Search Publications
An optically thin view of the flaring chromosphere: non-thermal widths in a chromospheric condensation during an X-class solar flare
Kowalski, Adam F.; Kerr, Graham S.; Allred, Joel C. +2 more
The bulk of solar flare energy is deposited in the chromosphere. Flare ribbons and footpoints in the chromosphere therefore offer great diagnostic potential of flare energy release and transport processes. High-quality observations from the Interface Region Imaging Spectrograph (IRIS) spacecraft have transformed our view of the Sun's atmospheric r…
Non-thermal broadening of coronal lines in a 3D MHD loop model
Peter, H.; Solanki, S. K.; De Moortel, I. +2 more
Observed spectral profiles of emission lines from the corona are found to have widths exceeding the thermal line width. To investigate the physical mechanism, we run a 3D magnetohydrodynamics model of a single, straightened loop in which we partially resolve turbulent motions that form in response to the driving by self-consistently evolving magne…
Spectroscopic diagnostic of the footpoints of the cool loops
Dwivedi, B. N.; Kayshap, Pradeep; Jelínek, P. +2 more
Statistically, the cool loop's footpoints are diagnosed using Si IV resonance lines observations provided by Interface Region Imaging Spectrograph (IRIS). The intensity and full width at half-maximum (FWHM) of the loop's footpoints in β-γ active regions (ARs) are higher than the corresponding parameters of footpoints in β ARs. However, the Doppler…
Effect of area divergence and frequency on damping of slow magnetoacoustic waves propagating along umbral fan loops
Gupta, Girjesh R.; Rawat, Ananya
Waves play an important role in the heating of solar atmosphere; however, observations of wave propagation and damping from the solar photosphere to corona through chromosphere and transition region are very rare. Recent observations have shown propagation of 3-min slow magnetoacoustic waves (SMAWs) along fan loops from the solar photosphere to co…
Imaging and spectroscopic observations of a confined solar filament eruption with two-stage evolution
Xu, Zhe; Xue, Zhike; Yan, Xiaoli +3 more
Solar filament eruptions are often characterized by stepwise evolution due to the involvement of multiple mechanisms, such as magnetohydrodynamic instabilities and magnetic reconnection. In this article, we investigated a confined filament eruption with a distinct two-stage evolution by using the imaging and spectroscopic observations from the Int…
Asymmetry of the spectral lines of the coronal hole and quiet Sun in the transition region
Kayshap, Pradeep; Safari, Hossein; Hosseini, Razieh +1 more
The asymmetry of line profiles, i.e. the secondary component, is crucial to understanding the energy release of coronal holes (CH), quiet Sun (QS), and bright points (BPs). We investigate the asymmetry of Si IV 1393.75 Å of the transition-region (TR) line recorded by Interface Region Imaging Spectrograph (IRIS) and co-spatial-temporal Atmospheric …
Exploring source region of 3-min slow magnetoacoustic waves observed in coronal fan loops rooted in sunspot umbra
Gupta, Girjesh R.; Rawat, Ananya
Sunspots host various oscillations and wave phenomena like umbral flashes, umbral oscillations, running penumbral waves, and coronal waves. All fan loops rooted in sunspot umbra constantly show a 3-min period propagating slow magnetoacoustic waves in the corona. However, their origin in the lower atmosphere is still unclear. In this work, we studi…
Centre-to-limb variations in coronal hole and quiet sun regions obtained with IRIS spectroscopic observations
Young, Peter R.; Kayshap, Pradeep
The centre-to-limb variations (CLV) of Gaussian fit parameters of the transition region Si IV 1402.77 Å spectral line in quiet Sun (QS) and coronal hole (CH) regions are presented. The results are derived from a full-disc mosaic scan obtained by the Interface Region Imaging Spectrograph on 2017 September 24. The CLV for a CH transition region line…
Searching for signatures of H α spicule-like features in the solar transition region
Shetye, Juie; Doyle, J. Gerry; Vilangot Nhalil, Nived
New instruments and telescopes covering the optical and ultraviolet spectral regions have revealed a range of small-scale dynamic features, many which may be related. For example, the range of spicule-like features hints towards a spectrum of features and not just two types; however, direct observational evidence in terms of tracking spicules acro…
Behaviour of molecular hydrogen emission in three solar flares
Fletcher, Lyndsay; Mulay, Sargam M.; Labrosse, Nicolas +1 more
We have systematically investigated ultraviolet (UV) emission from molecular hydrogen (H2) using the Interface Region Imaging Spectrograph (IRIS), during three X-ray flares of C5.1, C9.7, and X1.0 classes on 2014 October 25. Significant emission from five H2 spectral lines appeared in the flare ribbons, interpreted as photoex…