explanation blue bibcodes open ADS page with paths to full text
Author name code: stein
ADS astronomy entries on 2022-09-14
author:"Stein, Robert F." -title:"Icecube" -title:"neutrino" -title:"Cherenkov" -title:"Cosmic" -title:"IceCube" -title:"transient" -title:"Zwicky" -title:"LIGO" -title:"ZTF" -title:"AMPEL" -title:"tidal" -title:"NIR" -aff:"DESY" -aff:"Humboldt"
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Title: Towards Equitable, Diverse, and Inclusive science
collaborations: The Multimessenger Diversity Network
Authors: Bechtol, E.; IceCube; Abbasi, R.; Ackermann, M.; Adams, J.;
Aguilar, J.; Ahlers, M.; Ahrens, M.; Alispach, C. M.; Alves Junior,
A. A.; Amin, N. M. B.; An, R.; Andeen, K.; Anderson, T.; Anton,
G.; Arguelles, C.; Ashida, Y.; Axani, S.; Bai, X.; Balagopal V.,
A.; Barbano, A. M.; Barwick, S. W.; Bastian, B.; Basu, V.; Baur,
S.; Bay, R. C.; Beatty, J. J.; Becker, K. H.; Becker Tjus, J.;
Bellenghi, C.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson,
D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Boddenberg,
M.; Bontempo, F.; Borowka, J.; Boser, S.; Botner, O.; Bottcher, J.;
Bourbeau, E.; Bradascio, F.; Braun, J.; Bron, S.; Brostean-Kaiser,
J.; Browne, S. A.; Burgman, A.; Burley, R.; Busse, R.; Campana, M.;
Carnie-Bronca, E.; Chen, C.; Chirkin, D.; Choi, K.; Clark, B.; Clark,
K.; Classen, L.; Coleman, A.; Collin, G.; Conrad, J. M.; Coppin,
P.; Correa, P.; Cowen, D. F.; Cross, R.; Dappen, C.; Dave, P.; De
Clercq, C.; DeLaunay, J.; Dembinski, H.; Deoskar, K.; De Ridder, S.;
Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.; De With, M.;
DeYoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.; Dittmer, M.;
Dujmovic, H.; Dunkman, M.; DuVernois, M.; Dvorak, E.; Ehrhardt, T.;
Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson, P. A.; Fan,
K. L.; Fazely, A. R.; Fiedlschuster, S.; Fienberg, A.; Filimonov,
K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak, A.; Friedman,
E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher, J.; Ganster,
E.; Garcia, A.; Garrappa, S.; Gerhardt, L.; Ghadimi, A.; Glaser, C.;
Glauch, T.; Glusenkamp, T.; Goldschmidt, A.; Gonzalez, J.; Goswami,
S.; Grant, D.; Grégoire, T.; Griswold, S.; Gunduz, M.; Günther,
C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve, L.; Halzen, F.;
Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.; Haungs, A.;
Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.; Hettinger,
E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.; Hoffman, K.;
Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.;
Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.; Hussain, R.; In,
S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.; Jeong, M.;
Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.; Kappesser, D.;
Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.; Kellermann, M.;
Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher, T.; Kiryluk,
J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas, T.; Kopke, L.;
Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.; Kovacevich,
M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.; Lad, N.;
Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber, F. H.;
Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.; Lincetto,
M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal, C. J.;
Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma, W. Y.;
Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.; Maruyama,
R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.; Meagher, K.;
Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.; Mockler, D.;
Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab, R.; Nagai, R.;
Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen, H.; Nisa, M.;
Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler, M.; Olivas,
A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.; Parker, G.;
Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters, L.; Peterson,
J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann, M.; Pizzuto,
A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price,
P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.; Rameez, M.;
Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.; Reimann, R.;
Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman, M.; Riedel,
B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen, M.; Rott,
C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.; Saffer,
J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander, M.;
Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer,
A.; Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte,
R.; Turley, C.; Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.;
Valtonen-Mattila, N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom,
D.; van Santen, J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.;
Weaver, C.; Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt,
C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.;
Williams, D.; Wolf, M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu,
X.; Xu, Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.;
Bechtol, K.; BenZvi, S.; Bleve, C.; Castro, D.; Cenko, B.; Corlies,
L.; Furniss, A.; Hui, C. M.; Kaplan, D. L.; Key, J. S.; Madsen, J.;
McNally, F.; McLaughlin, M.; Mukherjee, R.; Ojha, R.; Sanders, J.;
Santander, M.; Schlieder, J.; Shoemaker, D. H.; Vigeland, S.
2022icrc.confE1383B Altcode: 2022PoS...395E1383B; 2021arXiv210712179B
The Multimessenger Diversity Network (MDN), formed in 2018, extends
the basic principle of multimessenger astronomy -- that working
collaboratively with different approaches enhances understanding and
enables previously impossible discoveries -- to equity, diversity,
and inclusion (EDI) in science research collaborations. With
support from the National Science Foundation INCLUDES program, the
MDN focuses on increasing EDI by sharing knowledge, experiences,
training, and resources among representatives from multimessenger
science collaborations. Representatives to the MDN become engagement
leads in their collaboration, extending the reach of the community of
practice. An overview of the MDN structure, lessons learned, and how
to join are presented.
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Title: Completing Aganta Kairos: Capturing Metaphysical Time on the
Seventh Continent
Authors: Madsen, J.; Mulot, L.; IceCube; Abbasi, R.; Ackermann, M.;
Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Alispach, C. M.;
Alves Junior, A. A.; Amin, N. M. B.; An, R.; Andeen, K.; Anderson,
T.; Anton, G.; Arguelles, C.; Ashida, Y.; Axani, S.; Bai, X.;
Balagopal V., A.; Barbano, A. M.; Barwick, S. W.; Bastian, B.; Basu,
V.; Baur, S.; Bay, R. C.; Beatty, J. J.; Becker, K. H.; Becker Tjus,
J.; Bellenghi, C.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson,
D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Boddenberg,
M.; Bontempo, F.; Borowka, J.; Boser, S.; Botner, O.; Bottcher, J.;
Bourbeau, E.; Bradascio, F.; Braun, J.; Bron, S.; Brostean-Kaiser,
J.; Browne, S. A.; Burgman, A.; Burley, R.; Busse, R.; Campana, M.;
Carnie-Bronca, E.; Chen, C.; Chirkin, D.; Choi, K.; Clark, B.; Clark,
K.; Classen, L.; Coleman, A.; Collin, G.; Conrad, J. M.; Coppin,
P.; Correa, P.; Cowen, D. F.; Cross, R.; Dappen, C.; Dave, P.; De
Clercq, C.; DeLaunay, J.; Dembinski, H.; Deoskar, K.; De Ridder, S.;
Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.; De With, M.;
DeYoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.; Dittmer, M.;
Dujmovic, H.; Dunkman, M.; DuVernois, M.; Dvorak, E.; Ehrhardt, T.;
Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson, P. A.; Fan,
K. L.; Fazely, A. R.; Fiedlschuster, S.; Fienberg, A.; Filimonov,
K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak, A.; Friedman,
E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher, J.; Ganster,
E.; Garcia, A.; Garrappa, S.; Gerhardt, L.; Ghadimi, A.; Glaser, C.;
Glauch, T.; Glusenkamp, T.; Goldschmidt, A.; Gonzalez, J.; Goswami,
S.; Grant, D.; Grégoire, T.; Griswold, S.; Gunduz, M.; Günther,
C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve, L.; Halzen, F.;
Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.; Haungs, A.;
Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.; Hettinger,
E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.; Hoffman, K.;
Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.;
Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.; Hussain, R.; In,
S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.; Jeong, M.;
Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.; Kappesser, D.;
Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.; Kellermann, M.;
Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher, T.; Kiryluk,
J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas, T.; Kopke, L.;
Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.; Kovacevich,
M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.; Lad, N.;
Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber, F. H.;
Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.; Lincetto,
M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal, C. J.;
Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma, W. Y.;
Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.; Maruyama,
R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.; Meagher, K.;
Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.; Mockler, D.;
Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab, R.; Nagai, R.;
Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen, H.; Nisa, M.;
Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler, M.; Olivas,
A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.; Parker, G.;
Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters, L.; Peterson,
J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann, M.; Pizzuto,
A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price,
P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.; Rameez, M.;
Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.; Reimann, R.;
Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman, M.; Riedel,
B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen, M.; Rott,
C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.; Saffer,
J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander, M.;
Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer,
A.; Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte,
R.; Turley, C.; Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.;
Valtonen-Mattila, N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom,
D.; van Santen, J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.;
Weaver, C.; Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt,
C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.;
Williams, D.; Wolf, M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu, X.;
Xu, Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.
2022icrc.confE1381M Altcode: 2022PoS...395E1381M; 2021arXiv210801687M
We present an overview of the art project Aganta Kairos (To Fish the
Metaphysical Time). This project celebrates the neutrino, the ghost
particle, which scientists consider a cosmic messenger and the artist
regards as a link between people who care about their relationship
to the cosmos and question their origins. The artwork is based on
a performance of celebration and seeks to build a human community
that encompasses different knowledge domains and interpretations
of the universe. This intersection of knowledge is realized during
the performance of placing a plaque, held with witnesses, and during
subsequent exhibitions. Images, sounds, videos, and sculpture testify
to the diversity of approaches to questioning our origins, ranging
from traditional western science to ancient shamanism. The sites
were selected for their global coverage and, for the South Pole,
Mediterranean, and Lake Baikal, their connection to ongoing neutrino
experiments. In December 2020, a plaque was installed at the South Pole
IceCube Laboratory, the seventh and final site. We provide examples
of images and links to additional images and videos.
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Title: Simulation Study of the Observed Radio Emission of Air Showers
by the IceTop Surface Extension
Authors: Coleman, A.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar,
J.; Ahlers, M.; Ahrens, M.; Alispach, C. M.; Alves Junior, A. A.;
Amin, N. M. B.; An, R.; Andeen, K.; Anderson, T.; Anton, G.; Arguelles,
C.; Ashida, Y.; Axani, S.; Bai, X.; Balagopal V., A.; Barbano, A. M.;
Barwick, S. W.; Bastian, B.; Basu, V.; Baur, S.; Bay, R. C.; Beatty,
J. J.; Becker, K. H.; Becker Tjus, J.; Bellenghi, C.; BenZvi, S.;
Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.;
Blaufuss, E.; Blot, S.; Boddenberg, M.; Bontempo, F.; Borowka, J.;
Boser, S.; Botner, O.; Bottcher, J.; Bourbeau, E.; Bradascio, F.;
Braun, J.; Bron, S.; Brostean-Kaiser, J.; Browne, S. A.; Burgman,
A.; Burley, R.; Busse, R.; Campana, M.; Carnie-Bronca, E.; Chen, C.;
Chirkin, D.; Choi, K.; Clark, B.; Clark, K.; Classen, L.; Collin, G.;
Conrad, J. M.; Coppin, P.; Correa, P.; Cowen, D. F.; Cross, R.; Dappen,
C.; Dave, P.; De Clercq, C.; DeLaunay, J.; Dembinski, H.; Deoskar, K.;
De Ridder, S.; Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.;
De With, M.; DeYoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.;
Dittmer, M.; Dujmovic, H.; Dunkman, M.; DuVernois, M.; Dvorak, E.;
Ehrhardt, T.; Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson,
P. A.; Fan, K. L.; Fazely, A. R.; Fiedlschuster, S.; Fienberg, A.;
Filimonov, K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak, A.;
Friedman, E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher, J.;
Ganster, E.; Garcia, A.; Garrappa, S.; Gerhardt, L.; Ghadimi, A.;
Glaser, C.; Glauch, T.; Glusenkamp, T.; Goldschmidt, A.; Gonzalez,
J.; Goswami, S.; Grant, D.; Grégoire, T.; Griswold, S.; Gunduz, M.;
Günther, C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve, L.; Halzen,
F.; Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.; Haungs,
A.; Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.; Hettinger,
E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.; Hoffman, K.;
Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.;
Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.; Hussain, R.; In,
S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.; Jeong, M.;
Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.; Kappesser, D.;
Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.; Kellermann, M.;
Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher, T.; Kiryluk,
J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas, T.; Kopke, L.;
Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.; Kovacevich,
M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.; Lad, N.;
Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber, F. H.;
Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.; Lincetto,
M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal, C. J.;
Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma, W. Y.;
Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.; Maruyama,
R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.; Meagher, K.;
Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.; Mockler, D.;
Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab, R.; Nagai, R.;
Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen, H.; Nisa, M.;
Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler, M.; Olivas,
A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.; Parker, G.;
Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters, L.; Peterson,
J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann, M.; Pizzuto,
A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price,
P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.; Rameez, M.;
Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.; Reimann, R.;
Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman, M.; Riedel,
B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen, M.; Rott,
C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.; Saffer,
J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander, M.;
Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer,
A.; Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte,
R.; Turley, C.; Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.;
Valtonen-Mattila, N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom,
D.; van Santen, J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.;
Weaver, C.; Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt,
C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.;
Williams, D.; Wolf, M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu, X.;
Xu, Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.
2022icrc.confE.317C Altcode: 2021arXiv210709666C; 2022PoS...395E.317C
Multi-detector observations of individual air showers are critical to
make significant progress to precisely determine cosmic-ray quantities
such as mass and energy of individual events and thus bring us a step
forward in answering the open questions in cosmic-ray physics. An
enhancement of IceTop, the surface array of the IceCube Neutrino
Observatory, is currently underway and includes adding antennas and
scintillators to the existing array of ice-Cherenkov tanks. The
radio component will improve the characterization of the primary
particles by providing an estimation of X$_\text{max}$ and a direct
sampling of the electromagnetic cascade, both important for per-event
mass classification. A prototype station has been operated at the
South Pole and has observed showers, simultaneously, with the tanks,
scintillator panels, and antennas. The observed radio signals of these
events are unique as they are measured in the 70 to 350\,MHz band,
higher than many other cosmic-ray experiments. We present a comparison
of the detected events with the waveforms from CoREAS simulations,
convoluted with the end-to-end electronics response, as a verification
of the analysis chain. Using the detector response and the measurements
of the prototype station as input, we update a Monte-Carlo-based study
on the potential of the enhanced surface array for the hybrid detection
of air showers by scintillators and radio antennas.
---------------------------------------------------------
Title: Concept Study of a Radio Array Embedded in a Deep Gen2-like
Optical Array.
Authors: Bishop, A.; Hokanson-Fasig, B.; Karle, A.; Lu, L.;
IceCube-Gen2; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J.;
Ahlers, M.; Ahrens, M.; Alispach, C. M.; Allison, P.; Alves Junior,
A. A.; Amin, N. M. B.; An, R.; Andeen, K.; Anderson, T.; Anton, G.;
Arguelles, C.; Arlen, T.; Ashida, Y.; Axani, S.; Bai, X.; Balagopal V.,
A.; Barbano, A. M.; Bartos, I.; Barwick, S. W.; Bastian, B.; Basu, V.;
Baur, S.; Bay, R. C.; Beatty, J. J.; Becker, K. H.; Becker Tjus, J.;
Bellenghi, C.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.;
Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Boddenberg, M.; Bohmer,
M.; Bontempo, F.; Borowka, J.; Boser, S.; Botner, O.; Bottcher, J.;
Bourbeau, E.; Bradascio, F.; Braun, J.; Bron, S.; Brostean-Kaiser,
J.; Browne, S. A.; Burgman, A.; Burley, R.; Busse, R.; Campana, M.;
Carnie-Bronca, E.; Cataldo, M.; Chen, C.; Chirkin, D.; Choi, K.;
Clark, B.; Clark, K.; Clark, R.; Classen, L.; Coleman, A.; Collin,
G.; Connolly, A.; Conrad, J. M.; Coppin, P.; Correa, P.; Cowen,
D. F.; Cross, R.; Dappen, C.; Dave, P.; Deaconu, C.; De Clercq, C.;
De Kockere, S.; DeLaunay, J.; Dembinski, H.; Deoskar, K.; De Ridder,
S.; Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.; De With,
M.; DeYoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.; Dittmer,
M.; Dujmovic, H.; Dunkman, M.; DuVernois, M.; Dvorak, E.; Ehrhardt,
T.; Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson, P. A.;
Fan, K. L.; Farrag, K.; Fazely, A. R.; Fiedlschuster, S.; Fienberg,
A.; Filimonov, K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak,
A.; Friedman, E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher,
J.; Ganster, E.; Garcia, A.; Garrappa, S.; Gartner, A.; Gerhardt,
L.; Gernhaeuser, R.; Ghadimi, A.; Giri, P.; Glaser, C.; Glauch, T.;
Glusenkamp, T.; Goldschmidt, A.; Gonzalez, J.; Goswami, S.; Grant,
D.; Grégoire, T.; Griswold, S.; Gunduz, M.; Günther, C.; Haack, C.;
Hallgren, A.; Halliday, R.; Hallmann, S.; Halve, L.; Halzen, F.; Minh,
M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.; Haugen, J.; Haungs,
A.; Hauser, S.; Hebecker, D.; Heinen, D.; Helbing, K.; Hendricks, B.;
Henningsen, F.; Hettinger, E. C.; Hickford, S.; Hignight, J.; Hill,
C.; Hill, G. C.; Hoffman, K.; Hoffmann, B.; Hoffmann, R.; Hoinka, T.;
Holzapfel, K.; Hoshina, K.; Huang, F.; Huber, M.; Huber, T.; Huege,
T.; Hughes, K.; Hultqvist, K.; Hunnefeld, M.; Hussain, R.; In, S.;
Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.; Jeong, M.;
Jones, B.; Kalekin, O.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.;
Kappesser, D.; Karg, T.; Karl, M.; Katori, T.; Katz, U.; Kauer, M.;
Keivani, A.; Kellermann, M.; Kelley, J. L.; Kheirandish, A.; Kin,
K. i.; Kintscher, T.; Kiryluk, J.; Klein, S.; Koirala, R.; Kolanoski,
H.; Kontrimas, T.; Kopke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.;
Koundal, P.; Kovacevich, M.; Kowalski, M.; Kozynets, T.; Krauss, C.;
Kravchenko, I.; Krebs, R.; Kun, E.; Kurahashi, N.; Lad, N.; Lagunas
Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber, F. H.; Lazar, J.;
Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.; Lincetto, M.; Liu,
Q.; Liubarska, M.; Lohfink, E.; LoSecco, J.; Lozano Mariscal, C. J.;
Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma, W. Y.; Madsen,
J.; Mahn, K.; Makino, Y.; Mancina, S.; Mandalia, S.; Maris, I. C.;
Marka, S.; Marka, Z.; Maruyama, R. H.; Mase, K.; McElroy, T.; McNally,
F.; Mead, J. V.; Meagher, K.; Medina, A.; Meier, M.; Meighen-Berger,
S.; Meyers, Z.; Micallef, J.; Mockler, D.; Montaruli, T.; Moore, R.;
Morse, R.; Moulai, M.; Naab, R.; Nagai, R.; Naumann, U.; Necker, J.;
Nelles, A.; Nguyen, L. V.; Niederhausen, H.; Nisa, M.; Nowicki, S.;
Nygren, D.; Oberla, E.; Obertacke Pollmann, A.; Oehler, M.; Olivas,
A.; Omeliukh, A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Papp, L.;
Park, N.; Parker, G.; Paudel, E. N.; Paul, L.; Perez de los Heros,
C.; Peters, L.; Petersen, T.; Peterson, J.; Philippen, S.; Pieloth,
D.; Pieper, S.; Pinfold, J.; Pittermann, M.; Pizzuto, A.; Plaisier,
I.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price,
P. B.; Pries, B.; Przybylski, G.; Pyras, L.; Raab, C.; Raissi, A.;
Rameez, M.; Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.;
Reimann, R.; Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman,
M.; Riedel, B.; Riegel, M.; Roberts, E.; Robertson, S.; Roellinghoff,
G.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.;
Safa, I.; Saffer, J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.;
Sandstrom, P.; Santander, M.; Sarkar, S.; Sarkar, S.; Satalecka, K.;
Scharf, M. K.; Schaufel, M.; Schieler, H.; Schindler, S.; Schlunder,
P.; Schmidt, T.; Schneider, A.; Schneider, J.; Schröder, F. G.;
Schumacher, L. J.; Schwefer, G.; Sclafani, S.; Seckel, D.; Seunarine,
S.; Shaevitz, M. H.; Sharma, A.; Shefali, S.; Silva, M.; Skrzypek,
B.; Smith, D.; Smithers, B.; Snihur, R.; Soedingrekso, J.; Soldin,
D.; Soldner-Rembold, S.; Southall, D.; Spannfellner, C.; Spiczak, G.;
Spiering, C.; Stachurska, J.; Stamatikos, M.; Stanev, T.; Stein, R.;
Stettner, J.; Steuer, A.; Stezelberger, T.; Sturwald, T.; Stuttard,
T.; Sullivan, G. W.; Taboada, I.; Taketa, A.; Tanaka, H.; Tenholt, F.;
Ter-Antonyan, S.; Tilav, S.; Tischbein, F.; Tollefson, K.; Tomankova,
L.; Tönnis, C.; Torres, J.; Toscano, S.; Tosi, D.; Trettin, A.;
Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte, R.; Turley, C.;
Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.; Valtonen-Mattila,
N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom, D.; van Santen,
J.; Veberic, D.; Verpoest, S.; Vieregg, A. G.; Vraeghe, M.; Walck,
C.; Watson, T.; Weaver, C.; Weigel, P.; Weindl, A.; Weinstock,
L. S.; Weiss, M.; Weldert, J.; Welling, C.; Wendt, C.; Werthebach, J.;
Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.; Williams, D.; Wissel, S.;
Wolf, M.; Woschnagg, K.; Wrede, G.; Wren, S.; Wulff, J.; Xu, X.; Xu,
Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.; Zierke, S.
2022icrc.confE1182B Altcode: 2021arXiv210800283B; 2022PoS...395E1182B
The IceCube Neutrino Observatory has discovered a diffuse astrophysical
flux up to 10 PeV and is now planning a large extension with
IceCube-Gen2, including an optical array and a large radio array at
shallow depth [1]. Neutrino searches for energies >100 PeV are best
done with such shallow radio detectors like the Askaryan Radio Array
(ARA) or similar (buried as deep as 200 meters below the surface)
as they are cheaper to deploy. This poster explores the potential
of opportunistically burying radio antennas within the planned
IceCube-Gen2 detector volume (between 1350 meters and 2600 meters below
the surface). A hybrid detection of events in optical and radio could
substantially improve the uncertainty of neutrino cascade direction
as radio signals do not scatter in ice. We show the first results
of simulating neutrinos from an astrophysical and a cosmogenic flux
interacting with 9760 ARA-style vertically polarized radio antennas
distributed evenly across 122 strings.
---------------------------------------------------------
Title: Development of a scintillation and radio hybrid detector
array at the South Pole
Authors: Oehler, M.; Turcotte, R.; Abbasi, R.; Ackermann, M.; Adams,
J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Alispach, C. M.; Alves
Junior, A. A.; Amin, N. M. B.; An, R.; Andeen, K.; Anderson, T.;
Anton, G.; Arguelles, C.; Ashida, Y.; Axani, S.; Bai, X.; Balagopal
V., A.; Barbano, A. M.; Barwick, S. W.; Bastian, B.; Basu, V.;
Baur, S.; Bay, R. C.; Beatty, J. J.; Becker, K. H.; Becker Tjus,
J.; Bellenghi, C.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson,
D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Boddenberg,
M.; Bontempo, F.; Borowka, J.; Boser, S.; Botner, O.; Bottcher, J.;
Bourbeau, E.; Bradascio, F.; Braun, J.; Bron, S.; Brostean-Kaiser,
J.; Browne, S. A.; Burgman, A.; Burley, R.; Busse, R.; Campana, M.;
Carnie-Bronca, E.; Chen, C.; Chirkin, D.; Choi, K.; Clark, B.; Clark,
K.; Classen, L.; Coleman, A.; Collin, G.; Conrad, J. M.; Coppin,
P.; Correa, P.; Cowen, D. F.; Cross, R.; Dappen, C.; Dave, P.; De
Clercq, C.; DeLaunay, J.; Dembinski, H.; Deoskar, K.; De Ridder, S.;
Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.; De With, M.;
DeYoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.; Dittmer, M.;
Dujmovic, H.; Dunkman, M.; DuVernois, M.; Dvorak, E.; Ehrhardt, T.;
Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson, P. A.; Fan,
K. L.; Fazely, A. R.; Fiedlschuster, S.; Fienberg, A.; Filimonov,
K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak, A.; Friedman,
E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher, J.; Ganster,
E.; Garcia, A.; Garrappa, S.; Gerhardt, L.; Ghadimi, A.; Glaser, C.;
Glauch, T.; Glusenkamp, T.; Goldschmidt, A.; Gonzalez, J.; Goswami,
S.; Grant, D.; Grégoire, T.; Griswold, S.; Gunduz, M.; Günther,
C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve, L.; Halzen, F.;
Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.; Haungs, A.;
Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.; Hettinger,
E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.; Hoffman,
K.; Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina, K.; Huang,
F.; Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.; Hussain, R.;
In, S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.; Jeong,
M.; Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.; Kappesser,
D.; Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.; Kellermann,
M.; Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher, T.;
Kiryluk, J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas, T.;
Kopke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.;
Kovacevich, M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.;
Lad, N.; Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber,
F. H.; Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.;
Lincetto, M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal,
C. J.; Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma,
W. Y.; Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.;
Maruyama, R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.;
Meagher, K.; Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.;
Mockler, D.; Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab,
R.; Nagai, R.; Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen,
H.; Nisa, M.; Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Olivas,
A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.; Parker, G.;
Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters, L.; Peterson,
J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann, M.; Pizzuto,
A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price,
P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.; Rameez, M.;
Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.; Reimann, R.;
Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman, M.; Riedel,
B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen, M.; Rott,
C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.; Saffer,
J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander, M.;
Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer,
A.; Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turley, C.;
Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.; Valtonen-Mattila,
N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom, D.; van Santen,
J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.; Weaver, C.;
Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt, C.; Werthebach,
J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.; Williams, D.; Wolf,
M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu, X.; Xu, Y.; Yanez, J. P.;
Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.
2022icrc.confE.225O Altcode: 2022PoS...395E.225O; 2021arXiv210709983O
At the IceCube Neutrino Observatory, a Surface Array Enhancement is
planned, consisting of 32 hybrid stations, placed within the current
IceTop footprint. This surface enhancement will considerably increase
the detection sensitivity to cosmic rays in the 100 TeV to 1 EeV primary
energy range, measure the effects of snow accumulation on the existing
IceTop tanks and serve as R&D for the possible future large-scale
surface array of IceCube-Gen2. Each station has one central hybrid DAQ,
which reads out 8 scintillation detectors and 3 radio antennas. The
radio antenna SKALA-2 is used in this array due to its low-noise,
high amplification and sensitivity in the 70-350 MHz frequency
band. Every scintillation detector has an active area of 1.5 m$^2$
organic plastic scintillators connected by wavelength-shifting fibers,
which are connected to a silicon photomultiplier. The signals from the
scintillation detectors are integrated and digitized by a local custom
electronics board and transferred to the central DAQ. When triggered
by the scintillation detectors, the filtered and amplified analog
waveforms from the radio antennas are read out and digitized by the
central DAQ. A full prototype station has been developed and built
and was installed at the South Pole in January 2020. It is planned
to install the full array by 2026. In this contribution the hardware
design of the array as well as the installation plans will be presented.
---------------------------------------------------------
Title: Discrimination of Muons for Mass Composition Studies of
Inclined Air Showers Detected with IceTop
Authors: Balagopal V., A.; IceCube; Abbasi, R.; Ackermann, M.; Adams,
J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Alispach, C. M.; Alves Junior,
A. A.; Amin, N. M. B.; An, R.; Andeen, K.; Anderson, T.; Anton, G.;
Arguelles, C.; Ashida, Y.; Axani, S.; Bai, X.; Barbano, A. M.; Barwick,
S. W.; Bastian, B.; Basu, V.; Baur, S.; Bay, R. C.; Beatty, J. J.;
Becker, K. H.; Becker Tjus, J.; Bellenghi, C.; BenZvi, S.; Berley, D.;
Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.;
Blot, S.; Boddenberg, M.; Bontempo, F.; Borowka, J.; Boser, S.; Botner,
O.; Bottcher, J.; Bourbeau, E.; Bradascio, F.; Braun, J.; Bron, S.;
Brostean-Kaiser, J.; Browne, S. A.; Burgman, A.; Burley, R.; Busse,
R.; Campana, M.; Carnie-Bronca, E.; Chen, C.; Chirkin, D.; Choi, K.;
Clark, B.; Clark, K.; Classen, L.; Coleman, A.; Collin, G.; Conrad,
J. M.; Coppin, P.; Correa, P.; Cowen, D. F.; Cross, R.; Dappen, C.;
Dave, P.; De Clercq, C.; DeLaunay, J.; Dembinski, H.; Deoskar, K.;
De Ridder, S.; Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.;
De With, M.; DeYoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.;
Dittmer, M.; Dujmovic, H.; Dunkman, M.; DuVernois, M.; Dvorak, E.;
Ehrhardt, T.; Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson,
P. A.; Fan, K. L.; Fazely, A. R.; Fiedlschuster, S.; Fienberg, A.;
Filimonov, K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak, A.;
Friedman, E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher, J.;
Ganster, E.; Garcia, A.; Garrappa, S.; Gerhardt, L.; Ghadimi, A.;
Glaser, C.; Glauch, T.; Glusenkamp, T.; Goldschmidt, A.; Gonzalez,
J.; Goswami, S.; Grant, D.; Grégoire, T.; Griswold, S.; Gunduz, M.;
Günther, C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve, L.; Halzen,
F.; Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.; Haungs,
A.; Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.; Hettinger,
E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.; Hoffman, K.;
Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina, K.; Huang, F.;
Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.; Hussain, R.; In,
S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.; Jeong, M.;
Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.; Kappesser, D.;
Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.; Kellermann, M.;
Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher, T.; Kiryluk,
J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas, T.; Kopke, L.;
Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.; Kovacevich,
M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.; Lad, N.;
Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber, F. H.;
Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.; Lincetto,
M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal, C. J.;
Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma, W. Y.;
Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.; Maruyama,
R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.; Meagher, K.;
Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.; Mockler, D.;
Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab, R.; Nagai, R.;
Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen, H.; Nisa, M.;
Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler, M.; Olivas,
A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.; Parker, G.;
Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters, L.; Peterson,
J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann, M.; Pizzuto,
A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price,
P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.; Rameez, M.;
Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.; Reimann, R.;
Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman, M.; Riedel,
B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen, M.; Rott,
C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.; Saffer,
J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander, M.;
Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer,
A.; Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte,
R.; Turley, C.; Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.;
Valtonen-Mattila, N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom,
D.; van Santen, J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.;
Weaver, C.; Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt,
C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.;
Williams, D.; Wolf, M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu, X.;
Xu, Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.
2022icrc.confE.212B Altcode: 2021arXiv210711293B; 2022PoS...395E.212B
IceTop, the surface array of IceCube, measures air showers from cosmic
rays within the energy range of 1 PeV to a few EeV and a zenith angle
range of up to $\approx$ 36$^\circ$. This detector array can also
measure air showers arriving at larger zenith angles at energies above
20 PeV. Air showers from lighter primaries arriving at the array will
produce fewer muons when compared to heavier cosmic-ray primaries. A
discrimination of these muons from the electromagnetic component in the
shower can therefore allow a measurement of the primary mass. A study
to discriminate muons using Monte-Carlo air showers of energies 20-100
PeV and within the zenith angular range of 45$^\circ$-60$^\circ$ will
be presented. The discrimination is done using charge and time-based
cuts which allows us to select muon-like signals in each shower. The
methodology of this analysis, which aims at categorizing the measured
air showers as light or heavy on an event-by-event basis, will be
discussed.
---------------------------------------------------------
Title: Multimessenger NuEM Alerts with AMON
Authors: Ayala, H.; Hawc; Abeysekara, A. U.; Albert, A.; Alfaro,
R.; Alvarez, C.; Álvarez Romero, J. d. D.; Camacho, J. R. Angeles;
Arteaga Velazquez, J. C.; Kollamparambil, A. B.; Avila Rojas, D. O.;
Ayala Solares, H. A.; Babu, R.; Baghmanyan, V.; Barber, A. S.;
Becerra Gonzalez, J.; Belmont-Moreno, E.; Berley, D.; Brisbois, C.;
Caballero Mora, K. S.; Capistrán, T.; Carramiñana, A.; Casanova,
S.; Chaparro-Amaro, O.; Cotti, U.; Cotzomi, J.; Coutiño de Leon,
S.; de la Fuente, E.; de León, C. L.; Diaz, L.; Diaz Hernandez,
R.; Díaz Vélez, J. C.; Dingus, B.; Durocher, M.; Ellsworth, R.;
Engel, K.; Espinoza Hernández, M. C.; Fan, J.; Fang, K.; Fernandez
Alonso, M.; Fick, B.; Fleischhack, H.; Flores, J. L.; Fraija, N. I.;
Garcia Aguilar, D.; Garcia-Gonzalez, J. A.; García-Luna, J. L.;
García-Torales, G.; Garfias, F.; Giacinti, G.; Goksu, H.; González,
M. M.; Goodman, J. A.; Harding, J. P.; Hernández Cadena, S.; Herzog,
I.; Hinton, J.; Hona, B.; Huang, D.; Hueyotl-Zahuantitla, F.; Hui, M.;
Humensky, B.; Hüntemeyer, P.; Iriarte, A.; Jardin-Blicq, A.; Jhee, H.;
Joshi, V.; Kieda, D.; Kunde, G. J.; Kunwar, S.; Lara, A.; Lee, J.; Lee,
W. H.; Lennarz, D.; Vargas, H. Leon; Linnemann, J.; Longinotti, A. L.;
Lopez-Coto, R.; Luis-Raya, G.; Lundeen, J.; Malone, K.; Marandon,
V.; Martinez, O.; Martinez Castellanos, I.; Martínez Huerta, H.;
Martínez-Castro, J.; Matthews, J.; McEnery, J.; Miranda-Romagnoli,
P.; Morales Soto, J. A.; Moreno Barbosa, E.; Mostafa, M.; Nayerhoda,
A.; Nellen, L.; Newbold, M.; Nisa, M. U.; Noriega-Papaqui, R.;
Olivera-Nieto, L.; Omodei, N.; Peisker, A.; Pérez Araujo, Y.;
Pérez Pérez, E. G.; Rho, C. D.; Rivière, C.; Rosa-Gonzalez, D.;
Ruiz-Velasco, E.; Ryan, J.; Salazar, H. I.; Salesa Greus, F.; Sandoval,
A.; Schneider, M.; Schoorlemmer, H.; Serna-Franco, J.; Sinnis, G.;
Smith, A. J.; Springer, W. R.; Surajbali, P.; Taboada, I.; Tanner,
M.; Torres, I.; Torres Escobedo, R.; Turner, R.; Ureña-Mena, F.;
Villaseñor, L.; Wang, X.; Watson, I. J.; Weisgarber, T.; Werner, F.;
Willox, E.; Wood, J.; Yodh, G.; Zepeda, A.; Zhou, H.; IceCube; Abbasi,
R.; Ackermann, M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.;
Alispach, C. M.; Alves Junior, A. A.; Amin, N. M. B.; An, R.; Andeen,
K.; Anderson, T.; Anton, G.; Arguelles, C.; Ashida, Y.; Axani, S.;
Bai, X.; Balagopal V., A.; Barbano, A. M.; Barwick, S. W.; Bastian,
B.; Basu, V.; Baur, S.; Bay, R. C.; Beatty, J. J.; Becker, K. H.;
Becker Tjus, J.; Bellenghi, C.; BenZvi, S.; Berley, D.; Bernardini,
E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.;
Boddenberg, M.; Bontempo, F.; Borowka, J.; Boser, S.; Botner, O.;
Bottcher, J.; Bourbeau, E.; Bradascio, F.; Braun, J.; Bron, S.;
Brostean-Kaiser, J.; Browne, S. A.; Burgman, A.; Burley, R.; Busse,
R.; Campana, M.; Carnie-Bronca, E.; Chen, C.; Chirkin, D.; Choi, K.;
Clark, B.; Clark, K.; Classen, L.; Coleman, A.; Collin, G.; Conrad,
J. M.; Coppin, P.; Correa, P.; Cowen, D. F.; Cross, R.; Dappen, C.;
Dave, P.; De Clercq, C.; DeLaunay, J.; Dembinski, H.; Deoskar, K.;
De Ridder, S.; Desai, A.; Desiati, P.; de Vries, K.; de Wasseige, G.;
De With, M.; DeYoung, T.; Dharani, S.; Diaz, A.; Diaz-Velez, J. C.;
Dittmer, M.; Dujmovic, H.; Dunkman, M.; DuVernois, M.; Dvorak, E.;
Ehrhardt, T.; Eller, P.; Engel, R.; Erpenbeck, H.; Evans, J.; Evenson,
P. A.; Fan, K. L.; Fazely, A. R.; Fiedlschuster, S.; Fienberg, A.;
Filimonov, K.; Finley, C.; Fischer, L.; Fox, D. B.; Franckowiak, A.;
Friedman, E.; Fritz, A.; Furst, P.; Gaisser, T. K.; Gallagher, J.;
Ganster, E.; Garcia, A.; Garrappa, S.; Gerhardt, L.; Ghadimi, A.;
Glaser, C.; Glauch, T.; Glusenkamp, T.; Goldschmidt, A.; Gonzalez,
J.; Goswami, S.; Grant, D.; Grégoire, T.; Griswold, S.; Gunduz,
M.; Günther, C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve, L.;
Halzen, F.; Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.;
Haungs, A.; Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.;
Hettinger, E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.;
Hoffman, K.; Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina,
K.; Huang, F.; Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.;
Hussain, R.; In, S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze,
G.; Jeong, M.; Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.;
Kappesser, D.; Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.;
Kellermann, M.; Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher,
T.; Kiryluk, J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas,
T.; Kopke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.;
Kovacevich, M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.;
Lad, N.; Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber,
F. H.; Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.;
Lincetto, M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal,
C. J.; Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma,
W. Y.; Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.;
Maruyama, R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.;
Meagher, K.; Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.;
Mockler, D.; Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab,
R.; Nagai, R.; Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen,
H.; Nisa, M.; Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler,
M.; Olivas, A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.;
Parker, G.; Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters,
L.; Peterson, J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann,
M.; Pizzuto, A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez,
M.; Price, P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.;
Rameez, M.; Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.;
Reimann, R.; Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman,
M.; Riedel, B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen,
M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.;
Saffer, J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander,
M.; Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer,
A.; Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte,
R.; Turley, C.; Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.;
Valtonen-Mattila, N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom,
D.; van Santen, J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.;
Weaver, C.; Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt,
C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.;
Williams, D.; Wolf, M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu, X.;
Xu, Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.
