Schou, Jesper

[["dc.bibliographiccitation.artnumber","A79"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","586"],["dc.contributor.author","Schunker, H."],["dc.contributor.author","Schou, J."],["dc.contributor.author","Ball, Warrick H."],["dc.contributor.author","Nielsen, M. B."],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2017-09-07T11:48:42Z"],["dc.date.available","2017-09-07T11:48:42Z"],["dc.date.issued","2015"],["dc.description.abstract","Context. Radial differential rotation is an important parameter for stellar dynamo theory and for understanding angular momentum transport.Aims. We investigate the potential of using a large number of similar stars simultaneously to constrain their average radial differential rotation gradient: we call this “ensemble fitting”.Methods. We use a range of stellar models along the main sequence, each with a synthetic rotation profile. The rotation profiles are step functions with a step of ΔΩ = −0.35 μHz, which is located at the base of the convection zone. These models are used to compute the rotational splittings of the p modes and to model their uncertainties. We then fit an ensemble of stars to infer the average ΔΩ.Results. All the uncertainties on the inferred ΔΩ for individual stars are of the order 1 μHz. Using 15 stellar models in an ensemble fit, we show that the uncertainty on the average ΔΩ is reduced to less than the input ΔΩ, which allows us to constrain the sign of the radial differential rotation. We show that a solar-like ΔΩ ≈ 30 nHz can be constrained by an ensemble fit of thousands of main-sequence stars. Observing the number of stars required to successfully exploit the ensemble fitting method will be possible with future asteroseismology missions, such as PLATO. We demonstrate the potential of ensemble fitting by showing that any systematic differences in the average ΔΩ between F, G, and K-type stars larger than 100 nHz could be detected."],["dc.identifier.doi","10.1051/0004-6361/201527485"],["dc.identifier.gro","3147043"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/13440"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4775"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Asteroseismic inversions for radial differential rotation of Sun-like stars: ensemble fits"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A44"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","634"],["dc.contributor.author","Proxauf, B."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Löptien, Björn"],["dc.contributor.author","Schou, Jesper"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Bogart, R. S."],["dc.date.accessioned","2020-12-10T18:11:54Z"],["dc.date.available","2020-12-10T18:11:54Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1051/0004-6361/201937007"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74179"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Exploring the latitude and depth dependence of solar Rossby waves using ring-diagram analysis"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A9"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","587"],["dc.contributor.author","Löptien, Björn"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Duvall, Thomas L."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Schou, J."],["dc.date.accessioned","2017-09-07T11:49:58Z"],["dc.date.available","2017-09-07T11:49:58Z"],["dc.date.issued","2016"],["dc.description.abstract","Context. Several upcoming and proposed space missions, such as Solar Orbiter, will be limited in telemetry and thus require data compression.Aims. We test the impact of data compression on local correlation tracking (LCT) of time series of continuum intensity images. We evaluate the effect of several lossy compression methods (quantization, JPEG compression, and a reduced number of continuum images) on measurements of solar differential rotation with LCT.Methods. We applied the different compression methods to tracked and remapped continuum intensity maps obtained by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. We derived 2D vector velocities using the local correlation tracking code Fourier Local Correlation Tracking (FLCT) and determined the additional bias and noise introduced by compression to differential rotation.Results. We find that probing differential rotation with LCT is very robust to lossy data compression when using quantization. Our results are severely affected by systematic errors of the LCT method and the HMI instrument. The sensitivity of LCT to systematic errors is a concern for Solar Orbiter."],["dc.identifier.doi","10.1051/0004-6361/201526805"],["dc.identifier.gro","3147451"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/13430"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/5015"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/ 312844"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/ 312495"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Data compression for local correlation tracking of solar granulation"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A8"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","595"],["dc.contributor.author","Barekat, A."],["dc.contributor.author","Schou, J."],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2017-09-07T11:49:43Z"],["dc.date.available","2017-09-07T11:49:43Z"],["dc.date.issued","2016"],["dc.identifier.doi","10.1051/0004-6361/201628673"],["dc.identifier.gro","3147399"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14280"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4992"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.publisher","EDP Sciences"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Solar-cycle variation of the rotational shear near the solar surface"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A42"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","571"],["dc.contributor.author","Löptien, Björn"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Schou, J."],["dc.date.accessioned","2017-09-07T11:48:41Z"],["dc.date.available","2017-09-07T11:48:41Z"],["dc.date.issued","2014"],["dc.description.abstract","Context. Several upcoming