Publications (79)
Plasmoid-mediated reconnection in solar UV bursts
H. Peter, Y. -M. Huang, L. P. Chitta +1
UV bursts are transients in the solar atmosphere with an increased impulsive emission in the extreme UV lasting for one to several tens of minutes. They often show spectral profile…
Spatial distributions of EUV brightenings in the quiet-Sun
C. J. Nelson, L. A. Hayes, D. Müller +16
The identification of large numbers of localised transient EUV brightenings, with small spatial scales, in the quiet-Sun corona has been one of the key early results from Solar Orb…
Limitations of force-free magnetic field extrapolations: revisiting basic assumptions
H. Peter, J. Warnecke, L. P. Chitta +1
Force-free extrapolations are widely used to study the magnetic field in the solar corona based on surface measurements. The extrapolations assume that the ratio of internal energy…
Observing the solar corona from a formation-flying mission. First results of Proba-3/ASPIICS
A. N. Zhukov, L. Dolla, M. Mierla +32
We report the first results from observations of the solar corona by the ASPIICS coronagraph aboard the Proba-3 mission. ASPIICS (Association of Spacecraft for Polarimetric and Ima…
EUV fine structure and variability associated with coronal rain revealed by Solar Orbiter/EUI HRIEUV and SPICE
P. Antolin, A. Dolliou, F. Auchère +34
Coronal rain is the most dramatic cooling phenomenon of the solar corona and an essential diagnostic tool for the coronal heating properties. A puzzling feature of the solar corona…
Observations and modeling of the onset of fast reconnection in the solar transition region
L. -J. Guo, B. De Pontieu, Y. -M. Huang +2
Magnetic reconnection is a fundamental plasma process that plays a critical role not only in energy release in the solar atmosphere, but also in fusion, astrophysical, and other sp…
Solar magnetism eXplorer (SolmeX)
H. Peter, L. Abbo, V. Andretta +36
The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper s…
Magnetic Jam in the Corona of the Sun
F. Chen, H. Peter, S. Bingert +1
The outer solar atmosphere, the corona, contains plasma at temperatures of more than a million K, more than 100 times hotter that solar surface. How this gas is heated is a fundame…
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…
Compact solar UV burst triggered in a magnetic field with a fan-spine topology
L. P. Chitta, H. Peter, P. R. Young +1
Solar UV bursts are small-scale features that exhibit intermittent brightenings that are thought to be due to magnetic reconnection. They are observed abundantly in the chromospher…
A solar coronal loop in a box: Energy generation and heating
C. Breu, H. Peter, R. Cameron +4
Coronal loops are the basic building block of the upper solar atmosphere. Comprehending how these are energized, structured, and evolve is key to understanding stellar coronae. Her…
Observationally driven 3D MHD model of the solar corona above an active region
Ph. -A. Bourdin, S. Bingert, H. Peter
Aims. The goal is to employ a 3D magnetohydrodynamics (MHD) model including spectral synthesis to model the corona in an observed solar active region. This will allow us to judge t…
Coronal heating through braiding of magnetic field lines
H. Peter, B. V. Gudiksen, A. Nordlund
Cool stars like our Sun are surrounded by a million degree hot outer atmosphere, the corona. Since more than 60 years the physical nature of the processes heating the corona to tem…
The Solar Orbiter Science Activity Plan: translating solar and heliospheric physics questions into action
I. Zouganelis, A. De Groof, A. P. Walsh +182
Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand…
The Chromospheric Telescope
C. Bethge, H. Peter, T. J. Kentischer +3
We introduce the Chromospheric Telescope (ChroTel) at the Observatorio del Teide in Izana on Tenerife as a new multi-wavelength imaging telescope for full-disk synoptic observation…
High-resolution observations of small-scale activity in coronal hole plumes
Ziwen Huang, L. P. Chitta, L. Teriaca +5
Plumes have been proposed to channel MHD waves and the solar wind into the heliosphere. High-speed propagating disturbances (PDs), though well detected in plumes, cannot yet be cle…
First observations from the SPICE EUV spectrometer on Solar Orbiter
A. Fludra, M. Caldwell, A. Giunta +28
We present first science observations taken during the commissioning activities of the Spectral Imaging of the Coronal Environment (SPICE) instrument on the ESA/NASA Solar Orbiter…