2022icrc.confE.958A Altcode: 2021arXiv210804920A; 2022PoS...395E.958A
The Astrophysical Multimessenger Observatory Network (AMON), has
developed a real-time multi-messenger alert system. The system performs
coincidence analyses of datasets from gamma-ray and neutrino detectors,
making the Neutrino-Electromagnetic (NuEM) alert channel. For these
analyses, AMON takes advantage of sub-threshold events, i.e., events
that by themselves are not significant in the individual detectors. The
main purpose of this channel is to search for gamma-ray counterparts
of neutrino events. We will describe the different analyses that make
up this channel and present a selection of recent results.
---------------------------------------------------------
Title: Density of GeV Muons Measured with IceTop
Authors: Soldin, D.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J.;
Ahlers, M.; Ahrens, M.; Alispach, C. M.; Alves Junior, A. A.; Amin,
N. M. B.; An, R.; Andeen, K.; Anderson, T.; Anton, G.; Arguelles,
C.; Ashida, Y.; Axani, S.; Bai, X.; Balagopal V., A.; Barbano, A. M.;
Barwick, S. W.; Bastian, B.; Basu, V.; Baur, S.; Bay, R. C.; Beatty,
J. J.; Becker, K. H.; Becker Tjus, J.; Bellenghi, C.; BenZvi, S.;
Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.;
Blaufuss, E.; Blot, S.; Boddenberg, M.; Bontempo, F.; Borowka, J.;
Boser, S.; Botner, O.; Bottcher, J.; Bourbeau, E.; Bradascio, F.;
Braun, J.; Bron, S.; Brostean-Kaiser, J.; Browne, S. A.; Burgman,
A.; Burley, R.; Busse, R.; Campana, M.; Carnie-Bronca, E.; Chen, C.;
Chirkin, D.; Choi, K.; Clark, B.; Clark, K.; Classen, L.; Coleman, A.;
Collin, G.; Conrad, J. M.; Coppin, P.; Correa, P.; Cowen, D. F.; Cross,
R.; Dappen, C.; Dave, P.; De Clercq, C.; DeLaunay, J.; Dembinski,
H.; Deoskar, K.; De Ridder, S.; Desai, A.; Desiati, P.; de Vries,
K.; de Wasseige, G.; De With, M.; DeYoung, T.; Dharani, S.; Diaz, A.;
Diaz-Velez, J. C.; Dittmer, M.; Dujmovic, H.; Dunkman, M.; DuVernois,
M.; Dvorak, E.; Ehrhardt, T.; Eller, P.; Engel, R.; Erpenbeck, H.;
Evans, J.; Evenson, P. A.; Fan, K. L.; Fazely, A. R.; Fiedlschuster,
S.; Fienberg, A.; Filimonov, K.; Finley, C.; Fischer, L.; Fox, D. B.;
Franckowiak, A.; Friedman, E.; Fritz, A.; Furst, P.; Gaisser, T. K.;
Gallagher, J.; Ganster, E.; Garcia, A.; Garrappa, S.; Gerhardt, L.;
Ghadimi, A.; Glaser, C.; Glauch, T.; Glusenkamp, T.; Goldschmidt, A.;
Gonzalez, J.; Goswami, S.; Grant, D.; Grégoire, T.; Griswold, S.;
Gunduz, M.; Günther, C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve,
L.; Halzen, F.; Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.;
Haungs, A.; Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.;
Hettinger, E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.;
Hoffman, K.; Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina,
K.; Huang, F.; Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.;
Hussain, R.; In, S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze,
G.; Jeong, M.; Jones, B.; Kang, D.; Kang, W.; Kang, X.; Kappes, A.;
Kappesser, D.; Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.;
Kellermann, M.; Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher,
T.; Kiryluk, J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas,
T.; Kopke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.;
Kovacevich, M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.;
Lad, N.; Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber,
F. H.; Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.;
Lincetto, M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal,
C. J.; Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma,
W. Y.; Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.;
Maruyama, R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.;
Meagher, K.; Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.;
Mockler, D.; Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab,
R.; Nagai, R.; Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen,
H.; Nisa, M.; Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler,
M.; Olivas, A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.;
Parker, G.; Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters,
L.; Peterson, J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann,
M.; Pizzuto, A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez,
M.; Price, P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.;
Rameez, M.; Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.;
Reimann, R.; Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman,
M.; Riedel, B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen,
M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.;
Saffer, J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander,
M.; Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali,
S.; Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso,
J.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska, J.;
Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer, A.;
Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte,
R.; Turley, C.; Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.;
Valtonen-Mattila, N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom,
D.; van Santen, J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.;
Weaver, C.; Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt,
C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.;
Williams, D.; Wolf, M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu, X.;
Xu, Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.
2022icrc.confE.342S Altcode: 2022PoS...395E.342S; 2021arXiv210709583S
We present a measurement of the density of GeV muons in near-vertical
air showers using three years of data recorded by the IceTop array at
the South Pole. We derive the muon densities as functions of energy
at reference distances of 600 m and 800 m for primary energies between
2.5 PeV and 40 PeV and between 9 PeV and 120 PeV, respectively, at an
atmospheric depth of about $690\,\mathrm{g/cm}^2$. The measurements are
consistent with the predicted muon densities obtained from Sibyll~2.1
assuming any physically reasonable cosmic ray flux model. However,
comparison to the post-LHC models QGSJet-II.04 and EPOS-LHC shows
that the post-LHC models yield a higher muon density than predicted
by Sibyll 2.1 and are in tension with the experimental data for air
shower energies between 2.5 PeV and 120 PeV.
---------------------------------------------------------
Title: Studies of a muon-based mass sensitive parameter for the
IceTop surface array
Authors: Kang, D.; Browne, S. A.; Haungs, A.; Abbasi, R.; Ackermann,
M.; Adams, J.; Aguilar, J.; Ahlers, M.; Ahrens, M.; Alispach, C. M.;
Alves Junior, A. A.; Amin, N. M. B.; An, R.; Andeen, K.; Anderson, T.;
Anton, G.; Arguelles, C.; Ashida, Y.; Axani, S.; Bai, X.; Balagopal V.,
A.; Barbano, A. M.; Barwick, S. W.; Bastian, B.; Basu, V.; Baur, S.;
Bay, R. C.; Beatty, J. J.; Becker, K. H.; Becker Tjus, J.; Bellenghi,
C.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder,
G.; Bindig, D.; Blaufuss, E.; Blot, S.; Boddenberg, M.; Bontempo,
F.; Borowka, J.; Boser, S.; Botner, O.; Bottcher, J.; Bourbeau, E.;
Bradascio, F.; Braun, J.; Bron, S.; Brostean-Kaiser, J.; Burgman,
A.; Burley, R.; Busse, R.; Campana, M.; Carnie-Bronca, E.; Chen, C.;
Chirkin, D.; Choi, K.; Clark, B.; Clark, K.; Classen, L.; Coleman, A.;
Collin, G.; Conrad, J. M.; Coppin, P.; Correa, P.; Cowen, D. F.; Cross,
R.; Dappen, C.; Dave, P.; De Clercq, C.; DeLaunay, J.; Dembinski,
H.; Deoskar, K.; De Ridder, S.; Desai, A.; Desiati, P.; de Vries,
K.; de Wasseige, G.; De With, M.; DeYoung, T.; Dharani, S.; Diaz, A.;
Diaz-Velez, J. C.; Dittmer, M.; Dujmovic, H.; Dunkman, M.; DuVernois,
M.; Dvorak, E.; Ehrhardt, T.; Eller, P.; Engel, R.; Erpenbeck, H.;
Evans, J.; Evenson, P. A.; Fan, K. L.; Fazely, A. R.; Fiedlschuster,
S.; Fienberg, A.; Filimonov, K.; Finley, C.; Fischer, L.; Fox, D. B.;
Franckowiak, A.; Friedman, E.; Fritz, A.; Furst, P.; Gaisser, T. K.;
Gallagher, J.; Ganster, E.; Garcia, A.; Garrappa, S.; Gerhardt, L.;
Ghadimi, A.; Glaser, C.; Glauch, T.; Glusenkamp, T.; Goldschmidt, A.;
Gonzalez, J.; Goswami, S.; Grant, D.; Grégoire, T.; Griswold, S.;
Gunduz, M.; Günther, C.; Haack, C.; Hallgren, A.; Halliday, R.; Halve,
L.; Halzen, F.; Minh, M. Ha; Hanson, K.; Hardin, J.; Harnisch, A. A.;
Hauser, S.; Hebecker, D.; Helbing, K.; Henningsen, F.; Hettinger,
E. C.; Hickford, S.; Hignight, J.; Hill, C.; Hill, G. C.; Hoffman,
K.; Hoffmann, R.; Hoinka, T.; Hokanson-Fasig, B.; Hoshina, K.; Huang,
F.; Huber, M.; Huber, T.; Hultqvist, K.; Hunnefeld, M.; Hussain,
R.; In, S.; Iovine, N.; Ishihara, A.; Jansson, M.; Japaridze, G.;
Jeong, M.; Jones, B.; Kang, W.; Kang, X.; Kappes, A.; Kappesser, D.;
Karg, T.; Karl, M.; Karle, A.; Katz, U.; Kauer, M.; Kellermann, M.;
Kelley, J. L.; Kheirandish, A.; Kin, K. i.; Kintscher, T.; Kiryluk,
J.; Klein, S.; Koirala, R.; Kolanoski, H.; Kontrimas, T.; Kopke, L.;
Kopper, C.; Kopper, S.; Koskinen, D. J.; Koundal, P.; Kovacevich,
M.; Kowalski, M.; Kozynets, T.; Kun, E.; Kurahashi, N.; Lad, N.;
Lagunas Gualda, C.; Lanfranchi, J.; Larson, M. J.; Lauber, F. H.;
Lazar, J.; Lee, J.; Leonard, K.; Leszczyńska, A.; Li, Y.; Lincetto,
M.; Liu, Q.; Liubarska, M.; Lohfink, E.; Lozano Mariscal, C. J.;
Lu, L.; Lucarelli, F.; Ludwig, A.; Luszczak, W.; Lyu, Y.; Ma, W. Y.;
Madsen, J.; Mahn, K.; Makino, Y.; Mancina, S.; Maris, I. C.; Maruyama,
R. H.; Mase, K.; McElroy, T.; McNally, F.; Mead, J. V.; Meagher, K.;
Medina, A.; Meier, M.; Meighen-Berger, S.; Micallef, J.; Mockler, D.;
Montaruli, T.; Moore, R.; Morse, R.; Moulai, M.; Naab, R.; Nagai, R.;
Naumann, U.; Necker, J.; Nguyen, L. V.; Niederhausen, H.; Nisa, M.;
Nowicki, S.; Nygren, D.; Obertacke Pollmann, A.; Oehler, M.; Olivas,
A.; O'Sullivan, E.; Pandya, H.; Pankova, D.; Park, N.; Parker, G.;
Paudel, E. N.; Paul, L.; Perez de los Heros, C.; Peters, L.; Peterson,
J.; Philippen, S.; Pieloth, D.; Pieper, S.; Pittermann, M.; Pizzuto,
A.; Plum, M.; Popovych, Y.; Porcelli, A.; Prado Rodriguez, M.; Price,
P. B.; Pries, B.; Przybylski, G.; Raab, C.; Raissi, A.; Rameez, M.;
Rawlins, K.; Rea, I. C.; Rehman, A.; Reichherzer, P.; Reimann, R.;
Renzi, G.; Resconi, E.; Reusch, S.; Rhode, W.; Richman, M.; Riedel,
B.; Roberts, E.; Robertson, S.; Roellinghoff, G.; Rongen, M.; Rott,
C.; Ruhe, T.; Ryckbosch, D.; Rysewyk Cantu, D.; Safa, I.; Saffer,
J.; Sanchez Herrera, S.; Sandrock, A.; Sandroos, J.; Santander, M.;
Sarkar, S.; Sarkar, S.; Satalecka, K.; Scharf, M. K.; Schaufel, M.;
Schieler, H.; Schindler, S.; Schlunder, P.; Schmidt, T.; Schneider,
A.; Schneider, J.; Schröder, F. G.; Schumacher, L. J.; Schwefer,
G.; Sclafani, S.; Seckel, D.; Seunarine, S.; Sharma, A.; Shefali, S.;
Silva, M.; Skrzypek, B.; Smithers, B.; Snihur, R.; Soedingrekso, J.;
Soldin, D.; Spannfellner, C.; Spiczak, G.; Spiering, C.; Stachurska,
J.; Stamatikos, M.; Stanev, T.; Stein, R.; Stettner, J.; Steuer,
A.; Stezelberger, T.; Sturwald, T.; Stuttard, T.; Sullivan, G. W.;
Taboada, I.; Tenholt, F.; Ter-Antonyan, S.; Tilav, S.; Tischbein,
F.; Tollefson, K.; Tomankova, L.; Tönnis, C.; Toscano, S.; Tosi,
D.; Trettin, A.; Tselengidou, M.; Tung, C.; Turcati, A.; Turcotte,
R.; Turley, C.; Twagirayezu, J. P.; Ty, B.; Unland Elorrieta, M.;
Valtonen-Mattila, N.; Vandenbroucke, J.; van Eijndhoven, N.; Vannerom,
D.; van Santen, J.; Verpoest, S.; Vraeghe, M.; Walck, C.; Watson, T.;
Weaver, C.; Weigel, P.; Weindl, A.; Weiss, M.; Weldert, J.; Wendt,
C.; Werthebach, J.; Weyrauch, M.; Whitehorn, N.; Wiebusch, C. H.;
Williams, D.; Wolf, M.; Woschnagg, K.; Wrede, G.; Wulff, J.; Xu, X.;
Xu, Y.; Yanez, J. P.; Yoshida, S.; Yu, S.; Yuan, T.; Zhang, Z.
2022icrc.confE.312K Altcode: 2022PoS...395E.312K; 2021arXiv210902506K
IceTop is the surface instrumentation of the IceCube Neutrino
Observatory at the South Pole. It is designed to measure extensive
air showers of cosmic rays in the primary energy range from PeV to
EeV. Air showers induced by heavier primary particles develop earlier
in the atmosphere and produce more muons observable at ground level
than lighter cosmic rays with the same primary energy. Therefore,
the fraction of muons to all charged particles measured by IceTop
characterizes the mass of primary particles. This analysis seeks
a muon-based mass sensitive parameter by using the charge signal
distribution for each individual cosmic ray event. In this contribution
we present the analysis method for the mass-sensitive parameter and
our studies of its possible application to the measurement of cosmic
ray mass composition with the IceTop surface array.
---------------------------------------------------------
Title: Advancing the Landscape of Multimessenger Science in the
Next Decade
Authors: Engel, Kristi; Lewis, Tiffany; Stein Muzio, Marco; Venters,
Tonia M.; Ahlers, Markus; Albert, Andrea; Allen, Alice; Ayala Solares,
Hugo Alberto; Anandagoda, Samalka; Andersen, Thomas; Antier, Sarah;
Alvarez-Castillo, David; Bar, Olaf; Beznosko, Dmitri; Bibrzyck,
Łukasz; Brazier, Adam; Brisbois, Chad; Brose, Robert; Brown, Duncan
A.; Bulla, Mattia; Burgess, J. Michael; Burns, Eric; Chirenti, Cecilia;
Ciprini, Stefano; Clay, Roger; Coughlin, Michael W.; Cummings, Austin;
D'Elia, Valerio; Dai, Shi; Dietrich, Tim; Di Lalla, Niccolò; Dingus,
Brenda; Durocher, Mora; Eser, Johannes; Filipović, Miroslav D.;
Fleischhack, Henrike; Foucart, Francois; Frontczak, Michał; Fryer,
Christopher L.; Gamble, Ronald S.; Gasparrini, Dario; Giardino, Marco;
Goodman, Jordan; Harding, J. Patrick; Hare, Jeremy; Holley-Bockelmann,
Kelly; Homola, Piotr; Hughes, Kaeli A.; Humensky, Brian; Inoue,
Yoshiyuki; Jaffe, Tess; Kargaltsev, Oleg; Kierans, Carolyn; Kneller,
James P.; Leto, Cristina; Lucarelli, Fabrizio; Martínez-Huerta,
Humberto; Maselli, Alessandro; Meli, Athina; Meyers, Patrick; Mueller,
Guido; Nasipak, Zachary; Negro, Michela; Niedźwiecki, Michał;
Noble, Scott C.; Omodei, Nicola; Oslowski, Stefan; Perri, Matteo;
Piekarczyk, Marcin; Pittori, Carlotta; Polenta, Gianluca; Prechelt,
Remy L.; Principe, Giacomo; Racusin, Judith; Rzecki, Krzysztof;
Sambruna, Rita M.; Schlieder, Joshua E.; Shoemaker, David; Smale,
Alan; Sośnicki, Tomasz; Stein, Robert; Stuglik, Sławomir; Teuben,
Peter; Thorpe, James Ira; Verbiest, Joris P.; Verrecchia, Franceso;
Vitale, Salvatore; Wadiasingh, Zorawar; Wibig, Tadeusz; Willox, Elijah;
Wilson-Hodge, Colleen A.; Wood, Joshua; Yang, Hui; Zhang, Haocheng
2022arXiv220310074E Altcode:
The last decade has brought about a profound transformation in
multimessenger science. Ten years ago, facilities had been built or
were under construction that would eventually discover the nature
of objects in our universe could be detected through multiple
messengers. Nonetheless, multimessenger science was hardly more than
a dream. The rewards for our foresight were finally realized through
IceCube's discovery of the diffuse astrophysical neutrino flux, the
first observation of gravitational waves by LIGO, and the first joint
detections in gravitational waves and photons and in neutrinos and
photons. Today we live in the dawn of the multimessenger era. The
successes of the multimessenger campaigns of the last decade
have pushed multimessenger science to the forefront of priority
science areas in both the particle physics and the astrophysics
communities. Multimessenger science provides new methods of testing
fundamental theories about the nature of matter and energy, particularly
in conditions that are not reproducible on Earth. This white paper will
present the science and facilities that will provide opportunities
for the particle physics community renew its commitment and maintain
its leadership in multimessenger science.
---------------------------------------------------------
Title: Classification of AT2021afpi, a possible counterpart to
IC211125A, as a classical nova
Authors: Stein, Robert; Karambelkar, Viraj; Kasliwal, Mansi M.;
Sharma, Yashvi; De, Kishalay; Franckowiak, Anna
2021ATel15069....1S Altcode:
AT2021afpi was a bright optical transient discovered by MASTER (ATEL
#15067), and reported by them as a possible electromagnetic counterpart
to high-energy neutrino IceCube-211125A (GCN #31126).
---------------------------------------------------------
Title: Searching for solar KDAR with DUNE
Authors: Abed Abud, A.; Abi, B.; Acciarri, R.; Acero, M. A.; Adames,
M. R.; Adamov, G.; Adams, D.; Adinolfi, M.; Aduszkiewicz, A.; Aguilar,
J.; Ahmad, Z.; Ahmed, J.; Ali-Mohammadzadeh, B.; Alion, T.; Allison,
K.; Alonso Monsalve, S.; Alrashed, M.; Alt, C.; Alton, A.; Amedo,
P.; Anderson, J.; Andreopoulos, C.; Andreotti, M.; Andrews, M. P.;
Andrianala, F.; Andringa, S.; Anfimov, N.; Ankowski, A.; Antoniassi,
M.; Antonova, M.; Antoshkin, A.; Antusch, S.; Aranda-Fernandez, A.;
Ariga, A.; Arnold, L. O.; Arroyave, M. A.; Asaadi, J.; Asquith, L.;
Aurisano, A.; Aushev, V.; Autiero, D.; Ayala-Torres, M.; Azfar, F.;
Back, A.; Back, H.; Back, J. J.; Backhouse, C.; Baesso, P.; Bagaturia,
I.; Bagby, L.; Balashov, N.; Balasubramanian, S.; Baldi, P.; Baller,
B.; Bambah, B.; Barao, F.; Barenboim, G.; Barker, G. J.; Barkhouse,
W.; Barnes, C.; Barr, G.; Barranco Monarca, J.; Barros, A.; Barros,
N.; Barrow, J. L.; Basharina-Freshville, A.; Bashyal, A.; Basque, V.;
Belchior, E.; Battat, J. B. R.; Battisti, F.; Bay, F.; Bazo Alba,
J. L.; Beacom, J. F.; Bechetoille, E.; Behera, B.; Bellantoni, L.;
Bellettini, G.; Bellini, V.; Beltramello, O.; Belver, D.; Benekos,
N.; Benitez Montiel, C.; Bento Neves, F.; Berger, J.; Berkman, S.;
Bernardini, P.; Berner, R. M.; Berns, H.; Bertolucci, S.; Betancourt,
M.; Betancur Rodríguez, A.; Bevan, A.; Bezerra, T. J. C.; Bhatnagar,
V.; Bhattacharjee, M.; Bhuller, S.; Bhuyan, B.; Biagi, S.; Bian, J.;
Biassoni, M.; Biery, K.; Bilki, B.; Bishai, M.; Bitadze, A.; Blake,
A.; Blaszczyk, F. D. M.; Blazey, G. C.; Blucher, E.; Boissevain, J.;
Bolognesi, S.; Bolton, T.; Bomben, L.; Bonesini, M.; Bongrand, M.;
Bonini, F.; Booth, A.; Booth, C.; Boran, F.; Bordoni, S.; Borkum, A.;
Boschi, T.; Bostan, N.; Bour, P.; Bourgeois, C.; Boyd, S. B.; Boyden,
D.; Bracinik, J.; Braga, D.; Brailsford, D.; Branca, A.; Brandt,
A.; Bremer, J.; Brew, C.; Brianne, E.; Brice, S. J.; Brizzolari, C.;
Bromberg, C.; Brooijmans, G.; Brooke, J.; Bross, A.; Brunetti, G.;
Brunetti, M.; Buchanan, N.; Budd, H.; Butorov, I.; Cagnoli, I.; Caiulo,
D.; Calabrese, R.; Calafiura, P.; Calcutt, J.; Calin, M.; Calvez, S.;
Calvo, E.; Caminata, A.; Campanelli, M.; Cankocak, K.; Caratelli, D.;
Carini, G.; Carlus, B.; Carneiro, M. F.; Carniti, P.; Caro Terrazas,
I.; Carranza, H.; Carroll, T.; Castaño Forero, J. F.; Castillo,
A.; Castromonte, C.; Catano-Mur, E.; Cattadori, C.; Cavalier, F.;
Cavanna, F.; Centro, S.; Cerati, G.; Cervelli, A.; Cervera Villanueva,
A.; Chalifour, M.; Chappell, A.; Chardonnet, E.; Charitonidis, N.;
Chatterjee, A.; Chattopadhyay, S.; Chen, H.; Chen, M.; Chen, Y.; Chen,
Z.; Cheon, Y.; Cherdack, D.; Chi, C.; Childress, S.; Chiriacescu,
A.; Chisnall, G.; Cho, K.; Choate, S.; Chokheli, D.; Chong, P. S.;
Choubey, S.; Christensen, A.; Christian, D.; Christodoulou, G.;
Chukanov, A.; Chung, M.; Church, E.; Cicero, V.; Clarke, P.; Coan,
T. E.; Cocco, A. G.; Coelho, J. A. B.; Conley, E.; Conley, R.; Conrad,
J. M.; Convery, M.; Copello, S.; Corwin, L.; Valentim, R.; Cremaldi,
L.; Cremonesi, L.; Crespo-Anadón, J. I.; Crisler, M.; Cristaldo,
E.; Cross, R.; Cudd, A.; Cuesta, C.; Cui, Y.; Cussans, D.; Dalager,
O.; da Motta, H.; Da Silva Peres, L.; David, C.; David, Q.; Davies,
G. S.; Davini, S.; Dawson, J.; De, K.; Debbins, P.; De Bonis, I.;
Decowski, M. P.; de Gouvêa, A.; De Holanda, P. C.; De Icaza Astiz,
I. L.; Deisting, A.; De Jong, P.; Delbart, A.; Delepine, D.; Delgado,
M.; Dell'Acqua, A.; De Lurgio, P.; de Mello Neto, J. R. T.; DeMuth,
D. M.; Dennis, S.; Densham, C.; Deptuch, G. W.; De Roeck, A.; De
Romeri, V.; De Souza, G.; Devi, R.; Dharmapalan, R.; Dias, M.; Diaz,
F.; Díaz, J. S.; Di Domizio, S.; Di Giulio, L.; Ding, P.; Di Noto,
L.; Distefano, C.; Diurba, R.; Diwan, M.; Djurcic, Z.; Doering,
D.; Dolan, S.; Dolek, F.; Dolinski, M. J.; Domine, L.; Douglas, D.;
Douillet, D.; Drake, G.; Drielsma, F.; Duarte, L.; Duchesneau, D.;
Duffy, K.; Dunne, P.; Durkin, T.; Duyang, H.; Dvornikov, O.; Dwyer,
D. A.; Dyshkant, A. S.; Eads, M.; Earle, A.; Edmunds, D.; Eisch, J.;
Emberger, L.; Emery, S.; Ereditato, A.; Erjavec, T.; Escobar, C. O.;
Eurin, G.; Evans, J. J.; Ewart, E.; Ezeribe, A. C.; Fahey, K.; Falcone,
A.; Fani', M.; Farnese, C.; Farzan, Y.; Fedoseev, D.; Felix, J.; Feng,
Y.; Fernandez-Martinez, E.; Fernandez Menendez, P.; Fernandez Morales,
M.; Ferraro, F.; Fields, L.; Filip, P.; Filthaut, F.; Fiorentini, A.;
Fiorini, M.; Fitzpatrick, R. S.; Flanagan, W.; Fleming, B.; Flight, R.;
Forero, D. V.; Fowler, J.; Fox, W.; Franc, J.; Francis, K.; Franco,
D.; Freeman, J.; Freestone, J.; Fried, J.; Friedland, A.; Fuentes
Robayo, F.; Fuess, S.; Furic, I. K.; Furmanski, A. P.; Gabrielli,
A.; Gago, A.; Gallagher, H.; Gallas, A.; Gallego-Ros, A.; Gallice,
N.; Galymov, V.; Gamberini, E.; Gamble, T.; Ganacim, F.; Gandhi, R.;
Gandrajula, R.; Gao, F.; Gao, S.; Garcia B., A. C.; Garcia-Gamez, D.;
García-Peris, A.; Gardiner, S.; Gastler, D.; Gauvreau, J.; Ge, G.;
Gelli, B.; Gendotti, A.; Gent, S.; Ghorbani-Moghaddam, Z.; Giammaria,
P.; Giammaria, T.; Gibin, D.; Gil-Botella, I.; Gilligan, S.; Girerd,
C.; Giri, A. K.; Gnani, D.; Gogota, O.; Gold, M.; Gollapinni, S.;
Gollwitzer, K.; Gomes, R. A.; Gomez Bermeo, L. V.; Gomez Fajardo,
L. S.; Gonnella, F.; Gonzalez-Cuevas, J. A.; Gonzalez Diaz, D.;
Gonzalez-Lopez, M.; Goodman, M. C.; Goodwin, O.; Goswami, S.; Gotti,
C.; Goudzovski, E.; Grace, C.; Graham, M.; Gran, R.; Granados, E.;
Granger, P.; Grant, A.; Grant, C.; Gratieri, D.; Green, P.; Greenler,
L.; Greer, J.; Grenard, J.; Griffith, W. C.; Groh, M.; Grudzinski,
J.; Grzelak, K.; Gu, W.; Guardincerri, E.; Guarino, V.; Guarise,
M.; Guenette, R.; Guerard, E.; Guerzoni, M.; Guglielmi, A.; Guo, B.;
Guthikonda, K. K.; Gutierrez, R.; Guzowski, P.; Guzzo, M. M.; Gwon,
S.; Ha, C.; Habig, A.; Hadavand, H.; Haenni, R.; Hahn, A.; Haiston,
J.; Hamacher-Baumann, P.; Hamernik, T.; Hamilton, P.; Han, J.; Harris,
D. A.; Hartnell, J.; Harton, J.; Hasegawa, T.; Hasnip, C.; Hatcher,
R.; Hatfield, K. W.; Hatzikoutelis, A.; Hayes, C.; Hayrapetyan,
K.; Hays, J.; Hazen, E.; He, M.; Heavey, A.; Heeger, K. M.; Heise,
J.; Hennessy, K.; Henry, S.; Hernandez Morquecho, M. A.; Herner,
K.; Hertel, L.; Hewes, J.; Higuera, A.; Hill, T.; Hillier, S. J.;
Himmel, A.; Hirsch, L. R.; Ho, J.; Hoff, J.; Holin, A.; Hoppe, E.;
Horton-Smith, G. A.; Hostert, M.; Hourlier, A.; Howard, B.; Howell,
R.; Hristova, I.; Hronek, M. S.; Huang, J.; Huang, J.; Hugon, J.;
Iles, G.; Ilic, N.; Iliescu, A. M.; Illingworth, R.; Ingratta, G.;
Ioannisian, A.; Isenhower, L.; Itay, R.; Izmaylov, A.; Jackson, C. M.;
Jain, V.; James, E.; Jang, W.; Jargowsky, B.; Jediny, F.; Jena, D.;
Jeong, Y. S.; Jesús-Valls, C.; Ji, X.; Jiang, L.; Jiménez, S.; Jipa,
A.; Johnson, R.; Johnston, N.; Jones, B.; Jones, S. B.; Judah, M.;
Jung, C. K.; Junk, T.; Jwa, Y.; Kabirnezhad, M.; Kaboth, A.; Kadenko,
I.; Kalra, D.; Kakorin, I.; Kalitkina, A.; Kamiya, F.; Kaneshige, N.;
Karagiorgi, G.; Karaman, G.; Karcher, A.; Karolak, M.; Karyotakis,
Y.; Kasai, S.; Kasetti, S. P.; Kashur, L.; Kazaryan, N.; Kearns,
E.; Keener, P.; Kelly, K. J.; Kemp, E.; Kemularia, O.; Ketchum, W.;
Kettell, S. H.; Khabibullin, M.; Khotjantsev, A.; Khvedelidze, A.;
Kim, D.; King, B.; Kirby, B.; Kirby, M.; Klein, J.; Koehler, K.;
Koerner, L. W.; Kohn, S.; Koller, P. P.; Kolupaeva, L.; Korablev,
D.; Kordosky, M.; Kosc, T.; Kose, U.; Kostelecký, V. A.; Kothekar,
K.; Krennrich, F.; Kreslo, I.; Kropp, W.; Kudenko, Y.; Kudryavtsev,
V. A.; Kulagin, S.; Kumar, J.; Kumar, P.; Kunze, P.; Kuruppu, C.;
Kus, V.; Kutter, T.; Kvasnicka, J.; Kwak, D.; Lambert, A.; Land,
B. J.; Lande, K.; Lane, C. E.; Lang, K.; Langford, T.; Langstaff,
M.; Larkin, J.; Lasorak, P.; Last, D.; Lastoria, C.; Laundrie, A.;
Laurenti, G.; Lawrence, A.; Lazanu, I.; LaZur, R.; Lazzaroni, M.; Le,
T.; Leardini, S.; Learned, J.; LeBrun, P.; LeCompte, T.; Lee, C.; Lee,
S. Y.; Lehmann Miotto, G.; Lehnert, R.; Leigui de Oliveira, M. A.;
Leitner, M.; Lepin, L. M.; Li, L.; Li, S. W.; Li, T.; Li, Y.; Liao,
H.; Lin, C. S.; Lin, Q.; Lin, S.; Ling, J.; Lister, A.; Littlejohn,
B. R.; Liu, J.; Lockwitz, S.; Loew, T.; Lokajicek, M.; Lomidze, I.;
Long, K.; Loo, K.; Lord, T.; LoSecco, J. M.; Louis, W. C.; Lu, X. -G.;
Luk, K. B.; Luo, X.; Luppi, E.; Lurkin, N.; Lux, T.; Luzio, V. P.;
MacFarlane, D.; Machado, A. A.; Machado, P.; Macias, C. T.; Macier,
J. R.; Maddalena, A.; Madera, A.; Madigan, P.; Magill, S.; Mahn,
K.; Maio, A.; Major, A.; Maloney, J. A.; Mandrioli, G.; Mandujano,
R. C.; Maneira, J.; Manenti, L.; Manly, S.; Mann, A.; Manolopoulos,
K.; Manrique Plata, M.; Manyam, V. N.; Manzanillas, L.; Marchan, M.;
Marchionni, A.; Marciano, W.; Marfatia, D.; Mariani, C.; Maricic,
J.; Marie, R.; Marinho, F.; Marino, A. D.; Marsden, D.; Marshak,
M.; Marshall, C. M.; Marshall, J.; Marteau, J.; Martin-Albo, J.;
Martinez, N.; Martinez Caicedo, D. A.; Martynenko, S.; Mascagna,
V.; Mason, K.; Mastbaum, A.; Masud, M.; Matichard, F.; Matsuno, S.;
Matthews, J.; Mauger, C.; Mauri, N.; Mavrokoridis, K.; Mawby, I.;
Mazza, R.; Mazzacane, A.; Mazzucato, E.; McAskill, T.; McCluskey,
E.; McConkey, N.; McFarland, K. S.; McGrew, C.; McNab, A.; Mefodiev,
A.; Mehta, P.; Melas, P.; Mena, O.; Menary, S.; Mendez, H.; Mendez,
P.; M, D. P.; Menegolli, A.; Meng, G.; Messier, M. D.; Metcalf, W.;
Mettler, T.; Mewes, M.; Meyer, H.; Miao, T.; Michna, G.; Miedema, T.;
Mikola, V.; Milincic, R.; Miller, G.; Miller, W.; Mills, J.; Milne,
C.; Mineev, O.; Miranda, O. G.; Miryala, S.; Mishra, C. S.; Mishra,
S. R.; Mislivec, A.; Mladenov, D.; Mocioiu, I.; Moffat, K.; Moggi,
N.; Mohanta, R.; Mohayai, T. A.; Mokhov, N.; Molina, J.; Molina Bueno,
L.; Montagna, E.; Montanari, A.; Montanari, C.; Montanari, D.; Montano
Zetina, L. M.; Moon, J.; Moon, S. H.; Mooney, M.; Moor, A. F.; Moreno,
D.; Morris, C.; Mossey, C.; Motuk, E.; Moura, C. A.; Mousseau, J.;
Mouster, G.; Mu, W.; Mualem, L.; Mueller, J.; Muether, M.; Mufson,
S.; Muheim, F.; Muir, A.; Mulhearn, M.; Munford, D.; Muramatsu,
H.; Murphy, S.; Musser, J.; Nachtman, J.; Nagu, S.; Nalbandyan, M.;
Nandakumar, R.; Naples, D.; Narita, S.; Nath, A.; Navas-Nicolás,
D.; Navrer-Agasson, A.; Nayak, N.; Nebot-Guinot, M.; Negishi, K.;
Nelson, J. K.; Nesbit, J.; Nessi, M.; Newbold, D.; Newcomer, M.;
Newhart, D.; Newton, H.; Nichol, R.; Nicolas-Arnaldos, F.; Niner, E.;
Nishimura, K.; Norman, A.; Norrick, A.; Northrop, R.; Novella, P.;
Nowak, J. A.; Oberling, M.; Ochoa-Ricoux, J. P.; Olivares Del Campo,
A.; Olivier, A.; Olshevskiy, A.; Onel, Y.; Onishchuk, Y.; Ott, J.;
Pagani, L.; Pakvasa, S.; Palacio, G.; Palamara, O.; Palestini, S.;
Paley, J. M.; Pallavicini, M.; Palomares, C.; Palomino-Gallo, J. L.;
Panduro Vazquez, W.; Pantic, E.; Paolone, V.; Papadimitriou, V.;
Papaleo, R.; Papanestis, A.; Paramesvaran, S.; Parke, S.; Parozzi,
E.; Parsa, Z.; Parvu, M.; Pascoli, S.; Pasqualini, L.; Pasternak,
J.; Pater, J.; Patrick, C.; Patrizii, L.; Patterson, R. B.; Patton,
S. J.; Patzak, T.; Paudel, A.; Paulos, B.; Paulucci, L.; Pavlovic,
Z.; Pawloski, G.; Payne, D.; Pec, V.; Peeters, S. J. M.; Pennacchio,
E.; Penzo, A.; Peres, O. L. G.; Perry, J.; Pershey, D.; Pessina,
G.; Petrillo, G.; Petta, C.; Petti, R.; Pia, V.; Piastra, F.;
Pickering, L.; Pietropaolo, F.; Plunkett, R.; Poling, R.; Pons, X.;
Poonthottathil, N.; Poppi, F.; Pordes, S.; Porter, J.; Potekhin,
M.; Potenza, R.; Potukuchi, B. V. K. S.; Pozimski, J.; Pozzato,
M.; Prakash, S.; Prakash, T.; Prest, M.; Prince, S.; Psihas, F.;
Pugnere, D.; Qian, X.; Queiroga Bazetto, M. C.; Raaf, J. L.; Radeka,
V.; Rademacker, J.; Radics, B.; Rafique, A.; Raguzin, E.; Rai, M.;
Rajaoalisoa, M.; Rakhno, I.; Rakotonandrasana, A.; Rakotondravohitra,
L.; Ramachers, Y. A.; Rameika, R.; Ramirez Delgado, M. A.; Ramson,
B.; Rappoldi, A.; Raselli, G.; Ratoff, P.; Raut, S.; Razakamiandra,
R. F.; Rea, E.; Real, J. S.; Rebel, B.; Reggiani-Guzzo, M.; Rehak,
T.; Reichenbacher, J.; Reitzner, S. D.; Rejeb Sfar, H.; Renshaw, A.;
Rescia, S.; Resnati, F.; Reynolds, A.; Ribas, M.; Riboldi, S.; Riccio,
C.; Riccobene, G.; Rice, L. C. J.; Ricol, J.; Rigamonti, A.; Rigaut,
Y.; Rivera, D.; Robert, A.; Rochester, L.; Roda, M.; Rodrigues, P.;
Rodriguez Alonso, M. J.; Rodriguez Bonilla, E.; Rodriguez Rondon,
J.; Rosauro-Alcaraz, S.; Rosenberg, M.; Rosier, P.; Roskovec, B.;
Rossella, M.; Rossi, M.; Rott, C.; Rout, J.; Roy, P.; Roy, S.; Rubbia,
A.; Rubbia, C.; Rubio, F. C.; Russell, B.; Ruterbories, D.; Rybnikov,
A.; Saa-Hernandez, A.; Saakyan, R.; Sacerdoti, S.; Safford, T.; Sahu,
N.; Sala, P.; Samios, N.; Samoylov, O.; Sanchez, M. C.; Sandberg,
V.; Sanders, D. A.; Sankey, D.; Santana, S.; Santos-Maldonado, M.;
Saoulidou, N.; Sapienza, P.; Sarasty, C.; Sarcevic, I.; Savage, G.;
Savinov, V.; Scaramelli, A.; Scarff, A.; Scarpelli, A.; Schaffer, T.;
Schellman, H.; Schifano, S.; Schlabach, P.; Schmitz, D.; Scholberg, K.;
Schukraft, A.; Segreto, E.; Selyunin, A.; Senise, C. R.; Sensenig, J.;
Seoane, M.; Seong, I.; Sergi, A.; Sgalaberna, D.; Shaevitz, M. H.;
Shafaq, S.; Shamma, M.; Sharankova, R.; Sharma, H. R.; Sharma, R.;
Kumar, R.; Shaw, T.; Shepherd-Themistocleous, C.; Sheshukov, A.; Shin,
S.; Shoemaker, I.; Shooltz, D.; Shrock, R.; Siegel, H.; Simard, L.;
Simon, F.; Sinclair, J.; Sinev, G.; Singh, J.; Singh, J.; Singh,
L.; Singh, V.; Sipos, R.; Sippach, F. W.; Sirri, G.; Sitraka, A.;
Siyeon, K.; Skarpaas, K.; Smith, A.; Smith, E.; Smith, P.; Smolik,
J.; Smy, M.; Snider, E. L.; Snopok, P.; Snowden-Ifft, D.; Soares
Nunes, M.; Sobel, H.; Soderberg, M.; Sokolov, S.; Solano Salinas,
C. J.; Söldner-Rembold, S.; Soleti, S. R.; Solomey, N.; Solovov,
V.; Sondheim, W. E.; Sorel, M.; Sotnikov, A.; Soto-Oton, J.; Sousa,
A.; Soustruznik, K.; Spagliardi, F.; Spanu, M.; Spitz, J.; Spooner,
N. J. C.; Spurgeon, K.; Staley, R.; Stancari, M.; Stanco, L.; Stanley,
R.; Stein, R.; Steiner, H. M.; Steklain Lisbôa, A. F.; Stewart,
J.; Stillwell, B.; Stock, J.; Stocker, F.; Stokes, T.; Strait, M.;
Strauss, T.; Striganov, S.; Stuart, A.; Suarez, J. G.; Sullivan, H.;
Summers, D.; Surdo, A.; Susic, V.; Suter, L.; Sutera, C. M.; Svoboda,
R.; Szczerbinska, B.; Szelc, A. M.; Tanaka, H. A.; Tapia Oregui, B.;
Tapper, A.; Tariq, S.; Tatar, E.; Tayloe, R.; Teklu, A. M.; Tenti,
M.; Terao, K.; Ternes, C. A.; Terranova, F.; Testera, G.; Thakore,
T.; Thea, A.; Thompson, J. L.; Thorn, C.; Timm, S. C.; Tishchenko,
V.; Todd, J.; Tomassetti, L.; Tonazzo, A.; Torbunov, D.; Torti,
M.; Tortola, M.; Tortorici, F.; Tosi, N.; Totani, D.; Toups, M.;
Touramanis, C.; Travaglini, R.; Trevor, J.; Trilov, S.; Tripathi, A.;
Trzaska, W. H.; Tsai, Y.; Tsai, Y. -T.; Tsamalaidze, Z.; Tsang, K. V.;
Tsverava, N.; Tufanli, S.; Tull, C.; Tyley, E.; Tzanov, M.; Uboldi,
L.; Uchida, M. A.; Urheim, J.; Usher, T.; Uzunyan, S.; Vagins, M. R.;
Vahle, P.; Valdiviesso, G. A.; Valencia, E.; Vallari, Z.; Vallazza,
E.; Valle, J. W. F.; Vallecorsa, S.; Van Berg, R.; Van de Water, R. G.;
Varanini, F.; Vargas, D.; Varner, G.; Vasel, J.; Vasina, S.; Vasseur,
G.; Vaughan, N.; Vaziri, K.; Ventura, S.; Verdugo, A.; Vergani, S.;
Vermeulen, M. A.; Verzocchi, M.; Vicenzi, M.; Vieira de Souza, H.;
Vignoli, C.; Vilela, C.; Viren, B.; Vrba, T.; Wachala, T.; Waldron,
A. V.; Wallbank, M.; Wallis, C.; Wang, H.; Wang, J.; Wang, L.; Wang,
M. H. L. S.; Wang, Y.; Wang, Y.; Warburton, K.; Warner, D.; Wascko,
M. O.; Waters, D.; Watson, A.; Weatherly, P.; Weber, A.; Weber, M.;
Wei, H.; Weinstein, A.; Wenman, D.; Wetstein, M.; White, A.; Whitehead,
L. H.; Whittington, D.; Wilking, M. J.; Wilkinson, C.; Williams, Z.;
Wilson, F.; Wilson, R. J.; Wisniewski, W.; Wolcott, J.; Wongjirad, T.;
Wood, A.; Wood, K.; Worcester, E.; Worcester, M.; Wret, C.; Wu, W.;
Wu, W.; Xiao, Y.; Xie, F.; Yandel, E.; Yang, G.; Yang, K.; Yang, S.;
Yang, T.; Yankelevich, A.; Yershov, N.; Yonehara, K.; Young, T.; Yu,
B.; Yu, H.; Yu, H.; Yu, J.; Yuan, W.; Zaki, R.; Zalesak, J.; Zambelli,
L.; Zamorano, B.; Zani, A.; Zazueta, L.; Zeller, G. P.; Zennamo, J.;
Zeug, K.; Zhang, C.; Zhao, M.; Zhivun, E.; Zhu, G.; Zilberman, P.;
Zimmerman, E. D.; Zito, M.; Zucchelli, S.; Zuklin, J.; Zutshi, V.;
Zwaska, R.; DUNE Collaboration
2021JCAP...10..065A Altcode:
The observation of 236 MeV muon neutrinos from kaon-decay-at-rest
(KDAR) originating in the core of the Sun would provide a unique
signature of dark matter annihilation. Since excellent angle and
energy reconstruction are necessary to detect this monoenergetic,
directional neutrino flux, DUNE with its vast volume and reconstruction
capabilities, is a promising candidate for a KDAR neutrino search. In
this work, we evaluate the proposed KDAR neutrino search strategies
by realistically modeling both neutrino-nucleus interactions and
the response of DUNE. We find that, although reconstruction of the
neutrino energy and direction is difficult with current techniques
in the relevant energy range, the superb energy resolution, angular
resolution, and particle identification offered by DUNE can still
permit great signal/background discrimination. Moreover, there are
non-standard scenarios in which searches at DUNE for KDAR in the Sun
can probe dark matter interactions.
