Cameron, Robert H.

[["dc.bibliographiccitation.firstpage","A183"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","664"],["dc.contributor.author","Baumgartner, C."],["dc.contributor.author","Birch, A. C."],["dc.contributor.author","Schunker, H."],["dc.contributor.author","Cameron, R. H."],["dc.contributor.author","Gizon, L."],["dc.date.accessioned","2022-10-04T10:22:20Z"],["dc.date.available","2022-10-04T10:22:20Z"],["dc.date.issued","2022"],["dc.description.abstract","Context.\n The twist of the magnetic field above a sunspot is an important quantity in solar physics. For example, magnetic twist plays a role in the initiation of flares and coronal mass ejections (CMEs). Various proxies for the twist above the photosphere have been found using models of uniformly twisted flux tubes, and are routinely computed from single photospheric vector magnetograms. One class of proxies is based on\n α\n \n z\n \n , the ratio of the vertical current to the vertical magnetic field. Another class of proxies is based on the so-called twist density,\n q\n , which depends on the ratio of the azimuthal field to the vertical field. However, the sensitivity of these proxies to temporal fluctuations of the magnetic field has not yet been well characterized.\n \n \n Aims.\n We aim to determine the sensitivity of twist proxies to temporal fluctuations in the magnetic field as estimated from time-series of SDO/HMI vector magnetic field maps.\n \n \n Methods.\n To this end, we introduce a model of a sunspot with a peak vertical field of 2370 Gauss at the photosphere and a uniform twist density\n q\n  = −0.024 Mm\n −1\n . We add realizations of the temporal fluctuations of the magnetic field that are consistent with SDO/HMI observations, including the spatial correlations. Using a Monte-Carlo approach, we determine the robustness of the different proxies to the temporal fluctuations.\n \n \n Results.\n The temporal fluctuations of the three components of the magnetic field are correlated for spatial separations up to 1.4 Mm (more than expected from the point spread function alone). The Monte-Carlo approach enables us to demonstrate that several proxies for the twist of the magnetic field are not biased in each of the individual magnetograms. The associated random errors on the proxies have standard deviations in the range between 0.002 and 0.006 Mm\n −1\n , which is smaller by approximately one order of magnitude than the mean value of\n q\n ."],["dc.identifier.doi","10.1051/0004-6361/202243357"],["dc.identifier.pii","aa43357-22"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/114646"],["dc.notes.intern","DOI-Import GROB-600"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","Impact of spatially correlated fluctuations in sunspots on metrics related to magnetic twist"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1469"],["dc.bibliographiccitation.issue","6498"],["dc.bibliographiccitation.journal","Science"],["dc.bibliographiccitation.lastpage","1472"],["dc.bibliographiccitation.volume","368"],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Cameron, Robert H."],["dc.contributor.author","Pourabdian, Majid"],["dc.contributor.author","Liang, Zhi-Chao"],["dc.contributor.author","Fournier, Damien"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Hanson, Chris S."],["dc.date.accessioned","2021-03-05T08:59:01Z"],["dc.date.available","2021-03-05T08:59:01Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1126/science.aaz7119"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/80330"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-393"],["dc.relation.eissn","1095-9203"],["dc.relation.issn","0036-8075"],["dc.title","Meridional flow in the Sun’s convection zone is a single cell in each hemisphere"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","Science Advances"],["dc.bibliographiccitation.volume","2"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Schunker, H."],["dc.contributor.author","Braun, D. C."],["dc.contributor.author","Cameron, R. H."