Catastrophic cooling and cessation of heating in the solar corona
H. Peter, S. Bingert, S. Kamio
Condensations in the more than 10^6 K hot corona of the Sun are commonly observed in the extreme ultraviolet (EUV). While their contribution to the total solar EUV radiation is sti…
A closer look at a coronal loop rooted in a sunspot umbra
L. P. Chitta, H. Peter, P. R. Young
Extreme UV (EUV) and X-ray loops in the solar corona connect regions of enhanced magnetic activity, but they are not usually rooted in the dark umbrae of sunspots because the stron…
Siphon flow in a cool magnetic loop
C. Bethge, C. Beck, H. Peter +1
We investigate the properties of a structure in the solar chromosphere in an active region to find out whether the feature is consistent with a siphon flow in a magnetic loop fille…
Non-thermal line broadening due to braiding-induced turbulence in solar coronal loops
D. I. Pontin, H. Peter, L. P. Chitta
Aims: Emission line profiles from solar coronal loops exhibit properties that are unexplained by current models. We investigate the non-thermal broadening associated with plasma he…
Structure of solar coronal loops: from miniature to large-scale
H. Peter, S. Bingert, J. A. Klimchuk +6
We will use new data from the High-resolution Coronal Imager (Hi-C) with unprecedented spatial resolution of the solar corona to investigate the structure of coronal loops down to…
Parametrization of coronal heating: spatial distribution and observable consequences
T. van Wettum, S. Bingert, H. Peter
We investigate the difference in the spatial distribution of the energy input for parametrizations of different mechanisms to heat the corona of the Sun and possible impacts on the…
Solar coronal heating from small-scale magnetic braids
L. P. Chitta, H. Peter, S. Parenti +19
Relaxation of braided coronal magnetic fields through reconnection is thought to be a source of energy to heat plasma in active region coronal loops. However, observations of activ…
The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter
F. Kahil, J. Hirzberger, S. K. Solanki +56
The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SO) spacecraft observed small extreme ultraviolet (EUV) bursts, termed campfires, that have been proposed to be bri…
Stellar coronal X-ray emission and surface magnetic flux
J. Zhuleku, J. Warnecke, H. Peter
Observations show that the coronal X-ray emission of the Sun and other stars depends on the surface magnetic field. Using power-law scaling relations between different physical par…
Continuous upflows and sporadic downflows observed in active regions
S. Kamio, H. Peter, W. Curdt +1
We present a study of the temporal evolution of coronal loops in active regions and its implications for the dynamics in coronal loops. We analyzed images of the Atmospheric Imagin…
Forward modeling of stellar coronae: from a 3D MHD model to synthetic EUV spectra
H. Peter, B. V. Gudiksen, A. Nordlund
A forward model is described in which we synthesize spectra from an ab-initio 3D MHD simulation of an outer stellar atmosphere, where the coronal heating is based on braiding of ma…
Hard X-rays from the deep solar atmosphere. An unusual UV burst with flare properties
L. P. Chitta, I. G. Hannah, L. Fletcher +4
Explosive transient events occur throughout the solar atmosphere. The differing manifestations range from coronal mass ejections to Ellerman bombs. The former may have negligible s…
Ultra-high-resolution Observations of Persistent Null-point Reconnection in the Solar Corona
X. Cheng, E. R. Priest, H. T. Li +21
Magnetic reconnection is a key mechanism involved in solar eruptions and is also a prime possibility to heat the low corona to millions of degrees. Here, we present ultra-high-reso…
The Solar Orbiter SPICE instrument -- An extreme UV imaging spectrometer
The SPICE Consortium, :, M. Anderson +88
The Spectral Imaging of the Coronal Environment (SPICE) instrument is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths. In this paper, we p…
Coronal voids and their magnetic nature
J. D. Nölke, S. K. Solanki, J. Hirzberger +68
Extreme ultraviolet (EUV) observations of the quiet solar atmosphere reveal extended regions of weak emission compared to the ambient quiescent corona. The magnetic nature of these…
Hot prominence spicules launched from turbulent cool solar prominences
L. P. Chitta, H. Peter, L. Li
A solar filament is a dense cool condensation that is supported and thermally insulated by magnetic fields in the rarefied hot corona. Its evolution and stability, leading to eithe…