---------------------------------------------------------
Title: Searching for solar KDAR with DUNE
Authors: DUNE Collaboration; Abed Abud, A.; Abi, B.; Acciarri, R.;
Acero, M. A.; Adames, M. R.; Adamov, G.; Adams, D.; Adinolfi, M.;
Aduszkiewicz, A.; Aguilar, J.; Ahmad, Z.; Ahmed, J.; Ali-Mohammadzadeh,
B.; Alion, T.; Allison, K.; Alonso Monsalve, S.; Alrashed, M.;
Alt, C.; Alton, A.; Amedo, P.; Anderson, J.; Andreopoulos, C.;
Andreotti, M.; Andrews, M. P.; Andrianala, F.; Andringa, S.;
Anfimov, N.; Ankowski, A.; Antoniassi, M.; Antonova, M.; Antoshkin,
A.; Antusch, S.; Aranda-Fernandez, A.; Ariga, A.; Arnold, L. O.;
Arroyave, M. A.; Asaadi, J.; Asquith, L.; Aurisano, A.; Aushev, V.;
Autiero, D.; Ayala-Torres, M.; Azfar, F.; Back, A.; Back, H.; Back,
J. J.; Backhouse, C.; Baesso, P.; Bagaturia, I.; Bagby, L.; Balashov,
N.; Balasubramanian, S.; Baldi, P.; Baller, B.; Bambah, B.; Barao,
F.; Barenboim, G.; Barker, G. J.; Barkhouse, W.; Barnes, C.; Barr,
G.; Barranco Monarca, J.; Barros, A.; Barros, N.; Barrow, J. L.;
Basharina-Freshville, A.; Bashyal, A.; Basque, V.; Belchior, E.;
Battat, J. B. R.; Battisti, F.; Bay, F.; Bazo Alba, J. L.; Beacom,
J. F.; Bechetoille, E.; Behera, B.; Bellantoni, L.; Bellettini, G.;
Bellini, V.; Beltramello, O.; Belver, D.; Benekos, N.; Benitez Montiel,
C.; Bento Neves, F.; Berger, J.; Berkman, S.; Bernardini, P.; Berner,
R. M.; Berns, H.; Bertolucci, S.; Betancourt, M.; Betancur Rodríguez,
A.; Bevan, A.; Bezerra, T. J. C.; Bhatnagar, V.; Bhattacharjee, M.;
Bhuller, S.; Bhuyan, B.; Biagi, S.; Bian, J.; Biassoni, M.; Biery, K.;
Bilki, B.; Bishai, M.; Bitadze, A.; Blake, A.; Blaszczyk, F. D. M.;
Blazey, G. C.; Blucher, E.; Boissevain, J.; Bolognesi, S.; Bolton, T.;
Bomben, L.; Bonesini, M.; Bongrand, M.; Bonini, F.; Booth, A.; Booth,
C.; Boran, F.; Bordoni, S.; Borkum, A.; Boschi, T.; Bostan, N.; Bour,
P.; Bourgeois, C.; Boyd, S. B.; Boyden, D.; Bracinik, J.; Braga,
D.; Brailsford, D.; Branca, A.; Brandt, A.; Bremer, J.; Brew, C.;
Brianne, E.; Brice, S. J.; Brizzolari, C.; Bromberg, C.; Brooijmans,
G.; Brooke, J.; Bross, A.; Brunetti, G.; Brunetti, M.; Buchanan,
N.; Budd, H.; Butorov, I.; Cagnoli, I.; Caiulo, D.; Calabrese, R.;
Calafiura, P.; Calcutt, J.; Calin, M.; Calvez, S.; Calvo, E.; Caminata,
A.; Campanelli, M.; Cankocak, K.; Caratelli, D.; Carini, G.; Carlus,
B.; Carneiro, M. F.; Carniti, P.; Caro Terrazas, I.; Carranza, H.;
Carroll, T.; Castaño Forero, J. F.; Castillo, A.; Castromonte, C.;
Catano-Mur, E.; Cattadori, C.; Cavalier, F.; Cavanna, F.; Centro,
S.; Cerati, G.; Cervelli, A.; Cervera Villanueva, A.; Chalifour,
M.; Chappell, A.; Chardonnet, E.; Charitonidis, N.; Chatterjee, A.;
Chattopadhyay, S.; Chen, H.; Chen, M.; Chen, Y.; Chen, Z.; Cheon,
Y.; Cherdack, D.; Chi, C.; Childress, S.; Chiriacescu, A.; Chisnall,
G.; Cho, K.; Choate, S.; Chokheli, D.; Chong, P. S.; Choubey, S.;
Christensen, A.; Christian, D.; Christodoulou, G.; Chukanov, A.; Chung,
M.; Church, E.; Cicero, V.; Clarke, P.; Coan, T. E.; Cocco, A. G.;
Coelho, J. A. B.; Conley, E.; Conley, R.; Conrad, J. M.; Convery,
M.; Copello, S.; Corwin, L.; Valentim, R.; Cremaldi, L.; Cremonesi,
L.; Crespo-Anadón, J. I.; Crisler, M.; Cristaldo, E.; Cross, R.;
Cudd, A.; Cuesta, C.; Cui, Y.; Cussans, D.; Dalager, O.; da Motta,
H.; Da Silva Peres, L.; David, C.; David, Q.; Davies, G. S.; Davini,
S.; Dawson, J.; De, K.; Debbins, P.; De Bonis, I.; Decowski, M. P.;
de Gouvêa, A.; De Holanda, P. C.; De Icaza Astiz, I. L.; Deisting,
A.; De Jong, P.; Delbart, A.; Delepine, D.; Delgado, M.; Dell'Acqua,
A.; De Lurgio, P.; de Mello Neto, J. R. T.; DeMuth, D. M.; Dennis, S.;
Densham, C.; Deptuch, G. W.; De Roeck, A.; De Romeri, V.; De Souza,
G.; Devi, R.; Dharmapalan, R.; Dias, M.; Diaz, F.; Díaz, J. S.;
Di Domizio, S.; Di Giulio, L.; Ding, P.; Di Noto, L.; Distefano, C.;
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F.; Dolinski, M. J.; Domine, L.; Douglas, D.; Douillet, D.; Drake,
G.; Drielsma, F.; Duarte, L.; Duchesneau, D.; Duffy, K.; Dunne,
P.; Durkin, T.; Duyang, H.; Dvornikov, O.; Dwyer, D. A.; Dyshkant,
A. S.; Eads, M.; Earle, A.; Edmunds, D.; Eisch, J.; Emberger, L.;
Emery, S.; Ereditato, A.; Erjavec, T.; Escobar, C. O.; Eurin, G.;
Evans, J. J.; Ewart, E.; Ezeribe, A. C.; Fahey, K.; Falcone, A.;
Fani, M.; Farnese, C.; Farzan, Y.; Fedoseev, D.; Felix, J.; Feng, Y.;
Fernandez-Martinez, E.; Fernandez Menendez, P.; Fernandez Morales,
M.; Ferraro, F.; Fields, L.; Filip, P.; Filthaut, F.; Fiorentini, A.;
Fiorini, M.; Fitzpatrick, R. S.; Flanagan, W.; Fleming, B.; Flight, R.;
Forero, D. V.; Fowler, J.; Fox, W.; Franc, J.; Francis, K.; Franco,
D.; Freeman, J.; Freestone, J.; Fried, J.; Friedland, A.; Fuentes
Robayo, F.; Fuess, S.; Furic, I. K.; Furmanski, A. P.; Gabrielli,
A.; Gago, A.; Gallagher, H.; Gallas, A.; Gallego-Ros, A.; Gallice,
N.; Galymov, V.; Gamberini, E.; Gamble, T.; Ganacim, F.; Gandhi, R.;
Gandrajula, R.; Gao, F.; Gao, S.; Garcia B., A. C.; Garcia-Gamez, D.;
García-Peris, M. Á.; Gardiner, S.; Gastler, D.; Gauvreau, J.; Ge, G.;
Gelli, B.; Gendotti, A.; Gent, S.; Ghorbani-Moghaddam, Z.; Giammaria,
P.; Giammaria, T.; Gibin, D.; Gil-Botella, I.; Gilligan, S.; Girerd,
C.; Giri, A. K.; Gnani, D.; Gogota, O.; Gold, M.; Gollapinni, S.;
Gollwitzer, K.; Gomes, R. A.; Gomez Bermeo, L. V.; Gomez Fajardo,
L. S.; Gonnella, F.; Gonzalez-Cuevas, J. A.; Gonzalez Diaz, D.;
Gonzalez-Lopez, M.; Goodman, M. C.; Goodwin, O.; Goswami, S.; Gotti,
C.; Goudzovski, E.; Grace, C.; Graham, M.; Gran, R.; Granados, E.;
Granger, P.; Grant, A.; Grant, C.; Gratieri, D.; Green, P.; Greenler,
L.; Greer, J.; Grenard, J.; Griffith, W. C.; Groh, M.; Grudzinski,
J.; Grzelak, K.; Gu, W.; Guardincerri, E.; Guarino, V.; Guarise,
M.; Guenette, R.; Guerard, E.; Guerzoni, M.; Guglielmi, A.; Guo, B.;
Guthikonda, K. K.; Gutierrez, R.; Guzowski, P.; Guzzo, M. M.; Gwon,
S.; Ha, C.; Habig, A.; Hadavand, H.; Haenni, R.; Hahn, A.; Haiston,
J.; Hamacher-Baumann, P.; Hamernik, T.; Hamilton, P.; Han, J.; Harris,
D. A.; Hartnell, J.; Harton, J.; Hasegawa, T.; Hasnip, C.; Hatcher,
R.; Hatfield, K. W.; Hatzikoutelis, A.; Hayes, C.; Hayrapetyan,
K.; Hays, J.; Hazen, E.; He, M.; Heavey, A.; Heeger, K. M.; Heise,
J.; Hennessy, K.; Henry, S.; Hernandez Morquecho, M. A.; Herner,
K.; Hertel, L.; Hewes, J.; Higuera, A.; Hill, T.; Hillier, S. J.;
Himmel, A.; Hirsch, L. R.; Ho, J.; Hoff, J.; Holin, A.; Hoppe, E.;
Horton-Smith, G. A.; Hostert, M.; Hourlier, A.; Howard, B.; Howell,
R.; Hristova, I.; Hronek, M. S.; Huang, J.; Huang, J.; Hugon, J.;
Iles, G.; Ilic, N.; Iliescu, A. M.; Illingworth, R.; Ingratta, G.;
Ioannisian, A.; Isenhower, L.; Itay, R.; Izmaylov, A.; Jackson, C. M.;
Jain, V.; James, E.; Jang, W.; Jargowsky, B.; Jediny, F.; Jena, D.;
Jeong, Y. S.; Jesús-Valls, C.; Ji, X.; Jiang, L.; Jiménez, S.; Jipa,
A.; Johnson, R.; Johnston, N.; Jones, B.; Jones, S. B.; Judah, M.;
Jung, C. K.; Junk, T.; Jwa, Y.; Kabirnezhad, M.; Kaboth, A.; Kadenko,
I.; Kakorin, I.; Kalitkina, A.; F.; Kalra, D.; Kamiya; Kaneshige, N.;
Karagiorgi, G.; Karaman, G.; Karcher, A.; Karolak, M.; Karyotakis,
Y.; Kasai, S.; Kasetti, S. P.; Kashur, L.; Kazaryan, N.; Kearns,
E.; Keener, P.; Kelly, K. J.; Kemp, E.; Kemularia, O.; Ketchum, W.;
Kettell, S. H.; Khabibullin, M.; Khotjantsev, A.; Khvedelidze, A.;
Kim, D.; King, B.; Kirby, B.; Kirby, M.; Klein, J.; Koehler, K.;
Koerner, L. W.; Kohn, S.; Koller, P. P.; Kolupaeva, L.; Korablev,
D.; Kordosky, M.; Kosc, T.; Kose, U.; Kostelecký, V. A.; Kothekar,
K.; Krennrich, F.; Kreslo, I.; Kropp, W.; Kudenko, Y.; Kudryavtsev,
V. A.; Kulagin, S.; Kumar, J.; Kumar, P.; Kunze, P.; Kuruppu, C.;
Kus, V.; Kutter, T.; Kvasnicka, J.; Kwak, D.; Lambert, A.; Land,
B. J.; Lande, K.; Lane, C. E.; Lang, K.; Langford, T.; Langstaff,
M.; Larkin, J.; Lasorak, P.; Last, D.; Lastoria, C.; Laundrie, A.;
Laurenti, G.; Lawrence, A.; Lazanu, I.; LaZur, R.; Lazzaroni, M.; Le,
T.; Leardini, S.; Learned, J.; LeBrun, P.; LeCompte, T.; Lee, C.; Lee,
S. Y.; Lehmann Miotto, G.; Lehnert, R.; Leigui de Oliveira, M. A.;
Leitner, M.; Lepin, L. M.; Li, L.; Li, S. W.; Li, T.; Li, Y.; Liao,
H.; Lin, C. S.; Lin, Q.; Lin, S.; Ling, J.; Lister, A.; Littlejohn,
B. R.; Liu, J.; Lockwitz, S.; Loew, T.; Lokajicek, M.; Lomidze, I.;
Long, K.; Loo, K.; Lord, T.; LoSecco, J. M.; Louis, W. C.; Lu, X. -G.;
Luk, K. B.; Luo, X.; Luppi, E.; Lurkin, N.; Lux, T.; Luzio, V. P.;
MacFarlane, D.; Machado, A. A.; Machado, P.; Macias, C. T.; Macier,
J. R.; Maddalena, A.; Madera, A.; Madigan, P.; Magill, S.; Mahn,
K.; Maio, A.; Major, A.; Maloney, J. A.; Mandrioli, G.; Mandujano,
R. C.; Maneira, J.; Manenti, L.; Manly, S.; Mann, A.; Manolopoulos,
K.; Manrique Plata, M.; Manyam, V. N.; Manzanillas, L.; Marchan, M.;
Marchionni, A.; Marciano, W.; Marfatia, D.; Mariani, C.; Maricic,
J.; Marie, R.; Marinho, F.; Marino, A. D.; Marsden, D.; Marshak,
M.; Marshall, C. M.; Marshall, J.; Marteau, J.; Martin-Albo, J.;
Martinez, N.; Martinez Caicedo, D. A.; Martynenko, S.; Mascagna,
V.; Mason, K.; Mastbaum, A.; Masud, M.; Matichard, F.; Matsuno, S.;
Matthews, J.; Mauger, C.; Mauri, N.; Mavrokoridis, K.; Mawby, I.;
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Mehta, P.; Melas, P.; Mena, O.; Menary, S.; Mendez, H.; Mendez, P.;
Méndez, D. P.; Menegolli, A.; Meng, G.; Messier, M. D.; Metcalf, W.;
Mettler, T.; Mewes, M.; Meyer, H.; Miao, T.; Michna, G.; Miedema, T.;
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C.; Mineev, O.; Miranda, O. G.; Miryala, S.; Mishra, C. S.; Mishra,
S. R.; Mislivec, A.; Mladenov, D.; Mocioiu, I.; Moffat, K.; Moggi,
N.; Mohanta, R.; Mohayai, T. A.; Mokhov, N.; Molina, J.; Molina Bueno,
L.; Montagna, E.; Montanari, A.; Montanari, C.; Montanari, D.; Montano
Zetina, L. M.; Moon, J.; Moon, S. H.; Mooney, M.; Moor, A. F.; Moreno,
D.; Morris, C.; Mossey, C.; Motuk, E.; Moura, C. A.; Mousseau, J.;
Mouster, G.; Mu, W.; Mualem, L.; Mueller, J.; Muether, M.; Mufson,
S.; Muheim, F.; Muir, A.; Mulhearn, M.; Munford, D.; Muramatsu,
H.; Murphy, S.; Musser, J.; Nachtman, J.; Nagu, S.; Nalbandyan, M.;
Nandakumar, R.; Naples, D.; Narita, S.; Nath, A.; Navas-Nicolás,
D.; Navrer-Agasson, A.; Nayak, N.; Nebot-Guinot, M.; Negishi, K.;
Nelson, J. K.; Nesbit, J.; Nessi, M.; Newbold, D.; Newcomer, M.;
Newhart, D.; Newton, H.; Nichol, R.; Nicolas-Arnaldos, F.; Niner, E.;
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Nowak, J. A.; Oberling, M.; Ochoa-Ricoux, J. P.; Olivares Del Campo,
A.; Olivier, A.; Olshevskiy, A.; Onel, Y.; Onishchuk, Y.; Ott, J.;
Pagani, L.; Pakvasa, S.; Palacio, G.; Palamara, O.; Palestini, S.;
Paley, J. M.; Pallavicini, M.; Palomares, C.; Palomino-Gallo, J. L.;
Panduro Vazquez, W.; Pantic, E.; Paolone, V.; Papadimitriou, V.;
Papaleo, R.; Papanestis, A.; Paramesvaran, S.; Parke, S.; Parozzi,
E.; Parsa, Z.; Parvu, M.; Pascoli, S.; Pasqualini, L.; Pasternak,
J.; Pater, J.; Patrick, C.; Patrizii, L.; Patterson, R. B.; Patton,
S. J.; Patzak, T.; Paudel, A.; Paulos, B.; Paulucci, L.; Pavlovic,
Z.; Pawloski, G.; Payne, D.; Pec, V.; Peeters, S. J. M.; Pennacchio,
E.; Penzo, A.; Peres, O. L. G.; Perry, J.; Pershey, D.; Pessina,
G.; Petrillo, G.; Petta, C.; Petti, R.; Pia, V.; Piastra, F.;
Pickering, L.; Pietropaolo, F.; Plunkett, R.; Poling, R.; Pons, X.;
Poonthottathil, N.; Poppi, F.; Pordes, S.; Porter, J.; Potekhin,
M.; Potenza, R.; Potukuchi, B. V. K. S.; Pozimski, J.; Pozzato,
M.; Prakash, S.; Prakash, T.; Prest, M.; Prince, S.; Psihas, F.;
Pugnere, D.; Qian, X.; Queiroga Bazetto, M. C.; Raaf, J. L.; Radeka,
V.; Rademacker, J.; Radics, B.; Rafique, A.; Raguzin, E.; Rai, M.;
Rajaoalisoa, M.; Rakhno, I.; Rakotonandrasana, A.; Rakotondravohitra,
L.; Ramachers, Y. A.; Rameika, R.; Ramirez Delgado, M. A.; Ramson,
B.; Rappoldi, A.; Raselli, G.; Ratoff, P.; Raut, S.; Razakamiandra,
R. F.; Rea, E.; Real, J. S.; Rebel, B.; Reggiani-Guzzo, M.; Rehak,
T.; Reichenbacher, J.; Reitzner, S. D.; Rejeb Sfar, H.; Renshaw, A.;
Rescia, S.; Resnati, F.; Reynolds, A.; Ribas, M.; Riboldi, S.; Riccio,
C.; Riccobene, G.; Rice, L. C. J.; Ricol, J.; Rigamonti, A.; Rigaut,
Y.; Rivera, D.; Robert, A.; Rochester, L.; Roda, M.; Rodrigues, P.;
Rodriguez Alonso, M. J.; Rodriguez Bonilla, E.; Rodriguez Rondon,
J.; Rosauro-Alcaraz, S.; Rosenberg, M.; Rosier, P.; Roskovec, B.;
Rossella, M.; Rossi, M.; Rott, C.; Rout, J.; Roy, P.; Roy, S.; Rubbia,
A.; Rubbia, C.; Rubio, F. C.; Russell, B.; Ruterbories, D.; Rybnikov,
A.; Saa-Hernandez, A.; Saakyan, R.; Sacerdoti, S.; Safford, T.; Sahu,
N.; Sala, P.; Samios, N.; Samoylov, O.; Sanchez, M. C.; Sandberg,
V.; Sanders, D. A.; Sankey, D.; Santana, S.; Santos-Maldonado, M.;
Saoulidou, N.; Sapienza, P.; Sarasty, C.; Sarcevic, I.; Savage, G.;
Savinov, V.; Scaramelli, A.; Scarff, A.; Scarpelli, A.; Schaffer, T.;
Schellman, H.; Schifano, S.; Schlabach, P.; Schmitz, D.; Scholberg, K.;
Schukraft, A.; Segreto, E.; Selyunin, A.; Senise, C. R.; Sensenig, J.;
Seoane, M.; Seong, I.; Sergi, A.; Sgalaberna, D.; Shaevitz, M. H.;
Shafaq, S.; Shamma, M.; Sharankova, R.; Sharma, H. R.; Sharma, R.;
Kumar, R.; Shaw, T.; Shepherd-Themistocleous, C.; Sheshukov, A.; Shin,
S.; Shoemaker, I.; Shooltz, D.; Shrock, R.; Siegel, H.; Simard, L.;
Simon, F.; Sinclair, J.; Sinev, G.; Singh, J.; Singh, J.; Singh,
L.; Singh, V.; Sipos, R.; Sippach, F. W.; Sirri, G.; Sitraka, A.;
Siyeon, K.; Skarpaas, K.; Smith, A.; Smith, E.; Smith, P.; Smolik,
J.; Smy, M.; Snider, E. L.; Snopok, P.; Snowden-Ifft, D.; Soares
Nunes, M.; Sobel, H.; Soderberg, M.; Sokolov, S.; Solano Salinas,
C. J.; Söldner-Rembold, S.; Soleti, S. R.; Solomey, N.; Solovov,
V.; Sondheim, W. E.; Sorel, M.; Sotnikov, A.; Soto-Oton, J.; Sousa,
A.; Soustruznik, K.; Spagliardi, F.; Spanu, M.; Spitz, J.; Spooner,
N. J. C.; Spurgeon, K.; Staley, R.; Stancari, M.; Stanco, L.; Stanley,
R.; Stein, R.; Steiner, H. M.; Steklain Lisbôa, A. F.; Stewart,
J.; Stillwell, B.; Stock, J.; Stocker, F.; Stokes, T.; Strait, M.;
Strauss, T.; Striganov, S.; Stuart, A.; Suarez, J. G.; Sullivan, H.;
Summers, D.; Surdo, A.; Susic, V.; Suter, L.; Sutera, C. M.; Svoboda,
R.; Szczerbinska, B.; Szelc, A. M.; Tanaka, H. A.; Tapia Oregui, B.;
Tapper, A.; Tariq, S.; Tatar, E.; Tayloe, R.; Teklu, A. M.; Tenti,
M.; Terao, K.; Ternes, C. A.; Terranova, F.; Testera, G.; Thakore,
T.; Thea, A.; Thompson, J. L.; Thorn, C.; Timm, S. C.; Tishchenko,
V.; Todd, J.; Tomassetti, L.; Tonazzo, A.; Torbunov, D.; Torti,
M.; Tortola, M.; Tortorici, F.; Tosi, N.; Totani, D.; Toups, M.;
Touramanis, C.; Travaglini, R.; Trevor, J.; Trilov, S.; Tripathi, A.;
Trzaska, W. H.; Tsai, Y.; Tsai, Y. -T.; Tsamalaidze, Z.; Tsang, K. V.;
Tsverava, N.; Tufanli, S.; Tull, C.; Tyley, E.; Tzanov, M.; Uboldi,
L.; Uchida, M. A.; Urheim, J.; Usher, T.; Uzunyan, S.; Vagins, M. R.;
Vahle, P.; Valdiviesso, G. A.; Valencia, E.; Vallari, Z.; Vallazza,
E.; Valle, J. W. F.; Vallecorsa, S.; Van Berg, R.; Van de Water, R. G.;
Varanini, F.; Vargas, D.; Varner, G.; Vasel, J.; Vasina, S.; Vasseur,
G.; Vaughan, N.; Vaziri, K.; Ventura, S.; Verdugo, A.; Vergani, S.;
Vermeulen, M. A.; Verzocchi, M.; Vicenzi, M.; Vieira de Souza, H.;
Vignoli, C.; Vilela, C.; Viren, B.; Vrba, T.; Wachala, T.; Waldron,
A. V.; Wallbank, M.; Wallis, C.; Wang, H.; Wang, J.; Wang, L.; Wang,
M. H. L. S.; Wang, Y.; Wang, Y.; Warburton, K.; Warner, D.; Wascko,
M. O.; Waters, D.; Watson, A.; Weatherly, P.; Weber, A.; Weber, M.;
Wei, H.; Weinstein, A.; Wenman, D.; Wetstein, M.; White, A.; Whitehead,
L. H.; Whittington, D.; Wilking, M. J.; Wilkinson, C.; Williams, Z.;
Wilson, F.; Wilson, R. J.; Wisniewski, W.; Wolcott, J.; Wongjirad, T.;
Wood, A.; Wood, K.; Worcester, E.; Worcester, M.; Wret, C.; Wu, W.;
Wu, W.; Xiao, Y.; Xie, F.; Yandel, E.; Yang, G.; Yang, K.; Yang, S.;
Yang, T.; Yankelevich, A.; Yershov, N.; Yonehara, K.; Young, T.; Yu,
B.; Yu, H.; Yu, H.; Yu, J.; Yuan, W.; Zaki, R.; Zalesak, J.; Zambelli,
L.; Zamorano, B.; Zani, A.; Zazueta, L.; Zeller, G. P.; Zennamo, J.;
Zeug, K.; Zhang, C.; Zhao, M.; Zhivun, E.; Zhu, G.; Zilberman, P.;
Zimmerman, E. D.; Zito, M.; Zucchelli, S.; Zuklin, J.; Zutshi, V.;
Zwaska, R.
2021arXiv210709109D Altcode:
The observation of 236 MeV muon neutrinos from kaon-decay-at-rest
(KDAR) originating in the core of the Sun would provide a unique
signature of dark matter annihilation. Since excellent angle and
energy reconstruction are necessary to detect this monoenergetic,
directional neutrino flux, DUNE with its vast volume and reconstruction
capabilities, is a promising candidate for a KDAR neutrino search. In
this work, we evaluate the proposed KDAR neutrino search strategies
by realistically modeling both neutrino-nucleus interactions and
the response of DUNE. We find that, although reconstruction of the
neutrino energy and direction is difficult with current techniques
in the relevant energy range, the superb energy resolution, angular
resolution, and particle identification offered by DUNE can still
permit great signal/background discrimination. Moreover, there are
non-standard scenarios in which searches at DUNE for KDAR in the Sun
can probe dark matter interactions.
