Nagashima, Kaori

[["dc.bibliographiccitation.artnumber","A41"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","593"],["dc.contributor.author","Nagashima, Kaori"],["dc.contributor.author","Sekii, Takashi"],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Birch, Aaron C."],["dc.date.accessioned","2017-09-07T11:49:58Z"],["dc.date.available","2017-09-07T11:49:58Z"],["dc.date.issued","2016"],["dc.identifier.doi","10.1051/0004-6361/201628129"],["dc.identifier.gro","3147462"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14282"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/5018"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.publisher","EDP Sciences"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/312844/EU/Exploitation of Space Data for Innovative Helio- and Asteroseismology/SPACEINN"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Statistics of the two-point cross-covariance function of solar oscillations"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A111"],["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.lastpage","9"],["dc.bibliographiccitation.volume","599"],["dc.contributor.author","Nagashima, Kaori"],["dc.contributor.author","Fournier, Damien"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2017-09-07T11:48:41Z"],["dc.date.available","2017-09-07T11:48:41Z"],["dc.date.issued","2017"],["dc.description.abstract","Context. In time-distance helioseismology, wave travel times are measured from the two-point cross-covariance function of solar oscillations and are used to image the solar convection zone in three dimensions. There is, however, also information in the amplitude of the cross-covariance function, for example, about seismic wave attenuation. Aims. We develop a convenient procedure to measure the amplitude of the cross-covariance function of solar oscillations. Methods. In this procedure, the amplitude of the cross-covariance function is linearly related to the cross-covariance function and can be measured even for high levels of noise. Results. As an example application, we measure the amplitude perturbations of the seismic waves that propagate through the sunspot in active region NOAA 9787. We can recover the amplitude variations due to the scattering and attenuation of the waves by the sunspot and associated finite-wavelength effects. Conclusions. The proposed definition of cross-covariance amplitude is robust to noise, can be used to relate measured amplitudes to 3D perturbations in the solar interior under the Born approximation, and provides independent information from the travel times."],["dc.identifier.doi","10.1051/0004-6361/201629846"],["dc.identifier.gro","3147023"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4762"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.submitter","chake"],["dc.relation.issn","0004-6361"],["dc.title","The amplitude of the cross-covariance function of solar oscillations as a diagnostic tool for wave attenuation and geometrical spreading"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A109"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","633"],["dc.contributor.author","Nagashima, Kaori"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Schou, Jesper"],["dc.contributor.author","Hindman, Bradley W."],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2020-12-10T18:11:53Z"],["dc.date.available","2020-12-10T18:11:53Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1051/0004-6361/201936662"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74174"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","An improved multi-ridge fitting method for ring-diagram helioseismic analysis"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A73"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","613"],["dc.contributor.author","Duvall, Thomas L."],["dc.contributor.author","Cally, Paul S."],["dc.contributor.author","Przybylski, Damien"],["dc.contributor.author","Nagashima, Kaori"],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2020-12-10T18:11:38Z"],["dc.date.available","2020-12-10T18:11:38Z"],["dc.date.issued","2018"],["dc.identifier.doi","10.1051/0004-6361/201732424"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74093"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Probing sunspots with two-skip time–distance helioseismology"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","3457"],["dc.bibliographiccitation.issue","9"],["dc.bibliographiccitation.journal","Solar Physics"],["dc.bibliographiccitation.lastpage","3481"],["dc.bibliographiccitation.volume","289"],["dc.contributor.author","Nagashima, Kaori"],["dc.contributor.author","Löptien, Björn"],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Cameron, Robert"],["dc.contributor.author","Couvidat, Sebastien"],["dc.contributor.author","Danilovic, Sanja"],["dc.contributor.author","Fleck, Bernhard"],["dc.contributor.author","Stein, Robert"],["dc.date.accessioned","2017-09-07T11:48:41Z"],["dc.date.available","2017-09-07T11:48:41Z"],["dc.date.issued","2014"],["dc.description.abstract","The Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) filtergrams, taken at six wavelengths around the Fe i 6173.3 Å line, contain information about the line-of-sight velocity over a range of heights in the solar atmosphere. Multi-height velocity inferences from these observations can be exploited to study wave motions and energy transport in the atmosphere. Using realistic convection-simulation datasets provided by the STAGGER and MURaM codes, we generate synthetic filtergrams and explore several methods for estimating Dopplergrams. We investigate at which height each synthetic Dopplergram correlates most strongly with the vertical velocity in the model atmospheres. On the basis of the investigation, we propose two Dopplergrams other than the standard HMI-algorithm Dopplergram produced from HMI filtergrams: a line-center Dopplergram and an average-wing Dopplergram. These two Dopplergrams correlate most strongly with vertical velocities at the heights of 30 – 40 km above (line center) and 30 – 40 km below (average wing) the effective height of the HMI-algorithm Dopplergram. Therefore, we can obtain velocity information from two layers separated by about a half of a scale height in the atmosphere, at best. The phase shifts between these multi-height Dopplergrams from observational data as well as those from the simulated data are also consistent with the height-difference estimates in the frequency range above the photospheric acoustic-cutoff frequency."],["dc.identifier.doi","10.1007/s11207-014-0543-5"],["dc.identifier.gro","3147024"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4763"],["dc.language.iso","en"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation.issn","0038-0938"],["dc.title","Interpreting the Helioseismic and Magnetic Imager (HMI) Multi-Height Velocity Measurements"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]