Ejection of cool plasma into the hot corona
P. Zacharias, H. Peter, S. Bingert
We investigate the processes that lead to the formation, ejection and fall of a confined plasma ejection that was observed in a numerical experiment of the solar corona. By quantif…
The Solar Orbiter mission -- Science overview
D. Müller, O. C. St. Cyr, I. Zouganelis +32
Solar Orbiter, the first mission of ESA's Cosmic Vision 2015-2025 programme and a mission of international collaboration between ESA and NASA, will explore the Sun and heliosphere…
Modeling the (upper) solar atmosphere including the magnetic field
H. Peter
The atmosphere of the Sun is highly structured and dynamic in nature. From the photosphere and chromosphere into the transition region and the corona plasma- changes from above…
Crossover from Jamming to Clogging Behaviors in Heterogeneous Environments
H. Peter, A. Libal, C. Reichhardt +1
Jamming describes a transition from a flowing or liquid state to a solid or rigid state in a loose assembly of particles such as grains or bubbles. In contrast, clogging describes…
Stellar X-rays and magnetic activity in 3D MHD coronal models
J. Zhuleku, J. Warnecke, H. Peter
Observations suggest a power-law relation between the coronal emission in X-rays, , and the total (unsigned) magnetic flux at the stellar surface, . The physics bas…
Diffraction in the ASPIICS coronagraph: observations and modeling
S. Shestov, A. N. Zhukov, R. Rougeot +11
Context: ASPIICS is a giant-baseline visible light solar coronagraph, which relies on the millimetric positioning performance of the precision formation flying Proba-3 mission of t…
First light observations of the solar wind in the outer corona with the Metis coronagraph
M. Romoli, E. Antonucci, V. Andretta +65
The investigation of the wind in the solar corona initiated with the observations of the resonantly scattered UV emission of the coronal plasma obtained with UVCS-SOHO, designed to…
Long-lived coronal loops in solar active regions
N. Vasantharaju, H. Peter, L. P. Chitta +1
Coronal loops are plasma structures in the solar atmosphere with temperatures reaching millions of Kelvin, shaped and sustained by the magnetic field. However, their morphology and…
Non-thermal broadening of coronal lines in a 3D MHD loop model
C. A. Breu, H. Peter, S. K. Solanki +2
Observed spectral profiles of emission lines from the corona are found to have widths exceeding the thermal line width. To investigate the physical mechanism, we run a 3D MHD model…
Impulsive coronal heating during the interaction of surface magnetic fields in the lower solar atmosphere
L. P. Chitta, H. Peter, E. R. Priest +1
Coronal plasma in the cores of solar active regions is impulsively heated to more than 5 MK. The nature and location of the magnetic energy source responsible for such impulsive he…
Beyond small-scale transients: a closer look at the diffuse quiet solar corona
J. Gorman, L. P. Chitta, H. Peter +9
Within the quiet Sun corona imaged at 1 MK, much of the field of view consists of diffuse emission that appears to lack the spatial structuring that is so evident in coronal loops…
Capturing transient plasma flows and jets in the solar corona
L. P. Chitta, S. K. Solanki, H. Peter +8
Intensity bursts in ultraviolet (UV) to X-ray wavelengths and plasma jets are typical signatures of magnetic reconnection and the associated impulsive heating of the solar atmosphe…
Imaging and spectroscopic observations of extreme-ultraviolet brightenings using EUI and SPICE on board Solar Orbiter
Ziwen Huang, L. Teriaca, R. Aznar Cuadrado +16
The smallest extreme-ultraviolet (EUV) brightening events that were detected so far, called campfires, have recently been uncovered by the High Resolution EUV telescope (HRIEUV), w…
SPICE Connection Mosaics to link the Sun's surface and the heliosphere
T. Varesano, D. M. Hassler, N. Zambrana Prado +28
We present an analysis of the first connection mosaic made by the SPICE instrument on board of the ESA / NASA Solar Orbiter mission on March 2nd, 2022. The data will be used to map…
Thermal Diagnostics with the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory: A Validated Method for Differential Emission Measure Inversions
Mark C. M. Cheung, P. Boerner, C. J. Schrijver +4
We present a new method for performing differential emission measure (DEM) inversions on narrow-band EUV images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynami…
