Search Publications
Fan-shaped jets above the light bridge of a sunspot driven by reconnection
Rouppe van der Voort, Luc; Leenaarts, Jorrit; Robustini, Carolina +1 more
We report on a fan-shaped set of high-speed jets above a strongly magnetized light bridge (LB) of a sunspot observed in the Hα line. We study the origin, dynamics, and thermal properties of the jets using high-resolution imaging spectroscopy in Hα from the Swedish 1m Solar Telescope and data from the Solar Dynamics Observatory and Hinode. The Hα j…
First evidence of non-Gaussian solar flare EUV spectral line profiles and accelerated non-thermal ion motion
Fletcher, Lyndsay; Jeffrey, Natasha L. S.; Labrosse, Nicolas
Context. The properties of solar flare plasma can be determined from the observation of optically thin lines. The emitting ion distribution determines the shape of the spectral line profile, with an isothermal Maxwellian ion distribution producing a Gaussian profile. Non-Gaussian line profiles may indicate more complex ion distributions.
Aims…
Internetwork magnetic field as revealed by two-dimensional inversions
Danilovic, S.; van Noort, M.; Rempel, M.
Context. Properties of magnetic field in the internetwork regions are still fairly unknown because of rather weak spectropolarimetric signals.
Aims: We address the matter by using the two-dimensional (2D) inversion code, which is able to retrieve the information on smallest spatial scales up to the diffraction limit, while being less suscepti…
Probing deep photospheric layers of the quiet Sun with high magnetic sensitivity
Franz, M.; Schmidt, W.; Solanki, S. K. +31 more
Context. Investigations of the magnetism of the quiet Sun are hindered by extremely weak polarization signals in Fraunhofer spectral lines. Photon noise, straylight, and the systematically different sensitivity of the Zeeman effect to longitudinal and transversal magnetic fields result in controversial results in terms of the strength and angular …
The spectroscopic imprint of the pre-eruptive configuration resulting into two major coronal mass ejections
Gontikakis, C.; Patsourakos, S.; Tsinganos, K. +1 more
Aims: We present a spectroscopic analysis of the pre-eruptive configuration of active region NOAA 11429, prior to two very fast coronal mass ejections (CMEs) on March 7, 2012 that are associated with this active region. We study the thermal components and the dynamics associated with the ejected flux ropes.
Methods: Using differential em…
Relation between trees of fragmenting granules and supergranulation evolution
Roudier, Th.; Malherbe, J. M.; Rieutord, M. +1 more
Context. The determination of the underlying mechanisms of the magnetic elements diffusion over the solar surface is still a challenge. Understanding the formation and evolution of the solar network (NE) is a challenge, because it provides a magnetic flux over the solar surface comparable to the flux of active regions at solar maximum.
Aims: …
Magnetic fields of opposite polarity in sunspot penumbrae
Franz, M.; Schmidt, W.; Solanki, S. K. +25 more
Context. A significant part of the penumbral magnetic field returns below the surface in the very deep photosphere. For lines in the visible, a large portion of this return field can only be detected indirectly by studying its imprints on strongly asymmetric and three-lobed Stokes V profiles. Infrared lines probe a narrow layer in the very deep ph…
Abnormal oscillation modes in a waning light bridge
Walsh, Robert W.; Yuan, Ding
Context. A sunspot acts as a waveguide in response to the dynamics of the solar interior; the trapped waves and oscillations could reveal its thermal and magnetic structures.
Aims: We study the oscillations in a sunspot intruded by a light bridge, and the details of these oscillations could reveal the fine structure of the magnetic topology. …
Observed and simulated power spectra of kinetic and magnetic energy retrieved with 2D inversions
Danilovic, S.; van Noort, M.; Rempel, M. +1 more
Context. Information on the origin of internetwork magnetic field is hidden at the smallest spatial scales.
Aims: We try to retrieve the power spectra with certainty to the highest spatial frequencies allowed by current instrumentation.
Methods: To accomplish this, we use a 2D inversion code that is able to recover information up to the …
Scaling laws of coronal loops compared to a 3D MHD model of an active region
Peter, H.; Bingert, S.; Bourdin, Ph. -A.
Context. The structure and heating of coronal loops have been investigated for decades. Established scaling laws relate fundamental quantities like the loop apex temperature, pressure, length, and coronal heating.
Aims: We test these scaling laws against a large-scale 3D magneto-hydrodynamics (MHD) model of the solar corona, which became feas…