Search Publications
On the generation of solar spicules and Alfvénic waves
De Pontieu, B.; Martínez-Sykora, J.; Hansteen, V. H. +3 more
In the lower solar atmosphere, the chromosphere is permeated by jets known as spicules, in which plasma is propelled at speeds of 50 to 150 kilometers per second into the corona. The origin of the spicules is poorly understood, although they are expected to play a role in heating the million-degree corona and are associated with Alfvénic waves tha…
Origin and Structures of Solar Eruptions I: Magnetic Flux Rope
Cheng, Xin; Guo, Yang; Ding, MingDe
Coronal mass ejections (CMEs) and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may intera…
Bombs and Flares at the Surface and Lower Atmosphere of the Sun
Leenaarts, J.; Hansteen, V. H.; Rouppe van der Voort, L. +3 more
A spectacular manifestation of solar activity is the appearance of transient brightenings in the far wings of the Hα line, known as Ellerman bombs (EBs). Recent observations obtained by the Interface Region Imaging Spectrograph have revealed another type of plasma “bombs” (UV bursts) with high temperatures of perhaps up to 8 × 104 K wit…
The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. I. Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29
Kowalski, Adam F.; Daw, Adrian; Carlsson, Mats +2 more
The 2014 March 29 X1 solar flare (SOL20140329T17:48) produced bright continuum emission in the far- and near-ultraviolet (NUV) and highly asymmetric chromospheric emission lines, providing long-sought constraints on the heating mechanisms of the lower atmosphere in solar flares. We analyze the continuum and emission line data from the Interface Re…
Intermittent Reconnection and Plasmoids in UV Bursts in the Low Solar Atmosphere
De Pontieu, B.; Martínez-Sykora, J.; Hansteen, V. H. +9 more
Magnetic reconnection is thought to drive a wide variety of dynamic phenomena in the solar atmosphere. Yet, the detailed physical mechanisms driving reconnection are difficult to discern in the remote sensing observations that are used to study the solar atmosphere. In this Letter, we exploit the high-resolution instruments Interface Region Imagin…
Two-dimensional Radiative Magnetohydrodynamic Simulations of Partial Ionization in the Chromosphere. II. Dynamics and Energetics of the Low Solar Atmosphere
Martínez-Sykora, Juan; De Pontieu, Bart; Nóbrega-Siverio, Daniel +3 more
We investigate the effects of interactions between ions and neutrals on the chromosphere and overlying corona using 2.5D radiative MHD simulations with the Bifrost code. We have extended the code capabilities implementing ion-neutral interaction effects using the generalized Ohm’s law, I.e., we include the Hall term and the ambipolar diffusion (Pe…
Observing the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA): High-Resolution Interferometric Imaging
de Gregorio-Monsalvo, I.; Kim, S.; De Pontieu, B. +25 more
Observations of the Sun at millimeter and submillimeter wavelengths offer a unique probe into the structure, dynamics, and heating of the chromosphere; the structure of sunspots; the formation and eruption of prominences and filaments; and energetic phenomena such as jets and flares. High-resolution observations of the Sun at millimeter and submil…
Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)
Krucker, Säm; Meyer-Vernet, Nicole; Del Zanna, Giulio +12 more
We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of indivi…
Solar Active Region Coronal Jets. II. Triggering and Evolution of Violent Jets
Panesar, Navdeep K.; Moore, Ronald L.; Sterling, Alphonse C. +2 more
We study a series of X-ray-bright, rapidly evolving active region coronal jets outside the leading sunspot of AR 12259, using Hinode/X-ray telescope, Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI), and Interface Region Imaging Spectrograph (IRIS) data. The detailed evolution of such r…
Probing the solar transition region: current status and future perspectives
Tian, Hui
The solar transition region (TR) is the temperature regime from roughly 0.02 MK to 0.8 MK in the solar atmosphere. It is the transition layer from the collisional and partially ionized chromosphere to the collisionless and fully ionized corona. The TR plays an important role in the mass and energy transport in both the quiet solar atmosphere and s…