---------------------------------------------------------
Title: Multi-proxy evidence for constant hydrological sources and
mild, wet climate in post-EECO Greater Green River Basin
Authors: Stein, R.; Sheldon, N. D.; Dzombak, R.; Allen, S. E.; Smith,
M. E.
2020AGUFMPP0240010S Altcode:
The early Eocene climatic optimum (EECO), a warm period ~50 million
years ago, is considered a model for warm-world conditions in a high
emissions anthropogenic climate change scenario. The Greater Green River
Basin, which accumulated sediment in a hypersaline lake (paleo-lake
Gosiute) at the foot of the forming Rocky Mountains, is known for its
high resolution, well-preserved records of the EECO from both floodplain
and lacustrine sediments. Due to the basin's proximity to multiple
potential sources of moisture and transported sediment to the west,
northeast and south, there is concern that inconsistent hydrological
inputs may interfere with climate signals. The Bridger Formation
(Southwest Wyoming, USA) records alluvial and fluvial sedimentation from
~50-45.5 million years ago and includes an extremely well-preserved and
well-characterized flora at the Blue Rim fossil quarries (constrained
using <SUP>40 </SUP>Ar/ <SUP>39 </SUP>Ar geochronological dating
to record before 49.29 Ma to 48.29 Ma). Using multiple geochemical
proxies and fossil evidence, we demonstrate that moisture and sediment
sources in the basin throughout the >1 million years of post-EECO
uplift of the Rocky Mountains stayed constant, and that variability in
biogeochemistry and floral preservation is related to changes in climate
and biota. Previous studies have found rainfall ranging from 1300 to
1900 mm yr <SUP>-1 </SUP> in the region with temperatures between 14
and 15°C, consistent with the wet forest ecosystem demonstrated in
preserved plant remains (dicotyledonous taxa including some climbers,
some monocots, and ferns). Multi-proxy floral- and paleosol-based
climate proxies (e.g. CIA-K, floral humidity province, Holdridge Life
Zones) demonstrate that the rim of paleo-lake Gosiute was a wet forest
with warm temperatures, high precipitation, moderate weathering, and
sediments coming from consistent provenance. Robust geochemical data
demonstrate that fluvial inputs stay constant and do not obfuscate
climate signals in Blue Rim's sediments.
---------------------------------------------------------
Title: Lateral heterogeneity in paleosol geochemistry and resampling
to improve proxy uncertainty
Authors: Dzombak, R.; Stein, R.; Sheldon, N. D.
2020AGUFMPP0460009D Altcode:
Paleosols (fossil soils) serve as key terrestrial records of climate
as they form at the surface, in constant contact with precipitation,
temperature, and the atmosphere. Many proxies exist to reconstruct
these variables, but typically, proxy uncertainty is limited to
calibration error and does not take other types of uncertainty
(e.g., spatial heterogeneity) into account. Specifically, we seek
to improve the uncertainty associated with using a small number of
paleosol profiles to represent landscape-scale climate and weathering
processes. A previous study (Hyland et al., 2016) analyzed a 1.5-km
laterally-continuous, consistently oxidized paleosol of the Eocene
Wasatch Fm. at Honeycomb Buttes in the Green River Basin (GRB),
and found it to be geochemically homogenous at that length-scale
except for δ<SUP>18</SUP>O of pedogenic carbonates. That work
focused on the reliability of pedogenic carbonate δ<SUP>18</SUP>O
for paleo-altimetry studies but did not address the uncertainty of
other paleoclimate proxies. To expand on this work, we sampled a 3-km
laterally-continuous floodplain paleosol of the Wasatch formation
at Oregon Buttes in the GRB. These 11 paleosol profiles had varying
redox conditions but were characterized by geochemical homogeneity with
respect to weathering indices and paleoclimate proxies. By resampling
a random subset (n=1 thru 11) of the profiles and recalculating
paleoclimate variables based only on their geochemistry, we improve
statistical uncertainties on some paleosol-based paleoclimate proxies,
which is critical because rarely is a single paleosol traceable
for hundreds of meters. Additionally, inter-basin comparison of
penecontemporaneous paleosols from the Wind River Basin (Hyland et
al., 2013) reinforces that paleoclimate interpretations should be
regionally limited. Paleosol-based paleoclimate studies should sample
multiple profiles whenever available to increase certainty and should
incorporate this type of uncertainty into their reconstructions.
---------------------------------------------------------
Title: Link between trees of fragmenting granules and deep downflows
in MHD simulation
Authors: Roudier, T.; Malherbe, J. M.; Stein, R. F.; Frank, Z.
2019A&A...622A.112R Altcode: 2019arXiv190103255R
Context. Trees of fragmenting granules (TFG) and associated flows
are suspected to play a major role in the formation of the network in
the quiet Sun. We investigate the counterparts, in terms of dynamics,
of surface structures detectable by high resolution observations in
deeper layers up to 15 Mm, which are only available from numerical
simulations. <BR /> Aims: The first aim is to demonstrate that TFG
can be evidenced either from surface intensitites, vertical (Vz),
or Doppler (Vdop) velocities. The second is to show that horizontal
flows, which are derived from intensities or Vz/Vdop flows, are in good
agreement, and that this is the case for observations and numerical
simulations. The third objective is to apply this new Vz-based method
to a 3D simulation to probe relationships between horizontal surface
flows, TFG, and deep vertical motions. <BR /> Methods: The TFG were
detected after oscillation filtering of intensities or Vz/Vdop flows,
using a segmentation and labelling technique. Surface horizontal
flows were derived from local correlation tracking (LCT) and from
intensities or Vz/Vdop flows. These methods were applied to Hinode
observations, 2D surface results of a first simulation, and 3D Vz
data of a second simulation. <BR /> Results: We find that TFG and
horizontal surface flows (provided by the LCT) can be detected either
from intensities or Vz/Vdop component, for high resolution observations
and numerical simulations. We apply this method to a 3D run providing
the Vz component in depth. This reveals a close relationship between
surface TFG (5 Mm mesoscale) and vertical downflows 5 Mm below the
surface. We suggest that the dynamics of TFG form larger scales
(the 15-20 Mm supergranulation) associated with 15 Mm downflowing
cells below the surface. <BR /> Conclusions: The TFG and associated
surface flows seem to be essential to understanding the formation
and evolution of the network at the meso and supergranular scale. <P
/>Movies associated to Figs. 3, 11, 12, and 14 are availabe at <A
href="https://www.aanda.org/10.1051/0004-6361/201834283/olm">https://www.aanda.org</A>
---------------------------------------------------------
Title: Dynamics of Trees of Fragmenting Granules in the Quiet Sun:
Hinode/SOT Observations Compared to Numerical Simulation
Authors: Malherbe, J. -M.; Roudier, T.; Stein, R.; Frank, Z.
2018SoPh..293....4M Altcode: 2018arXiv180401870M
We compare horizontal velocities, vertical magnetic fields, and the
evolution of trees of fragmenting granules (TFG, also named families of
granules) derived in the quiet Sun at disk center from observations
at solar minimum and maximum of the Solar Optical Telescope (SOT
on board Hinode) and results of a recent 3D numerical simulation
of the magneto-convection. We used 24-hour sequences of a 2D field
of view (FOV) with high spatial and temporal resolution recorded by
the SOT Broad band Filter Imager (BFI) and Narrow band Filter Imager
(NFI). TFG were evidenced by segmentation and labeling of continuum
intensities. Horizontal velocities were obtained from local correlation
tracking (LCT) of proper motions of granules. Stokes V provided a
proxy of the line-of-sight magnetic field (BLOS). The MHD simulation
(performed independently) produced granulation intensities, velocity,
and magnetic field vectors. We discovered that TFG also form in the
simulation and show that it is able to reproduce the main properties
of solar TFG: lifetime and size, associated horizontal motions, corks,
and diffusive index are close to observations. The largest (but not
numerous) families are related in both cases to the strongest flows
and could play a major role in supergranule and magnetic network
formation. We found that observations do not reveal any significant
variation in TFG between solar minimum and maximum.
---------------------------------------------------------
Title: The asteroseismic surface effect from a grid of 3D convection
simulations - I. Frequency shifts from convective expansion of
stellar atmospheres
Authors: Trampedach, Regner; Aarslev, Magnus J.; Houdek, Günter;
Collet, Remo; Christensen-Dalsgaard, Jørgen; Stein, Robert F.;
Asplund, Martin
2017MNRAS.466L..43T Altcode: 2016arXiv161102638T
We analyse the effect on adiabatic stellar oscillation frequencies
of replacing the near-surface layers in 1D stellar structure models
with averaged 3D stellar surface convection simulations. The main
difference is an expansion of the atmosphere by 3D convection,
expected to explain a major part of the asteroseismic surface effect,
a systematic overestimation of p-mode frequencies due to inadequate
surface physics. We employ pairs of 1D stellar envelope models and 3D
simulations from a previous calibration of the mixing-length parameter,
α. That calibration constitutes the hitherto most consistent matching
of 1D models to 3D simulations, ensuring that their differences are not
spurious, but entirely due to the 3D nature of convection. The resulting
frequency shift is identified as the structural part of the surface
effect. The important, typically non-adiabatic, modal components of
the surface effect are not included in this analysis, but relegated to
future papers. Evaluating the structural surface effect at the frequency
of maximum mode amplitude, ν<SUB>max </SUB>, we find shifts from δν =
-0.8 μHz for giants at log g = 2.2 to - 35 μHz for a (T<SUB>eff</SUB>
= 6901 K, log g = 4.29) dwarf. The fractional effect δν(ν<SUB>max
</SUB>)/ν<SUB>max </SUB>, ranges from -0.1 per cent for a cool dwarf
(4185 K, 4.74) to -6 per cent for a warm giant (4962 K, 2.20).
---------------------------------------------------------
Title: The Surface of Stellar Models - Now with more 3D simulations!
Authors: Trampedach, Regner; Christensen-Dalsgaard, Jørgen; Asplund,
Martin; Stein, Robert F.; Nordlund, Åke
2015EPJWC.10106064T Altcode:
We have constructed a grid of 3D hydrodynamic simulations of deep
convective and line-blanketed atmospheres. We have developed a
new consistent method for computing and employing T(τ) relations
from these simulations, as surface boundary conditions for 1D
stellar structure models. These 1D models have, in turn, had their
mixing-length, α, calibrated against the averaged structure of
each of the simulations. Both α and T(τ) vary significantly with
T<SUB>eff</SUB> and log g.
---------------------------------------------------------
Title: Improvements to stellar structure models, based on a grid of 3D
convection simulations - II. Calibrating the mixing-length formulation
Authors: Trampedach, Regner; Stein, Robert F.; Christensen-Dalsgaard,
Jørgen; Nordlund, Åke; Asplund, Martin
2014MNRAS.445.4366T Altcode: 2014arXiv1410.1559T
We perform a calibration of the mixing length of convection in stellar
structure models against realistic 3D radiation-coupled hydrodynamics
simulations of convection in stellar surface layers, determining
the adiabat deep in convective stellar envelopes. The mixing-length
parameter α is calibrated by matching averages of the 3D simulations
to 1D stellar envelope models, ensuring identical atomic physics
in the two cases. This is done for a previously published grid of
solar-metallicity convection simulations, covering from 4200 to 6900 K
on the main sequence, and from 4300 to 5000 K for giants with log g =
2.2. Our calibration results in an α varying from 1.6 for the warmest
dwarf, which is just cool enough to admit a convective envelope, and
up to 2.05 for the coolest dwarfs in our grid. In between these is a
triangular plateau of α ∼ 1.76. The Sun is located on this plateau
and has seen little change during its evolution so far. When stars
ascend the giant branch, they largely do so along tracks of constant
α, with α decreasing with increasing mass.
---------------------------------------------------------
Title: Interpreting the Helioseismic and Magnetic Imager (HMI)
Multi-Height Velocity Measurements
Authors: Nagashima, Kaori; Löptien, Björn; Gizon, Laurent; Birch,
Aaron C.; Cameron, Robert; Couvidat, Sebastien; Danilovic, Sanja;
Fleck, Bernhard; Stein, Robert
2014SoPh..289.3457N Altcode: 2014arXiv1404.3569N; 2014SoPh..tmp...84N
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.
---------------------------------------------------------
Title: Improvements to stellar structure models, based on a grid of
3D convection simulations - I. T(τ) relations
Authors: Trampedach, Regner; Stein, Robert F.; Christensen-Dalsgaard,
Jørgen; Nordlund, Åke; Asplund, Martin
2014MNRAS.442..805T Altcode: 2014arXiv1405.0236T
Relations between temperature, T, and optical depth, τ, are often
used for describing the photospheric transition from optically thick
to optically thin in stellar structure models. We show that this is
well justified, but also that currently used T(τ) relations are often
inconsistent with their implementation. As an outer boundary condition
on the system of stellar structure equations, T(τ) relations have an
undue effect on the overall structure of stars. In this age of precision
asteroseismology, we need to re-assess both the method for computing
and for implementing T(τ) relations, and the assumptions they rest
on. We develop a formulation for proper and consistent evaluation
of T(τ) relations from arbitrary 1D or 3D stellar atmospheres,
and for their implementation in stellar structure and evolution
models. We extract radiative T(τ) relations, as described by our
new formulation, from 3D simulations of convection in deep stellar
atmospheres of late-type stars from dwarfs to giants. These simulations
employ realistic opacities and equation of state, and account for
line blanketing. For comparison, we also extract T(τ) relations from
1DMARCSmodel atmospheres using the same formulation. T(τ) relations
from our grid of 3D convection simulations display a larger range of
behaviours with surface gravity, compared with those of conventional
theoretical 1D hydrostatic atmosphere models based on the mixing-length
theory for convection. The 1D atmospheres show little dependence on
gravity. 1D atmospheres of main-sequence stars also show an abrupt
transition to the diffusion approximation at τ ≃ 2.5, whereas the
3D simulations exhibit smooth transitions that occur at the same depth
for M ≃ 0.8 M<SUB>⊙</SUB>, and higher in the atmosphere for both
more and less massive main-sequence stars. Based on these results,
we recommend no longer using scaled solar T(τ) relations. Files with
T(τ) relations for our grid of simulations are made available to the
community, together with routines for interpolating in this irregular
grid. We also provide matching tables of atmospheric opacity, for
consistent implementation in stellar structure models.
---------------------------------------------------------
Title: Subsurface Structure of Active Regions
Authors: Stein, Robert F.; Nordlund, Aake
2014AAS...22410302S Altcode:
Magneto-convection simulations with horizontal, untwisted magnetic
field advected into the domain at large (20Mm) depth spontaneously
form magnetic loops which emerge as active regions. An active regions
emerges as a fragmented, braided magnetic loop. This is what makes the
magnetic flux first appear with mixed polarities, that then counter
stream into the leading and following spots at the loop legs. After
emergence, braided vertical legs are left behind which extend to large
depths in the convection zone at the down flow boundaries of the large
underlying convective cells. Movies of the emergence process and the
subsurface structure underneath the active region will be presented.
---------------------------------------------------------
Title: VizieR Online Data Catalog: T(tau) relations code (Trampedach+,
2014)
Authors: Trampedach, R.; Stein, R. F.; Christensen-Dalsgaard, J.;
Nordlund, A.; Asplund, M.
2014yCat..74420805T Altcode:
Radiative T({tau})-relations, in the form of generalised Hopf functions,
computed from a grid of 37, solar metallicity, realistic, 3D convection
simulations with radiative transfer. <P />(6 data files).
---------------------------------------------------------
Title: Simulations of Magnetic Flux Emergence
Authors: Stein, Robert; Nordlund, Aake
2014cosp...40E3196S Altcode:
Magnetic flux emerges from the solar surface on a wide range of
scales. We review recent simulations of both large and small scale
flux emergence. In our own simulations, we represent the magnetic flux
produced by the global dynamo as uniform, untwisted, horizontal field
advected into the simulation domain by supergranule scale inflows
at the bottom. Our computational domain extends from the temperature
minimum (half a megameter above the visible surface) to 20 Mm below
the surface, which is 10% of the depth of the convection zone, but
contains 2/3 of its scale heights. We investigate how magnetic flux
rises through the upper solar convection zone and emerges through
the surface. Convective up-flows and magnetic buoyancy bring field
toward the surface. Convective down-flows pin down field and prevent
its rise. Most of the field gets pumped downward by the convection,
but some field rises to the surface. The convective motions both
confine the flux concentrations (without the need for twist) and shred
them. This process creates a hierarchy of magnetic loops with smaller
loops riding "piggy-back", in a serpentine pattern, on larger loops. As
a result, magnetic flux emerges in a mixed polarity, "pepper and salt"
pattern. The small loops appear as horizontal field over granules
with their vertical legs in the bounding intergranular lanes. The
fields are quickly swept into the intergranular lanes. As the larger,
parent, flux concentrations reach the surface with their legs rooted
in the the downflow boundaries of the underlying, supergranule-scale,
convective cells near the bottom of the simulation domain, the
surface field counter-streams into separate, opposite polarity
concentrations, creating pores and spots. The subsurface magnetic
field lines of the pores and spots formed by the magneto-convection
(without being imposed as an initial condition) are braided, some
tightly, some loosely and they connect in complicated ways to the
surrounding field at large depths. The pores evolve on the timescale
of the underlying supergranules. Thus, long lives of solar active
regions imply that they are rooted in larger, more slowly evolving,
deeper convective structures. Based on these simulations we summarize
the robust properties of emerging magnetic flux.
---------------------------------------------------------
Title: Models of solar surface dynamics: impact on eigenfrequencies
and radius
Authors: Piau, L.; Collet, R.; Stein, R. F.; Trampedach, R.; Morel,
P.; Turck-Chièze, S.
2014MNRAS.437..164P Altcode: 2013arXiv1309.7179P; 2013MNRAS.tmp.2547P
We study the effects of different descriptions of the solar surface
convection on the eigenfrequencies of p modes. 1D evolution calculations
of the whole Sun and 3D hydrodynamic and magnetohydrodynamic simulations
of the current surface are performed. These calculations rely on
realistic physics. Averaged stratifications of the 3D simulations are
introduced in the 1D solar evolution or in the structure models. The
eigenfrequencies obtained are compared to those of 1D models relying
on the usual phenomenologies of convection and to observations of the
Michelson Doppler Imager instrument aboard the Solar Heliospheric
Observatory (SoHO). We also investigate how the magnetic activity
could change the eigenfrequencies and the solar radius, assuming that,
3 Mm below the surface, the upgoing plasma advects a 1.2 kG horizontal
field. All models and observed eigenfrequencies are fairly close below 3
mHz. Above 3 mHz the eigenfrequencies of the phenomenological convection
models are above the observed eigenfrequencies. The frequencies
of the models based on the 3D simulations are slightly below the
observed frequencies. Their maximum deviation is ≈3 μHz at 3 mHz
but drops below 1 μHz at 4 mHz. Replacing the hydrodynamic by the
magnetohydrodynamic simulation increases the eigenfrequencies. The shift
is negligible below 2.2 mHz and then increases linearly with frequency
to reach ≈1.7 μHz at 4 mHz. The impact of the simulated activity
is a 14 mas shrinking of the solar layers near the optical depth unity.
---------------------------------------------------------
Title: Models of the 5-Minute Oscillation and their Excitation
Authors: Stein, R. F.
2013ASPC..478...19S Altcode:
How our ideas about the nature of the p-mode oscillations have
evolved will be discussed first. In the beginning, two basic models
were considered: the effect of the acoustic cutoff frequency on
mode excitation and propagation and the existence of a resonant
cavity. The issue with the latter was the location of the cavity. Next
the evolution of our ideas on the excitation of the modes will be
described. Initially, the oscillations were thought to be driven by
convection. Then the possibility of overstability was explored. Now
we are back to the initial idea of stochastic excitation by convective
turbulence.
---------------------------------------------------------
Title: The Stagger-grid: A grid of 3D stellar atmosphere
models. I. Methods and general properties
Authors: Magic, Z.; Collet, R.; Asplund, M.; Trampedach, R.; Hayek,
W.; Chiavassa, A.; Stein, R. F.; Nordlund, Å.
2013A&A...557A..26M Altcode: 2013arXiv1302.2621M
<BR /> Aims: We present the Stagger-grid, a comprehensive grid of
time-dependent, three-dimensional (3D), hydrodynamic model atmospheres
for late-type stars with realistic treatment of radiative transfer,
covering a wide range in stellar parameters. This grid of 3D models is
intended for various applications besides studies of stellar convection
and atmospheres per se, including stellar parameter determination,
stellar spectroscopy and abundance analysis, asteroseismology,
calibration of stellar evolution models, interferometry, and extrasolar
planet search. In this introductory paper, we describe the methods
we applied for the computation of the grid and discuss the general
properties of the 3D models as well as of their temporal and spatial
averages (here denoted ⟨3D⟩ models). <BR /> Methods: All our models
were generated with the Stagger-code, using realistic input physics for
the equation of state (EOS) and for continuous and line opacities. Our ~
220 grid models range in effective temperature, T<SUB>eff</SUB>, from
4000 to 7000 K in steps of 500 K, in surface gravity, log g, from 1.5
to 5.0 in steps of 0.5 dex, and metallicity, [Fe/H], from - 4.0 to +
0.5 in steps of 0.5 and 1.0 dex. <BR /> Results: We find a tight scaling
relation between the vertical velocity and the surface entropy jump,
which itself correlates with the constant entropy value of the adiabatic
convection zone. The range in intensity contrast is enhanced at lower
metallicity. The granule size correlates closely with the pressure
scale height sampled at the depth of maximum velocity. We compare the
⟨3D⟩ models with currently widely applied one-dimensional (1D)
atmosphere models, as well as with theoretical 1D hydrostatic models
generated with the same EOS and opacity tables as the 3D models, in
order to isolate the effects of using self-consistent and hydrodynamic
modeling of convection, rather than the classical mixing length theory
approach. For the first time, we are able to quantify systematically
over a broad range of stellar parameters the uncertainties of 1D
models arising from the simplified treatment of physics, in particular
convective energy transport. In agreement with previous findings,
we find that the differences can be rather significant, especially
for metal-poor stars. <P />Appendices A-C are available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>Full
Table C.1 is available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A26">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A26</A>
---------------------------------------------------------
Title: VizieR Online Data Catalog: STAGGER-grid of 3D stellar
models. I. (Magic+, 2013)
Authors: Magic, Z.; Collet, R.; Asplund, M.; Trampedach, R.; Hayek,
W.; Chiavassa, A.; Stein, R. F.; Nordlund, A.
2013yCat..35570026M Altcode: 2013yCat..35579026M
The 3D model atmospheres presented here were constructed with
a custom version of the Stagger-code, a state-of-the-art,
multipurpose, radiative-magnetohydrodynamics (R-MHD)
code originally developed by Nordlund & Galsgaard (1995,
http://www.astro.ku.dk/~kg/Papers/MHD_code.ps.gz), and continuously
improved over the years by its user community. <P />(1 data file).
---------------------------------------------------------
Title: A Grid of Three-dimensional Stellar Atmosphere Models of Solar
Metallicity. I. General Properties, Granulation, and Atmospheric
Expansion
Authors: Trampedach, Regner; Asplund, Martin; Collet, Remo; Nordlund,
Åke; Stein, Robert F.
2013ApJ...769...18T Altcode: 2013arXiv1303.1780T
Present grids of stellar atmosphere models are the workhorses in
interpreting stellar observations and determining their fundamental
parameters. These models rely on greatly simplified models of
convection, however, lending less predictive power to such models of
late-type stars. We present a grid of improved and more reliable stellar
atmosphere models of late-type stars, based on deep, three-dimensional
(3D), convective, stellar atmosphere simulations. This grid is to be
used in general for interpreting observations and improving stellar
and asteroseismic modeling. We solve the Navier Stokes equations in
3D and concurrent with the radiative transfer equation, for a range
of atmospheric parameters, covering most of stellar evolution with
convection at the surface. We emphasize the use of the best available
atomic physics for quantitative predictions and comparisons with
observations. We present granulation size, convective expansion of the
acoustic cavity, and asymptotic adiabat as functions of atmospheric
parameters.
---------------------------------------------------------
Title: Granules in the Quiet and Magnetic Sun
Authors: Stein, Robert; Abramenko, Valentyna; Nordlund, Aake
2013enss.confE..17S Altcode:
High resolution magneto-convection simulations reveal that there are
significant differences in granulation in quiet and magnetic regions
of the Sun. In non-magnetic regions the granules have scalloped edges
(not smooth intergranualr lanes) in the emergent continuum radiation
and the vertical velocity at the edges of the intergranular lanes form
a branching tree structure extending into the granules. In magnetic
regions the intergranular lanes are smooth in both intensity and
vertical velocity but with swirls (vortices) in both. These differences
are borderline visible in data from the Big Bear NST.
---------------------------------------------------------
Title: Extracting multi-height velocity information from SDO/HMI
Dopplergrams
Authors: Nagashima, Kaori; Gizon, Laurent; Birch, Aaron; Loeptien,
Bjoern; Couvidat, Sebastien; Fleck, Bernhard; Stein, Robert
2013enss.confE..76N Altcode:
Multi-height velocity information in the solar atmosphere is useful for
many studies of the structure and dynamics of the solar atmosphere. We
discuss the possibility of measuring the vertical velocity at multiple
layers in the solar atmosphere using the six filtergrams of the Fe
I 6173A absorption line obtained by SDO/HMI. In the standard HMI
pipeline processing, these filtergrams are combined to estimate a
single Doppler velocity. Here we construct three Dopplergrams by
computing pair-wise differences between intensities in the blue
and red wings of the line. We use realistic numerical simulations
of convection to evaluate the range of heights that contribute to
each of our multi-height velocity estimates. The cross-spectra of
the Dopplergrams contain interesting information about vertical wave
propagation in the solar atmosphere.
---------------------------------------------------------
Title: Approach to Integrate Global-Sun Models of Magnetic Flux
Emergence and Transport for Space Weather Studies
Authors: Mansour, Nagi Nicolas; Wray, A.; Mehrotra, P.; Henney, C.;
arge, N.; Manchester, C.; Godinez, H.; Koller, J.; Kosovichev, A.;
Scherrer, P.; Zhao, J.; Stein, R.; Duvall, T.; Fan, Y.
2013enss.confE.125M Altcode:
The Sun lies at the center of space weather and is the source of its
variability. The primary input to coronal and solar wind models is
the activity of the magnetic field in the solar photosphere. Recent
advancements in solar observations and numerical simulations provide
a basis for developing physics-based models for the dynamics of
the magnetic field from the deep convection zone of the Sun to the
corona with the goal of providing robust near real-time boundary
conditions at the base of space weather forecast models. The goal is
to develop new strategic capabilities that enable characterization
and prediction of the magnetic field structure and flow dynamics of
the Sun by assimilating data from helioseismology and magnetic field
observations into physics-based realistic magnetohydrodynamics (MHD)
simulations. The integration of first-principle modeling of solar
magnetism and flow dynamics with real-time observational data via
advanced data assimilation methods is a new, transformative step in
space weather research and prediction. This approach will substantially
enhance an existing model of magnetic flux distribution and transport
developed by the Air Force Research Lab. The development plan is to use
the Space Weather Modeling Framework (SWMF) to develop Coupled Models
for Emerging flux Simulations (CMES) that couples three existing models:
(1) an MHD formulation with the anelastic approximation to simulate
the deep convection zone (FSAM code), (2) an MHD formulation with
full compressible Navier-Stokes equations and a detailed description
of radiative transfer and thermodynamics to simulate near-surface
convection and the photosphere (Stagger code), and (3) an MHD
formulation with full, compressible Navier-Stokes equations and an
approximate description of radiative transfer and heating to simulate
the corona (Module in BATS-R-US). CMES will enable simulations of the
emergence of magnetic structures from the deep convection zone to the
corona. Finally, a plan will be summarized on the development of a
Flux Emergence Prediction Tool (FEPT) in which helioseismology-derived
data and vector magnetic maps are assimilated into CMES that couples
the dynamics of magnetic flux from the deep interior to the corona.
---------------------------------------------------------
Title: Active Region Emergence
Authors: Stein, Robert; Nordlund, Aake
2013enss.confE..16S Altcode:
Neither a tachocline nor a globally coherent flux tube is necessary
to form an active region. Dynamo action in the convection zone and
magneto-convection together can produce active regions. We report
on a small scale model of such a process. For a global scale flux
tube to emerge from the tachocline and rise through the convective
zone, while maintaining its coherence and emerging with the proper
orientation and at the correct latitudes such coherent flux tubes must
have a field strength of 40-50 kG at the base of the convection zone
(Weber 2011). How they are formed with greater than equipartition
field strength, stored in and released from the tachocline has
long been a mystery. Recent simulations show that another scenario
is possible. Global scale magnetic wreaths are produced by dynamo
action inside the convection zone which reverse polarity (Nelson
2013). Both these global and also local surface simulations have
shown that convective motions produce magnetic loops from these
large scale wreaths which rise to the surface and produce active
regions. The local simulations of magnetic flux emergence show that
the field initially emerges over a confined area with horizontal
fields emerging over granules with mixed polarity vertical legs at
their ends in the intergranular lanes. The fields are quickly swept
into the intergranular lanes and then stream into separate, opposite
polarity concentrations producing pores and spots as is observed. These
simulations also provide insight into the subsurface structure of
spontaneously formed pores and spots.
---------------------------------------------------------
Title: Ab Initio Active Region Formation
Authors: Stein, Robert F.; Nordlund, A.
2013AAS...22141502S Altcode:
The tachocline is not necessary to produce active regions with their
global properties. Dynamo action within the convection zone can produce
large scale reversing polarity magnetic fields as shown by ASH code
and Charboneau et al simulations. Magneto-convection acting on this
large scale field produces Omega-loops which emerge through the surface
to produce active regions. The field first emerges as small bipoles
with horizontal field over granules anchored in vertical fields in the
intergranular lanes. The fields are quickly swept into the intergranular
lanes and produce a mixed polarity "pepper and salt" pattern. The
opposite polarities then migrate toward separate unipolar regions
due to the underlying large scale loop structure. When sufficient
flux concentrates, pores and sunspots form. We will show movies of
magneto-convection simulations of the emerging flux, its migration,
and concentration to form pores and spots, as well as the underlying
magnetic field evolution. In addition, the same atmospheric data has
been used as input to the LILIA Stokes Inversion code to calculate
Stokes spectra for the Fe I 630 nm lines and then invert them to
determine the magnetic field. Comparisons of the inverted field with the
simulation field shows that small-scale, weak fields, less than 100 G,
can not be accurately determined because of vertical gradients that are
difficult to match in fitting the line profiles. Horizontal smoothing
by telescope diffraction further degrades the inversion accuracy.
---------------------------------------------------------
Title: Flux Emergence and Pore Formation: What ATST can See
Authors: Stein, R. F.; Nordlund, Å.
2012ASPC..463...83S Altcode:
Pores form spontaneously in flux emergence simulations where minimally
structured (uniform, untwisted, horizontal) magnetic field rises from
a depth of 20 Mm. With 1 kG incident field pores formed after about
a turnover time (2 days). To compare what ATST will see with current
telescopes a very high resolution (6 km) magneto-convection simulation
was carried out with an initially uniform, vertical field. Stokes
V-profiles were compared for the simulation and as modified for the
diffraction pattern for the ATST and the SST.
---------------------------------------------------------
Title: Realistic numerical simulations of solar convection: emerging
flux, pores, and Stokes spectra
Authors: Georgobiani, D.; Stein, R.; Nordlund, A.
2012IAUSS...6E.102G Altcode:
We report on magneto-convection simulations of magnetic flux
emerging through the upper layers of the solar convection zone into
the photosphere. Simulations by Georgobiani, Stein and Nordlund start
from minimally structured, uniform, untwisted horizontal field advected
into the computational domain by supergranule scale inflows at 20 Mm
depth. At the opposite extreme, simulations by Cheung (2007, 2008,
2011) start with a coherent flux tube inserted into or forced into
the bottom of the computational domain. Several robust results have
emerged from the comparison of results from these two very different
initial states. First, rising magnetic flux gets deformed into
undulating, serpentine shapes by the influence of the convective up-
and down-flows. The flux develops fine structure and appears at the
surface first as a "pepper and salt" pattern of mixed polarity. Where
magnetic flux approaches the surface, granules become darker and
elongated in the direction of the field. Subsequently, the underlying
large scale magnetic structures make the field collect into unipolar
regions. Magneto-convection produces a complex, small-scale magnetic
field topology, whatever the initial state. A heirarchy of magnetic
loops corresponding to the different scales of convective motions are
produced. Vertical vortex tubes form at intergranule lane vertices which
can lead to tornado-like magnetic fields in the photosphere. Gradients
in field strength and velocity produce asymmetric Stokes spectra. Where
emerging Omega loops leave behind nearly vertical legs, long lived
pores can spontaneously form. The field in the pores first becomes
concentrated and evacuated near the surface and the evacuated flux
concentration then extends downward.
---------------------------------------------------------
Title: Helioseismic Data from Emerging Flux Simulations
Authors: Stein, R. F.; Lagerfjärd, A.; Nordlund, Å.; Georgobiani, D.
2012ASPC..462..345S Altcode:
Data from solar magneto-convection emerging flux simulations is
available for validating helioseismic inversion procedures. In these
simulations a uniform, untwisted, horizontal magnetic field is advected
by inflows at the bottom of the domain 48 Mm wide by 20 Mm deep and
rises to the surface. The evolution for different field strengths at
20 Mm depth has been investigated. The field emerges first in a mixed
polarity pepper and salt pattern, but then collects into separate,
unipolar concentrations and when enough flux has reached the surface,
pores are produced. In one case the field strength was artificially
increased and then the pores grew into spot-like structures with
penumbral-like borders. The online data consists of slices of vertical
and horizontal velocity and magnetic field strength at continuum
optical depths of 0.01, 0.1 and 1 as well as the emergent intensity
at one minute intervals plus four hour averages (with 2 hour cadence)
of the three-dimensional (3D) density, velocity, temperature, energy,
sound speed and magnetic field. The data can be found as links from the
web page: http://steinr.pa.msu.edu/∼bob/data.html. These calculation
were performed on the supercomputers of the NASA Advanced Supercomputing
Division and were supported by grants from NASA and NSF.
---------------------------------------------------------
Title: Emerging Flux Simulations
Authors: Stein, R. F.; Lagerfjärd, A.; Nordlund, Å.; Georgobiani, D.
2012ASPC..454..193S Altcode:
We simulate the rise through the upper convection zone and emergence
through the solar surface of initially uniform, untwisted, horizontal
magnetic flux that is advected into a domain 48 Mm wide by 20 Mm deep,
with the same entropy as the non-magnetic plasma. The magnetic field
is transported upward by the diverging upflows and pulled down in
the downdrafts, which produces a hierarchy of loop-like structures of
increasingly smaller scale as the surface is approached. 20 kG fields at
the bottom significantly modify the convective flows, leading to long
thin cells of ascending fluid aligned with the magnetic field. Their
magnetic buoyancy makes them rise to the surface faster than the
fluid rise time. A large scale magnetic loop is produced that, as
it emerges through the surface, leads to the formation of a bipolar
pore-like structure.
---------------------------------------------------------
Title: Solar Surface Magneto-Convection
Authors: Stein, Robert F.
2012LRSP....9....4S Altcode:
We review the properties of solar magneto-convection in the top half of
the convection zones scale heights (from 20 Mm below the visible surface
to the surface, and then through the photosphere to the temperature
minimum). Convection is a highly non-linear and nonlocal process, so
it is best studied by numerical simulations. We focus on simulations
that include sufficient detailed physics so that their results can be
quantitatively compared with observations.
---------------------------------------------------------
Title: On the Formation of Active Regions
Authors: Stein, Robert F.; Nordlund, Åke
2012ApJ...753L..13S Altcode: 2012arXiv1207.4248S
Magnetoconvection can produce an active region without an initial
coherent flux tube. A simulation was performed where a uniform,
untwisted, horizontal magnetic field of 1 kG strength was advected into
the bottom of a computational domain 48 Mm wide by 20 Mm deep. The
up and down convective motions produce a hierarchy of magnetic loops
with a wide range of scales, with smaller loops riding "piggy-back"
in a serpentine fashion on larger loops. When a large loop approaches
the surface, it produces a small active region with a compact leading
spot and more diffuse following spots.
---------------------------------------------------------
Title: Magneto-convection
Authors: Stein, R. F.
2012RSPTA.370.3070S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Emerging Flux Simulations and Proto-Active Regions
Authors: Stein, R. F.; Lagerfjärd, A.; Nordlund, &.; Georgobiani, D.
