J. Woch

Max Planck Institute for Solar System Research

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N. Krupp

Max Planck Institute for Solar System Research

102

A. Lagg

Max Planck Institute for Solar System Research

R. Lundin

Swedish Institute of Space Physics

S. K. Solanki

Max Planck Institute for Solar System Research

E. Dubinin

Max Planck Institute for Solar System Research

S. Barabash

Swedish Institute of Space Physics

M. Fräenz

Max Planck Institute for Solar System Research

A. J. Coates

University College London

M. Yamauchi

Swedish Institute of Space Physics

P. Wurz

University of Bern

Cooperative Institutions

Max Planck Institute for Solar System Research

211

Max Planck Society

147

Centre National de la Recherche Scientifique

131

Southwest Research Institute

102

University College London

Goddard Space Flight Center

National Institute for Astrophysics

Johns Hopkins University Applied Physics Laboratory

Swedish Institute of Space Physics

Max Planck Institute for Astronomy

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Spectropolarimetric investigation of magnetohydrodynamic wave modes in the photosphere: First results from PHI on board Solar Orbiter

Astronomy and Astrophysics (2023)

D. Calchetti M. Stangalini S. Jafarzadeh G. Valori K. Albert

Context. In November 2021, Solar Orbiter started its nominal mission phase. The remote-sensing instruments on board the spacecraft acquired scientific data during three observing windows surrounding the perihelion of the first orbit of this phase. Aims. The aim of the analysis is the detection of magnetohydrodynamic (MHD) wave modes in an active region by exploiting the capabilities of spectropolarimetric measurements. Mthods. The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (SO/PHI) on board the Solar Orbiter acquired a high-cadence data set of an active region. This is studied in the paper. B- ω and phase-difference analyses are applied on line-of-sight velocity and circular polarization maps and other averaged quantities. Results. We find that several MHD modes at different frequencies are excited in all analysed structures. The leading sunspot shows a linear dependence of the phase lag on the angle between the magnetic field and the line of sight of the observer in its penumbra. The magnetic pore exhibits global resonances at several frequencies, which are also excited by different wave modes. Conclusions. The SO/PHI measurements clearly confirm the presence of magnetic and velocity oscillations that are compatible with one or more MHD wave modes in pores and a sunspot. Improvements in modelling are still necessary to interpret the relation between the fluctuations of different diagnostics.

Photosphere

Orbiter

Sunspot

10.1051/0004-6361/202245826

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Citations (3)

Coronal voids and their magnetic nature

arXiv (Cornell University) (2023)

J. D. Nölke S. K. Solanki J. Hirzberger Hardi Peter L. P. Chitta

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 coronal features is not well understood. We study the magnetic properties of the weakly emitting extended regions, which we name coronal voids. In particular, we aim to understand whether these voids result from a reduced heat input into the corona or if they are associated with mainly unipolar and possibly open magnetic fields, similar to coronal holes. We defined the coronal voids via an intensity threshold of 75% of the mean quiet-Sun (QS) EUV intensity observed by the high-resolution EUV channel (HRIEUV) of the Extreme Ultraviolet Imager on Solar Orbiter. The line-of-sight magnetograms of the same solar region recorded by the High Resolution Telescope of the Polarimetric and Helioseismic Imager allowed us to compare the photospheric magnetic field beneath the coronal voids with that in other parts of the QS. The coronal voids studied here range in size from a few granules to a few supergranules and on average exhibit a reduced intensity of 67% of the mean value of the entire field of view. The magnetic flux density in the photosphere below the voids is 76% (or more) lower than in the surrounding QS. Specifically, the coronal voids show much weaker or no network structures. The detected flux imbalances fall in the range of imbalances found in QS areas of the same size. Conclusions. We conclude that coronal voids form because of locally reduced heating of the corona due to reduced magnetic flux density in the photosphere. This makes them a distinct class of (dark) structure, different from coronal holes.

Coronal hole

Nanoflares

Extreme ultraviolet

Corona (planetary geology)

Helmet streamer

Coronal loop

Coronal radiative losses

Photosphere

Extreme Ultraviolet Lithography

10.48550/arxiv.2309.09789

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Citations (0)

The velocity structure of moving magnetic feature pairs around sunspots: support for the U-loop model

Astronomy and Astrophysics (2007)

J. Zhang S. K. Solanki J. Woch Jing Wang

Context.Moving magnetic feature (MMF) pairs are among the most significant fine-scale structures around sunspots. Several models have been proposed to interpret the origin and evolution of MMF pairs. These models provide important clues to understanding MMF pairs.