helioseismology space missions are very limited in telemetry and will have to perform extensive data compression. This requires the development of new methods of data compression.Aims. We give an overview of the influence of lossy data compression on local helioseismology. We investigate the effects of several lossy compression methods (quantization, JPEG compression, and smoothing and subsampling) on power spectra and time-distance measurements of supergranulation flows at disk center.Methods. We applied different compression methods to tracked and remapped Dopplergrams obtained by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory. We determined the signal-to-noise ratio of the travel times computed from the compressed data as a function of the compression efficiency.Results. The basic helioseismic measurements that we consider are very robust to lossy data compression. Even if only the sign of the velocity is used, time-distance helioseismology is still possible. We achieve the best results by applying JPEG compression on spatially subsampled data. However, our conclusions are only valid for supergranulation flows at disk center and may not be valid for all helioseismology applications."],["dc.identifier.doi","10.1051/0004-6361/201424315"],["dc.identifier.fs","609658"],["dc.identifier.gro","3147017"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11404"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4759"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/312844/EU//SPACEINN"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/312495/EU//SOLARNET"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Image compression in local helioseismology"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A11"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","642"],["dc.contributor.author","Solanki, S. K."],["dc.contributor.author","del Toro Iniesta, J. C."],["dc.contributor.author","Woch, J."],["dc.contributor.author","Gandorfer, A."],["dc.contributor.author","Hirzberger, J."],["dc.contributor.author","Alvarez-Herrero, A."],["dc.contributor.author","Appourchaux, T."],["dc.contributor.author","Martínez Pillet, V."],["dc.contributor.author","Pérez-Grande, I."],["dc.contributor.author","Schmidt, W."],["dc.contributor.author","Lange, T."],["dc.contributor.author","Müller, D."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Müller, R."],["dc.contributor.author","Albert, K."],["dc.contributor.author","Löptien, Björn"],["dc.contributor.author","Meyer, S."],["dc.contributor.author","Soltau, D."],["dc.contributor.author","Schou, Jesper"],["dc.date.accessioned","2021-03-05T08:58:36Z"],["dc.date.available","2021-03-05T08:58:36Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1051/0004-6361/201935325"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/80195"],["dc.notes.intern","DOI Import GROB-393"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","The Polarimetric and Helioseismic Imager on Solar Orbiter"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A181"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","635"],["dc.contributor.author","Böning, Vincent G. A."],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Duvall, Thomas L."],["dc.contributor.author","Schou, Jesper"],["dc.date.accessioned","2020-12-10T18:11:55Z"],["dc.date.available","2020-12-10T18:11:55Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1051/0004-6361/201937331"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74186"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Characterizing the spatial pattern of solar supergranulation using the bispectrum"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","43"],["dc.bibliographiccitation.issue","6918"],["dc.bibliographiccitation.journal","Nature"],["dc.bibliographiccitation.lastpage","44"],["dc.bibliographiccitation.volume","421"],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Duvall, T. L."],["dc.contributor.author","Schou, J."],["dc.date.accessioned","2021-03-05T08:58:27Z"],["dc.date.available","2021-03-05T08:58:27Z"],["dc.date.issued","2003"],["dc.identifier.doi","10.1038/nature01287"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/80141"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-393"],["dc.relation.eissn","1476-4687"],["dc.relation.haserratum","/handle/2/80142"],["dc.relation.issn","0028-0836"],["dc.title","Wave-like properties of solar supergranulation"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","568"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Nature Astronomy"],["dc.bibliographiccitation.lastpage","573"],["dc.bibliographiccitation.volume","2"],["dc.contributor.author","Löptien, Björn"],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Schou, Jesper"],["dc.contributor.author","Proxauf, Bastian"],["dc.contributor.author","Duvall, Thomas L."],["dc.contributor.author","Bogart, Richard S."],["dc.contributor.author","Christensen, Ulrich R."],["dc.date.accessioned","2020-05-18T14:29:12Z"],["dc.date.available","2020-05-18T14:29:12Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1038/s41550-018-0460-x"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/65540"],["dc.relation.issn","2397-3366"],["dc.title","Global-scale equatorial Rossby waves as an essential component of solar internal dynamics"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","L12"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","568"],["dc.contributor.author","Nielsen, M. B."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Schunker, H."],["dc.contributor.author","Schou, J."],["dc.date.accessioned","2017-09-07T11:48:42Z"],["dc.date.available","2017-09-07T11:48:42Z"],["dc.date.issued","2014"],["dc.identifier.doi","10.1051/0004-6361/201424525"],["dc.identifier.fs","609660"],["dc.identifier.gro","3147028"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/10930"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4765"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.publisher","EDP Sciences"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Rotational splitting as a function of mode frequency for six Sun-like stars"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]