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Löptien, Björn"],["dc.contributor.author","Rempel, M."],["dc.date.accessioned","2017-09-07T11:49:43Z"],["dc.date.available","2017-09-07T11:49:43Z"],["dc.date.issued","2016"],["dc.description.abstract","Magnetic field emerges at the surface of the Sun as sunspots and active regions. This process generates a poloidal magnetic field from a rising toroidal flux tube; it is a crucial but poorly understood aspect of the solar dynamo. The emergence of magnetic field is also important because it is a key driver of solar activity. We show that measurements of horizontal flows at the solar surface around emerging active regions, in combination with numerical simulations of solar magnetoconvection, can constrain the subsurface rise speed of emerging magnetic flux. The observed flows imply that the rise speed of the magnetic field is no larger than 150 m/s at a depth of 20 Mm, that is, well below the prediction of the (standard) thin flux tube model but in the range expected for convective velocities at this depth. We conclude that convective flows control the dynamics of rising flux tubes in the upper layers of the Sun and cannot be neglected in models of flux emergence."],["dc.identifier.doi","10.1126/sciadv.1600557"],["dc.identifier.gro","3147404"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4994"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.submitter","chake"],["dc.relation.issn","2375-2548"],["dc.title","A low upper limit on the subsurface rise speed of solar active regions"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A65"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","637"],["dc.contributor.author","Damiani, C."],["dc.contributor.author","Cameron, R. H."],["dc.contributor.author","Birch, A. C."],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2021-03-05T08:58:36Z"],["dc.date.available","2021-03-05T08:58:36Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1051/0004-6361/201936251"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/80196"],["dc.notes.intern","DOI Import GROB-393"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","Rossby modes in slowly rotating stars: depth dependence in distorted polytropes with uniform rotation"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A116"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","640"],["dc.contributor.author","Schunker, Hannah"],["dc.contributor.author","Baumgartner, C."],["dc.contributor.author","Birch, A. C."],["dc.contributor.author","Cameron, R. H."],["dc.contributor.author","Braun, D. C."],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2021-03-05T08:58:37Z"],["dc.date.available","2021-03-05T08:58:37Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.1051/0004-6361/201937322"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/80198"],["dc.notes.intern","DOI Import GROB-393"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","Average motion of emerging solar active region polarities"],["dc.title.alternative","II. Joy’s law"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","L6"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","652"],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Cameron, Robert H."],["dc.contributor.author","Bekki, Yuto"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Bogart, Richard S."],["dc.contributor.author","Sacha Brun, Allan"],["dc.contributor.author","Damiani, Cilia"],["dc.contributor.author","Fournier, Damien"],["dc.contributor.author","Hyest, Laura"],["dc.contributor.author","Jain, Kiran"],["dc.contributor.author","Proxauf, Bastian"],["dc.date.accessioned","2021-09-01T06:42:17Z"],["dc.date.available","2021-09-01T06:42:17Z"],["dc.date.issued","2021"],["dc.description.abstract","The oscillations of a slowly rotating star have long been classified into spheroidal and toroidal modes. The spheroidal modes include the well-known 5-min acoustic modes used in helioseismology. Here we report observations of the Sun’s toroidal modes, for which the restoring force is the Coriolis force and whose periods are on the order of the solar rotation period. By comparing the observations with the normal modes of a differentially rotating spherical shell, we are able to identify many of the observed modes. These are the high-latitude inertial modes, the critical-latitude inertial modes, and the equatorial Rossby modes. In the model, the high-latitude and critical-latitude modes have maximum kinetic energy density at the base of the convection zone, and the high-latitude modes are baroclinically unstable due to the latitudinal entropy gradient. As a first application of inertial-mode helioseismology, we constrain the superadiabaticity and the turbulent viscosity in the deep convection zone."],["dc.description.abstract","The oscillations of a slowly rotating star have long been classified into spheroidal and toroidal modes. The spheroidal modes include the well-known 5-min acoustic modes used in helioseismology. Here we report observations of the Sun’s toroidal modes, for which the restoring force is the Coriolis force and whose periods are on the order of the solar rotation period. By comparing the observations with the normal modes of a differentially rotating spherical shell, we are able to identify many of the observed