2012ASPC..455..133S Altcode: 2011arXiv1102.1049S
The emergence of minimally structured (uniform and horizontal) magnetic
field from a depth of 20 Mm has been simulated. The field emerges first
in a mixed polarity pepper and salt pattern, but then collects into
separate, unipolar concentrations and produces pores. The field strength
was then artificially increased to produce spot-like structures. The
field strength at continuum optical depth unity peaks at 1 kG, with
a maximum of 4 kG. Where the vertical field is strong, the spots
persist (at present an hour of solar time has been simulated). Where
the field is weak, the spot gets filled in and disappears. Stokes
profiles have been calculated and processed with the Hinode annular
Modulation Transfer Function, the slit diffraction, and frequency
smoothing. These data are available at steinr.pa.msu.edu/∼bob/stokes.
---------------------------------------------------------
Title: Spontaneous Pore Formation in Magneto-Convection Simulations
Authors: Stein, R.; Nordlund, A.
2012ASPC..456...39S Altcode:
Pores form spontaneously in simulations of minimaly structured (uniform,
untwisted, horizontal) magnetic field emerging from a depth of 20
Mm in a 48 Mm wide domain. The input field strength at the bottom
was slowly increased from 200 G to 1 kG with an e-folding time of 5
hours and thereafter held constant. After about a turnover time (2
days) pores formed. The pore's magnetic concentration first developed
near the surface when magnetic loops passed into the solar atmosphere
(through the upper boundary at the temperature minimum) leaving behind
their vertical legs. The magnetic concentration then extended downward
all the way to the bottom at 20 Mm depth. The minimum intensity in the
pore is 20% of the average intensity. The magnetic flux has reached
about 2×10<SUP>20</SUP> Mx and the field is nearly vertical in the
pore interior and inclined more than 45<SUP>o</SUP> to the vertical
at the edges. The pores have existed for 10 hours so far.
---------------------------------------------------------
Title: Pore Formation and Evolution
Authors: Stein, Robert F.; Nordlund, A.
2012AAS...22020620S Altcode:
Pores form spontaneously in magneto-convection simulations over a
wide range of initial conditions. These simulations were initiated
by convective inflows at the bottom advecting minimally structured,
uniform, untwisted, horizontal field into the computational
domain. Typically a pore forms when a magnetic loop rises through
the upper boundary of the simulation domain leaving behind its two
nearly vertical legs. In one case the pore formed directly in one of
the legs and in another it assembled from smaller individual magnetic
flux concentrations. The flux concentration that becomes a pore first
forms near the surface and then extends downwards. The cooling and
evacuation of the flux concentration also begin near the surface and
extend downward. Eventually, the entire 20 Mm depth of the box was
included. The turnover time at 20 Mm depth is about 2 days. So far
the longest lived pore has existed for about half a day. One of the
pores is slowly rotating. Supported by NSF grant AGS 1141921 and NASA
grant NNX08AF44G.
---------------------------------------------------------
Title: Photospheric Magnetic Fields from Magneto-Convection
Simulations
Authors: Stein, Robert F.; Nordlund, Aake; Georgobiani, Dali
2012decs.confE..95S Altcode:
We present the properties of photospheric magnetic fields from
magneto-convection simulations and as they would be observed by Hinode,
for both quiet Sun and plage regions. This will include statistical
properties, morphology, Stokes spectra, energy fluxes and correlations
with convection dynamics. The rate of flux emergence will be discussed
as a constraint on model parameters.
---------------------------------------------------------
Title: Simulations of the solar atmosphere and solar limbs
Authors: Piau, L.; Stein, R. F.; Melo, S.; Turck-Chièze, S.;
Thuillier, G.; Hauchecorne, A.
2011sf2a.conf..407P Altcode:
We perform simulations of the solar atmosphere either using the
1D hydrostatic code Atlas12 or the 3D (magneto)hydrodynamic code
Stagger. The former numerical tool relies on a phenomenology of
convection whereas the later one addresses the surface convection
directly and accounts for its dynamical effects. Once the average
atmosphere stratification is obtained it is used to perform radiative
transfer at speficic wavelengths in order to compute the solar limb
darkening. We report a ≈ 60 mas shift between inflection point
positions of limb profiles computed from 1D and 3D models. This is due
to turbulent support present in 3D simulations but not 1D. We further
report a slight decrease of the turbulent support when a moderate
magnetic field is included in the simulation which suggests that the
solar radius should be anti-correlated with the solar activity cycle.
---------------------------------------------------------
Title: Turbulent Diffusion in the Photosphere as Derived from
Photospheric Bright Point Motion
Authors: Abramenko, V. I.; Carbone, V.; Yurchyshyn, V.; Goode, P. R.;
Stein, R. F.; Lepreti, F.; Capparelli, V.; Vecchio, A.
2011ApJ...743..133A Altcode: 2011arXiv1111.4456A
On the basis of observations of solar granulation obtained with the
New Solar Telescope of Big Bear Solar Observatory, we explored proper
motion of bright points (BPs) in a quiet-sun area, a coronal hole, and
an active region plage. We automatically detected and traced BPs and
derived their mean-squared displacements as a function of time (starting
from the appearance of each BP) for all available time intervals. In all
three magnetic environments, we found the presence of a super-diffusion
regime, which is the most pronounced inside the time interval of 10-300
s. Super-diffusion, measured via the spectral index, γ, which is the
slope of the mean-squared displacement spectrum, increases from the
plage area (γ = 1.48) to the quiet-sun area (γ = 1.53) to the coronal
hole (γ = 1.67). We also found that the coefficient of turbulent
diffusion changes in direct proportion to both temporal and spatial
scales. For the minimum spatial scale (22 km) and minimum time scale
(10 s), it is 22 and 19 km<SUP>2</SUP> s<SUP>-1</SUP> for the coronal
hole and the quiet-sun area, respectively, whereas for the plage area
it is about 12 km<SUP>2</SUP> s<SUP>-1</SUP> for the minimum time
scale of 15 s. We applied our BP tracking code to three-dimensional
MHD model data of solar convection and found the super-diffusion with
γ = 1.45. An expression for the turbulent diffusion coefficient as
a function of scales and γ is obtained.
---------------------------------------------------------
Title: Manganese-rich brown layers in Arctic Ocean sediments:
Composition, formation mechanisms, and diagenetic overprint
Authors: März, C.; Stratmann, A.; Matthiessen, J.; Meinhardt, A. -K.;
Eckert, S.; Schnetger, B.; Vogt, C.; Stein, R.; Brumsack, H. -J.
2011GeCoA..75.7668M Altcode:
We present inorganic geochemical analyses of pore waters and sediments
of two Late Quaternary sediment cores from the western Arctic Ocean
(southern Mendeleev Ridge, RV Polarstern Expedition ARK-XXIII/3),
focussing on the composition and origin of distinct, brown-colored,
Mn-rich sediment layers. Carbonate enrichments occur in association
with these layers as peaks in Ca/Al, Mg/Al, Sr/Al and Sr/Mg, suggesting
enhanced input of both ice-rafted and biogenic carbonate. For the first
time, we show that the Mn-rich layers layers are also consistently
enriched in the scavenged trace metals Co, Cu, Mo and Ni. Distinct
bioturbation patterns, specifically well-defined brown burrows into
the underlying sediments, suggest these metal enrichments formed close
to the sediment-water interface. The geochemical signature of these
metal- and carbonate-rich layers most probably documents formation
under warmer climate conditions with an intensified continental
hydrological cycle and only seasonal sea ice cover. Both rivers and sea
ice delivered trace metals to the Arctic Ocean, while enhanced seasonal
productivity exported reactive organic matter to the sea floor. The
coeval deposition of organic matter, Mn (oxyhydr)oxides and trace
metals triggered intense diagenetic Mn cycling at the sediment-water
interface. These processes resulted in the formation of Mn and trace
metal enrichments, and the degradation of labile organic matter. With
the onset of cooler conditions, reduced riverine runoff and/or a
solid sea ice cover terminated the input of riverine trace metal and
fresh organic matter, resulting in deposition of grayish-yellowish,
metal-poor sediments. Oxygen depletion of Arctic bottom waters under
these cooler conditions is not supported by our data, and did not cause
the sedimentary Mn distribution. While the original composition and
texture of the brown layers resulted from specific climatic conditions
and corresponding diagenetic processes, pore water data show that
diagenetic Mn redistribution is still affecting the organic-poor deeper
sediments. Given persistent steady state conditions, purely authigenic
Mn-rich brown layers may form, while others may be partly or completely
dissolved. The degree of diagenetic Mn redistribution largely depends
on the depositional environment, the Mn and organic matter availability,
and apparently affected the Co/Mo ratios of Mn-rich layers. Thus, brown
Arctic layers are not necessarily synchronous features, and should not
be correlated across the Arctic Ocean without additional age control.
---------------------------------------------------------
Title: Realistic MHD Simulations of Magneto-Convection
Authors: Stein, Robert F.
2011sdmi.confE..85S Altcode:
We review recent progress in magneto-convection simulatins, especially
magnetic flux emergence. Very different simulations have shown that flux
first emerges in a random, mixed polarity, "pepper-and-salt" pattern
and then collects into unipolar regions due to the underlying larger
scale field topology. Convection predominantly drags the magnetic field
downward, but upflows and buoyancy bring some flux to the surface in
the form of serpentine small Omega_ and U- loops riding piggy back
on the larger loops rising from the deeper convection zone. Flux
concentrations first develop close to the surface and then extend
downward. In our simulations, we find that strong flux concentrations
develop pores. They have a filamentary structure near the surface and
extend down through the entire 20 Mm depth of the simulation domain. As
expected, the magnetic field is nearly vertical in pore interiors and
becomes nearly horizontal at the pore boundaries.
---------------------------------------------------------
Title: Magnetic Fields: Modeling And ATST Observations
Authors: Stein, Robert F.; Georgobiani, D.; Nordlund, A.; Lagerfjard,
A.
2011SPD....42.0804S Altcode: 2011BAAS..43S.0804S
We have performed magneto-convection simulations starting from
snapshots of hydrodynamic convection with initial conditions both
of uniform vertical magnetic field and with minimally structured
(uniform, untwisted), horizontal magnetic field advected into
the computational domain from a depth of 20 Mm. One clear result
is that while the magnetic field can collect into large-scale
concentrations - pores and sunspots - most of the magnetic flux is
in small concentrations with steep horizontal gradients in the field
and plasma properties. Furthermore, the field strength distribution
is a power law with slope between -1 and -2, so most of the field
at the surface is weak. A large aperture telescope, such as ATST, is
needed both to collect sufficient photons to measure the ubiquitous
weak fields and to resolve the small-scale magnetic features. <P
/>We present results on flux emergence, pore formation, and Stokes
spectra as they would appear in Hinode and ATST compared with the
raw simulation.For those interested in analyzing the simulation data,
it is available online at steinr.pa.msu.edu/ bob/data.html. There are
slices of the velocity and magnetic field vectors at continuum optical
depths of 1, 0.1, and 0.01 and the emergent intensity have been saved
at 1 minute intervals. Four hour averages, with 2 hour cadence for the
3D cube for variables: velocity, magnetic field, density, temperature,
sound speed, and internal energy have been computed. Stokes spectra
have been computed for the Hinode FeI 630 nm lines, processed with the
Hinode annular mtf, the slit diffraction and frequency smoothing. <P
/>This work has been supported by NASA grants NNX07AO71G, NNX07AH79G and
NNX08AH44G and NSF grant AST0605738. The simulations where performed
on the Pleiades cluster of the NASA Advanced Supercomputing Division
at the Ames Research Center.
---------------------------------------------------------
Title: The Mass Mixing Length in Convective Stellar Envelopes
Authors: Trampedach, Regner; Stein, Robert F.
2011ApJ...731...78T Altcode: 2011arXiv1102.1102T
The scale length over which convection mixes mass in a star can
be calculated as the inverse of the vertical derivative of the
unidirectional (up or down) mass flux. This is related to the mixing
length in the mixing length theory of stellar convection. We give
the ratio of mass mixing length to pressure scale height for a grid
of three-dimensional surface convection simulations, covering from
4300 K to 6900 K on the main sequence, and up to giants at log g =
2.2, all for solar composition. These simulations also confirm what is
already known from solar simulations that convection does not proceed by
discrete convective elements, but rather as a continuous, slow, smooth,
warm upflow and turbulent, entropy deficient, fast down drafts. This
convective topology also results in mixing on a scale comparable to
the classic mixing length formulation, and is simply a consequence of
mass conservation on flows in a stratified atmosphere.
---------------------------------------------------------
Title: Solar Flux Emergence Simulations
Authors: Stein, R. F.; Lagerfjärd, A.; Nordlund, Å.; Georgobiani, D.
2011SoPh..268..271S Altcode: 2009arXiv0912.4938S; 2010SoPh..tmp...34S
We simulate the rise through the upper convection zone and emergence
through the solar surface of initially uniform, untwisted, horizontal
magnetic flux, with the same entropy as the nonmagnetic plasma,
that is advected into a domain 48 Mm wide by 20 Mm deep. The magnetic
field is advected upward by the diverging upflows and pulled down in
the downdrafts, which produces a hierarchy of loop-like structures
of increasingly smaller scale as the surface is approached. There are
significant differences between the behavior of fields of 10 kG and 20
or 40 kG strength at 20 Mm depth. The 10 kG fields have little effect
on the convective flows and show small magnetic-buoyancy effects,
reaching the surface in the typical fluid rise time from 20 Mm depth
of 32 hours. 20 and 40 kG fields significantly modify the convective
flows, leading to long, thin cells of ascending fluid aligned with
the magnetic field and their magnetic buoyancy makes them rise to the
surface faster than the fluid rise time. The 20 kG field produces a
large-scale magnetic loop that as it emerges through the surface leads
to the formation of a bipolar, pore-like structure.
---------------------------------------------------------
Title: Flux Emergence Simulations
Authors: Stein, Robert F.; Lagerfjard, Anders; Nordlund, Ake;
Giorgobiani, Dali
2010shin.confE..82S Altcode:
In a supergranule scale domain (48 Mm wide by 20 Mm deep) we have
simulated the rise and emergence through the solar surface of initially
minimally structured (uniform and untwisted) horizontal magnetic flux
with the same entropy as the non-magnetic surrounding plasma. We have
studied two cases with field strengths of 20 and 5 kG are advected into
the domain at 20 Mm depth. The stronger field has significant buoyancy,
while the weaker does not. The 20 kG field significantly modifies the
convection, the 5 kG field does not. The fields initially emerge in a
mixed polarity salt and pepper pattern. Subsequently, the different
polarities collect in isolated, unipolar regions due to the action
of underlying, large scale magnetic loop structures. The vertical
field distribution has peaks at 0 and 2 kG at continuum optical depth
0.1. Where the field is strong it tends to be vertical and where
it is weak it tends to be horizontal. Pores are produced and as the
unsigned vertical flux increases they become larger. Stokes profiles
have been calculated.
---------------------------------------------------------
Title: Developing Physics-Based Procedures for Local Helioseismic
Probing of Sunspots and Magnetic Regions
Authors: Birch, Aaron; Braun, D. C.; Crouch, A.; Rempel, M.; Fan,
Y.; Centeno, R.; Toomre, J.; Haber, D.; Hindman, B.; Featherstone,
N.; Duvall, T., Jr.; Jackiewicz, J.; Thompson, M.; Stein, R.; Gizon,
L.; Cameron, R.; Saidi, Y.; Hanasoge, S.; Burston, R.; Schunker, H.;
Moradi, H.
2010AAS...21630805B Altcode:
We have initiated a project to test and improve the local helioseismic
techniques of time-distance and ring-diagram analysis. Our goals are
to develop and implement physics-based methods that will (1) enable the
reliable determinations of subsurface flow, magnetic field, and thermal
structure in regions of strong magnetic fields and (2) be quantitatively
tested with realistic solar magnetoconvection simulations in the
presence of sunspot-like magnetic fields. We are proceeding through a
combination of improvements in local helioseismic measurements, forward
modeling of the helioseismic wavefield, kernel computations, inversions,
and validation through numerical simulations. As improvements over
existing techniques are made they will be applied to the SDO/HMI
observations. This work is funded through the the NASA Heliophysics
Science Division through the Solar Dynamics Observatory (SDO) Science
Center program.
---------------------------------------------------------
Title: Supergranule Scale Flux Emergence Simulations
Authors: Stein, Robert F.; Lagerfjard, A.; Nordlund, A.; Georgobiani,
D.
2010AAS...21621103S Altcode:
We simulate the rise of initially horizontal, untwisted magnetic flux
from 20 Mm depth through the near surface convection to the solar
surface in a domain 48 Mm wide. The magnetic field is transported
upward by diverging upflows aided by magnetic buoyancy, and pushed
down by downdrafts, which produces a hierarchy of loop like structures,
of increasingly smaller scale as the surface is approached. We compare
two cases with field strengths of 5 and 20 kG at 20 Mm depth. In the
stronger field strength case, the magnetic field significantly disturbs
the convection below 3 Mm, inhibiting the vertical motion, shutting
off convective energy transport and producing elongated cellular
structures in the field direction. Shallower than 3 Mm the convection
appears normal, but with concentrated vertical magnetic concentrations
("flux tubes") extending through the surface and producing pores where
the field is greatest. Even in the weaker field case, the magnetic
field inhibits vertical motions and the convective transport of
energy although the convective cellular pattern is not significantly
distorted. This work was supported by NSF grant AST065738 and NASA
grants NNX08AH44G, NNX07AH79G and NNX07AO71G. The simulations were
performed at the NASA Advanced Supercomputing Division of the Ames
Research Center.
---------------------------------------------------------
Title: The Thermal Relaxation Time
Authors: Stein, Robert F.; Nordlund, A.
2010AAS...21631302S Altcode: 2010BAAS...41Q.888S
The thermal relaxation time for an atmosphere is the ratio of the
thermal energy content to the energy flux, which can be much longer
than the dynamic turn over time. We will discuss this issue and provide
examples from simulations of solar convection in a domain extending
from the surface to 20 Mm below the surface. At 20 Mm the turnover time
is 2 days. The thermal relaxation time at 10 Mm depth is 2 years and
at 20 Mm depth it is 19 years. This work was supported by NASA grants
NNX07AH79G and NNX08AH44G and NSF grant AST0605738.
---------------------------------------------------------
Title: Supergranulation-Scale Convection Simulations
Authors: Stein, R. F.; Nordlund, Å.; Georgoviani, D.; Benson, D.;
Schaffenberger, W.
2009ASPC..416..421S Altcode:
Results of realistic simulations of solar surface convection on the
scale of supergranules (96 Mm wide by 20 Mm deep) are presented. The
simulations cover only 10% of the geometric depth of the solar
convection zone, but half its pressure scale heights. They include the
hydrogen ionization zone, and the first and most of the second helium
ionization zones. The horizontal velocity spectrum is a power law,
and the horizontal size of the dominant convective cells increases
with increasing depth. Convection is driven by buoyancy work, which
is largest close to the surface, but significant over the entire
domain. Close to the surface, buoyancy driving is balanced by the
divergence of the kinetic energy flux, but deeper down it is balanced
by dissipation. The damping length of the turbulent kinetic energy
is 4 pressure scale heights. The mass mixing length is 1.8 scale
heights. Two thirds of the area is upflowing fluid except very close
to the surface. The internal (ionization) energy flux is the largest
contributor to the convective flux for temperatures less than 40,000
K and the thermal energy flux is the largest contributor at higher
temperatures. This data set is useful for validating local helioseismic
inversion methods. Sixteen hours of data are available as four hour
averages, with two hour cadence, at steinr.msu.edu/~bob/96averages,
as idl save files. The variables stored are the density, temperature,
sound speed, and three velocity components. In addition, the three
velocity components at 200 km above mean continuum optical depth unity
are available at 30 second cadence.
---------------------------------------------------------
Title: Solar Magneto-Convection Simulations of Emergin Flux
Authors: Stein, R. F.; Lagerfjard, A.; Nordlund, A.; Geogobiani, D.;
Benson, D.
2009AGUFMSH11B..05S Altcode:
We present preliminary results of magneto-convection simulations
of the rise of initially horizontal magnetic flux from 20 Mm deep
through the solar surface in a domain 48 Mm wide. The magnetic field
is advected upward by the diverging upflows and pulled down in the
downdrafts which produces a hierarchy of loop like structures, of
increasingly smaller scale as the surface is approached. Stronger
fields rise faster due to magnetic buoyancy (lower density in the
strong field region). Slow, large scale, diverging motions sweep the
magnetic field to the boundaries of supergranular like structures to
form a magnetic network. The field strength varies with depth as the
cube root of the density.
---------------------------------------------------------
Title: Comparing the Hinode and SOHO/MDI Data to the Simulated Large
Scale Solar Convection
Authors: Georgobiani, D.; Zhao, J.; Kosovichev, A.; Benson, D.; Stein,
R. F.; Nordlund, Å.
2009ASPC..415..421G Altcode:
Large-scale simulations of solar turbulent convection produce realistic
data and provide a unique opportunity to study solar oscillations
and test various techniques commonly used for the analysis of solar
observations. We applied helioseismic methods to the sets of simulated
as well as observed data and find remarkable similarities. Power
spectra, k-ν diagrams, time-distance diagrams exhibit similar details,
although sometimes subtle differences are present.
---------------------------------------------------------
Title: Supergranulation Scale Convection Simulations
Authors: Stein, R. F.; Lagerfjård, A.; Nordlund, Å.; Georgobiani,
D.; Benson, D.; Schaffenberger, W.
2009ASPC..415...63S Altcode:
Results of realistic simulations of solar surface convection on
the scale of supergranules (48 and 96 Mm wide by 20 Mm deep) are
presented. The simulations include the hydrogen, first and most
of the second helium ionization zones. Horizontal magnetic field is
advected into the domain by upflows at the bottom. Upflows stretch the
field lines upward, while downflows push them down, thus producing
loop like magnetic structures. The mass mixing length is 1.8 scale
heights. Two thirds of the area is upflowing fluid except very close
to the surface. The internal (ionization) energy flux is the largest
contributor to the convective flux for temperatures less than 40,000
K and the thermal energy flux is the largest contributor at higher
temperatures. The data is available for evaluating local helioseismic
procedures.
---------------------------------------------------------
Title: Solar Surface Convection
Authors: Nordlund, Åke; Stein, Robert F.; Asplund, Martin
2009LRSP....6....2N Altcode:
We review the properties of solar convection that are directly
observable at the solar surface, and discuss the relevant underlying
physics, concentrating mostly on a range of depths from the temperature
minimum down to about 20 Mm below the visible solar surface.
---------------------------------------------------------
Title: Impact of the physical processes in the modeling of HD 49933
Authors: Piau, L.; Turck-Chièze, S.; Duez, V.; Stein, R. F.
2009A&A...506..175P Altcode: 2009arXiv0907.4336P
Context: On its asteroseismic side, the initial run of CoRoT was
partly devoted to the solar like star HD 49933. The eigenmodes of this
F dwarf have been observed with unprecedented accuracy. <BR />Aims:
We investigate quantitatively the impact of changes in the modeling
parameters like mass and composition. More importantly we investigate
how a sophisticated physics affects the seismological picture of
HD 49933. We consider the effects of diffusion, rotation and the
changes in convection efficiency. <BR />Methods: We use the CESAM
stellar evolution code coupled to the ADIPLS adiabatic pulsation
package to build secular models and their associated oscillation
frequencies. We also exploited the hydrodynamical code STAGGER to
perform surface convection calculations. The seismic variables used in
this work are: the large frequency separation, the derivative of the
surface phase shift, and the eigenfrequencies ν<SUB>ℓ=0,n=14</SUB>
and ν<SUB>ℓ=0,n=27</SUB>. <BR />Results: Mass and uncertainties on
the composition have much larger impacts on the seismic variables we
consider than the rotation. The derivative of the surface phase shift is
a promising variable for the determination of the helium content. The
seismological variables of HD 49933 are sensitive to the assumed solar
composition and also to the presence of diffusion in the models.
---------------------------------------------------------
Title: Accurate Radiation Hydrodynamics and MHD Modeling of 3-D
Stellar Atmospheres
Authors: Nordlund, Å.; Stein, R. F.
2009AIPC.1171..242N Altcode:
Stellar atmospheres provide a unique and valuable testing ground
for radiation hydrodynamics and MHD. Spectral line synthesis based
on reasonably affordable 3-D models can potentially reach very high
accuracy, with widths, strengths, and shapes of photospheric spectral
lines matching observations to within fractions of a percent, with “no
free parameters” i.e., using only the effective temperature, surface
acceleration of gravity, and element abundances as input parameters,
and without the need for artificial fitting parameters such as micro-
and macro-turbulence. When combined with accurate atomic parameters
the results can be used to determine the abundance of individual
chemical elements more accurately than was possible in the past,
when spectral line synthesis was based on one-dimensional modeling
and artificial fitting parameters. A necessary condition for reaching
the desired accuracy is that the radiative energy transfer in the
photosphere is treated with sufficient accuracy. Since at different
levels in stellar atmospheres different wavelength regions dominate
the energy exchange between the gas and the radiation field this is
a non-trivial and potentially very computer intensive problem. We
review the computationally efficient methods that are being used to
achieve accurate solutions to this problem, addressing in particular
the relation to the solar “oxygen abundance problem.” In this context
we also briefly comment on “look-alike” radiative transfer methods
such as Flux Limited Diffusion.
---------------------------------------------------------
Title: Magnetohydrodynamic Characteristic Boundary Conditions
Authors: Schaffenberger, Werner; Stein, R.
2009SPD....40.0930S Altcode:
We implemented MHD characteristic boundary conditions for a non-ideal
plasma in the "stagger-code" (Gudiksen and Nordlund, 2005, ApJ 618,
1020). The aim of these boundary conditions is to reduce reflection
at the boundaries which is important for the simulation of wave
propagation. We present some test simulations of propagating waves
demonstrating the capability of these boundary conditions.
---------------------------------------------------------
Title: Solar Magneto-Convection Simulations
Authors: Stein, Robert F.; Lagerfjard, A.; Nordlund, A.; Benson, D.;
Georgobiani, D.; Schaffenberger, W.
2009SPD....40.0401S Altcode:
We present preliminary results of magneto-convection simulations
of the rise of initially horizontal magnetic flux from 20 Mm deep
through the solar surface in a domain 48 Mm wide. The magnetic field
is stretched upward in the diverging upflows and pulled down in the
downdrafts which produces a hierarchy of loop like structures. The
strength varies with depth as the square root of the density. The field
is swept to the boundaries of small supergranular like structures to
form a magnetic network.
---------------------------------------------------------
Title: Simulated Large Scale Solar Convection Versus Observations:
A Multiwavelength Approach
Authors: Georgobiani, Dali; Zhao, J.; Kosovichev, A. G.; Benson, D.;
Stein, R. F.; Nordlund, A.
2009SPD....40.0301G Altcode:
The realistic 3D radiative-hydrodynamic simulations of the upper layers
of solar convection provide a perfect opportunity to validate various
techniques, widely used in solar physics and helioseismology. Our
aim is to perform multiwavelength analysis of large scale flows. We
analyze the simulated intensity and velocities at certain heights
in the solar atmosphere, and compare our results with the outcome
of the similar analysis of the SOHO/MDI and Hinode observations. To
fine tune the comparison, we use the instrumental response functions
to weigh the simulated parameters at different heights to emulate
the observational lines. We find the remarkable similarity between
the simulated and observed power spectra, their spatial parts, and
time-distance diagrams. This demonstrates one more time that the
simulations can be efficiently used to perform and validate local
helioseismology techniques, and to study solar flows and structures
beneath the surface, inaccessible for direct observations.
---------------------------------------------------------
Title: Supergranulation Scale Convection Simulations
Authors: Stein, Robert F.; Georgobiani, Dali; Schafenberger, Werner;
Nordlund, Åke; Benson, David
2009AIPC.1094..764S Altcode: 2009csss...15..764S
Results of realistic simulations of solar surface convection on the
scale of supergranules (96 Mm wide by 20 Mm deep) are presented. The
simulations cover only 10% of the geometric depth of the solar
convection zone, but half its pressure scale heights. They include the
hydrogen, first and most of the second helium ionization zones. The
horizontal velocity spectrum is a power law and the horizontal
size of the dominant convective cells increases with increasing
depth. Convection is driven by buoyancy work which is largest close
to the surface, but significant over the entire domain. Close to the
surface buoyancy driving is balanced by the divergence of the kinetic
energy flux, but deeper down it is balanced by dissipation. The
damping length of the turbulent kinetic energy is 4 pressure scale
heights. The mass mixing length is 1.8 scale heights. Two thirds of the
area is upflowing fluid except very close to the surface. The internal
(ionization) energy flux is the largest contributor to the convective
flux for temperatures less than 40,000 K and the thermal energy flux
is the largest contributor at higher temperatures.
---------------------------------------------------------
Title: Solar Dynamo and Magnetic Self-Organization
Authors: Kosovichev, A. G.; Arlt, R.; Bonanno, A.; Brandenburg,
A.; Brun, A. S.; Busse, F.; Dikpati, M.; Hill, F.; Gilman, P. A.;
Nordlund, A.; Ruediger, G.; Stein, R. F.; Sekii, T.; Stenflo, J. O.;
Ulrich, R. K.; Zhao, J.
2009astro2010S.160K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Supergranulation Scale Connection Simulations
Authors: Stein, R. F.; Nordlund, A.; Georgobiani, D.; Benson, D.;
Schaffenberger, W.
2008arXiv0811.0472S Altcode:
Results of realistic simulations of solar surface convection on the
scale of supergranules (96 Mm wide by 20 Mm deep) are presented. The
simulations cover only 10% of the geometric depth of the solar
convection zone, but half its pressure scale heights. They include the
hydrogen, first and most of the second helium ionization zones. The
horizontal velocity spectrum is a power law and the horizontal
size of the dominant convective cells increases with increasing
depth. Convection is driven by buoyancy work which is largest close
to the surface, but significant over the entire domain. Close to the
surface buoyancy driving is balanced by the divergence of the kinetic
energy flux, but deeper down it is balanced by dissipation. The
damping length of the turbulent kinetic energy is 4 pressure scale
heights. The mass mixing length is 1.8 scale heights. Two thirds of the
area is upflowing fluid except very close to the surface. The internal
(ionization) energy flux is the largest contributor to the convective
flux for temperatures less than 40,000 K and the thermal energy flux is
the largest contributor at higher temperatures. This data set is useful
for validating local helioseismic inversion methods. Sixteen hours
of data are available as four hour averages, with two hour cadence,
at steinr.msu.edu/~bob/96averages, as idl save files. The variables
stored are the density, temperature, sound speed, and three velocity
components. In addition, the three velocity components at 200 km above
mean continuum optical depth unity are available at 30 sec. cadence.
---------------------------------------------------------
Title: Surface convection in Population II stars
Authors: Piau, Laurent; Stein, Robert F.
2008IAUS..252..253P Altcode:
The initial surface abundances of Population II stars have been altered
by the interplay between convection, rotational mixing and diffusion. In
particular the shallower the outer convection zone the stronger the
diffusion impact. We present preliminary results on constraining the
extension of the convection zones of Population II stars thanks to 3D
hydrodynamical simulations.
---------------------------------------------------------
Title: Surface Convection
Authors: Stein, Robert F.; Benson, David; Georgobiani, Dali; Nordlund,
Åke; Schaffenberger, Werner
2007AIPC..948..111S Altcode:
What are supergranules? Why do they stand out? Preliminary results from
realistic simulations of solar convection on supergranule scales (96 Mm
wide by 20 Mm deep) are presented. The solar surface velocity amplitude
is a decreasing power law from the scale of granules up to giant cells
with a slight enhancement at supergranule scales. The simulations show
that the size of the horizontal convective cells increases gradually
and continuously with increasing depth. Without magnetic fields
present there is, as yet, no enhancement at supergranule scales at the
surface. A hypothesis is presented that it is the balance between the
rate of magnetic flux emergence and the horizontal sweeping of magnetic
flux by convective motions that determines the size of the magnetic
network and produces the extra power at supergranulation scales.
---------------------------------------------------------
Title: Helioseismic Holography of Simulated Solar Convection and
Prospects for the Detection of Small-Scale Subsurface Flows
Authors: Braun, D. C.; Birch, A. C.; Benson, D.; Stein, R. F.;
Nordlund, Å.
2007ApJ...669.1395B Altcode: 2007arXiv0708.0214B
We perform helioseismic holography on realistic solar convection
simulations and compare the observed travel-time perturbations
with the expected travel times from the horizontal flows in the
simulations computed from forward models under the assumption of
the Born approximation. We demonstrate reasonable agreement between
the observed and model travel times, which reinforces the validity
of helioseismic holography in the detection of subsurface horizontal
flows. An assessment is made of the uncertainty of the measured p-mode
travel times from the rms of the residuals. From the variation of the
signal-to-noise ratio with depth we conclude that the helioseismic
detection of individual flow structures with spatial scales of
supergranulation or smaller is not possible for depths below about 5 Mm
below the surface over timescales of less than a day. The travel-time
noise estimated from these simulations appears to be similar to noise
in measurements made using solar observations. We therefore suggest
that similar limitations exist regarding the detection of analogous
subsurface flows in the Sun. A study of the depth dependence of
the contribution to the travel-time perturbations for focus depths
between 3 and 7 Mm is made, showing that approximately half of the
observed signal originates within the first 2 Mm below the surface. A
consequence of this is a rapid decrease (and reversal in some cases)
of the travel-time perturbations with depth due to the contribution to
the measurements of oppositely directed surface flows in neighboring
convective cells. This confirms an earlier interpretation of similar
effects reported from observations of supergranulation.
---------------------------------------------------------
Title: Solar Magneto-Convection Simulations
Authors: Stein, R. F.; Benson, D.; Nordlund, A.
2007ASPC..369...87S Altcode:
We review recent realistic simulations of solar surface
magneto-convection in small meso-granule scale Cartesian domains
and global scale interior magneto-convection in spherical
shells. Implications for the solar dynamo are also discussed.
---------------------------------------------------------
Title: Helioseismic Holography of Simulated Solar Convection and
Prospects for the Detection of Small-Scale Subsurface Flows
Authors: Braun, Douglas; Birch, A. C.; Benson, D.; Stein, R. F.;
Nordlund, A.
2007AAS...210.2201B Altcode: 2007BAAS...39..124B
We perform helioseismic holography on the solar convection simulations
of Benson, Stein, and Nordlund and compare the observed acoustic
travel-time perturbations with the expected travel times from the
horizontal flows in the simulations computed from forward models under
the assumption of the Born approximation. The agreement between the
observed and model travel times reinforces the validity of helioseismic
holography in the detection of subsurface horizontal flows. However,
from the variation of the signal-to-noise ratio with depth, we conclude
that the local helioseismic detection of individual supergranule-size
(or smaller) flow patterns is not possible for depths below about
5 Mm below the surface over time scales less than a day. We suggest
that similar limitations exist regarding the detection of analogous
subsurface flows in the Sun. We also study the depth dependence of
the contribution to the travel-time perturbations for the simulated
flows. For holography measurements focused down to 7 Mm, we find
that approximately half of the observed signal originates within
the first 2 Mm below the surface. A consequence of this is a a rapid
decrease (and possible reversal) of the travel-time perturbations with
increasing focus depth due to the contribution to the measurements of
oppositely directed surface flows in neighboring convective cells. This
confirms an earlier interpretation of similar effects reported from
holographic analyses of observations of supergranulation. <P />This
work is supported by NASA contracts NNH05CC76C and NNH04CC05C, NSF
grant AST-0406225 , and a subcontract through the HMI project at
Stanford University awarded to NWRA, and by NASA grant NNG04GB92G and
NSF grant AST-0605738 to MSU.
---------------------------------------------------------
Title: Validating Time-Distance Helioseismology by Use of Realistic
Simulations of Solar Convection
Authors: Zhao, Junwei; Georgobiani, D.; Kosovichev, A. G.; Benson,
D.; Stein, R. F.; Nordlund, A.
2007AAS...210.2203Z Altcode: 2007BAAS...39..124Z
Recent progress in realistic simulations of solar convection have
enabled us to evaluate the robustness of solar interior structures
and dynamics obtained by methods of local helioseismology. We
present results of testing the time-distance method using realistic
simulations. By computing acoustic wave propagation time and distance
relations for different depths of the simulated data, we confirm that
acoustic waves propagate into the interior and then turn back to the
photosphere. For the surface gravity waves (f-mode), we calculate
perturbations of their travel times, caused by localized downdrafts,
and demonstrate that the spatial pattern of these perturbations
(representing so-called sensitivity kernels) is similar to the
patterns obtained from the real Sun, displaying characteristic
hyperbolic structures. We then test the time-distance measurements
and inversions by calculating acoustic travel times from a sequence
of vertical velocities at the photosphere of the simulated data, and
inferring a mean 3D flow fields by performing inversion based on the
ray approximation. The inverted horizontal flow fields agree very well
with the simulated data in subsurface areas up to 3 Mm deep, but differ
in deeper areas. These initial tests provide important validation of
time-distance helioseismology measurements of supergranular-scale
convection, illustrate limitations of this technique, and provide
guidance for future improvements.
