86 citations · 725 across the 37 of their papers we have counts for
32 papers · 1 filter
Solar spicule population properties inferred from IRIS Mg II k off-limb spectra using likelihood-free Bayesian inference
Jiri Stepan, Stanislav Gunar, Akiko Tei +1
Solar spicules are ubiquitous and strongly overlap in off-limb observations, which complicates the interpretation of individual events. We aim to infer population-level properties…
Determining the magnetic field of active region plages using the whole CLASP2/2.1 spectral window
David Afonso Delgado, Tanausú del Pino Alemán, Javier Trujillo Bueno +16
The Chromospheric LAyer SpectroPolarimeter missions, CLASP2 and CLASP2.1, demonstrated that the near-UV spectral region between 279.30 and 280.68 nm is suitable for studying the ma…
The uncertainty of magnetic fields in 3D non-local thermodynamic equilibrium inversions
Jiri Stepan, Tanausu del Pino Aleman, Andres Vicente Arevalo
We describe our approach to solve the problem of ensuring the solenoidality of the magnetic field vector in three-dimensional (3D) inversions, as well as the estimation of the unce…
The He I 10830 A line: Radiative transfer and differential illumination effects
Andres Vicente Arevalo, Jiri Stepan, Tanausu del Pino Aleman +1
We study the formation of the Stokes profiles of the He I multiplet at 10830 A when relaxing two of the approximations that are often considered in the modeling of this multiplet,…
Quiet Sun Center to Limb Variation of the Linear Polarization Observed by CLASP2 Across the Mg II h & k Lines
L. A. Rachmeler, J. Trujillo Bueno, D. E. McKenzie +25
The CLASP2 (Chromospheric LAyer SpectroPolarimeter 2) sounding rocket mission was launched on 2019 April 11. CLASP2 measured the four Stokes parameters of the Mg II h & k spectral…
Novel framework for the three-dimensional NLTE inverse problem
Jiri Stepan, Tanausu del Pino Aleman, Javier Trujillo Bueno
The inversion of spectropolarimetric observations of the solar upper atmosphere is one of the most challenging goals in solar physics. If we account for all relevant ingredients of…
Mapping Solar Magnetic Fields from the Photosphere to the Base of the Corona
Ryohko Ishikawa, Javier Trujillo Bueno, Tanausu del Pino Aleman +25
Routine ultraviolet imaging of the Sun's upper atmosphere shows the spectacular manifestation of solar activity; yet we remain blind to its main driver, the magnetic field. Here we…
Evaluating the reliability of a simple method to map the magnetic field azimuth in the solar chromosphere
Jan Jurcak, Jiri Stepan, Javier Trujillo Bueno
The Zeeman effect is of limited utility for probing the magnetism of the quiet solar chromosphere. The Hanle effect in some spectral lines is sensitive to such magnetism, but the i…
Improved near optimal angular quadratures for polarised radiative transfer in 3D MHD models
Jaume Jaume Bestard, Jiří Štěpán, Javier Trujillo Bueno
Accurate angular quadratures are crucial for the numerical solution of three-dimensional (3D) radiative transfer problems, especially when the spectral line polarisation produced b…
Magnetic Imaging of the Outer Solar Atmosphere (MImOSA): Unlocking the driver of the dynamics in the upper solar atmosphere
H. Peter, E. Alsina Ballester, V. Andretta +20
The magnetic activity of the Sun directly impacts the Earth and human life. Likewise, other stars will have an impact on the habitability of planets orbiting these host stars. The…
On the Possibilities of Detecting Helium D Line Polarization with Metis
Petr Heinzel, Jiří Štěpán, Alessandro Bemporad +4
Space coronagraph Metis on board of the Solar Orbiter offers us new capabilities for studying eruptive prominences and coronal mass ejections (CME). Its two spectral channels, hydr…
Near optimal angular quadratures for polarised radiative transfer
Jiri Stepan, Jaume Jaume Bestard, Javier Trujillo Bueno
In three-dimensional (3D) radiative transfer (RT) problems, the tensor product quadratures are generally not optimal in terms of the number of discrete ray directions needed for a…
