Search Publications
Thermal instability and non-equilibrium in solar coronal loops: from coronal rain to long-period intensity pulsations
Antolin, Patrick
The complex interaction of the magnetic field with matter is the key to some of the most puzzling observed phenomena at multiple scales across the Universe, from tokamak plasma confinement experiments in the laboratory to the filamentary structure of the interstellar medium. A major astrophysical puzzle is the phenomenon of coronal heating, upon w…
Spectral Signatures of Chromospheric Condensation in a Major Solar Flare
Allred, Joel; Graham, David R.; Zangrilli, Luca +3 more
We study the evolution of chromospheric line and continuum emission during the impulsive phase of the X-class SOL2014-09-10T17:45 solar flare. We extend previous analyses of this flare to multiple chromospheric lines of Fe I, Fe II, Mg II, C I, and Si II observed with the Interface Region Imaging Spectrograph, combined with radiative-hydrodynamica…
Ion-neutral Interactions and Nonequilibrium Ionization in the Solar Chromosphere
Martínez-Sykora, Juan; De Pontieu, Bart; Nóbrega-Siverio, Daniel +4 more
The thermal structure of the chromosphere is regulated through a complex interaction of various heating processes, radiative cooling, and the ionization degree of the plasma. Here, we study the impact on the thermal properties of the chromosphere when including the combined action of nonequilibrium ionization (NEI) of hydrogen and helium and ion-n…
Hot Plasma Flows and Oscillations in the Loop-top Region During the 2017 September 10 X8.2 Solar Flare
Reeves, Katharine K.; Polito, Vanessa; Chen, Bin +4 more
In this study, we investigate motions in the hot plasma above the flare loops during the 2017 September 10 X8.2 flare event. We examine the region to the south of the main flare arcade, where there is data from the Interface Region Imaging Spectrograph (IRIS) and the Extreme ultraviolet Imaging Spectrometer (EIS) on Hinode. We find that there are …
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…
IRIS Observations of Short-term Variability in Moss Associated with Transient Hot Coronal Loops
Polito, Vanessa; Testa, Paola; De Pontieu, Bart
We observed rapid variability (≲60 s) at the footpoints of transient, hot (∼8-10 MK) coronal loops in active region cores, with the Interface Region Imaging Spectrograph (IRIS). The high spatial (∼0"33) and temporal (≲5-10 s) resolution of IRIS is often crucial for the detection of this variability. We show how, in combination with 1D RADYN loop m…
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…
Magnetic reconnection in partially ionized plasmas
Ni, Lei; Murphy, Nicholas A.; Ji, Hantao +1 more
Magnetic reconnection has been intensively studied in fully ionized plasmas. However, plasmas are often partially ionized in astrophysical environments. The interactions between the neutral particles and ionized plasmas might strongly affect the reconnection mechanisms. We review magnetic reconnection in partially ionized plasmas in different envi…