modes. These are the high-latitude inertial modes, the critical-latitude inertial modes, and the equatorial Rossby modes. In the model, the high-latitude and critical-latitude modes have maximum kinetic energy density at the base of the convection zone, and the high-latitude modes are baroclinically unstable due to the latitudinal entropy gradient. As a first application of inertial-mode helioseismology, we constrain the superadiabaticity and the turbulent viscosity in the deep convection zone."],["dc.identifier.doi","10.1051/0004-6361/202141462"],["dc.identifier.pii","aa41462-21"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/89024"],["dc.notes.intern","DOI-Import GROB-455"],["dc.relation.eissn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.title","Solar inertial modes: Observations, identification, and diagnostic promise"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","A53"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","625"],["dc.contributor.author","Schunker, Hannah"],["dc.contributor.author","Birch, A. C."],["dc.contributor.author","Cameron, R. H."],["dc.contributor.author","Braun, D. C."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Burston, R. B."],["dc.date.accessioned","2020-12-10T18:11:46Z"],["dc.date.available","2020-12-10T18:11:46Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1051/0004-6361/201834627"],["dc.identifier.eissn","1432-0746"],["dc.identifier.issn","0004-6361"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74133"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Average motion of emerging solar active region polarities"],["dc.title.alternative","I. Two phases of emergence"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","257"],["dc.bibliographiccitation.issue","1-4"],["dc.bibliographiccitation.journal","Space Science Reviews"],["dc.bibliographiccitation.lastpage","258"],["dc.bibliographiccitation.volume","156"],["dc.contributor.author","Gizon, L."],["dc.contributor.author","Schunker, H."],["dc.contributor.author","Baldner, C. S."],["dc.contributor.author","Basu, S."],["dc.contributor.author","Birch, A. C."],["dc.contributor.author","Bogart, R. S."],["dc.contributor.author","Braun, D. C."],["dc.contributor.author","Cameron, R. H."],["dc.contributor.author","Duvall Jr., T. L."],["dc.contributor.author","Hanasoge, S. M."],["dc.contributor.author","Jackiewicz, J."],["dc.contributor.author","Roth, M."],["dc.contributor.author","Stahn, T."],["dc.contributor.author","Thompson, M. J."],["dc.contributor.author","Zharkov, S."],["dc.date.accessioned","2017-09-07T11:48:39Z"],["dc.date.available","2017-09-07T11:48:39Z"],["dc.date.issued","2010"],["dc.identifier.doi","10.1007/s11214-010-9688-1"],["dc.identifier.gro","3146992"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4741"],["dc.language.iso","en"],["dc.notes.status","final"],["dc.notes.submitter","chake"],["dc.relation.eissn","1572-9672"],["dc.relation.iserratumof","/handle/2/4740"],["dc.relation.issn","0038-6308"],["dc.title","Erratum to: Helioseismology of Sunspots: A Case Study of NOAA Region 9787"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.subtype","erratum_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.journal","Experimental Astronomy"],["dc.contributor.author","Harra, Louise"],["dc.contributor.author","Andretta, Vincenzo"],["dc.contributor.author","Appourchaux, Thierry"],["dc.contributor.author","Baudin, Frédéric"],["dc.contributor.author","Bellot-Rubio, Luis"],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Boumier, Patrick"],["dc.contributor.author","Cameron, Robert H."],["dc.contributor.author","Carlsson, Matts"],["dc.contributor.author","Corbard, Thierry"],["dc.contributor.author","Schmutz, W."],["dc.date.accessioned","2021-09-01T06:42:39Z"],["dc.date.available","2021-09-01T06:42:39Z"],["dc.date.issued","2021"],["dc.description.abstract","Abstract A mission to view the solar poles from high helio-latitudes (above 60°) will build on the experience of Solar Orbiter as well as a long heritage of successful solar missions and instrumentation (e.g. SOHO Domingo et al. (Solar Phys. 162 (1-2), 1–37 1995), STEREO Howard et al. (Space Sci. Rev. 136 (1-4), 67–115 2008), Hinode Kosugi et al. (Solar Phys. 243 (1), 3–17 2007), Pesnell et al. Solar Phys. 275 (1–2), 3–15 2012), but will focus for the first time on the solar poles, enabling scientific investigations that cannot be done by any other mission. One of the major mysteries of the Sun is the solar cycle. The activity cycle of the Sun drives the structure and behaviour of the heliosphere and of course, the driver of space weather. In addition, solar activity and variability provides