A Si IV/O IV electron density diagnostic for the analysis of IRIS solar spectra
P. R. Young, F. P. Keenan, R. O. Milligan +1
Solar spectra of ultraviolet bursts and flare ribbons from the Interface Region Imaging Spectrograph (IRIS) have suggested high electron densities of cm at transi…
Hot Explosions in the Cool Atmosphere of the Sun
H. Peter, H. Tian, W. Curdt +20
The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that consti…
Stereoscopic observations reveal coherent morphology and evolution of solar coronal loops
B. Ram, L. P. Chitta, S. Mandal +2
Coronal loops generally trace magnetic lines of force in the upper solar atmosphere. Understanding the loop morphology and its temporal evolution has implications for coronal heati…
Swirls in the Solar Corona
C. Breu, H. Peter, R. Cameron +1
Vortex flows have been found in the photosphere, chromosphere and low corona in observations and simulations. It has been suggested that vortices play an important role for channel…
Prevalence of Small-scale Jets from the Networks of the Solar Transition Region and Chromosphere
H. Tian, E. E. DeLuca, S. R. Cranmer +24
As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations…
Solar Activity: Triennial Report of IAU Commission 10 (2006-2009)
J. A. Klimchuk, L. van Driel-Gesztelyi, C. J. Schrijver +9
Commission 10 deals with solar activity in all of its forms, ranging from the smallest nanoflares to the largest coronal mass ejections. This report reviews scientific progress ove…
Fleeting Small-scale Surface Magnetic Fields Build the Quiet-Sun Corona
L. P. Chitta, S. K. Solanki, J. C. del Toro Iniesta +19
Arch-like loop structures filled with million Kelvin hot plasma form the building blocks of the quiet-Sun corona. Both high-resolution observations and magnetoconvection simulation…
Magnetic structure of coronal dark halos
J. D. Nölke, S. K. Solanki, J. Hirzberger +5
At low coronal temperatures around or below 1 MK distinct areas in the surroundings of active regions (AR) show emission at a level significantly below the emission coming from the…
Evidence of external reconnection between an erupting mini-filament and ambient loops observed by Solar Orbiter/EUI
Z. F. Li, X. Cheng, M. D. Ding +16
Mini-filament eruptions are one of the most common small-scale transients in the solar atmosphere. However, their eruption mechanisms are still not understood thoroughly. Here, wit…
Energetics of magnetic transients in a solar active region plage
L. P. Chitta, A. R. C. Sukarmadji, L. Rouppe van der Voort +1
Densely packed coronal loops are rooted in plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plages are patches of mostly uni…
Observations of Subarcsecond Bright Dots in the Transition Region above Sunspots with the Interface Region Imaging Spectrograph
H. Tian, L. Kleint, H. Peter +5
Observations with the Interface Region Imaging Spectrograph (IRIS) have revealed numerous sub-arcsecond bright dots in the transition region above sunspots. These bright dots are s…
Constant cross section of loops in the solar corona
H. Peter, S. Bingert
The corona of the Sun is dominated by emission from loop-like structures. When observed in X-ray or extreme ultraviolet emission, these million K hot coronal loops show a more or l…
Magnetic field diagnostics and spatio-temporal variability of the solar transition region
H. Peter
Magnetic field diagnostics of the transition region from the chromosphere to the corona faces us with the problem that one has to apply extreme UV spectro-polarimetry. While for co…
A magnetic avalanche as the central engine powering a solar flare
L. P. Chitta, D. I. Pontin, E. R. Priest +17
Solar flares are the most powerful, magnetically driven, explosions in the heliosphere. The nature of magnetic energy release in the solar corona that heats the plasma and accelera…
Dynamics of solar coronal loops II. Catastrophic cooling and high-speed downflows
D. A. N. Mueller, H. Peter, V. H. Hansteen
This work addresses the problem of plasma condensation and ``catastrophic cooling'' in solar coronal loops. We have carried out numerical calculations of coronal loops and find sev…
A multiple spacecraft detection of the 2 April 2022 M-class flare and filament eruption during the first close Solar Orbiter perihelion
M. Janvier, S. Mzerguat, P. R. Young +56
The Solar Orbiter mission completed its first remote-sensing observation windows in the spring of 2022. On 2/4/2022, an M-class flare followed by a filament eruption was seen both…