IRIS Mg II Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole
Akiko Tei, Stanislav Gunar, Petr Heinzel +4
We investigated the off-limb spicules observed in the Mg II h and k lines by IRIS in a solar polar coronal hole. We analyzed the large dataset of obtained spectra to extract quanti…
CLASP Constraints on the Magnetization and Geometrical Complexity of the Chromosphere-Corona Transition Region
J. Trujillo Bueno, J. Štěpán, L. Belluzzi +25
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a suborbital rocket experiment that on 3rd September 2015 measured the linear polarization produced by scattering proce…
Comparison of theoretical and observed Ca~{\sc ii}~8542 Stokes profiles in quiet regions at the centre of the solar disc
Jan Jurcak, Jiri Stepan, Javier Trujillo Bueno +1
Interpreting the Stokes profiles observed in quiet regions of the solar chromosphere is a challenging task. The Stokes Q and U profiles are dominated by the scattering polarisation…
A Statistical Inference Method for Interpreting the CLASP Observations
J. Stepan, J. Trujillo Bueno, L. Belluzzi +25
On 3rd September 2015, the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) successfully measured the linear polarization produced by scattering processes in the hydrogen Lyman…
A novel investigation of the small-scale magnetic activity of the quiet Sun via the Hanle effect in the Sr I 4607 Å line
T. del Pino Alemán, J. Trujillo Bueno, J. Štěpán +1
One of the key research problems in stellar physics is to decipher the small-scale magnetic activity of the quiet solar atmosphere. Recent magneto-convection simulations that accou…
Discovery of Scattering Polarization in the Hydrogen Lyman- Line of the Solar Disk Radiation
R. Kano, J. Trujillo Bueno, A. Winebarger +25
There is a thin transition region (TR) in the solar atmosphere where the temperature rises from 10,000 K in the chromosphere to millions of degrees in the corona. Little is known a…
The Hanle and Zeeman polarization signals of the solar Ca II 8542 Å line
Jiří Štěpán, Javier Trujillo Bueno
We highlight the main results of a three-dimensional (3D) multilevel radiative transfer investigation about the solar disk-center polarization of the Ca {\sc ii} 8542 Å line. First…
Three-dimensional radiative transfer simulations of the scattering polarization of the hydrogen Ly line in a MHD model of the chromosphere-corona transition region
Jiri Stepan, Javier Trujillo Bueno, Jorrit Leenaarts +1
Probing the magnetism of the upper solar chromosphere requires measuring and modeling the scattering polarization produced by anisotropic radiation pumping in UV spectral lines. He…
On the inversion of the scattering polarization and the Hanle effect signals in the hydrogen Lyman- line
R. Ishikawa, A. Asensio Ramos, L. Belluzzi +5
Magnetic field measurements in the upper chromosphere and above, where the gas-to-magnetic pressure ratio is lower than unity, are essential for understanding the thermal struc…
Scattering polarization in solar flares
Jiri Stepan, Petr Heinzel
There is an ongoing debate about the origin and even the very existence of a high degree of linear polarization of some chromospheric spectral lines observed in solar flares. The s…
PORTA: A three-dimensional multilevel radiative transfer code for modeling the intensity and polarization of spectral lines with massively parallel computers
Jiri Stepan, Javier Trujillo Bueno
The interpretation of the intensity and polarization of the spectral line radiation produced in the atmosphere of the Sun and of other stars requires solving a radiative transfer p…
The Hanle effect of Ly in an MHD model of the Solar Transition Region
Jiri Stepan, Javier Trujillo Bueno, Mats Carlsson +1
In order to understand the heating of the solar corona it is crucial to obtain empirical information on the magnetic field in its lower boundary (the transition region). To this en…