---------------------------------------------------------
Title: Application of convection simulations to oscillation excitation
and local helioseismology
Authors: Stein, Robert F.; Benson, David; Georgobiani, Dali; Nordlund,
Åke
2007IAUS..239..331S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Realistic Solar Convection Simulations
Authors: Stein, Robert F.; Nordlund, A.
2007AAS...210.2205S Altcode: 2007BAAS...39..125S
We report on the progress of our supergranule scale realistic solar
convection simulations with horizontal dimensions of 96 Mm and 48 Mm (57
hours) and a depth of 20 Mm. Snapshots are saved at 1 min intervals. The
results from these simulations are available to the community. They
are especially useful for testing local helioseismic <P />techniques as
is reported elsewhere at this meeting. The simulations were performed
on the NASA Advanced Supercomputing Division "Columbia" computer and
was supported by NASA grant NNG04GB92G and NSF grant AST 0605738.
---------------------------------------------------------
Title: Validation of Time-Distance Helioseismology by Use of Realistic
Simulations of Solar Convection
Authors: Zhao, Junwei; Georgobiani, Dali; Kosovichev, Alexander G.;
Benson, David; Stein, Robert F.; Nordlund, Åke
2007ApJ...659..848Z Altcode: 2006astro.ph.12551Z
Recent progress in realistic simulations of solar convection have
given us an unprecedented opportunity to evaluate the robustness of
solar interior structures and dynamics obtained by methods of local
helioseismology. We present results of testing the time-distance
method using realistic simulations. By computing acoustic wave
propagation time and distance relations for different depths of the
simulated data, we confirm that acoustic waves propagate into the
interior and then turn back to the photosphere. This demonstrates
that in numerical simulations properties of acoustic waves (p-modes)
are similar to the solar conditions, and that these properties can be
analyzed by the time-distance technique. For surface gravity waves
(f-modes), we calculate perturbations of their travel times caused
by localized downdrafts and demonstrate that the spatial pattern of
these perturbations (representing so-called sensitivity kernels)
is similar to the patterns obtained from the real Sun, displaying
characteristic hyperbolic structures. We then test time-distance
measurements and inversions by calculating acoustic travel times from
a sequence of vertical velocities at the photosphere of the simulated
data and inferring mean three-dimensional flow fields by performing
inversion based on the ray approximation. The inverted horizontal
flow fields agree very well with the simulated data in subsurface
areas up to 3 Mm deep, but differ in deeper areas. Due to the cross
talk effects between the horizontal divergence and downward flows,
the inverted vertical velocities are significantly different from the
mean convection velocities of the simulation data set. These initial
tests provide important validation of time-distance helioseismology
measurements of supergranular-scale convection, illustrate limitations
of this technique, and provide guidance for future improvements.
---------------------------------------------------------
Title: Local Helioseismology and Correlation Tracking Analysis of
Surface Structures in Realistic Simulations of Solar Convection
Authors: Georgobiani, Dali; Zhao, Junwei; Kosovichev, Alexander G.;
Benson, David; Stein, Robert F.; Nordlund, Åke
2007ApJ...657.1157G Altcode: 2006astro.ph..8204G
We apply time-distance helioseismology, local correlation tracking, and
Fourier spatial-temporal filtering methods to realistic supergranule
scale simulations of solar convection and compare the results with
high-resolution observations from the Solar and Heliospheric Observatory
(SOHO) Michelson Doppler Imager (MDI). Our objective is to investigate
the surface and subsurface convective structures and test helioseismic
measurements. The size and grid of the computational domain are
sufficient to resolve various convective scales from granulation to
supergranulation. The spatial velocity spectrum is approximately a
power law for scales larger than granules, with a continuous decrease
in velocity amplitude with increasing size. Aside from granulation
no special scales exist, although a small enhancement in power at
supergranulation scales can be seen. We calculate the time-distance
diagram for f- and p-modes and show that it is consistent with the SOHO
MDI observations. From the simulation data we calculate travel-time
maps for surface gravity waves (f-mode). We also apply correlation
tracking to the simulated vertical velocity in the photosphere to
calculate the corresponding horizontal flows. We compare both of these
to the actual large-scale (filtered) simulation velocities. All three
methods reveal similar large-scale convective patterns and provide an
initial test of time-distance methods.
---------------------------------------------------------
Title: Excitation of solar-like oscillations across the HR diagram
Authors: Samadi, R.; Georgobiani, D.; Trampedach, R.; Goupil, M. J.;
Stein, R. F.; Nordlund, Å.
2007A&A...463..297S Altcode: 2006astro.ph.11762S
Aims:We extend semi-analytical computations of excitation rates for
solar oscillation modes to those of other solar-like oscillating stars
to compare them with recent observations <BR />Methods: Numerical
3D simulations of surface convective zones of several solar-type
oscillating stars are used to characterize the turbulent spectra
as well as to constrain the convective velocities and turbulent
entropy fluctuations in the uppermost part of the convective zone of
such stars. These constraints, coupled with a theoretical model for
stochastic excitation, provide the rate P at which energy is injected
into the p-modes by turbulent convection. These energy rates are
compared with those derived directly from the 3D simulations. <BR
/>Results: The excitation rates obtained from the 3D simulations
are systematically lower than those computed from the semi-analytical
excitation model. We find that P<SUB>max</SUB>, the P maximum, scales as
(L/M)<SUP>s</SUP> where s is the slope of the power law and L and M are
the mass and luminosity of the 1D stellar model built consistently
with the associated 3D simulation. The slope is found to depend
significantly on the adopted form of χ_k, the eddy time-correlation;
using a Lorentzian, χ_k^L, results in s=2.6, whereas a Gaussian,
χ_k^G, gives s=3.1. Finally, values of V_max, the maximum in the mode
velocity, are estimated from the computed power laws for P_max and we
find that V<SUB>max</SUB> increases as (L/M)<SUP>sv</SUP>. Comparisons
with the currently available ground-based observations show that the
computations assuming a Lorentzian χ<SUB>k</SUB> yield a slope, sv,
closer to the observed one than the slope obtained when assuming a
Gaussian. We show that the spatial resolution of the 3D simulations
must be high enough to obtain accurate computed energy rates.
---------------------------------------------------------
Title: Velocities Measured in Small-Scale Solar Magnetic Elements
Authors: Langangen, Øystein; Carlsson, Mats; Rouppe van der Voort,
Luc; Stein, R. F.
2007ApJ...655..615L Altcode: 2006astro.ph.11741L
We have obtained high-resolution spectrograms of small-scale magnetic
structures with the Swedish 1-m Solar Telescope. We present Doppler
measurements at 0.2" spatial resolution of bright points, ribbons,
and flowers, and their immediate surroundings, in the C I λ5380.3 line
(formed in the deep photosphere) and the two Fe I lines at 5379.6 and
5386.3 Å. The velocity inside the flowers and ribbons are measured to
be almost zero, while we observe downflows at the edges. These downflows
are increasing with decreasing height. We also analyze realistic
magnetoconvective simulations to obtain a better understanding of the
interpretation of the observed signal. We calculate how the Doppler
signal depends on the velocity field in various structures. Both the
smearing effect of the nonnegligible width of this velocity response
function along the line of sight and of the smearing from the telescope
and atmospheric point-spread function are discussed. These studies lead
us to the conclusion that the velocity inside the magnetic elements
is really upflow of order 1-2 km s<SUP>-1</SUP>, while the downflows
at the edges really are much stronger than observed, of order 1.5-3.3
km s<SUP>-1</SUP>.
---------------------------------------------------------
Title: Supergranulation Scale Convection Simulations
Authors: Benson, D.; Stein, R.; Nordlund, Å.
2006ASPC..354...92B Altcode:
Initial results are reported for 3D simulations of solar convection on
a supergranular scale (48 Mm wide by 20 Mm deep). Results from several
solar hours of simulation at the 48 Mm scale are available as well as 24
solar hours on the 24 Mm scale. Relaxation is rapid near the surface,
but very slow at large depths and large horizontal scales. These
simulations will help separate the role of the second Helium ionization
zone from the effect of the increasing scale height with depth and will
be of use in analyzing local helioseismic inversion techniques. Since
Coriolis forces become significant on these spatio-temporal scales,
f-plane rotation will be added to investigate the nature of the surface
shear layer. Magnetic fields will also be added to study the development
and maintenance of the magnetic network.
---------------------------------------------------------
Title: Solar MHD Theory and Observations: A High Spatial Resolution
Perspective
Authors: Leibacher, John; Stein, Robert F.; Uitenbroek, Han
2006ASPC..354.....L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spatial and Temporal Spectra of Solar Convection
Authors: Georgobiani, D.; Stein, R. F.; Nordlund, Å.
2006ASPC..354..109G Altcode:
Recent observations support the theory that solar-type oscillations
are stochastically excited by turbulent convection in the outer
layers of the solar-like stars. The acoustic power input rates
depend on the details of the turbulent energy spectrum. <P />We
use numerical simulations to study the spectral properties of solar
convection. We find that spatial turbulent energy spectra vary at
different temporal frequencies, while temporal turbulent spectra show
various features at different spatial wavenumbers, and their best fit
at all frequencies is a generalized power law Power = Amplitude ×
(frequency^2 + width^2)^{-n(k)}, where n(k) depends on the spatial
wavenumber. Therefore, it is impossible to separate the spatial and
temporal components of the turbulent spectra.
---------------------------------------------------------
Title: Supergranule scale convection simulations
Authors: Stein, R. F.; Benson, D.; Georgobiani, D.; Nordlund, Å.
2006ESASP.624E..79S Altcode: 2006soho...18E..79S
No abstract at ADS
---------------------------------------------------------
Title: Rapid Temporal Variability of Faculae: High-Resolution
Observations and Modeling
Authors: De Pontieu, B.; Carlsson, M.; Stein, R.; Rouppe van der Voort,
L.; Löfdahl, M.; van Noort, M.; Nordlund, Å.; Scharmer, G.
2006ApJ...646.1405D Altcode:
We present high-resolution G-band observations (obtained with the
Swedish 1 m Solar Telescope) of the rapid temporal variability of
faculae, which occurs on granular timescales. By combining these
observations with magnetoconvection simulations of a plage region, we
show that much of this variability is not intrinsic to the magnetic
field concentrations that are associated with faculae, but rather
a phenomenon associated with the normal evolution and splitting of
granules. We also show examples of facular variability caused by
changes in the magnetic field, with movies of dynamic behavior of
the striations that dominate much of the facular appearance at 0.1"
resolution. Examples of these dynamics include merging, splitting,
rapid motion, apparent fluting, and possibly swaying.
---------------------------------------------------------
Title: Solar supergranulation-scale simulations
Authors: Stein, R. F.; Benson, D.; Nordlund, A.
2006IAUJD..17E..15S Altcode:
In order to understand the nature of supergranulation and provide a
test bed for calibrating local helioseismic methods we have performed
a realistic solar surface convection simulation on supergranulation
scales (48 Mm wide by 20 Mm deep), whose duration is currently
48 hours. The simulation includes f-plane rotation and develops a
surface shear layer. There is a gradual increase in the horizontal
scale of upflows with increasing depth due to merging of downflows
advected by the larger scale diverging upflows from below. There is
a rich spectrum of p-modes excited in the simulation. This data set
is available for studying solar oscillations and local helioseismic
inversion techniques. We will shortly be initiating an even larger-
scale simulation, 96 Mm wide, containing an active region.
---------------------------------------------------------
Title: Supergranulation-Scale Simulations of the Solar Convection Zone
Authors: Benson, David; Stein, R. F.; Nordlund, A.
2006SPD....37.3003B Altcode: 2006BAAS...38..256B
We report on the status of solar surface supergranulation scale
simulations (48Mm x 48Mm x 20Mm (deep)). Effects of f-plane rotation
at a latitude of 30 degrees are included. These simulations were
bootstrapped from smaller width calculations which were relaxed for 3
turnover times (6 days) and have now relaxed for another turnover time
at the full width. The size of dominant structures increases with depth,
due to the halting of some downdrafts and the merging of others as they
descend, to form the boundaries of the larger horizontal upflows. These
large scale structures are also visible at the surface with a velocity
amplitude that decreases linearly with increasing size. We thank NASA
and NSF for their support of this work.
---------------------------------------------------------
Title: Time-Distance and Correlation Tracking Analysesof Convective
Structures using Realistic Large-ScaleSimulations of Solar Convection
Authors: Georgobiani, Dali; Zhao, J.; Kosovichev, A. G.; Benson, D.;
Stein, R. F.; Nordlund, A.
2006SPD....37.0509G Altcode: 2006BAAS...38..224G
Recent large-scale simulations of solar turbulentconvection and
oscillations produce a wealth of realisticdata and provide a great
opportunity to study solaroscillations and test various techniques,
such aslocal helioseismology or local correlation trackingmethods,
widely used for the analysis of the realobserved solar data.The
application of the time-distance analysis to theartificial data produced
with a realistic 3D radiativehydrodynamic code successfully reproduces
thetime-distance diagram and travel time maps. Resultingtravel times are
similar to the travel times obtainedfrom the SOHO/MDI observations. To
further validatethe model, the inversion will be performed in
orderto infer the interior velocities at various depthsand compare
them with the simulated data.f-mode time-distanceanalysis as well as
local correlation tracking can be usedto study the morphology of the
simulated convection. Bothmethods reveal the large-scale convective
structures, whichare also directly visible in the time-averaged
simulatedflow fields.
---------------------------------------------------------
Title: Solar Small-Scale Magnetoconvection
Authors: Stein, R. F.; Nordlund, Å.
2006ApJ...642.1246S Altcode:
Magnetoconvection simulations on mesogranule and granule scales near
the solar surface are used to study the effect of convective motions on
magnetic fields: the sweeping of magnetic flux into downflow lanes, the
twisting of magnetic field lines, and the emergence and disappearance
of magnetic flux tubes. From weak seed fields, convective motions
produce highly intermittent magnetic fields in the intergranular lanes
that collect over the boundaries of the underlying mesogranular scale
cells. Instances of both emerging magnetic flux loops and magnetic
flux disappearing from the surface occur in the simulations. We show
an example of a flux tube collapsing to kilogauss field strength and
a case of flux disappearance due to submergence of the flux. We note
that observed Stokes profiles of small magnetic structures are severely
distorted by telescope diffraction and seeing, so caution is needed
in interpreting low-resolution vector magnetograms of small-scale
magnetic structures.
---------------------------------------------------------
Title: Simulation of Quiet-Sun Waves in the Ca II Infrared Triplet
Authors: Pietarila, A.; Socas-Navarro, H.; Bogdan, T.; Carlsson, M.;
Stein, R. F.
2006ApJ...640.1142P Altcode: 2005astro.ph.10744P
The Ca II infrared triplet lines around 8540 Å are good candidates
for observing chromospheric magnetism. Model spectra of these lines
are obtained by combining a radiation hydrodynamic simulation with a
Stokes synthesis code. The simulation shows interesting time-varying
behavior of the Stokes V profiles as waves propagate through the
formation region of the lines. Disappearing and reappearing lobes
in the Stokes V profiles as well as profile asymmetries are closely
related to the atmospheric velocity gradients.
---------------------------------------------------------
Title: Simulated Solar Plages
Authors: Stein, R. F.; Carlsson, M.; de Pontieu, B.; Scharmer, G.;
Nordlund, Å.; Benson, D.
2006apri.meet...30S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Time-distance analysis of realistic simulations of solar
convection
Authors: Georgobiani, D.; Zhao, J.; Benson, D.; Stein, R. F.;
Kosovichev, A. G.; Nordlund, A.
2005AGUFMSH41A1117G Altcode:
The results of the new realistic large-scale simulations of solar
turbulent convection provide an unprecedented opportunity to study
solar oscillations and perform similar local helioseismology techniques
as for the real solar data. The results offer an unique opportunity
to compare the simulated flow fields with the flows and sounds speed
variations inferred from the time-distance analysis. Applying some
of the existing local helioseismology methods to the simulated solar
convection and comparing to the observed results, one can validate
the accuracy of these methods. We apply the time-distance analysis
to the simulated data and successfully obtain the time-distance
curve and travel time maps. Our travel times are consistent with the
SOHO/MDI observations. The next step is to perform inversion to infer
the interior flow fields at various depths and compare them with the
simulated data in order to validate the model. This work is currently
in progress.
---------------------------------------------------------
Title: Effect of the radiative background flux in convection
Authors: Brandenburg, A.; Chan, K. L.; Nordlund, Å.; Stein, R. F.
2005AN....326..681B Altcode: 2005astro.ph..8404B
Numerical simulations of turbulent stratified convection are used
to study models with approximately the same convective flux, but
different radiative fluxes. As the radiative flux is decreased, for
constant convective flux: the entropy jump at the top of the convection
zone becomes steeper, the temperature fluctuations increase and the
velocity fluctuations decrease in magnitude, and the distance that
low entropy fluid from the surface can penetrate increases. Velocity
and temperature fluctuations follow mixing length scaling laws.
---------------------------------------------------------
Title: Spectrum and amplitudes of internal gravity waves excited by
penetrative convection in solar-type stars
Authors: Dintrans, B.; Brandenburg, A.; Nordlund, Å.; Stein, R. F.
2005A&A...438..365D Altcode: 2005astro.ph..2138D
The excitation of internal gravity waves by penetrative convective
plumes is investigated using 2-D direct simulations of compressible
convection. The wave generation is quantitatively studied from the
linear response of the radiative zone to the plumes penetration,
using projections onto the g-modes solutions of the associated linear
eigenvalue problem for the perturbations. This allows an accurate
determination of both the spectrum and amplitudes of the stochastically
excited modes. Using time-frequency diagrams of the mode amplitudes,
we then show that the lifetime of a mode is around twice its period
and that during times of significant excitation up to 40% of the total
kinetic energy may be contained into g-modes.
---------------------------------------------------------
Title: Excitation of Solar-like Oscillations: From PMS to MS Stellar
Models
Authors: Samadi, R.; Goupil, M. -J.; Alecian, E.; Baudin, F.;
Georgobiani, D.; Trampedach, R.; Stein, R.; Nordlund, Å.
2005JApA...26..171S Altcode:
The amplitude of solar-like oscillations results from a balance between
excitation and damping. As in the sun, the excitation is attributed
to turbulent motions that stochastically excite the p modes in the
upper-most part of the convective zone. We present here a model for the
excitation mechanism. Comparisons between modeled amplitudes and helio
and stellar seismic constraints are presented and the discrepancies
discussed. Finally the possibility and the interest of detecting
such stochastically excited modes in pre-main sequence stars are
also discussed.
---------------------------------------------------------
Title: Supergranulation Scale Solar Convection Simulations
Authors: Benson, D.; Stein, R.; Nordlund, A.
2005AGUSMSP11C..05B Altcode:
Supergranulation scale (50 Mm wide by 20 Mm deep) simulations of solar
convection are being relaxed thermally and dynamically. The initial
state was made by duplicating a periodic smaller simulation of 24
Mm wide by 9 Mm deep and extending it in depth assuming constant
entropy upflows and extrapolating the downflows. Relaxation is
rapid near the surface, but very slow at large depths and large
horizontal scales. Initial results are reported. These simulations
will help separate the role of the second helium ionization zone from
the effect of the increasing scale height with depth. This large
size is also necessary for analyzing local helioseismic inversion
techniques. Coriolis forces becomes significant on these spatio-temporal
scales and we have added f-plane rotation to investigate the nature
of the surface shear layer. Eventually, magnetic fields will be added
to study the development and maintenance of the magnetic network.
---------------------------------------------------------
Title: Excitation of P-Modes in the Sun and Stars
Authors: Stein, Robert; Georgobiani, Dali; Trampedach, Regner; Ludwig,
Hans-Günter; Nordlund, Åke
2005HiA....13..411S Altcode:
We describe the stochastic excitation of p-mode oscillations by solar
convection. We discuss the role of Reynolds stresses and entropy
fluctuations what controls the excitation spectrum the depth of the
driving and the location of the driving. We then present results for
a range of other stars and discuss the similarities and differences
with the Sun.
---------------------------------------------------------
Title: Chromospheric Heating and Dynamics
Authors: Carlsson, M.; Stein, R. F.
2004ASPC..325..243C Altcode:
We review observations of the dynamics and energetics of the solar
chromosphere. The observations are interpreted with the help of
detailed radiation hydrodynamic modelling. It is concluded that
acoustic waves play an important role for the dynamics and energetics
of the chromosphere but additional heating is necessary, even for the
internetwork regions. This additional heating is strongly correlated
with the observed magnetic field strength.
---------------------------------------------------------
Title: Excitation rates of p modes: mass luminosity relation across
the HR diagram
Authors: Samadi, R.; Georgobiani, D.; Trampedach, R.; Goupil, M. J.;
Stein, R. F.; Nordlund, Å.
2004sf2a.conf..323S Altcode: 2004astro.ph.10043S
We compute the rates P at which energy is injected into the p modes for
a set of 3D simulations of outer layers of stars. We found that Pmax
- the maximum in P - scales as (L/M)^s where s is the slope of the
power law, L and M are the luminosity and the mass of the 1D stellar
models associated with the simulations. The slope is found to depend
significantly on the adopted representation for the turbulent eddy-time
correlation function, chi_k. According to the expected performances
of COROT, it will likely be possible to measure Pmax as a function
of L/M and to constrain the properties of stellar turbulence as the
turbulent eddy time-correlation.
---------------------------------------------------------
Title: Mode Conversion in Magneto-Atmospheres
Authors: Bogdan, T. J.; Carlsson, M.; Hansteen, V.; Heggland, L.;
Leer, E.; McMurry, A. D.; Stein, R. F.
2004AGUFMSH13A1162B Altcode:
Numerical simulations of wave propagation in a simple magneto-atmosphere
are employed to illustrate the complex nature of wave transformation
and conversion taking place in solar and stellar atmospheres. An
isothermal atmosphere threaded by a potential poloidal magnetic
field, and a superposed uniform toroidal field, is treated in a local
cartesian approximation. Spatial variations are restricted to the
two poloidal dimensions, but the toroidal field ensures that all
three MHD waves are present in the simulation. As in our previous
purely two-dimensional simulations (Bogdan et al. ApJ 599, 626-60,
2003), mode mixing and transformation take place at surfaces where
the magnetic and thermal pressures are equal. In the present case,
the upward propagating acoustic-gravity (MAG) wave is converted into
roughly equal parts transmitted fast, intermediate (Alfven), and
slow magneto-acoustic-gravity waves in passing through this mixing
layer. Unlike the fast and slow waves, the Alfven wave is weakly
damped, and is able to deposit its energy and momentum in the upper
chromosphere and corona. The fast and slow MAG waves are decoupled
on either side of mixing layer owing to their disparate propagation
speeds. Under certain fortuitous circumstances, the Alfven wave also
decouples from the fast and slow MAG waves.
---------------------------------------------------------
Title: Supergranulation Scale Solar Convection Simulations
Authors: Benson, D.; Stein, R.; Nordlund, A.
2004AAS...20517401B Altcode: 2005BAAS...37..377B
Solar convection simulations have been started on small supergranulation
scales of 24 x 24 Mm x 9 Mm deep. The initial state was made by
duplicating a periodic smaller simulation of 12 x 12 Mm x 9 Mm
deep and adding a small velocity perturbation. This state has now
relaxed for about 2 hours. Near the surface, the initial pattern
has disappeared, but in deeper layers the predominant duplication
in each horizontal direction is still present. We estimate it will
take about width/horizontal velocity at depth = 24 Mm / (0.15 km/s) =
43 hours to dynamically relax and develop structures on the scale of
24 Mm. Since this is the size of small supergranules, we expect that
one of these will eventually develop after a few turnover times. The
evolution of the convective structure at various depths is shown. <P
/>Eventually, a region 48 x 48 Mm x 18 Mm deep will be simulated. This
will help separate the role of the second helium ionization zone from
the effect of the increasing scale height with depth. This large
size is also necessary for analyzing local helioseismic inversion
techniques. Coriolis forces become significant on these spatio-temporal
scales. We will investigate the surface shear layer that should develop
with the inclusion of f-plane rotation. Finally, magnetic fields will
be added to study the development and maintenance of the magnetic
network. <P />This work is supported by NASA grants NAG 512450 and
NNG046-B92G and NSF grant AST0205500.
---------------------------------------------------------
Title: High Degree Solar Oscillations in 3d Numerical Simulations
Authors: Georgobiani, D.; Stein, R. F.; Nordlund, Å.; Kosovichev,
A. G.; Mansour, N. N.
2004ESASP.559..267G Altcode: 2004soho...14..267G
No abstract at ADS
---------------------------------------------------------
Title: Oscillation Power Spectra of the Sun and of CEN a: Observations
Versus Models
Authors: Samadi, R.; Goupil, M. J.; Baudin, F.; Georgobiani, D.;
Trampedach, R.; Stein, R.; Nordlund, A.
2004ESASP.559..615S Altcode: 2004astro.ph..9325S; 2004soho...14..615S
Hydrodynamical, 3D simulations of the outer layers of the Sun and Alpha
Cen A are used to obtain constraints on the properties of turbulent
convection in such stars. These constraints enable us to compute -
on the base of a theoretical model of stochastic excitation - the
rate P at which p modes are excited by turbulent convection in those
two stars. Results are then compared with solar seismic observations
and recent observations of Alpha Cen A. For the Sun, a good agreement
between observations and computed P is obtained. For Alpha Cen A a
large discrepancy is obtained which origin cannot be yet identified:
it can either be caused by the present data quality which is not
sufficient for our purpose or by the way the intrinsic amplitudes and
the life-times of the modes are determined or finally attributed to
our present modelling. Nevertheless, data with higher quality or/and
more adapted data reductions will likely provide constraints on the
p-mode excitation mechanism in Alpha Cen A.
---------------------------------------------------------
Title: Observational Manifestations of Solar Magnetoconvection:
Center-to-Limb Variation
Authors: Carlsson, Mats; Stein, Robert F.; Nordlund, Åke; Scharmer,
Göran B.
2004ApJ...610L.137C Altcode: 2004astro.ph..6160C
We present the first center-to-limb G-band images synthesized from
high-resolution simulations of solar magnetoconvection. Toward the
limb the simulations show “hilly” granulation with dark bands on
the far side, bright granulation walls, and striated faculae, similar
to observations. At disk center G-band bright points are flanked
by dark lanes. The increased brightness in magnetic elements is due
to their lower density compared with the surrounding intergranular
medium. One thus sees deeper layers where the temperature is higher. At
a given geometric height, the magnetic elements are cooler than the
surrounding medium. In the G band, the contrast is further increased
by the destruction of CH in the low-density magnetic elements. The
optical depth unity surface is very corrugated. Bright granules have
their continuum optical depth unity 80 km above the mean surface,
the magnetic elements 200-300 km below. The horizontal temperature
gradient is especially large next to flux concentrations. When viewed
at an angle, the deep magnetic elements' optical surface is hidden by
the granules and the bright points are no longer visible, except where
the “magnetic valleys” are aligned with the line of sight. Toward
the limb, the low density in the strong magnetic elements causes unit
line-of-sight optical depth to occur deeper in the granule walls behind
than for rays not going through magnetic elements, and variations
in the field strength produce a striated appearance in the bright
granule walls.
---------------------------------------------------------
Title: Millimeter observations and chromospheric dynamics
Authors: Loukitcheva, M.; Solanki, S. K.; Carlsson, M.; Stein, R. F.
2004A&A...419..747L Altcode:
The intensities of submillimeter and millimeter continua, which are
formed in LTE and depend linearly on temperature, may be able to provide
a test of models of the Solar chromosphere. We have taken a collection
of submillimeter and millimeter wave observed brightness temperatures
T<SUB>b</SUB> of the quiet Sun from the literature and compared it
with brightness temperatures computed from the standard static models
of Fontenla, Avrett and Loeser (FAL) and the dynamic simulations of
Carlsson & Stein (CS). The analysis of the dynamic simulations
of Carlsson & Stein reveals that radio emission at millimeter
wavelengths is extremely sensitive to dynamic processes in the
chromosphere, if these are spatially and temporally resolved. The most
striking result is that the dynamic picture of the solar internetwork
chromosphere is consistent with currently available millimeter and
submillimeter brightness observations. The spectrum obtained by
averaging over the spectra from all time-steps of CS simulations
provides a good fit to observed temporally and spatially averaged
millimeter data in spite of the absence of a permanent temperature
rise at low chromospheric heights in the simulations. This does not by
itself rule out the presence of a chromospheric temperature rise as
present in the FAL models, since a combination of such models also
reproduces the (low resolution) data relatively well. Millimeter
observations indicate that using radio techniques it is possible
to extend observations of the solar oscillatory component to the
heights above those previously observed in the photospheric and low
chromospheric spectral lines and submillimeter continuum. For more
precise diagnostics of chromospheric dynamics, high temporal and spatial
resolution interferometric observations in the millimeter-wavelength
region would be particularly useful. <P />Table \ref{tab:table} is
only available in electronic form at http://www.edpsciences.org
---------------------------------------------------------
Title: G-band Images from MHD Convection Simulations
Authors: Stein, R. F.; Carlsson, M.; Nordlund, A.; Scharmer, G.
2004AAS...204.8804S Altcode: 2004BAAS...36..820S
High resolution magneto-convection simulations are used to calculate
G-band and G-continuum images at various angles. Towards the limb
the simulations show "hilly" granulation, bright granulation walls,
intergranular striations and "sticking out" G-band bright features
similar to observations. The increased brightness in magnetic
elements is due to their lower density compared with the surrounding
intergranular medium, so that one sees deeper layers where the
temperature is higher. At a given geometric height, the magnetic
elements are not hotter than the surrounding medium. In the G-band,
the contrast is further increased by the destruction of CH in the
low density magnetic elements. The optical depth unity surface is
very corrugated. Bright granules have their continuum optical depth
unity 80 km above the mean surface, the magnetic elements 200-300 km
below. At large angles, the deep lying magnetic elements are hidden
by the granules and the bright points are no longer visible. Where
the "magnetic valleys" are aligned with the line of sight, they are
visible as elongated structures seemingly "sticking out". Even when
the deep hot surface is hidden, the low density in the strong magnetic
elements causes unit line-of-sight optical depth to occur deeper in
the granule walls behind then for rays not going through magnetic
elements. Flux concentrations in intergranular lanes therefore cause
a striped intensity pattern. This work is funded by NSF grants AST
0205500 and ATM 99881112 and NASA grants NAG 5 12450 and NNGO4GB92G.
---------------------------------------------------------
Title: Excitation of Radial P-Modes in the Sun and Stars
Authors: Stein, Robert; Georgobiani, Dali; Trampedach, Regner; Ludwig,
Hans-Günter; Nordlund, Åke
2004SoPh..220..229S Altcode:
P-mode oscillations in the Sun and stars are excited stochastically
by Reynolds stress and entropy fluctuations produced by convection in
their outer envelopes. The excitation rate of radial oscillations of
stars near the main sequence from K to F and a subgiant K IV star have
been calculated from numerical simulations of their surface convection
zones. P-mode excitation increases with increasing effective temperature
(until envelope convection ceases in the F stars) and also increases
with decreasing gravity. The frequency of the maximum excitation
decreases with decreasing surface gravity.
---------------------------------------------------------
Title: Stochastic excitation of gravity waves by overshooting
convection in solar-type stars
Authors: Dintrans, Boris; Brandenburg, Axel; Nordlund, Ake; Stein,
R. F.
2004astro.ph..3093D Altcode:
The excitation of gravity waves by penetrative convective plumes is
investigated using 2D direct simulations of compressible convection. The
oscillation field is measured by a new technique based on the projection
of our simulation data onto the theoretical g-modes solutions of the
associated linear eigenvalue problem. This allows us to determine both
the excited modes and their corresponding amplitudes accurately.
---------------------------------------------------------
Title: High resolution limb images synthesized from 3D MHD simulations
Authors: Carlsson, Mats; Stein, Robert F.; Nordlund, Åke; Scharmer,
Göran B.
2004IAUS..223..233C Altcode: 2005IAUS..223..233C
We present the first center-to-limb G-band images synthesized from
high resolution simulations of solar magneto-convection. Towards the
limb the simulations show "hilly" granulation with dark bands on the
far side, bright granulation walls and striated faculae, similar
to observations. At disk center G-band bright points are flanked
by dark lanes. The increased brightness in magnetic elements is due
to their lower density compared with the surrounding intergranular
medium. One thus sees deeper layers where the temperature is higher. At
a given geometric height, the magnetic elements are cooler than the
surrounding medium. In the G-band, the contrast is further increased
by the destruction of CH in the low density magnetic elements. The
optical depth unity surface is very corrugated. Bright granules have
their continuum optical depth unity 80 km above the mean surface,
the magnetic elements 200-300 km below. The horizontal temperature
gradient is especially large next to flux concentrations. When viewed
at an angle, the deep magnetic elements optical surface is hidden by
the granules and the bright points are no longer visible, except where
the "magnetic valleys" are aligned with the line of sight. Towards
the limb, the low density in the strong magnetic elements causes
unit line-of-sight optical depth to occur deeper in the granule
walls behind than for rays not going through magnetic elements and
variations in the field strength produce a striated appearance in the
bright granule walls.
---------------------------------------------------------
Title: Magneto-Convection: Structure and Dynamics
Authors: Stein, Robert F.; Nordlund, Åke
2004IAUS..223..179S Altcode: 2005IAUS..223..179S
We present results from realistic, high resolution, simulations of solar
magneto-convection. Simulations were run with both a mean vertical and
a mean horizontal field. The magnetic field is quickly swept out of the
granules and meso-granules and concentrated in the intergranular lanes.
---------------------------------------------------------
Title: Theory and Simulations of Solar Atmosphere Dynamics
Authors: Stein, R. F.; Bogdan, T. J.; Carlsson, M.; Hansteen, V.;
McMurry, A.; Rosenthal, C. S.; Nordlund, Å.
2004ESASP.547...93S Altcode: 2004soho...13...93S
Numerical simulations are used to study the generation and propagation
of waves in the solar atmosphere. Solar p-mode oscillations are excited
by turbulent pressure work and entropy fluctuations (non-adiabatic gas
pressure work) near the solar surface. Interactions between short and
long period waves and radiative energy transfer control the formation of
shocks. The magnetic structure of the atmosphere induces coupling among
various MHD wave modes, with intense coupling and wave transformation
at the beta equal one surface, which likely is the location of the
so-called "magnetic canopy".
---------------------------------------------------------
Title: Waves in the Magnetized Solar Atmosphere. II. Waves from
Localized Sources in Magnetic Flux Concentrations
Authors: Bogdan, T. J.; Carlsson, M.; Hansteen, V. H.; McMurry, A.;
Rosenthal, C. S.; Johnson, M.; Petty-Powell, S.; Zita, E. J.; Stein,
R. F.; McIntosh, S. W.; Nordlund, Å.
2003ApJ...599..626B Altcode:
Numerical simulations of wave propagation in a two-dimensional
stratified magneto-atmosphere are presented for conditions that
are representative of the solar photosphere and chromosphere. Both
the emergent magnetic flux and the extent of the wave source are
spatially localized at the lower photospheric boundary of the
simulation. The calculations show that the coupling between the
fast and slow magneto-acoustic-gravity (MAG) waves is confined to
thin quasi-one-dimensional atmospheric layers where the sound speed
and the Alfvén velocity are comparable in magnitude. Away from this
wave conversion zone, which we call the magnetic canopy, the two MAG
waves are effectively decoupled because either the magnetic pressure
(B<SUP>2</SUP>/8π) or the plasma pressure (p=Nk<SUB>B</SUB>T)
dominates over the other. The character of the fluctuations observed
in the magneto-atmosphere depend sensitively on the relative location
and orientation of the magnetic canopy with respect to the wave source
and the observation point. Several distinct wave trains may converge
on and simultaneously pass through a given location. Their coherent
superposition presents a bewildering variety of Doppler and intensity
time series because (1) some waves come directly from the source while
others emerge from the magnetic canopy following mode conversion, (2)
the propagation directions of the individual wave trains are neither
co-aligned with each other nor with the observer's line of sight, and
(3) the wave trains may be either fast or slow MAG waves that exhibit
different characteristics depending on whether they are observed in
high-β or low-β plasmas (β≡8πp/B<SUP>2</SUP>). Through the
analysis of four numerical experiments a coherent and physically
intuitive picture emerges of how fast and slow MAG waves interact
within two-dimensional magneto-atmospheres.
---------------------------------------------------------
Title: MHD Waves in Magnetic Flux Concentrations
Authors: Bogdan, T. J.; Carlsson, M.; Hansteen, V.; Zita, E. J.;
Stein, R. F.; McIntosh, S. W.