Deciphering The Slow-rise Precursor of a Major Coronal Mass Ejection
X. Cheng, C. Xing, G. Aulanier +3
Coronal mass ejections (CMEs) are explosive plasma phenomena prevalently occurring on the Sun and probably on other magnetically active stars. However, how their pre-eruptive confi…
Spectroscopic observation of a transition region network jet
J. Gorman, L. P. Chitta, H. Peter
Ubiquitous transition region (TR) network jets are considered to be substantial sources of mass and energy to the corona and solar wind. We conduct a case study of a network jet to…
First Perihelion of EUI on the Solar Orbiter mission
D. Berghmans, P. Antolin, F. Auchère +34
Context. The Extreme Ultraviolet Imager (EUI), onboard Solar Orbiter consists of three telescopes: the two High Resolution Imagers in EUV (HRIEUV) and in Lyman-α (HRILya), and the…
Data-constrained 3D MHD Simulation of a Spiral Jet Caused by an Unstable Flux Rope Embedded in Fan-spine Configuration
Z. F. Li, J. H. Guo, X. Cheng +5
Spiral jets are impulsive plasma ejections that typically show an apparent rotation motion. Their generation, however, is still nont understood thoroughly. Based on a high-resoluti…
Picoflare jets power the solar wind emerging from a coronal hole on the Sun
L. P. Chitta, A. N. Zhukov, D. Berghmans +17
Coronal holes are areas on the Sun with open magnetic field lines. They are a source region of the solar wind, but how the wind emerges from coronal holes is not known. We observed…
Extreme-ultraviolet bursts and nanoflares in the quiet-Sun transition region and corona
L. P. Chitta, H. Peter, P. R. Young
The quiet solar corona consists of myriads of loop-like features, with magnetic fields originating from network and internetwork regions on the solar surface. The continuous intera…
Observational Evidence of S-Web Source of the Slow Solar Wind
D. Baker, P. Demoulin, S. L. Yardley +25
From 2022 March 18-21, active region (AR) 12967 was tracked simultaneously by Solar Orbiter (SO) at 0.35 au and Hinode/EIS at Earth. During this period, strong blue-shifted plasma…
Coronal hole picoflare jets are progenitors of both fast and Alfvénic slow solar wind
L. P. Chitta, Z. Huang, R. D'Amicis +19
Solar wind, classified by its bulk speed and the Alfvénic nature of its fluctuations, generates the heliosphere. The elusive physical processes responsible for the generation of t…
The ASPIICS solar coronagraph aboard the Proba-3 formation flying mission. Scientific objectives and instrument design
A. N. Zhukov, C. Thizy, D. Galano +67
We describe the scientific objectives and instrument design of the ASPIICS coronagraph launched aboard the Proba-3 mission of the European Space Agency (ESA) on 5 December 2024. Pr…
Asymmetries of solar coronal extreme ultraviolet emission lines
H. Peter
The profiles of emission lines formed in the corona contain information on the dynamics and the heating of the hot plasma. Only recently has data with sufficiently high spectral re…
EUV brightenings in the quiet-Sun: Signatures in spectral and imaging data from the Interface Region Imaging Spectrograph
C. J. Nelson, F. Auchère, R. Aznar Cuadrado +13
Localised transient EUV brightenings, sometimes named `campfires', occur throughout the quiet-Sun. However, there are still many open questions about such events, in particular reg…
Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields
L. P. Chitta, H. Peter, S. K. Solanki +12
How and where are coronal loops rooted in the solar lower atmosphere? The details of the magnetic environment and its evolution at the footpoints of coronal loops are crucial to un…
Nature of the energy source powering solar coronal loops driven by nanoflares
L. P. Chitta, H. Peter, S. K. Solanki
Magnetic energy is required to heat the corona, the outer atmosphere of the Sun, to millions of degrees. We study the nature of the magnetic energy source that is probably responsi…
A model for the formation of the active region corona driven by magnetic flux emergence
F. Chen, H. Peter, S. Bingert +1
We present the first model that couples the formation of the corona of a solar active region to a model of the emergence of a sunspot pair. This allows us to study when, where, and…
Small-scale impulsive EUV emission enhancements along network loops
A. Dolliou, H. Peter, S. Mandal +4
Network loops are a common feature in the quiet Sun. The physical processes sustaining their energy budget is still under discussion. We rely on a multi-instrumental (Solar Orbiter…