fluctuating input into the Earth climate models, and these same physical processes are applicable to stellar systems hosting exoplanets. One of the main obstructions to understanding the solar cycle, and hence all solar activity, is our current lack of understanding of the polar regions. In this White Paper, submitted to the European Space Agency in response to the Voyage 2050 call, we describe a mission concept that aims to address this fundamental issue. In parallel, we recognise that viewing the Sun from above the polar regions enables further scientific advantages, beyond those related to the solar cycle, such as unique and powerful studies of coronal mass ejection processes, from a global perspective, and studies of coronal structure and activity in polar regions. Not only will these provide important scientific advances for fundamental stellar physics research, they will feed into our understanding of impacts on the Earth and other planets’ space environment."],["dc.description.abstract","Abstract A mission to view the solar poles from high helio-latitudes (above 60°) will build on the experience of Solar Orbiter as well as a long heritage of successful solar missions and instrumentation (e.g. SOHO Domingo et al. (Solar Phys. 162 (1-2), 1–37 1995), STEREO Howard et al. (Space Sci. Rev. 136 (1-4), 67–115 2008), Hinode Kosugi et al. (Solar Phys. 243 (1), 3–17 2007), Pesnell et al. Solar Phys. 275 (1–2), 3–15 2012), but will focus for the first time on the solar poles, enabling scientific investigations that cannot be done by any other mission. One of the major mysteries of the Sun is the solar cycle. The activity cycle of the Sun drives the structure and behaviour of the heliosphere and of course, the driver of space weather. In addition, solar activity and variability provides fluctuating input into the Earth climate models, and these same physical processes are applicable to stellar systems hosting exoplanets. One of the main obstructions to understanding the solar cycle, and hence all solar activity, is our current lack of understanding of the polar regions. In this White Paper, submitted to the European Space Agency in response to the Voyage 2050 call, we describe a mission concept that aims to address this fundamental issue. In parallel, we recognise that viewing the Sun from above the polar regions enables further scientific advantages, beyond those related to the solar cycle, such as unique and powerful studies of coronal mass ejection processes, from a global perspective, and studies of coronal structure and activity in polar regions. Not only will these provide important scientific advances for fundamental stellar physics research, they will feed into our understanding of impacts on the Earth and other planets’ space environment."],["dc.identifier.doi","10.1007/s10686-021-09769-x"],["dc.identifier.pii","9769"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/89113"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-455"],["dc.relation.eissn","1572-9508"],["dc.relation.issn","0922-6435"],["dc.title","A journey of exploration to the polar regions of a star: probing the solar poles and the heliosphere from high helio-latitude"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","249"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Space Science Reviews"],["dc.bibliographiccitation.lastpage","273"],["dc.bibliographiccitation.volume","144"],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Schunker, H."],["dc.contributor.author","Baldner, C. S."],["dc.contributor.author","Basu, S."],["dc.contributor.author","Birch, Aaron C."],["dc.contributor.author","Bogart, R. S."],["dc.contributor.author","Braun, D. C."],["dc.contributor.author","Cameron, R. H."],["dc.contributor.author","Duvall, Thomas L."],["dc.contributor.author","Hanasoge, Shravan M."],["dc.contributor.author","Jackiewicz, J."],["dc.contributor.author","Roth, M."],["dc.contributor.author","Stahn, Thorsten"],["dc.contributor.author","Thompson, M. J."],["dc.contributor.author","Zharkov, S."],["dc.date.accessioned","2017-09-07T11:48:39Z"],["dc.date.available","2017-09-07T11:48:39Z"],["dc.date.issued","2008"],["dc.identifier.doi","10.1007/s11214-008-9466-5"],["dc.identifier.gro","3146991"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4740"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.publisher","Springer Nature"],["dc.relation.haserratum","/handle/2/4741"],["dc.relation.issn","0038-6308"],["dc.title","Helioseismology of Sunspots: A Case Study of NOAA Region 9787"],["dc.type","journal_article"],["dc.type.internalPublication","unknown"],["dc.type.peerReviewed","no"],["dspace.entity.type","Publication"]]