2003AGUFMSH42B0535B Altcode:
Results from 2D MHD simulations of waves in a stratified isothermal
atmosphere will be presented and analyzed. The waves are generated
by a localized piston source situated on the lower, photospheric,
boundary of the computational domain. A combination of fast and slow
magneto-atmospheric waves propagates with little mutual interaction
until they encounter the surface where the sound speed and the Alfven
speed are comparable in magnitude. The waves couple strongly in this
region and emerge with different amplitudes and phases. Owing to
this mode mixing and the large variation in the Alfven speed in the
magneto-atmosphere, the fluctuations observed at a given location are
often a superposition of both fast and slow waves which have traversed
different paths and have undergone different transformations during
their journies.
---------------------------------------------------------
Title: On the Origin of the Basal Emission from Stellar Atmospheres:
Analysis of Solar C II Lines
Authors: Judge, Philip G.; Carlsson, Mats; Stein, Robert F.
2003ApJ...597.1158J Altcode:
Combining a variety of data with radiation hydrodynamic simulations,
we examine the heating of the Sun's internetwork chromosphere
and the hypothesis that the chromospheric “basal” emission
arises because of acoustic wave dissipation. We focus on the
2s2p<SUP>2</SUP><SUP>2</SUP>D-2s<SUP>2</SUP>2p<SUP>2</SUP>P<SUP>o</SUP>
multiplet of C II near 1335 Å, whose basal level of chromospheric
emission has been reliably determined for stars and the Sun by
Schrijver and colleagues. By accounting for center-to-limb variations
and the different spectral bandpasses of the instruments used, we find
that Schrijver's C II solar basal intensity substantially exceeds
stellar values, and that it can be identified with intensities seen
in typical internetwork regions with the SUMER instrument on the SOHO
spacecraft. Some time-series data sets of internetwork regions are
then examined and compared with simulations made specifically for a
typical observational data set, with vertical velocities at the lower
boundaries fixed from observations with the MDI instrument on SOHO. The
simulations can qualitatively account for the observed internetwork UV
continuum fluctuations seen with SUMER, formed 0.6-0.85 Mm above the
photosphere. However, they fail to capture almost any property of the
observed internetwork C II multiplet, which is formed substantially
higher. The time-averaged simulations can account for between 1/7
and 1/4 of the C II basal intensities; they predict oscillatory power
between 5 and 10 mHz, whereas internetwork observations are dominated by
low-frequency (<2 mHz) power of solar origin. The average simulated
C II intensities, which have a large contribution from the transition
region heated by conduction down from a coronal upper boundary,
fall short even of the smaller stellar basal intensities by a factor
of >=2. Together with known properties of weak, internetwork
photospheric magnetic fields, we conclude that the internetwork
upper chromosphere is probably dominated by magnetic heating. Thus,
the solar basal (and internetwork) intensities of the C II 1335 Å
multiplet originate from magnetic, and not acoustic, mechanisms,
in contradiction to the commonly accepted picture
---------------------------------------------------------
Title: What Causes p-Mode Asymmetry Reversal?
Authors: Georgobiani, Dali; Stein, Robert F.; Nordlund, Åke
2003ApJ...596..698G Altcode: 2002astro.ph..5141G
The solar acoustic p-mode line profiles are asymmetric. Velocity spectra
have more power on the low-frequency sides, whereas intensity profiles
show the opposite sense of asymmetry. Numerical simulations of the
upper convection zone have resonant p-modes with the same asymmetries
and asymmetry reversal as the observed modes. The temperature
and velocity power spectra at optical depth τ<SUB>cont</SUB>=1
have the opposite asymmetry, as is observed for the intensity and
velocity spectra. At a fixed geometrical depth, corresponding to
<τ<SUB>cont</SUB>>=1, however, the temperature and velocity
spectra have the same asymmetry. This indicates that the asymmetry
reversal in the simulation is produced by radiative transfer effects and
not by correlated noise. The cause of this reversal is the nonlinear
amplitude of the displacements in the simulation and the nonlinear
dependence of the H<SUP>-</SUP> opacity on temperature. Where the
temperature is hotter the opacity is larger and photons escape from
higher, cooler layers. This reduces the fluctuations in the radiation
temperature compared to the gas temperature. The mode asymmetry reversal
in the simulation is a small frequency-dependent differential effect
within this overall reduction. Because individual solar modes have
smaller amplitudes than the simulation modes, this effect will be
smaller on the Sun.
---------------------------------------------------------
Title: Dynamic Modelling of the Outer Atmosphere of α Tau
Authors: McMurry, A. D.; Carlsson, M.; Stein, R. F.
2003csss...12..323M Altcode:
Using one-dimensional radiation-hydrodynamics simulations a model of
the outer atmosphere of α Tau is created. The reaction of the model
to acoustic waves is explored. It is found that high frequency waves
are radiatively damped out in the photosphere. The lower frequency
waves above the Hydrodynamic acoustic cutoff frequency do produce some
chromospheric heating.
---------------------------------------------------------
Title: Numerical 3D constraints on convective eddy time-correlations:
Consequences for stochastic excitation of solar p modes
Authors: Samadi, R.; Nordlund, Å.; Stein, R. F.; Goupil, M. J.;
Roxburgh, I.
2003A&A...404.1129S Altcode: 2003astro.ph..4457S
A 3D simulation of the upper part of the solar convective zone is used
to obtain information on the frequency component, chi<SUB>k</SUB>
, of the correlation product of the turbulent velocity field. This
component plays an important role in the stochastic excitation of
acoustic oscillations. A time analysis of the solar simulation shows
that a Gaussian function does not correctly reproduce the nu -dependency
of chi<SUB>k</SUB> inferred from the 3D simuation in the frequency range
where the acoustic energy injected into the solar p modes is important
(nu =~ 2 - 4 mHz). The nu -dependency of chi<SUB>k</SUB> is fitted
with different analytical functions which can then conveniently be
used to compute the acoustic energy supply rate P injected into the
solar radial oscillations. With constraints from a 3D simulation,
adjustment of free parameters to solar data is no longer necessary
and is not performed here. The result is compared with solar seismic
data. Computed values of P obtained with the analytical function
which fits best chi<SUB>k</SUB> are found ~ 2.7 times larger than
those obtained with the Gaussian model and reproduce better the solar
seismic observations. This non-Gaussian description also leads to
a Reynolds stress contribution of the same order as the one arising
from the advection of the turbulent fluctuations of entropy by the
turbulent motions. Some discrepancy between observed and computed
P values still exist at high frequency and possible causes for this
discrepancy are discussed.
---------------------------------------------------------
Title: Numerical constraints on the model of stochastic excitation
of solar-type oscillations
Authors: Samadi, R.; Nordlund, Å.; Stein, R. F.; Goupil, M. J.;
Roxburgh, I.
2003A&A...403..303S Altcode: 2003astro.ph..3198S
Analyses of a 3D simulation of the upper layers of a solar convective
envelope provide constraints on the physical quantities which enter
the theoretical formulation of a stochastic excitation model of solar
p modes, for instance the convective velocities and the turbulent
kinetic energy spectrum. These constraints are then used to compute
the acoustic excitation rate for solar p modes, P. The resulting
values are found ~ 5 times larger than the values resulting from a
computation in which convective velocities and entropy fluctuations are
obtained with a 1D solar envelope model built with the time-dependent,
nonlocal Gough (\cite{Gough77}) extension of the mixing length
formulation for convection (GMLT). This difference is mainly due to
the assumed mean anisotropy properties of the velocity field in the
excitation region. The 3D simulation suggests much larger horizontal
velocities compared to vertical ones than in the 1D GMLT solar
model. The values of P obtained with the 3D simulation constraints
however are still too small compared with the values inferred from
solar observations. Improvements in the description of the turbulent
kinetic energy spectrum and its depth dependence yield further increased
theoretical values of P which bring them closer to the observations. It
is also found that the source of excitation arising from the advection
of the turbulent fluctuations of entropy by the turbulent movements
contributes ~ 65-75 % to the excitation and therefore remains dominant
over the Reynolds stress contribution. The derived theoretical values
of P obtained with the 3D simulation constraints remain smaller by a
factor ~ 3 compared with the solar observations. This shows that the
stochastic excitation model still needs to be improved.
---------------------------------------------------------
Title: Magnetoconvection and micropores
Authors: Bercik, D. J.; Nordlund, A.; Stein, R. F.
2003ESASP.517..201B Altcode: 2003soho...12..201B
We report on results from a series of radiative magnetoconvection
simulations in a 12 Mm×12 Mm×3 Mm near-surface solar layer. Initially
unipolar, vertical magnetic field at average field strengths of 0 G,
200 G and 400 G is imposed on a fully relaxed hydrodynamic convective
state. Magnetic field is swept to the intergranular boundaries by
the convective flows, where it is compressed to kilogauss field
strenghts. The shapes and intensities of magnetic features typically
evolve on the same time scale as the granulation pattern; however,
the underlying magnetic structure evolves on a much longer time
scale. Occasionally, dark, high field strength features form that have
properties consistent with observed micropores. The micropores primarily
form when a small granule submerges and the surrounding magnetic field
moves into the resulting dark "hole". The fluid flow inside micropores
is suppressed by the strong magnetic field. The surrounding walls of
a micropore experiences a net cooling through vertical radiation. The
resulting thermodynamic structure of micropores stabilize them against
destruction, allowing some micropores to exist for many granulation
time scales.
---------------------------------------------------------
Title: Understanding the convective Sun
Authors: Trampedach, Regner; Georgobiani, Dali; Stein, Robert F.;
Nordlund, Åke
2003ESASP.517..195T Altcode: 2003soho...12..195T
Hydrodynamical simulations of the surface layers of the Sun, has greatly
improved our understanding and interpretation of solar observations. I
review some past successes in matching spectral lines, improving the
agreement with high-degree p-mode frequencies and matching the depth of
the solar convection zone without adjustable convection-parameters. Our
solar simulations contain p-modes, and are used for studying the
asymmetry of p-mode peaks and to calibrate the conversion between the
observed velocity proxies and the actual velocities.
---------------------------------------------------------
Title: Asymmetry reversal in solar acoustic modes
Authors: Georgobiani, Dali; Stein, Robert F.; Nordlund, Åke
2003ESASP.517..279G Altcode: 2003soho...12..279G
The power spectra of solar acoustic modes are asymmetric, with velocity
having more power on the low frequency side of the peak and intensity
having more power on the high frequency side. This effect exists in both
observations and simulations, and it is believed to be caused by the
correlated background noise. We study the temperature near the solar
surface by means of a 3D hydrodynamic simulation of convection with a
detailed treatment of radiation. The temperature spectrum at optical
depth τ<SUB>cont</SUB> = 1 has opposite asymmetry to the velocity
spectrum, whereas the temperature measured at a fixed geometrical depth,
corresponding to <τ<SUB>cont</SUB>> = 1, has the same asymmetry
as velocity. We believe that the asymmetry reversal in temperature
at τ<SUB>cont</SUB> = 1 (and therefore in intensity) occurs partly
because of the radiative transfer effects. High temperature sensitivity
of the opacity suppresses temperature fluctuations on opposite sides
of the mode peaks differently, thus causing the asymmetry reversal.
---------------------------------------------------------
Title: Radiative Transfer in 3D Numerical Simulations
Authors: Stein, R. F.; Nordlund, Å.
2003ASPC..288..519S Altcode: 2002astro.ph..9510S; 2003sam..conf..519S
We simulate convection near the solar surface, where the continuum
optical depth is of order unity. Hence, to determine the radiative
heating and cooling in the energy conservation equation, we must solve
the radiative transfer equation (instead of using the diffusion or
optically thin cooling approximations). A method efficient enough to
calculate the radiation for thousands of time steps is needed. We
explicitly solve the Feautrier equation along a vertical and four
straight, slanted, rays (at four azimuthal angles which are rotated
every time step) assuming LTE and using a 4 bin opacity distribution
function. We will discuss details of our approach. We also present some
results showing comparison of simulated and observed line profiles in
the Sun, the importance of 3D transfer, stokes profiles for intergranule
magnetic fields and micropores, and the effect of radiation on p-mode
asymmetries.
---------------------------------------------------------
Title: Characterizing the Dynamic Properties of the Solar Turbulence
with 3-D Simulations: Consequences in Term of p-mode Excitation
Authors: Samadi, R.; Nordlund, Å.; Stein, R. F.; Goupil, M. -J.;
Roxburgh, I.
2003IAUS..210P..C2S Altcode: 2002astro.ph..8577S
A 3D simulation of the upper part of the solar convective zone is used
to derive constraints about the averaged and dynamic properties of
solar turbulent convection. Theses constraints are then used to compute
the acoustic energy supply rate P(nu) injected into the solar radial
oscillations according to the theoretical expression in Samadi &
Goupil (2001). The result is compared with solar seismic data. Assuming,
as it is usually done, a gaussian model for the frequency (nu)
component chi_k(nu) of the model of turbulence, it is found that the
computed P(nu) is underestimated compared with the solar seismic data
by a factor ~ 2.5. A frequency analysis of the solar simulation shows
that the gaussian model indeed does not correctly model chi_k(nu) in
the frequency range where the acoustic energy injected into the solar
p-modes is important (nu ~ 2 - 4 mHz). One must consider an additional
non-gaussian component for chi_k(nu) to reproduce its behavior. Computed
values of P obtained with this non-gaussian component reproduce better
the solar seismic observations. This non-gaussian component leads to
a Reynolds stress contribution of the same order than the one arising
from the advection of the turbulent fluctuations of entropy by the
turbulent motions.
---------------------------------------------------------
Title: Solar Surface Magneto-Convection
Authors: Stein, R. F.; Bercik, D.; Nordlund, Å.
2003ASPC..286..121S Altcode: 2003ctmf.conf..121S; 2002astro.ph..9470S
Magneto-convection simulations on meso-granule and granule scales near
the solar surface are used to study small scale dynamo activity, the
emergence and disappearance of magnetic flux tubes, and the formation
and evolution of micropores. From weak seed fields, convective motions
produce highly intermittent magnetic fields in the intergranular lanes
which collect over the boundaries of the underlying meso-granular scale
cells. Instances of both emerging magnetic flux loops and magnetic
flux disappearing from the surface occur in the simulations. We show
an example of a flux tube collapsing to kG field strength and discuss
how the nature of flux disappearance can be investigated. Observed
stokes profiles of small magnetic structures are severely distorted by
telescope diffraction and seeing. Because of the strong stratification,
there is little recycling of plasma and field in the surface
layers. Recycling instead occurs by exchange with the deep layers of
the convection zone. Plasma and field from the surface descend through
the convection zone and rise again toward the surface. Because only
a tiny fraction of plasma rising up from deep in the convection zone
reaches the surface due to mass conservation, little of the magnetic
energy resides in the near surface layers. Thus the dynamo acting on
weak incoherent fields is global, rather than a local surface dynamo.
---------------------------------------------------------
Title: Solar Surface Magnetoconvection
Authors: Stein, R. F.; Nordlund, Å.
2003IAUS..210..169S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar and Stellar Oscillations
Authors: Stein, Robert; Nordlund, Aake; Georgobiani, Dali; Trampedach,
Regner; Ludwig, Hans-Guenther
2003IAUJD..12E..41S Altcode:
We describe the stochastic excitation of p-mode oscillations by solar
convection. We discuss the role of Reynolds stresses and entropy
fluctuations what controls the excitation spectrum the depth of the
driving and the location of the driving. We then present results for
a range of other stars and discuss the similarities and differences
with the Sun.
---------------------------------------------------------
Title: On the generation of internal gravity waves by penetrative
convection
Authors: Dintrans, B.; Brandenburg, A.; Nordlund, Å.; Stein, R. F.
2003sf2a.conf..511D Altcode: 2003sf2a.confE.216D
Gravity waves propagating in the radiative zones of solar-type stars are
suspected to play a major role in the transport processes. However, the
problem of their excitation remains open as a simple kappa-mechanism
based on hydrogen and helium ionization zones is not applicable
here. One possibility concerns the excitation by overshooting convection
from neighboring convection zones. Strong downward plumes are known
to penetrate substantial distances into the adjacent stable zone so
that internal gravity waves can be randomly generated. We will present
results coming from 2D-simulations of overshooting convection, for
which a new detection method based on the anelastic subspace allows
us to precisely measure internal waves which are stochastically excited.
---------------------------------------------------------
Title: Towards 3D NLTE Radiation Magneto-Hydrodynamics
Authors: Carlsson, M.; Stein, R. F.
2003ASPC..288..505C Altcode: 2003sam..conf..505C
The problem of 3D Radiation Magneto-Hydrodynamics is too complex to
solve numerically in the general case; approximations are needed to
bring the numerical complexity to tractable levels. These approximations
are problem dependent. We will use the case of the Solar chromosphere
to illustrate these issues. The implementation of a 1D Radiation
Hydrodynamics code with a rather detailed and realistic treatment
of the coupling between radiation and matter is described. Scaling
properties and parallelization issues are discussed. Various
strategies and on-going work for the implementation of a 3D Radiation
Magneto-Hydrodynamics code are described.
---------------------------------------------------------
Title: Stochastic Excitation of Gravity Waves by Overshooting
Convection in Solar-Type Stars
Authors: Dintrans, Boris; Brandenburg, Axel; Nordlund, Åke; Stein,
Robert F.
2003Ap&SS.284..237D Altcode:
The excitation of gravity waves by penetrative convective plumes is
investigated using 2D direct simulations of compressible convection. The
oscillation field is measured by a new technique based on the projection
of our simulation data onto the theoretical g-modes solutions of the
associated linear eigenvalue problem. This allows us to determine both
the excited modes and their corresponding amplitudes accurately.
---------------------------------------------------------
Title: Modelling Acoustic Shocks in Outer Atmospheres of Cool
Giant Stars
Authors: McMurry, A. D.; Carlsson, M.; Stein, R. F.
2003IAUS..210P..B7M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Wave processes in the solar upper atmosphere
Authors: Carlsson, Mats; Stein, Robert F.
2002ESASP.505..293C Altcode: 2002IAUCo.188..293C; 2002solm.conf..293C
The existence of a wide variety of wave-like phenomena are inferred
from observations of the solar upper atmosphere. Acoustic waves play
an important role for the dynamics and energetics of the chromosphere
but additional heating seems necessary even for the internetwork
regions. We show that it is unlikely that this extra heating is due
to high frequency acoustic waves due to the lack of their preferential
excitation and the strong radiative damping of high frequency waves in
the photosphere. When acoustic waves reach the height where the magnetic
pressure equals the gas pressure they will undergo mode conversion,
refraction and reflection. We discuss these processes and show that
the critical quantity is the angle between the magnetic field and the
velocity polarization; at angles smaller than 30 degrees much of the
acoustic, fast mode from the photosphere is transmitted as an acoustic,
slow mode propagating along the field lines. At larger angles, most of
the energy is refracted/reflected and returns as a fast mode creating
an interference pattern between the upward and downward propagating
waves. In 3D, this interference between waves at small angles creates
patterns with large horizontal phase speeds, especially close to
magnetic field concentrations. When damping from shock dissipation and
radiation is taken into account, the waves in the low-mid chromosphere
have mostly the character of upward propagating acoustic waves and it
is only close to the reflecting layer we get similar amplitudes for
the upward propagating and refracted/reflected waves.
---------------------------------------------------------
Title: Solar Surface Magneto-Convection and Dynamo Action
Authors: Stein, Robert F.; Nordlund, Åke
2002ESASP.505...83S Altcode: 2002IAUCo.188...83S; 2002solm.conf...83S
Magneto-convection simulations on meso-granule and granule scales near
the solar surface are used to study small scale dynamo activity and the
emergence and disappearance of magnetic flux tubes. Convective motions
produce highly intermittent magnetic fields in the intergranular lanes
which collect over the boundaries of the underlying meso-granular scale
cells. When observing these magnetic fields, it is important to note
that the telescope point spread function and seeing significantly
reduce the amplitudes of the observed Stokes profiles. Because of
the strong stratification, there is little recycling of plasma and
field in these surface layers. Recycling instead occurs by exchange
with the deep layers of the convection zone. Plasma and field from
the surface descend to the bottom of the convection zone, where they
rise again toward the surface. Because the turnover time in the deep
convection zone is of order a month, and because only a tiny fraction
of plasma rising up from the bottom of the convection zone reaches the
surface due to mass conservation, the time constant for this dynamo
is long and little of the magnetic energy resides in the near surface
layers. Thus the dynamo acting on weak incoherent fields is global,
rather than a local surface dynamo.
---------------------------------------------------------
Title: A simulation of solar convection at supergranulation scale
Authors: Rieutord, M.; Ludwig, H. -G.; Roudier, T.; Nordlund, .;
Stein, R.
2002NCimC..25..523R Altcode: 2001astro.ph.10208R
We present here numerical simulations of surface solar convection
which cover a box of 30$\times30\times$3.2 Mm$^3$ with a resolution of
315$\times315\times$82, which is used to investigate the dynamics of
scales larger than granulation. No structure resembling supergranulation
is present; possibly higher Reynolds numbers (i.e. higher numerical
resolution), or magnetic fields, or greater depth are necessary. The
results also show interesting aspects of granular dynamics which are
briefly presented, like extensive p-mode ridges in the k-$\omega$
diagram and a ringlike distribution of horizontal vorticity around
granules. At large scales, the horizontal velocity is much larger
than the vertical velocity and the vertical motion is dominated by
p-mode oscillations.
---------------------------------------------------------
Title: Solar convection and magneto-convection simulations
Authors: Stein, R. F.; Bercik, D.; Nordlund, A.
2002NCimC..25..513S Altcode: 2001astro.ph.12117S
Magneto-convection simulations with two scenarios have been
performed: In one, horizontal magnetic field is advected into the
computational domain by fluid entering at the bottom. In the other,
an initially uniform vertical magnetic field is imposed on a snapshot
of non-magnetic convection and allowed to evolve. In both cases,
the field is swept into the intergranular lanes and the boundaries
of the underlying mesogranules. The largest field concentrations at
the surface reach pressure balance with the surrounding gas. They
suppress both horizontal and vertical flows, which reduces the heat
transport. They cool, become evacuated and their optical depth unity
surface is depressed by several hundred kilometers. Micropores form,
typically where a small granule disappears and surrounding flux tubes
squeeze into its previous location.
---------------------------------------------------------
Title: Waves in magnetic flux concentrations: The critical role of
mode mixing and interference
Authors: Bogdan, T. J.; Rosenthal, C. S.; Carlsson, M.; Hansteen, V.;
McMurry, A.; Zita, E. J.; Johnson, M.; Petty-Powell, S.; McIntosh,
S. W.; Nordlund, Å.; Stein, R. F.; Dorch, S. B. F.
2002AN....323..196B Altcode:
Time-dependent numerical simulations of nonlinear wave propagation
in a two-dimensional (slab) magnetic field geometry show wave mixing
and interference to be important aspects of oscillatory phenomena in
starspots and sunspots. Discrete sources located within the umbra
generate both fast and slow MHD waves. The latter are compressive
acoustic waves which are guided along the magnetic field lines and
steepen into N-waves with increasing height in the spot atmosphere. The
former are less compressive, and accelerate rapidly upward through the
overlying low-beta portion of the umbral photosphere and chromosphere
(beta equiv 8pi p/ B<SUP>2</SUP>). As the fast wave fronts impinge
upon the beta ~ 1 penumbral “magnetic canopy" from above, they
interfere with the outward-propagating field-guided slow waves, and
they also mode convert to (non-magnetic) acoustic-gravity waves as
they penetrate into the weak magnetic field region which lies between
the penumbral canopy and the base of the surrounding photosphere. In
a three-dimensional situation, one expects additional generation,
mixing and interference with the remaining torsional Alfvén waves.
---------------------------------------------------------
Title: Dynamic Hydrogen Ionization
Authors: Carlsson, Mats; Stein, R. F.
2002ApJ...572..626C Altcode: 2002astro.ph..2313C
We investigate the ionization of hydrogen in a dynamic solar
atmosphere. The simulations include a detailed non-LTE treatment
of hydrogen, calcium, and helium but lack other important
elements. Furthermore, the omission of magnetic fields and the
one-dimensional approach make the modeling unrealistic in the upper
chromosphere and higher. We discuss these limitations and show
that the main results remain valid for any reasonable chromospheric
conditions. As in the static case, we find that the ionization of
hydrogen in the chromosphere is dominated by collisional excitation in
the Lyα transition followed by photoionization by Balmer continuum
photons-the Lyman continuum does not play any significant role. In
the transition region, collisional ionization from the ground
state becomes the primary process. We show that the timescale for
ionization/recombination can be estimated from the eigenvalues of a
modified rate matrix where the optically thick Lyman transitions that
are in detailed balance have been excluded. We find that the timescale
for ionization/recombination is dominated by the slow collisional
leakage from the ground state to the first excited state. Throughout the
chromosphere the timescale is long (10<SUP>3</SUP>-10<SUP>5</SUP> s),
except in shocks where the increased temperature and density shorten
the timescale for ionization/recombination, especially in the upper
chromosphere. Because the relaxation timescale is much longer than
dynamic timescales, hydrogen ionization does not have time to reach
its equilibrium value and its fluctuations are much smaller than the
variation of its statistical equilibrium value appropriate for the
instantaneous conditions. Because the ionization and recombination
rates increase with increasing temperature and density, ionization
in shocks is more rapid than recombination behind them. Therefore,
the ionization state tends to represent the higher temperature of the
shocks, and the mean electron density is up to a factor of 6 higher
than the electron density calculated in statistical equilibrium from
the mean atmosphere. The simulations show that a static picture and
a dynamic picture of the chromosphere are fundamentally different
and that time variations are crucial for our understanding of the
chromosphere itself and the spectral features formed there.
---------------------------------------------------------
Title: Consequences of the non gaussian character of the stochastic
excitation for solar-type oscillations
Authors: Samadi, R.; Nordlund, A.; Stein, R. F.; Goupil, M. -J.;
Roxburgh, I.
2002sf2a.conf..489S Altcode: 2002astro.ph.10028S
Stochastic excitation of stellar p-modes of low massive stars (M <
2Mo) are attribued to regular turbulent cells moving in the upper
convective zone. The current calculation of the acoustic energy supply
rate P - which ensures the p-modes excitation - is mainly based on this
simplifying picture and thus assume a crude description of the static
and dynamic properties of the turbulent medium. With the help of a 3D
simulation of the solar convective zone, we show that the gaussian model
does not sastisfactory model the dynamical behavior of the turbulent
medium in the frequency range where the acoustic energy injected into
the solar p-modes is important (frequency : 2 - 4 mHz). Instead, one
has to consider an additionnal component - which slowly decreases with
frequency - to reproduce better the dynamic of the turbulence. This
non-gaussian component is suggested arising from presence of plumes
in the solar convection region. Inclusion of it leads to a Reynolds
stress contribution of the same order than the one arising from the
advection of the turbulent fluctuations of entropy by the turbulent
movements. In the present work we investigate some consequences of this
non-gaussian component for the p-modes excitation in low massive stars
(M < 2Mo) and compare our computations of P with previous estimates.
---------------------------------------------------------
Title: Dynamics and energetics of the solar chromosphere
Authors: Carlsson, Mats; Stein, Robert F.
2002ESASP.508..245C Altcode: 2002soho...11..245C
We present a summary of results from a number of observational programs
carried out with the SUMER instrument on board SOHO. Most datasets
show clear quasi-periodic dynamic behavior ("grains") in contiunuum
intensities with frequencies 3-10 mHz. Corresponding grains are seen
in intensities and velocities in neutral lines, normally with phase
differences consistent with upward propagating sound-waves. We compare
the observations with 1D radiation hydrodynamic simulations using
MDI Doppler-shifts to set the lower boundary. For continua formed in
the mid-chromosphere we find that the simulations give a good match
to the intensity fluctuations but that the minimum intensity is too
low. We find that high frequency acoustic waves (missing from the
current simulations) are unlikely to give the extra heating necessary
because of the strong radiative damping (90-99%) of such waves in
the photosphere. In continua formed in the low chromosphere the mean
intensity is similar in the simulations and the observations but
the simulated fluctuations are too large. The reported findings are
consistent with a picture where a basic intensity level is set by a
magnetic heating process even in the darkest internetwork areas with
superimposed intensity variations caused by acoustic waves.
---------------------------------------------------------
Title: Observational Signatures of a Solar Small-Scale Global Dynamo
Authors: Keller, C. U.; Stein, R. F.; Nordlund, A.
2002AAS...200.8908K Altcode: 2002BAAS...34..792K
There is ample theoretical and observational evidence for the existence
of a dynamo operating in the solar convection zone that produces
small-scale, weak magnetic fields. The next generation of solar
telescopes such as the 4-m Advanced Technology Solar Telescope and
the 1.5-m GREGOR will be able to provide observational data on these
magnetic fields. In order to guide the development of instruments and
observational procedures to investigate these small-scale magnetic
fields, we have calculated polarized spectral line profiles from
numerical simulations of a small-scale global dynamo and analyzed
them as if they were actual observations of the Sun. The simulated
observations include realistic noise, spatial smearing from a partially
correcting AO system, and spectral smearing and scattered light from a
spectrograph. We identify the unique signatures of these magnetic fields
and relate them to the physical conditions in the numerical simulations.
---------------------------------------------------------
Title: Is there a Surface Dynamo?
Authors: Stein, Robert
2002smra.progE..22S Altcode:
No abstract at ADS
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Title: --------
Authors: Stein, R.
2002ocnd.confE..29S Altcode:
No abstract at ADS
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Title: Waves in the Magnetized Solar Atmosphere. I. Basic Processes
and Internetwork Oscillations
Authors: Rosenthal, C. S.; Bogdan, T. J.; Carlsson, M.; Dorch,
S. B. F.; Hansteen, V.; McIntosh, S. W.; McMurry, A.; Nordlund, Å.;
Stein, R. F.
2002ApJ...564..508R Altcode:
We have modeled numerically the propagation of waves through magnetic
structures in a stratified atmosphere. We first simulate the propagation
of waves through a number of simple, exemplary field geometries in
order to obtain a better insight into the effect of differing field
structures on the wave speeds, amplitudes, polarizations, direction
of propagation, etc., with a view to understanding the wide variety of
wavelike and oscillatory processes observed in the solar atmosphere. As
a particular example, we then apply the method to oscillations in the
chromospheric network and internetwork. We find that in regions where
the field is significantly inclined to the vertical, refraction by
the rapidly increasing phase speed of the fast modes results in total
internal reflection of the waves at a surface whose altitude is highly
variable. We conjecture a relationship between this phenomenon and the
observed spatiotemporal intermittancy of the oscillations. By contrast,
in regions where the field is close to vertical, the waves continue
to propagate upward, channeled along the field lines but otherwise
largely unaffected by the field.
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Title: Are granules good tracers of solar surface velocity fields?
Authors: Rieutord, M.; Roudier, T.; Ludwig, H. -G.; Nordlund, Å.;
Stein, R.
2001A&A...377L..14R Altcode: 2001astro.ph..8284R
Using a numerical simulation of compressible convection with radiative
transfer mimicking the solar photosphere, we compare the velocity
field derived from granule motions to the actual velocity field of
the plasma. We thus test the idea that granules may be used to trace
large-scale velocity fields at the sun's surface. Our results show that
this is indeed the case provided the scale separation is sufficient. We
thus estimate that neither velocity fields at scales less than 2500
km nor time evolution at scales shorter than 0.5 hr can be faithfully
described by granules. At larger scales the granular motions correlate
linearly with the underlying fluid motions with a slope of ≲2 reaching
correlation coefficients up to ~ 0.9.
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Title: Magnetohydrodynamic turbulence in warped accretion discs
Authors: Torkelsson, Ulf; Ogilvie, Gordon I.; Brandenburg, Axel;
Pringle, James E.; Nordlund, Åke; Stein, Robert F.
2001AIPC..586..681T Altcode: 2001tsra.conf..681T; 2001astro.ph..3057T
Warped, precessing accretion discs appear in a range of astrophysical
systems, for instance the X-ray binary Her X-1 and in the active
nucleus of NGC4258. In a warped accretion disc there are horizontal
pressure gradients that drive an epicyclic motion. We have studied
the interaction of this epicyclic motion with the magneto-hydrodynamic
turbulence in numerical simulations. We find that the turbulent stress
acting on the epicyclic motion is comparable in size to the stress that
drives the accretion, however an important ingredient in the damping
of the epicyclic motion is its parametric decay into inertial waves. .
---------------------------------------------------------
Title: Wave Propagation in a Magnetized Atmosphere
Authors: Bogdan, T. J.; Rosenthal, C. S.; Carlsson, M.; McIntosh,
S.; Dorch, S.; Hansteen, V.; McMurry, A.; Nordlund, Å; Stein, R. F.
2001AGUSM..SH41A01B Altcode:
Numerical simulations of MHD wave propagation in plane-parallel
atmospheres threaded by non-trivial potential magnetic fields will be
presented, and their implications for understanding distinctions between
intranetwork and internetwork oscillations will be discussed. Our
findings basically confirm the conjecture of McIntosh et al. (2001,
ApJ 548, L237), that the two-dimensional surface where the Alfvén
and sound speeds coincide (i.e., where the plasma-β , the ratio of
gas to magnetic pressure, is of order unity) plays a fundamental
role in mediating the conversion between the fast-, intermediate-
(Alfvén), and slow-Magneto-Atmospheric-Gravity (MAG) waves. For
example, upward-propagating acoustic waves generated at the base of
the internetwork photosphere suffer significant downward reflection
when they encounter this β ≈ 1 surface. Close to the network, this
surface descends from the upper chromosphere and low corona (which
pertains in the internetwork cell interiors) down into the photosphere,
and so chromospheric oscillation `shadows' are predicted to surround
the network. In the network, strong vertical magnetic fields further
depress the β ≈ 1 surface below the surface layers where the
(magnetic field-aligned) acoustic waves (i.e., slow MAG-waves) are
generated. For frequencies in excess of the cutoff frequency, these
acoustic waves suffer little reflection from the overlying atmosphere
and they steepen as they progress upward.
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Title: Waves in the Magnetised Solar Atmosphere
Authors: Rosenthal, C. S.; Carlsson, M.; Hansteen, V.; McMurry,
A.; Bogdan, T. J.; McIntosh, S.; Nordlund, A.; Stein, R. F.; Dorch,
S. B. F.
2001IAUS..203..170R Altcode:
We have simulated the propagation of magneto-acoustic disturbances
through various magneto-hydrostatic structures constructed to mimic
the solar magnetic field. As waves propagate from regions of strong
to weak magnetic field and vice-versa different types of wave modes
(transverse and longitudinal) are coupled. In closed-field geometries
we see the trapping of wave energy within loop-like structures. In
open-field regions we see wave energy preferentially focussed away
from strong-field regions. We discuss these oscillations in terms
of various wave processes seen on the Sun - umbral oscillations,
penumbral running waves, internetwork oscillations etc.
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Title: Solar Oscillations and Convection. I. Formalism for Radial
Oscillations
Authors: Nordlund, Å.; Stein, R. F.
2001ApJ...546..576N Altcode: 2000astro.ph..6336N
We present a formalism for investigating the interaction between p-mode
oscillations and convection by analyzing realistic, three-dimensional
simulations of the near-surface layers of the solar convection
zone. By choosing suitable definitions for fluctuations and averages,
we obtain a separation that retains exact equations. The equations for
the horizontal averages contain one part that corresponds directly to
the wave equations for a one-dimensional medium, plus additional terms
that arise from the averaging and correspond to the turbulent pressure
gradient in the momentum equation and the divergence of the convective
and kinetic energy fluxes in the internal energy equation. These
terms cannot be evaluated in closed form, but they may be measured
in numerical simulations. The additional terms may cause the mode
frequencies to shift, relative to what would be obtained if only the
terms corresponding to a one-dimensional medium were retained-most
straightforwardly by changing the mean stratification and more subtly by
changing the effective compressibility of the medium. In the presence of
time-dependent convection, the additional terms also have a stochastic
time dependence, which acts as a source of random excitation of the
coherent modes. In the present paper, we derive an expression for the
excitation power and test it by applying it to a numerical experiment
of sufficient duration for the excited modes to be spectrally resolved.
---------------------------------------------------------
Title: Solar Oscillations and Convection. II. Excitation of Radial
Oscillations
Authors: Stein, R. F.; Nordlund, Å.
