffectiveness of the CMEs being studied. The purpose of this study is to extend their survey by analyzing the halo-CME data for 1996–2006. The correlation of filament axial direction on the solar surface and the corresponding Bz signatures at L1 are used to form a more extensive analysis for the results previously presented by Aparna & Martens. This study utilizes Solar and Heliospheric Observatory Extreme-ultraviolet Imaging Telescope 195 Å, Michelson Doppler Imager magnetogram images, and Kanzelhöhe Solar Observatory and Big Bear Solar Observatory Hα images for each particular time period, along with ACE data for interplanetary magnetic field signatures. Utilizing all these, we have found that the trend in Aparna & Martens’ study of a high likelihood of correlation between the axial field direction on the solar surface and Bz orientation persists for the data between 1996 and 2006, for which we find a match percentage of 65%.

Consider the simple, finite, connected and undirected graph H = (V, E) in which V and E denotes the vertex set and edge set of the graph H. The r-dynamic coloring of a graph H is the proper p-coloring of the vertices of the graph H in which |c(N(a)| ≥ min{r, d(a)}, for each a ∈ V ( H ) . The lowest p which allows H an r-dynamic coloring with p colors is called the r-dynamic chromatic number of the graph H and it is denoted as X r (H). Let H 1 and H 2 be two graphs with vertex disjoint sets of n 1 and n 2vertices. The neighborhood corona of two graphs H 1 and H 2 is obtained by taking one copy of the graph H 1 and n 1 copies of the graph H 2 and by joining each neighbor of the ith vertex of H 1 to each and every vertex of the ith copy of H 2. It is denoted as H 1 ⋄ H 2 . In this paper, we determine the r-dynamic chromatic number of the neighborhood corona of path graph Pm with path Pn , complete graph Kn , cycle Cn and star graph K1,n . These graphs are denoted as P m ⋄ P n , P m ⋄ K n , P m ⋄ C n and P m ⋄ K 1 , n respectively.

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