Using multi-wavelength observations of SoHO/MDI, SOT-Hinode/bluecontinuum (4504Å), G-band (4305Å), Ca II H (3968Å) and TRACE 171Å, we present the observational signature of highly twisted magnetic loop in AR 10960 during the period 04:43 UT-04:52 UT at 4 June, 2007. SOT-Hinode/bluecontinuum (4504Å) observations show that penumbral filaments of positive polarity sunspot have counter-clock wise twist, which may be caused by the clockwise rotation of the spot umbrae. The coronal loop, whose one footpoint is anchored in this sunspot, shows strong right-handed twist in chromospheric SOT-Hinode/Ca II H (3968Å) and coronal TRACE 171Å images. The length and the radius of the loop are L ∼80 Mm and a ∼4.0 Mm respectively. The distance between neighboring turns of magnetic field lines (i.e. pitch) is estimated as ≈ 10 Mm. The total twist angle, Φ ∼12π (estimated for the homogeneous distribution of the twist along the loop), is much larger than the Kruskal -Shafranov instability criterion. We detected clear double structure of the loop top during 04:47-04:51 UT on TRACE 171Å images, which is consistent with simulated kink instability in curved coronal loops (Török et al. 2004). We suggest, that the kink instability of this twisted magnetic loop triggered B5.0 class solar flare, which occurred between 04:40 UT and 04:51 UT in this active region.

Using simultaneous high spatial (1.3 arcsec) and temporal (5 and 10 s) resolution Hα observations from the 15 cm Solar Tower Telescope at Aryabhatta Research Institute of Observational Sciences (ARIES), we study the oscillations in the relative intensity to explore the possibility of sausage oscillations in the chromospheric cool post‐flare loop. We use the standard wavelet tool, and find the oscillation period of ≈587 s near the loop apex, and ≈349 s near the footpoint. We suggest that the oscillations represent the fundamental and the first harmonics of the fast‐sausage waves in the cool post‐flare loop. Based on the period ratio P1/P2∼1.68, we estimate the density scaleheight in the loop as ∼17 Mm. This value is much higher than the equilibrium scaleheight corresponding to Hα temperature, which probably indicates that the cool post‐flare loop is not in hydrostatic equilibrium. Seismologically estimated Alfvén speed outside the loop is ∼300–330  km s−1. The observation of multiple oscillations may play a crucial role in understanding the dynamics of lower solar atmosphere, complementing such oscillations already reported in the upper solar atmosphere (e.g. hot flaring loops).

Jets (transient/collimated plasma ejections) occur frequently throughout the solar corona and contribute mass/energy to the corona and solar wind. By combining numerical simulations and high-resolution observations, we have made substantial progress recently on determining the energy buildup and release processes in these jets. Here we describe a study of 27 equatorial coronal-hole jets using Solar Dynamics Observatory/AIA and HMI observations on 2013 June 27-28 and 2014 January 8-10. Out of 27 jets, 18 (67%) are associated with mini-filament ejections; the other 9 (33%) do not show mini-filament eruptions but do exhibit mini-flare arcades and other eruptive signatures. This indicates that every jet in our sample involved a filament-channel eruption. From the complete set of events, 6 jets (22%) are apparently associated with tiny flux-cancellation events at the polarity inversion line, and 2 jets (7%) are associated with sympathetic eruptions of filaments from neighboring bright points. Potential-field extrapolations of the source-region photospheric magnetic fields reveal that all jets originated in the fan-spine topology of an embedded bipole associated with an extreme ultraviolet coronal bright point. Hence, all our jets are in agreement with the breakout model of solar eruptions. We present selected examples and discuss the implications for the jet energy build-up and initiation mechanisms.

We report decaying quasi-periodic intensity oscillations in the X-ray (6-12 keV) and extreme ultraviolet (EUV) channels (131, 94, 1600, 304Å) observed by the Fermi GBM (Gamma-ray Burst Monitor) and SDO/AIA (Solar Dynamic Observatory/Atmospheric Imaging Assembly), respectively, during a C-class flare. The estimated period of oscillation and decay time in the X-ray channel (6-12 keV) was about 202 s and 154 s, respectively. A similar oscillation period was detected at the footpoint of the arcade loops in the AIA 1600 and 304Å channels. Simultaneously, AIA hot channels (94 and 131Å) reveal propagating EUV disturbances bouncing back and forth between the footpoints of the arcade loops. The period of the oscillation and decay time were about 409 s and 1,121 s, respectively. The characteristic phase speed of the wave is about 560 km s −1 for about 115 Mm loop length, which is roughly consistent with the sound speed at the temperature about 10-16 MK (480-608 km s −1 ). These EUV oscillations are consistent with the SOHO/SUMER (Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation) Doppler-shift oscillations interpreted as the global standing slow magnetoacoustic wave excited by a flare. The flare occurred at one of the footpoints of the arcade loops, where the magnetic topology was a 3D fan-spine with a null-point. Repetitive reconnection at this footpoint could cause the periodic acceleration of non-thermal electrons that propagated to the opposite footpoint along the arcade and precipitating there, causing the observed 202-s periodicity. Other possible interpretations, e.g. the second harmonics of the slow mode are also discussed.