Search Publications
First direct observation of a torsional Alfvén oscillation at coronal heights
Kohutova, P.; Verwichte, E.; Froment, C.
Context. Torsional Alfvén waves are promising candidates for the transport of energy across different layers of the solar atmosphere. They have been predicted theoretically for decades. Previous detections of Alfvén waves so far have however mostly relied on indirect signatures.
Aims: We present the first direct observational evidence of a fu…
Case study of multi-temperature coronal jets for emerging flux MHD models
Nóbrega-Siverio, Daniel; Aulanier, Guillaume; Schmieder, Brigitte +4 more
Context. Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still actively debated.
Aims: We study six recurrent jets that occurred in active region NOAA 12644 on April 4, 2017. They are observed in all the hot filters of AIA as well as cool surges in IRIS slit-jaw high spatial and temporal resoluti…
Ellerman bombs and UV bursts: reconnection at different atmospheric layers
Nóbrega-Siverio, Daniel; Ortiz, Ada; Hansteen, Viggo H. +1 more
The emergence of magnetic flux through the photosphere and into the outer solar atmosphere produces, amongst other dynamical phenomena, Ellerman bombs (EBs), which are observed in the wings of Hα and are due to magnetic reconnection in the photosphere below the chromospheric canopy. Signs of magnetic reconnection are also observed in other spectra…
The multi-thermal chromosphere. Inversions of ALMA and IRIS data
De Pontieu, B.; Leenaarts, J.; da Silva Santos, J. M. +4 more
Context. Numerical simulations of the solar chromosphere predict a diverse thermal structure with both hot and cool regions. Observations of plage regions in particular typically feature broader and brighter chromospheric lines, which suggests that they are formed in hotter and denser conditions than in the quiet Sun, but also implies a nonthermal…
Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere
Peter, H.; Chitta, L. P.; Solanki, S. K. +1 more
Coronal plasma in the cores of solar active regions is impulsively heated to more than 5 MK. The nature and location of the magnetic energy source responsible for such impulsive heating is poorly understood. Using observations of seven active regions from the Solar Dynamics Observatory, we found that a majority of coronal loops hosting hot plasma …
The role of small-scale surface motions in the transfer of twist to a solar jet from a remote stable flux rope
Aulanier, Guillaume; Schmieder, Brigitte; Joshi, Reetika +2 more
Context. Jets often have a helical structure containing ejected plasma that is both hot and also cooler and denser than the corona. Various mechanisms have been proposed to explain how jets are triggered, primarily attributed to a magnetic reconnection between the emergence of magnetic flux and environment or that of twisted photospheric motions t…
High-resolution observations of the solar photosphere, chromosphere, and transition region. A database of coordinated IRIS and SST observations
Gošić, M.; De Pontieu, B.; Sainz Dalda, A. +30 more
NASA's Interface Region Imaging Spectrograph (IRIS) provides high-resolution observations of the solar atmosphere through ultraviolet spectroscopy and imaging. Since the launch of IRIS in June 2013, we have conducted systematic observation campaigns in coordination with the Swedish 1 m Solar Telescope (SST) on La Palma. The SST provides complement…
Propagation of waves above a plage as observed by IRIS and SDO
Srivastava, A. K.; Mathioudakis, M.; Jelínek, P. +2 more
Context. Magnetohydrodynamic waves are proposed as the mechanism that transport sufficient energy from the photosphere to heat the transition region (TR) and corona. However, various aspects of these waves, such as their nature, propagation characteristics, and role in the atmospheric heating process, remain poorly understood and require further i…
Evolution of supersonic downflows in a sunspot
Mathioudakis, M.; Krishna Prasad, S.; Nelson, C. J.
Context. Supersonic downflows have been observed in transition region spectra above numerous sunspots, however, little research has been conducted to date into how persistent these signatures are within sunspots on timescales longer than a few hours.
Aims: We aim to analyse the lead sunspot of AR 12526 to infer the properties and evolution of…
Sunspot penumbral filaments intruding into a light bridge and the resultant reconnection jets
Zhang, J.; Hou, Y. J.; Li, T. +5 more
Context. Penumbral filaments and light bridges are prominent structures inside sunspots and are important for understanding the nature of sunspot magnetic fields and magneto-convection underneath.
Aims: We investigate an interesting event where several penumbral filaments intrude into a sunspot light bridge. In doing so we aim to gain further…