52 citations · 212 across the 27 of their papers we have counts for
25 papers · 1 filter
Multi-Height Spectropolarimetric Signatures of Magnetoacoustic Waves in Solar Plage
Taylor Sitterson, João M. da Silva Santos, Joshua Bentley +5
We analyze high-cadence spectropolarimetric observations of solar plage obtained with the Visible Spectro-Polarimeter (ViSP) on the Daniel K. Inouye Solar Telescope (DKIST) to inve…
Multi-wavelength synthesis of a flux rope-trapped mini-prominence eruption and post-flare coronal rain
Samrat Sen, Alexander G. M. Pietrow, Veronika Jercic +1
Small-scale eruptive phenomena in the solar corona including miniature flux ropes and associated cool plasma condensations are not fully understood despite increasing high-resoluti…
A matter of class and flare Flare productivity in solar active regions and power-law constraints on the flare frequency distribution
A. G. M. Pietrow
Solar active regions are the source of virtually all significant space weather events, therefore the relationship between their observable properties and flare production is import…
The Fe I 4377 Å Line as a Solar Faculae Indicator: Insights from Spectral Ratio Analysis
Katlyn L. Hobbs, Christopher A. Watson, Jean C. Costes +21
Faculae are a dominant source of stellar activity noise in radial velocity measurements, yet their low contrast and broad surface distribution make them difficult to track in disc-…
From simulations to observations of cool plasma: What we can learn from synthetic spectra
V. Jerčić, T. A. Kucera, A. G. M. Pietrow +2
Cool plasma of coronal rain or prominences and filaments is ubiquitous in the solar corona. We explored the synthetic spectra of MgII h&k lines in detail and analyse how well a non…
Center-to-limb variations of solar active regions: Observations of spots, faculae, and network in the 6173 Å continuum
A. G. M. Pietrow, S. Sumra, D. J. M. Petit dit de la Roche +3
Accurate modeling of stellar active regions (ARs) remains a major bottleneck for radial-velocity and transmission-spectroscopy studies aimed at finding Earth-like planets. While mu…
Fine-scale downflows above flare ribbons captured by Solar Orbiter/EUI
Zheng Sun, Alexander G. M. Pietrow, Malcolm K. Druett +8
In solar flares, flare ribbons map chromospheric footpoints where flare energy deposition occurs. These locations are associated with field aligned energy transport from the corona…
HelioSpectrotron 5000: An interactive multi-resolution solar spectral atlas
A. G. M. Pietrow
HelioSpectrotron 5000 (HS5000) is an interactive, multi-resolution solar spectral atlas designed to facilitate direct comparison between high-resolution reference spectra and obser…
The calm before the storm: High spatial resolution mosaic of active region NOAA 14274 at the onset of an X1.2 flare
Carsten Denker, Robert Kamlah, Meetu Verma +1
Active region NOAA 14274 produced some of the strongest flares of Solar Cycle 25, including the X1.2 and X5.1 flares on 10 and 11 November 2025, respectively. We present the first…
High-spectral Resolution, Multi-wavelength Center-to-limb Observations of the Sun
Meetu Verma, Carsten Denker, Alexander G. M. Pietrow +2
The center-to-limb variations (CLVs) of photospheric and chromospheric spectral lines were obtained in 2025 July and August using drift scans from the echelle spectrograph of the 0…
On the center-to-limb variations of the He I 10830 Å triplet
A. G. M. Pietrow, C. Kuckein, M. Verma +4
We present high-resolution spectroscopic observations of the quiet-Sun center-to-limb variations (CLV) of the He I triplet at 10830 Å and the nearby Si I 10827 Å line, observed wit…
Automatic detection of Ellerman bombs in the H line
A. Faryad, A. G. M. Pietrow, M. Verma +1
Ellerman bombs (EBs) are small and short-lived magnetic reconnection events in the lower solar atmosphere, most commonly reported in the line wings of the H line. These events a…
Differential rotation of solar α sunspots and implications for stellar light curves
Emily Joe Lößnitz, Alexander G. M. Pietrow, Hritam Chakraborty +5
Differential rotation is a key driver of magnetic activity and dynamo processes in the Sun and other stars, especially as the rate differs across the solar layers, but also in acti…
Synthesizing Sun-as-a-star flare spectra from high-resolution solar observations
M. De Wilde, A. G. M. Pietrow, M. K. Druett +22
Spatially resolved observations of the Sun and the astronomical sample size of stellar bodies are the respective key strengths of solar and stellar observations. However, the large…
Multi-wavelength observations of substructures in solar flare ribbons
Vishal Singh, Eamon Scullion, Gert J. J. Botha +6
Solar flare ribbons are extensive brightenings in the chromosphere during flares, often showing fine scale structuring that reflects the underlying energy release. Using high caden…
Solar active region evolution and imminent flaring activity through a color-coded visualization of photospheric vector magnetograms
I. Kontogiannis, A. G. M. Pietrow, M. K. Druett +3
The emergence of magnetic flux, its transition to complex configurations, and the pre-eruptive state of active regions are probed using photospheric magnetograms. We aim to pinpoin…
Spectral variations within solar flare ribbons
A. G. M. Pietrow, M. K. Druett, V. Singh
Solar flare ribbons are intense brightenings of principally chromospheric material that are responsible for a large fraction of the chromospheric emission in solar and stellar flar…
3D non-LTE modeling of the stellar center-to-limb variation for transmission spectroscopy studies
G. Canocchi, K. Lind, C. Lagae +5
Context. Transmission spectroscopy is one of the most powerful techniques to characterize transiting exoplanets since it allows to measure the abundance of the atomic and molecular…
Center-to-limb variation of spectral lines and their effect on full-disk observations
Alexander G. M. Pietrow, Adur Pastor Yabar
An accurate description of the center-to-limb variation (CLV) of stellar spectra is becoming an increasingly critical factor in both stellar and exoplanet characterization. In part…
Spectral Background-Subtracted Activity Maps
Carsten Denker, Meetu Verma, Alexander G. M. Pietrow +2
High-resolution solar spectroscopy provides a wealth of information from photospheric and chromospheric spectral lines. However, the volume of data easily exceeds hundreds of milli…
Stellar surface information from the Ca II H&K lines I. Intensity profiles of the solar activity components
M. Cretignier, A. G. M. Pietrow, S. Aigrain
The detection of Earth-like planets with the radial-velocity method is currently limited by the presence of stellar activity signatures. On rotational timescales, spots and plages…
A comparative study of two X2.2 and X9.3 solar flares observed with HARPS-N: Reconciling Sun-as-a-star spectroscopy and high-spatial resolution solar observations in the context of the solar-stellar connection
A. G. M. Pietrow, M. Cretignier, M. K. Druett +14
Stellar flares cannot be spatially resolved, which complicates ascertaining the physical processes behind particular spectral signatures. Due to their proximity to Earth, solar fla…
Solar oxygen abundance using SST/CRISP center-to-limb observations of the O I 7772 Å line
A. G. M. Pietrow, R. Hoppe, M. Bergemann +1
Solar oxygen abundance measurements based on the O I near-infrared triplet have been a much-debated subject for several decades since non-local thermodynamic equilibrium (NLTE) cal…
Center-to-limb variation of spectral lines and continua observed with SST/CRISP and SST/CHROMIS
A. G. M. Pietrow, D. Kiselman, O. Andriienko +3
Observations of center-to-limb variations (CLV) of spectral lines and continua provide a good test for the accuracy of models of solar and stellar atmospheric structure and spectra…