Sunspot

Feature (linguistics)

10.1051/0004-6361:20077900

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Citations (15)

ASPERA-3: Analyser of space plasmas and energetic ions for mars express

S. Barabash R. Lundin H. Andersson J. Gimholt M. Holmström

S. Barabash, R. Lundin, H. Andersson, J. Gimholt, M. Holmstrom, O. Norberg, M. Yamauchi, K. Asamura, A.J. Coates, D.R. Linder, D.O. Kataria, C.C. Curtis, K.C. Hsieh, B.R. Sandel, A. Fedorov, A. Grigoriev, E. Budnik, M. Grande, M. Carter, D.H. Reading, H. Koskinen, E. Kallio, P. Riihela, T. Sales, J. Kozyra, N. Krupp, S. Livi, J. Woch, J. Luhmann, S. McKenna-Lawlor, S. Orsini, R. Cerulli-Irelli, M. Maggi, A. Morbidini, A. Mura, A. Milillo, E. Roelof, D. Williams, J.-A. Sauvaud, J.-J. Thocaven, T. Moreau, D. Winningham, R. Frahm, J. Scherrer, J. Sharber, P. Wurz & P. Bochsler

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Citations (47)

Metis: the Solar Orbiter visible light and ultraviolet coronal imager

Astronomy and Astrophysics (2019)

E. Antonucci M. Romoli V. Andretta Silvano Fineschi P. Heinzel

Metis is the first solar coronagraph designed for a space mission capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona from 1.7 $R_\odot$ to about 9 $R_\odot$. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close vantage point (down to 0.28 AU), achieving out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, will allow longer-term studies of the coronal features. Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H I Lyman-{\alpha} line at 121.6 nm. The coronal images in both the UV Lyman-{\alpha} and polarised visible light are obtained at high spatial resolution with a spatial scale down to about 2000 km and 15000 km at perihelion, in the cases of the visible and UV light, respectively. A temporal resolution down to 1 second can be achieved when observing coronal fluctuations in visible light. The Metis measurements will allow for complete characterisation of the main physical parameters and dynamics of the electron and neutral hydrogen/proton plasma components of the corona in the region where the solar wind undergoes acceleration and where the onset and initial propagation of coronal mass ejections take place, thus significantly improving our understanding of the region connecting the Sun to the heliosphere.

Coronagraph

Orbiter

Corona (planetary geology)

Zodiacal light

Solar observatory

Coronal hole

Extreme ultraviolet

Solar radius

10.1051/0004-6361/201935338

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Citations (157)

Sausage, kink, and fluting MHD wave modes identified in solar magnetic pores by Solar Orbiter/PHI

arXiv (Cornell University) (2024)

S. Jafarzadeh Luiz A. C. A. Schiavo V. Fedun S. K. Solanki M. Stangalini

Solar pores are intense concentrations of magnetic flux that emerge through the Sun's photosphere. When compared to sunspots, they are much smaller in diameter and hence can be impacted and buffeted by neighbouring granular activity to generate significant magnetohydrodynamic (MHD) wave energy flux within their confines. However, observations of solar pores from ground-based telescope facilities may struggle to capture subtle motions synonymous with higher-order MHD wave signatures due to seeing effects produced in the Earth's atmosphere. Hence, we have exploited timely seeing-free and high-quality observations of four small magnetic pores from the Polarimetric and Helioseismic Imager (PHI) on board the Solar Orbiter spacecraft. Through acquisition of data under stable observing conditions, we have been able to measure the area fluctuations and horizontal displacements of the solar pores. Cross correlations between perturbations in intensity, area, line-of-sight velocity, and magnetic fields, coupled with the first-time application of novel Proper Orthogonal Decomposition (POD) techniques on the boundary oscillations, provide a comprehensive diagnosis of the embedded MHD waves as sausage and kink modes. Additionally, the previously elusive m = 2 fluting mode is identified in the most magnetically isolated of the four pores. An important consideration lies in how the identified wave modes contribute towards the transfer of energy into the upper solar atmosphere. We find that the four pores examined have approximately 56%, 72%, 52%, and 34% of their total wave energy associated with the identified sausage modes, and around 23%, 17%, 39%, and 49% to their kink modes, respectively, while the first pore also has around an 11% contribution linked to the fluting mode. This study marks the first-time identification of concurrent sausage, kink, and fluting MHD wave modes in solar magnetic pores.

Orbiter

10.1051/0004-6361/202449685

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Citations (0)

Comparative analysis of Venus and Mars magnetotails

Planetary and Space Science (2008)

A. Fedorov C. Ferrier J. A. Sauvaud S. Barabash Tielong Zhang

Magnetosheath

Current sheet

Plasma sheet

Jupiter (rocket family)

10.1016/j.pss.2007.12.012