2001ApJ...546..585S Altcode: 2000astro.ph..8048S
Solar p-mode oscillations are excited by the work of stochastic,
nonadiabatic, pressure fluctuations on the compressive modes. We
evaluate the expression for the radial mode excitation rate derived
by Nordlund & Stein using numerical simulations of near-surface
solar convection. We first apply this expression to the three radial
modes of the simulation and obtain good agreement between the predicted
excitation rate and the actual mode damping rates as determined from
their energies and the widths of their resolved spectral profiles. These
radial simulation modes are essentially the same as the solar modes
at the resonant frequencies, where the solar modes have a node at
the depth of the bottom of the simulation domain. We then apply this
expression for the mode excitation rate to the solar modes and obtain
excellent agreement with the low l damping rates determined from data
obtained by the “global oscillations at low frequencies” (GOLF)
instrument on SOHO. Excitation occurs close to the surface, mainly
in the intergranular lanes and near the boundaries of granules (where
turbulence and radiative cooling are large). The nonadiabatic pressure
fluctuations near the surface are produced by small instantaneous local
imbalances between the divergence of the radiative and convective fluxes
near the solar surface. Below the surface, the nonadiabatic pressure
fluctuations are produced primarily by turbulent-pressure fluctuations
(Reynolds stresses). The frequency dependence of the mode excitation
is due to effects of the mode structure and the pressure fluctuation
spectrum. Excitation is small at low frequencies because of mode
properties-the mode compression decreases and the mode mass increases
at low frequency. Excitation is small at high frequencies because of
the pressure fluctuation spectrum-pressure fluctuations become small
at high frequencies because they are due to convection, which is a
long-timescale phenomenon compared with the dominant p-mode periods.
---------------------------------------------------------
Title: Models of the solar oscillations
Authors: Georgobiani, Dali; Stein, Robert F.; Nordlund, Aake
2001ESASP.464..583G Altcode: 2001soho...10..583G
The shallow upper layer of the solar convection zone is simulated
using the three-dimensional hydrodynamic code of Stein &
Nordlund. The simulation oscillation modes behave similarly to
the SOHO/MDI observations; namely, they have the same asymmetries
and phase relations. Therefore, one can study the properties of the
modes from the simulations to investigate behavior below the surface,
which cannot be observed directly. The asymmetry of the line profiles
varies with depth. At the surface, the velocity asymmetry is the same
as in the SOHO/MDI observations, but deeper down it becomes flipped in
comparison to the surface asymmetry. This behavior is well represented
by the simple model of a potential well with the source inside (or
outside). The simulations can be used to determine the depth of the
driving at different frequencies, while the simulation modes show a
strong correlation of excitation with emergent intensity.
---------------------------------------------------------
Title: Magneto-Convection in Micropores
Authors: Bercik, D. J.; Stein, R. F.; Nordlund, A.
2000AAS...197.3105B Altcode: 2000BAAS...32.1447B
We report results from a series of magneto-convection simulations. An
initially vertical magnetic field is evolved in a 12 Mm x 12 Mm x 3
Mm solar near-surface layer at average field strengths of 0 G, 200 G
and 400 G. Small dark features develop, that have sizes and lifetimes
comparable to micropores observed on the solar surface. We present the
properties of these micropore features, including structure, formation
and evolution. This work is supported by grants from NASA and NSF.
---------------------------------------------------------
Title: Solar Photosphere: Mesogranulation
Authors: Stein, R.
2000eaa..bookE2014S Altcode:
Mesogranulation is a horizontal cellular pattern in the convective
motions at the surface of the Sun with sizes of 5-10 Mm. Convection
is the transport of energy by rising warm fluid and sinking cool
fluid. How convection appears at the solar surface depends on how it
is viewed. In the emergent intensity, solar convection is visible as
a cellular pattern called granulation (see SOLAR PHOTOSPHER...
---------------------------------------------------------
Title: The response of a turbulent accretion disc to an imposed
epicyclic shearing motion
Authors: Torkelsson, Ulf; Ogilvie, Gordon I.; Brandenburg, Axel;
Pringle, James E.; Nordlund, Åke; Stein, Robert F.
2000MNRAS.318...47T Altcode: 2000astro.ph..5199T
We excite an epicyclic motion, the amplitude of which depends on the
vertical position, z, in a simulation of a turbulent accretion disc. An
epicyclic motion of this kind may be caused by a warping of the disc. By
studying how the epicyclic motion decays, we can obtain information
about the interaction between the warp and the disc turbulence. A
high-amplitude epicyclic motion decays first by exciting inertial
waves through a parametric instability, but its subsequent exponential
damping may be reproduced by a turbulent viscosity. We estimate the
effective viscosity parameter, α<SUB>v</SUB>, pertaining to such a
vertical shear. We also gain new information on the properties of the
disc turbulence in general, and measure the usual viscosity parameter,
α<SUB>h</SUB>, pertaining to a horizontal (Keplerian) shear. We
find that, as is often assumed in theoretical studies, α<SUB>v</SUB>
is approximately equal to α<SUB>h</SUB> and both are much less than
unity, for the field strengths achieved in our local box calculations
of turbulence. In view of the smallness (~0.01) of α<SUB>v</SUB> and
α<SUB>h</SUB> we conclude that for βp<SUB>gas</SUB>p<SUB>mag</SUB>~10
the time-scale for diffusion or damping of a warp is much shorter than
the usual viscous time-scale. Finally, we review the astrophysical
implications.
---------------------------------------------------------
Title: Astrophysical convection and dynamos
Authors: Brandenburg, A.; Nordlund, A.; Stein, R. F.
2000gac..conf...85B Altcode:
Convection can occur in various astrophysical settings. In this review
some aspects of solar convection are highlighted. In deeper layers
of the solar convection zone, rotation becomes important and can
lead to effects such as downward pumping of vorticity and magnetic
fields. Rotation has the tendency to partially evacuate vortex tubes
making them lighter. This effect can sometimes reverse the core of
a downdraft and make it buoyant. The problem of different thermal
and dynamic a time scales is addressed and finally the formation of
magnetic structures by convection is discussed.
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Title: Line formation in solar granulation. II. The photospheric
Fe abundance
Authors: Asplund, M.; Nordlund, Å.; Trampedach, R.; Stein, R. F.
2000A&A...359..743A Altcode: 2000astro.ph..5321A
The solar photospheric Fe abundance has been determined using realistic
ab initio 3D, time-dependent, hydrodynamical model atmospheres. The
study is based on the excellent agreement between the predicted
and observed line profiles directly rather than equivalent widths,
since the intrinsic Doppler broadening from the convective motions and
oscillations provide the necessary non-thermal broadening. Thus, three
of the four hotly debated parameters (equivalent widths, microturbulence
and damping enhancement factors) in the center of the recent solar Fe
abundance dispute regarding Fe i lines no longer enter the analysis,
leaving the transition probabilities as the main uncertainty. Both Fe i
(using the samples of lines of both the Oxford and Kiel studies) and
Fe ii lines have been investigated, which give consistent results:
log epsilon_FeI = 7.44 +/- 0.05 and log epsilon_FeII = 7.45 +/-
0.10. Also the wings of strong Fe i lines return consistent abundances,
log epsilon_FeII = 7.42 +/- 0.03, but due to the uncertainties inherent
in analyses of strong lines we give this determination lower weight
than the results from weak and intermediate strong lines. In view of
the recent slight downward revision of the meteoritic Fe abundance
log epsilon_Fe = 7.46 +/- 0.01, the agreement between the meteoritic
and photospheric values is very good, thus appearingly settling the
debate over the photospheric Fe abundance from Fe i lines.
---------------------------------------------------------
Title: The effects of numerical resolution on hydrodynamical surface
convection simulations and spectral line formation
Authors: Asplund, M.; Ludwig, H. -G.; Nordlund, Å.; Stein, R. F.
2000A&A...359..669A Altcode: 2000astro.ph..5319A
The computationally demanding nature of radiative-hydrodynamical
simulations of stellar surface convection warrants an investigation
of the sensitivity of the convective structure and spectral synthesis
to the numerical resolution and dimension of the simulations, which
is presented here. With too coarse a resolution the predicted spectral
lines tend to be too narrow, reflecting insufficient Doppler broadening
from the convective motions, while at the currently highest affordable
resolution the line shapes have converged essentially perfectly to
the observed profiles. Similar conclusions are drawn from the line
asymmetries and shifts. Due to the robustness of the pressure and
temperature structures with respect to the numerical resolution, strong
Fe lines with pronounced damping wings and H i lines are essentially
immune to resolution effects, and can therefore be used for improved
T_eff and log g determinations even at very modest resolutions. In
terms of abundances, weak Fe i and Fe ii lines show a very small
dependence ( =~ 0.02 dex) while for intermediate strong lines with
significant non-thermal broadening the sensitivity increases (<~ 0.10
dex). Problems arise when using 2D convection simulations to describe
an inherent 3D phenomenon, which translates to inaccurate atmospheric
velocity fields and temperature and pressure structures. In 2D the
theoretical line profiles tend to be too shallow and broad compared with
the 3D calculations and observations, in particular for intermediate
strong lines. In terms of abundances, the 2D results are systematically
about 0.1 dex lower than for the 3D case for Fe i lines. Furthermore,
the predicted line asymmetries and shifts are much inferior in 2D
with discrepancies amounting to ~ 200 m s<SUP>-1</SUP>. Given these
shortcomings and computing time considerations it is better to use
3D simulations of even modest resolution than high-resolution 2D
simulations.
---------------------------------------------------------
Title: Line formation in solar granulation. I. Fe line shapes,
shifts and asymmetries
Authors: Asplund, M.; Nordlund, Å.; Trampedach, R.; Allende Prieto,
C.; Stein, R. F.
2000A&A...359..729A Altcode: 2000astro.ph..5320A
Realistic ab-initio 3D, radiative-hydrodynamical convection simulations
of the solar granulation have been applied to Fe i and Fe ii line
formation. In contrast to classical analyses based on hydrostatic 1D
model atmospheres the procedure contains no adjustable free parameters
but the treatment of the numerical viscosity in the construction
of the 3D, time-dependent, inhomogeneous model atmosphere and the
elemental abundance in the 3D spectral synthesis. However, the numerical
viscosity is introduced purely for numerical stability purposes and is
determined from standard hydrodynamical test cases with no adjustments
allowed to improve the agreement with the observational constraints
from the solar granulation. The non-thermal line broadening is mainly
provided by the Doppler shifts arising from the convective flows in
the solar photosphere and the solar oscillations. The almost perfect
agreement between the predicted temporally and spatially averaged
line profiles for weak Fe lines with the observed profiles and the
absence of trends in derived abundances with line strengths, seem to
imply that the micro- and macroturbulence concepts are obsolete in
these 3D analyses. Furthermore, the theoretical line asymmetries and
shifts show a very satisfactory agreement with observations with an
accuracy of typically 50-100 m s<SUP>-1</SUP> on an absolute velocity
scale. The remaining minor discrepancies point to how the convection
simulations can be refined further.
---------------------------------------------------------
Title: Magnetoconvection and the Solar Dynamo
Authors: Nordlund, Å.; Dorch, S. B. F.; Stein, R. F.
2000JApA...21..307N Altcode:
No abstract at ADS
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Title: The Dynamic Solar Chromosphere
Authors: Carlsson, M.; Stein, R. F.
2000SPD....31.1102C Altcode: 2000BAAS...32..843C
The natural state of the Solar chromosphere is dynamic. Any
photospheric disturbance will grow and naturally form shocks over
the twenty scale-heights in density between the photosphere and
the corona. Observations in the resonance lines from singly ionized
calcium and in the ultraviolet region of the spectrum observed with
the Solar and Heliospheric Observatory satellite also show a dynamic
chromosphere. The dynamic picture is further supported by numerical
simulations. Static and dynamic pictures of the chromosphere are
fundamentally different. The simulations also show that time variations
are crucial for our understanding of the chromosphere itself and for
the spectral features formed there.
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Title: Magnetohydrodynamic Turbulence in Accretion Discs
Authors: Torkelsson, U.; Brandenburg, A.; Nordlund, A.; Stein, R. F.
2000IAUS..195..241T Altcode:
We present results from numerical simulations of magnetohydrodynamic
turbulence in accretion discs. Our simulations show that the turbulent
stresses that drive the accretion are less stratified than the matter;
thus, the surface layers are more strongly heated than the interior
of the disc.
---------------------------------------------------------
Title: Realistic Solar Convection Simulations
Authors: Stein, Robert F.; Nordlund, Åke
2000SoPh..192...91S Altcode:
We report on realistic simulations of solar surface convection that
are essentially parameter-free, but include detailed physics in the
equation of state and radiative energy exchange. The simulation results
are compared quantitatively with observations. Excellent agreement is
obtained for the distribution of the emergent continuum intensity,
the profiles of weak photospheric lines, the p-mode frequencies,
the asymmetrical shape of the mode velocity and intensity spectra,
the p-mode excitation rate, and the depth of the convection zone. We
describe how solar convection is non-local. It is driven from a thin
surface thermal boundary layer where radiative cooling produces low
entropy gas which forms the cores of the downdrafts in which most of the
buoyancy work occurs. Turbulence and vorticity are mostly confined to
the intergranular lanes and underlying downdrafts. Finally, we present
some preliminary results on magneto-convection.
---------------------------------------------------------
Title: Numerical Simulations of Oscillation Modes of the Solar
Convection Zone
Authors: Georgobiani, D.; Kosovichev, A. G.; Nigam, R.; Nordlund,
Å.; Stein, R. F.
2000ApJ...530L.139G Altcode: 1999astro.ph.12485G
We use the three-dimensional hydrodynamic code of Stein & Nordlund
to realistically simulate the upper layers of the solar convection zone
in order to study physical characteristics of solar oscillations. Our
first result is that the properties of oscillation modes in the
simulation closely match the observed properties. Recent observations
from the Solar and Heliospheric Observatory (SOHO)/Michelson Doppler
Imager (MDI) and Global Oscillations Network Group have confirmed the
asymmetry of solar oscillation line profiles, initially discovered
by Duvall et al. In this Letter, we compare the line profiles in
the power spectra of the Doppler velocity and continuum intensity
oscillations from the SOHO/MDI observations with the simulation. We
also compare the phase differences between the velocity and intensity
data. We have found that the simulated line profiles are asymmetric
and have the same asymmetry reversal between velocity and intensity
as observed. The phase difference between the velocity and intensity
signals is negative at low frequencies, and phase jumps in the vicinity
of modes are also observed. Thus, our numerical model reproduces the
basic observed properties of solar oscillations and allows us to study
the physical properties which are not observed.
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Title: Realistic Solar Surface Convection Simulations
Authors: Stein, Robert F.; Nordlund, Åke
2000NYASA.898...21S Altcode:
We perform essentially parameter free simulations with realistic physics
of convection near the solar surface. We summarize the physics that is
included and compare the simulation results with observations. Excellent
agreement is obtained for the depth of the convection zone, the
p-mode frequencies, the p-mode excitation rate, the distribution of
the emergent continuum intensity, and the profiles of weak photospheric
lines. We describe how solar convection is nonlocal. It is driven from a
thin surface thermal boundary layer where radiative cooling produces low
entropy gas which forms the cores of the downdrafts in which most of the
buoyancy work occurs. We show that turbulence and vorticity are mostly
confined to the intergranular lanes and underlying downdrafts. Finally,
we illustrate our current work on magneto-convection.
---------------------------------------------------------
Title: 3-D Convection Models: Are They Compatible with 1-D Models?
Authors: Nordlund, Å.; Stein, R. F.
2000ASPC..203..362N Altcode: 2000ilss.conf..362N; 2000IAUCo.176..362N
We review properties of stellar convection, as derived from detailed 3-D
numerical modeling, and assess to what extent 1-D models are able to
provide a fair representation of stellar structure in various regions
of the HR diagram. We point out a number of problems and discrepancies
that are inevitable when using conventional 1-D models. The problems
originate mainly in the surface layers,where horizontal fluctuations
become particularly large, and where convective energy transport gives
way to radiation. We conclude that it is necessary (and possible)
to use three-dimensional models of these layers, in order to avoid
the uncertainties and inaccuracies associated with 1-D representations.
---------------------------------------------------------
Title: Convective contributions to the frequencies of solar
oscillations
Authors: Rosenthal, C. S.; Christensen-Dalsgaard, J.; Nordlund, Å.;
Stein, R. F.; Trampedach, R.
1999A&A...351..689R Altcode: 1998astro.ph..3206R
Differences between observed and theoretical eigenfrequencies of the Sun
have characteristics which identify them as arising predominantly from
properties of the oscillations in the vicinity of the solar surface:
in the super-adiabatic, convective boundary layer and above. These
frequency differences may therefore provide useful information about
the structure of these regions, precisely where the theory of solar
structure is most uncertain. In the present work we use numerical
simulations of the outer part of the Sun to quantify the influence
of turbulent convection on solar oscillation frequencies. Separating
the influence into effects on the mean model and effects on the
physics of the modes, we find that the main model effects are due
to the turbulent pressure that provides additional support against
gravity, and thermal differences between average 3-D models and 1-D
models. Surfaces of constant pressure in the visible photosphere are
elevated by about 150 km, relative to a standard envelope model. As a
result, the turning points of high-frequency modes are raised, while
those of the low-frequency modes remain essentially unaffected. The
corresponding gradual lowering of the mode frequencies accounts for
most of the frequency difference between observations and standard
solar models. Additional effects are expected to come primarily from
changes in the physics of the modes, in particular from the modulation
of the turbulent pressure by the oscillations.
---------------------------------------------------------
Title: 3D hydrodynamical model atmospheres of metal-poor
stars. Evidence for a low primordial Li abundance
Authors: Asplund, Martin; Nordlund, Åke; Trampedach, Regner; Stein,
Robert F.
1999A&A...346L..17A Altcode: 1999astro.ph..5059A
Realistic 3-dimensional (3D), radiative hydrodynamical surface
convection simulations of the metal-poor halo stars HD 140283 and
HD 84937 have been performed. Due to the dominance of adiabatic
cooling over radiative heating very low atmospheric temperatures are
encountered. The lack of spectral lines in these metal-poor stars
thus causes much steeper temperature gradients than in classical 1D
hydrostatic model atmospheres where the temperature of the optically
thin layers is determined by radiative equilibrium. The modified
atmospheric structures cause changes in the emergent stellar spectra. In
particular, the primordial Li abundances may have been overestimated
by 0.2-0.35 dex with 1D model atmospheres. However, we caution that
our result assumes local thermodynamic equilibrium (LTE), while the
steep temperature gradients may be prone to e.g. over-ionization.
---------------------------------------------------------
Title: The dynamic solar chromosphere and the ionization of hydrogen
Authors: Carlsson, Mats; Stein, Robert F.
1999AIPC..471...23C Altcode: 1999sowi.conf...23C
Basic physical considerations, observations and numerical simulations
show that the solar chromosphere is very dynamic. The enhanced
chromospheric emission, which corresponds to an outwardly increasing
semiempirical temperature structure, can even be produced by wave
motion without any increase in the mean gas temperature. Hence,
the sun may not have a classical chromosphere in magnetic field free
internetwork regions. This dynamic picture of the solar internetwork
chromosphere is consistent with ground based observations of the Call
resonance lines and with observations from the SOHO satellite. The
simulations also show that a static picture and a dynamic picture of
the chromosphere are fundamentally different and that time variations
are crucial for our understanding of the chromosphere itself and
the spectral features formed there. Whether the dynamic nature of
the chromosphere is important for solar wind models depends on their
sensitivity to chromospheric conditions. Contrary to some claims in
the literature, the ionization of hydrogen in the upper chromosphere
is dominated by collisional excitation in the Lyman line followed by
photo-ionization by Balmer continuum photons-the Lyman continuum does
not play any significant role. In the transition region, collisional
ionization takes over as the major process. Ionization/recombination
time-scales can be on the order of hundreds of seconds causing the
ionization balance in the chromosphere to be significantly out of
equilibrium with higher ionization than the equilibrium value. The
hydrogen ionization zone is also considerably thicker than is claimed
from dimension analyses; the ionization fraction goes from 1% to 40%
over a height range of 600 km.
---------------------------------------------------------
Title: Near Surface Magneto-Convection
Authors: Bercik, D. J.; Stein, R. F.; Nordlund, A.
1999AAS...194.5501B Altcode: 1999BAAS...31..910B
The emergence of magnetic flux alters the structure of the solar
surface. We use simulations of magneto-convection of a near surface
layer to investigate the dynamical interaction between magnetic fields
and convection. The results of these simulations are presented to show
the behavior of emerging flux tubes as well as the three dimensional
structure and evolution of bright points and small pores.
---------------------------------------------------------
Title: Realistic Simulations of Solar Surface Convection
Authors: Stein, R. F.; Bercik, D.; Georgobiani, D.; Nordlund, A.
1999AAS...194.2104S Altcode: 1999BAAS...31R.858S
Results from realistic simulations of near surface solar convection
will be summarized and compared with observations. Solar convection
is driven by radiative cooling from an extremely thin surface thermal
boundary layer, which produces low entropy fluid. Its topology is
controlled by mass conservation and consists of turbulent downdrafts
penetrating nearly laminar upflows. The horizontal scales increase with
depth. Good agreement is found with the of the depth of the convection
zone, p-mode frequencies, excitation, line asymmetries and intensity -
velocity phase differences from helioseismology; with observations of
granulation and profiles of weak Fe lines. This work was supported by
grants from NSF, NASA, and the Danish Research Council. The calculations
were performed at NCSA, MSU and UNIC.
---------------------------------------------------------
Title: Three-dimensional simulations of solar oscillations: line
profiles and asymmetries
Authors: Georgobiani, D. G.; Nigam, R.; Kosovichev, A. G.; Stein,
R. F.; Nordlund, A.
1999AAS...194.5605G Altcode: 1999BAAS...31..912G
In order to study spectral characteristics of the solar oscillations,
we use the Stein-Nordlund 3d hydrodynamic code to generate lond
temporal sequencies of realistically simulated upper layers of the
solar convective zone. The simulation domain ranges from 0.5 Mm above
the surface of tau =1 to 2.5 Mm below this surface, and is 6 Mm by
6 Mm wide. We have generated 24 hours of solar time. We calculate
power spectra of the vertical velocity and temperature at different
heights and the emergent intensity at the surface. Here, we present the
profiles of velocity, intensity and temperature for both radial (l = 0)
and first nonradial (l = 700) mode. We compare line profiles from the
simulation with the power spectra of the Doppler velocity and continuum
intensity from the SOHO/MDI observations. Both simulated and observed
profiles demonstrate similar types of asymmetry, and the asymmetry
reversal between the local quantities like velocity and temperature, and
emergent intensity profiles is also present in the simulated data. The
preliminary results are promising as they allow us to establish a
connection between the observational data and realistic simulations,
and enable us to understand better the physics of solar oscillations.
---------------------------------------------------------
Title: Magneto-Convection
Authors: Stein, R. F.; Georgobiani, D.; Bercik, D. J.; Brandenburg,
A.; Nordlund, Å.
1999ASPC..173..193S Altcode: 1999sstt.conf..193S
No abstract at ADS
---------------------------------------------------------
Title: Solar Convection and MHD
Authors: Nordlund, Å.; Stein, R. F.
1999ASSL..240..293N Altcode: 1999numa.conf..293N
No abstract at ADS
---------------------------------------------------------
Title: Realistic Solar Convection Simulations
Authors: Stein, Robert F.; Nordlund, Aake
1999soho....9E..14S Altcode:
We have performed essentially parameter free simulations with
realistic physics of convection near the solar surface. We summarize
the physics that is included and compare the simulation results
with observations. Excellent agreement is obtained for the depth of
the convection zone, the p-mode frequencies, the p-mode excitation
rate, the distribution of the emergent continuum intensity, and the
profiles of weak photospheric lines. We describe how solar convection
is non-local. It is driven from a thin surface thermal boundary layer
where radiative cooling produces low entropy gas which forms the cores
of the downdrafts in which most of the buoyancy work occurs. We show
that turbulence and vorticity are mostly confined to the intergranular
lanes and underlying downdrafts. Finally, we illustrate our current
work on magneto-convection.
---------------------------------------------------------
Title: Stellar Evolution with a Variable Mixing-Length Parameter
Authors: Trampedach, R.; Stein, R. F.; Christensen-Dalsgaard, J.;
Nordlund, Å.
1999ASPC..173..233T Altcode: 1999sstt.conf..233T
No abstract at ADS
---------------------------------------------------------
Title: The Excitation of Solar Oscillations -- Observations and
Simulations
Authors: Goode, P.; Strous, L.; Rimmele, T.; Stein, R.; Nordlund, Å.
1999ASPC..183..456G Altcode: 1999hrsp.conf..456G
No abstract at ADS
---------------------------------------------------------
Title: The Dynamics of Turbulent Viscosity
Authors: Torkelsson, U.; Ogilvie, G. I.; Pringle, J. E.; Brandenburg,
A.; Nordlund, Å.; Stein, R. F.
1999ASPC..161..422T Altcode: 1999hepa.conf..422T
No abstract at ADS
---------------------------------------------------------
Title: Convection Simulations
Authors: Nordlund, Å.; Stein, R. F.
1999ASPC..173...91N Altcode: 1999sstt.conf...91N
No abstract at ADS
---------------------------------------------------------
Title: Solar P-Mode Spectrum Asymmetries: Testing Theories With
Numerical Simulations
Authors: Georgobiani, Dali; Nigam, Rakesh; Kosovichev, Alexander G.;
Stein, Robert F.
1999soho....9E..58G Altcode:
We use a 36 hour sequence of 3-D hydrodynamic simulations of solar
convection to study the line profiles of the acoustic modes and their
asymmetries. We construct power spectra of the emergent intensity
and the vertical velocity at a fixed height of 200 km above the t = 1
surface, as well as their phase differences. We compare the synthetic
results with those obtained from the SOHO/MDI observations. The
simulations and observations show similar direction of asymmetry
and reversal of asymmetry between the velocity and intensity. Our
preliminary results confirm the theoretical model of Nigam (Nigam et
al. 1998). To make the simulation results more realistic, the intensity
and velocity will in future be obtained from the synthetic NiI 6768
line used in the observations.
---------------------------------------------------------
Title: Dynamics of Magnetic Flux Elements in the Solar Photosphere
Authors: van Ballegooijen, A. A.; Nisenson, P.; Noyes, R. W.; Löfdahl,
M. G.; Stein, R. F.; Nordlund, Å.; Krishnakumar, V.
1998ApJ...509..435V Altcode: 1998astro.ph..2359V
The interaction of magnetic fields and convection is investigated in
the context of the coronal heating problem. We study the motions of
photospheric magnetic elements using a time series of high-resolution
G-band and continuum filtergrams obtained at the Swedish Vacuum
Solar Telescope at La Palma. The G-band images show bright points
arranged in linear structures (“filigree”) located in the lanes
between neighboring granule cells. We measure the motions of these
bright points using an object tracking technique, and we determine
the autocorrelation function describing the temporal variation of
the bright point velocity. The correlation time of the velocity is
about 100 s. To understand the processes that determine the spatial
distribution of the bright points, we perform simulations of horizontal
motions of magnetic flux elements in response to solar granulation
flows. Models of the granulation flow are derived from the observed
granulation intensity images using a simple two-dimensional model
that includes both inertia and horizontal temperature gradients; the
magnetic flux elements are assumed to be passively advected by this
granulation flow. The results suggest that this passive advection model
is in reasonable agreement with the observations, indicating that on
a timescale of 1 hr the flux tubes are not strongly affected by their
anchoring at large depth. Finally, we use potential-field modeling
to extrapolate the magnetic and velocity fields to larger height. We
find that the velocity in the chromosphere can be locally enhanced at
the separatrix surfaces between neighboring flux tubes. The predicted
velocities are several km s<SUP>-1</SUP>, significantly larger than
those of the photospheric flux tubes. The implications of these results
for coronal heating are discussed.
---------------------------------------------------------
Title: Stellar background power spectra from hydrodynamical
simulations of stellar atmospheres
Authors: Trampedach, R.; Christensen-Dalsgaard, J.; Nordlund, A.;
Stein, R. F.
1998mons.proc...59T Altcode:
The non-p-mode contribution to the temporal irradiance or velocity
spectra of the Sun has for a long time been considered as noise,
but in recent years it has gradually been appreciated as the signal of
granulation. Accordingly these spectra are now referred to as background
spectra. We hope that further analysis of these background spectra
will serve two purposes: to provide information about convection in
other stars; and, as the background still constitutes a noise source
when looking for p- and in particular g-modes of solar type stars,
to provide us with stricter limits as to what is observable. Based on
hydrodynamical simulations of convection in the atmospheres of the Sun,
alpha Cen A and Procyon, we calculate irradiance and velocity spectra
and infer a few properties of these spectra. Due to the limited
horizontal extent of the simulations (covering 6-8 granules each)
we only get a signal from the granulation, whereas effects of meso-
and supergranulation are missing in our signal. At the high-frequency
end we are limited by the horizontal resolution of the simulations.
---------------------------------------------------------
Title: Simulations of Solar Granulation. I. General Properties
Authors: Stein, R. F.; Nordlund, Å.
1998ApJ...499..914S Altcode:
Numerical simulations provide information on solar convection not
available by direct observation. We present results of simulations of
near surface solar convection with realistic physics: an equation of
state including ionization and three-dimensional, LTE radiative transfer
using a four-bin opacity distribution function. Solar convection is
driven by radiative cooling in the surface thermal boundary layer,
producing the familiar granulation pattern. In the interior of granules,
warm plasma ascends with ~10% ionized hydrogen. As it approaches and
passes through the optical surface, the plasma cools, recombines,
and loses entropy. It then turns over and converges into the dark
intergranular lanes and further into the vertices between granulation
cells. These vertices feed turbulent downdrafts below the solar surface,
which are the sites of buoyancy work that drives the convection. Only
a tiny fraction of the fluid ascending at depth reaches the surface to
cool, lose entropy, and form the cores of these downdrafts. Granules
evolve by pushing out against and being pushed in by their neighboring
granules, and by being split by overlying fluid that cools and is
pulled down by gravity. Convective energy transport properties that
are closely related to integral constraints such as conservation
of energy and mass are exceedingly robust. Other properties, which
are less tightly constrained and/or involve higher order moments or
derivatives, are found to depend more sensitively on the numerical
resolution. At the highest numerical resolution, excellent agreement
between simulated convection properties and observations is found. In
interpreting observations it is crucial to remember that surfaces of
constant optical depth are corrugated. The surface of unit optical
depth in the continuum is higher above granules and lower in the
intergranular lanes, while the surface of optical depth unity in
a spectral line is corrugated in ways that are influenced by both
thermal and Doppler effects.
---------------------------------------------------------
Title: Exploring magnetohydrodynamic turbulence on the computer
Authors: Torkelsson, Ulf; Ogilvie, Gordon I.; Brandenburg, Axel;
Nordlund, A. ˚Ke; Stein, Robert F.
1998AIPC..431...69T Altcode: 1998apas.conf...69T
Although numerical simulations have established magnetohydrodynamic
turbulence as a possible candidate for the angular momentum transport
mechanism in accretion discs there is still a need for a deeper
understanding of the physics of the shear-induced turbulence. There
are two complementary pathways to this goal, to analyze the results of
a simulation at depth or to start from a simple state, whose evolution
can be understood by semi-analytical methods and `extrapolate' to the
turbulent state that we want to understand. We will show examples of
these two approaches.
---------------------------------------------------------
Title: The new chromosphere
Authors: Carlsson, M.; Stein, R. F.
1998IAUS..185..435C Altcode:
Numerical simulations have shown that enhanced chromospheric emission,
which corresponds to an outwardly increasing semiempirical temperature
structure, can be produced by wave motion without any increase in
the mean gas temperture. Hence, the sun may not have a classical
chromosphere in magnetic field free internetwork regions. This dynamic
picture of the solar internetwork chromosphere is also consistent
with ground based observations of the CaII resonance lines and of CO
absorption lines and with observations from the SOHO satellite. The
simulations also show that a static picture and a dynamic picture of
the chromosphere are fundamentally different and that time variations
are crucial for our understanding of the chromosphere itself and for
the spectral features formed there.
---------------------------------------------------------
Title: The excitation and damping of p-modes
Authors: Nordlund, A.; Stein, R. F.
1998IAUS..185..199N Altcode:
Numerical simulations of convection in the surface layers of the Sun
may be used to study the excitation and damping of p-modes. This may
be done in two ways: either passively, by looking at the modes that
spontaneously develop in the numerical simulations, or actively, by
performing numerical experiments specifically aimed at measuring the
excitation and damping of the oscillations. Because the simulation
boxes have smaller “mode mass” than the real Sun, the time scales
for growth and decay are correspondingly smaller, and because of the
smaller volumes, the mode spectrum is much sparser, with only a few
modes spanning the 3 mHz band that contains millions of modes in the
Sun. The total rms amplitude of the modes is expected to be similar
to that of the Sun, though, since the ratio of excitation to damping
remains the same. We report on the results of both passive measurements
and active experiments. We find that the main source of excitation
is the entropy fluctions associated with the convective downdrafts,
and that the main damping mechanism is that part of the turbulent
pressure that is in quadrature with the mode, and from the point of
view of the p-modes acts as a turbulent diffusion of momentum.
---------------------------------------------------------
Title: Convection and p-modes
Authors: Stein, R. F.; Nordlund, Å.
1998ESASP.418..693S Altcode: 1998soho....6..693S
The solar p-modes are driven (and damped) and have their resonant
frequencies altered by interaction with the turbulent solar
convection. We present results on both the eigenfrequency modification
and mode driving derived from realistic 3D simulations of the upper
solar convection zone. Convection enlarges the resonant cavity for high
frequency modes, thereby lowering their frequencies, in improving the
agreement with the observed modes (Rosenthal et al./ 1998). This is
due to (i) turbulent pressure raising the layers above the region of
large superadiabatic gradient, and (ii) the average plasma temperature
is higher than predicted by 1D calculations for the same effective
temperature, which increases the scale height, because we do not see the
high temperatures in the granules due to the temperature sensitivity of
the H- opacity, yet they contribute to the average stratification. The
p-modes are driven by non-adiabatic pressure fluctuations (entropy
fluctuations) producing a net stochastic PdV work (Stein and Norlund
1991, Nordlund and Stein 1998). At low frequencies, the total pressure
fluctuation is very small since hydrostatic equilibrium must be
maintained. Both gas and turbulent pressure fluctuations are large,
but are out of phase and cancel each other. With increasing frequency
the magnitude of the pressure fluctuations decrease as approximately
nu<SUP>-4</SUP>. The peak in the total pressure fluctuation occurs at ~4
mHz, and in this range the gas pressure fluctuations dominate over the
turbulent pressure fluctuations. This work was supported by NASA grant
NAG5-4031, NSF grant AST 9521785 and the Danish Research Foundation,
through its establishment of the Theoretical Astrophysics Center.
---------------------------------------------------------
Title: Solar Magneto-Convection
Authors: Stein, R. F.; Bercik, D. J.; Brandenburg, A.; Georgobiani,
D.; Nordlund, A.
1998AAS...191.7417S Altcode: 1998BAAS...30..758S
We present results of realistic simulations of magneto-convection near
the solar surface. The simulations were performed with two magnetic
field topologies - (1) a unipolar, initially vertical field, and (2)
a bipolar field, where fluid entering at the base of the computational
domain advects in horizontal field. As the unipolar flux is increased,
the magnetic field concentrates in the intergranule lanes and develops
large, dark, cool regions. These regions surround smaller areas where
convection has not been suppressed. In contrast, for the bipolar case,
the strongest fields appear as bright points in the intergranule lanes.
---------------------------------------------------------
Title: Tests of Convective Frequency Effects with SOI/MDI High-Degree
Data
Authors: Rosenthal, C. S.; Christensen-Dalsgaard, J.; Kosovichev,
A. G.; Nordlund, A. A.; Reiter, J.; Rhodes, E. J., Jr.; Schou, J.;
Stein, R. F.; Trampedach, R.
1998ESASP.418..521R Altcode: 1998astro.ph..7066R; 1998soho....6..521R
Advances in hydrodynamical simulations have provided new insight into
the effects of convection on the frequencies of solar oscillations. As
more accurate observations become available, this may lead to an
improved understanding of the dynamics of convection and the interaction
between convection and pulsation (Rosenthal et al. 1999). Recent
high-resolution observations from the SOI/MDI instrument on the
SOHO spacecraft have provided the so-far most-detailed observations
of high-degree modes of solar oscillations, which are particularly
sensitive to the near-surface properties of the Sun. Here we present
preliminary results of a comparison between these observations and
frequencies computed for models based on realistic simulations of
near-surface convection. Such comparisons may be expected to help
in identifying the causes for the remaining differences between the
observed frequencies and those of solar models.
---------------------------------------------------------
Title: Solar Magneto-Convection
Authors: Bercik, David J.; Basu, Shantanu; Georgobiani, Dali; Nordlund,
Ake; Stein, Robert F.
1998ASPC..154..568B Altcode: 1998csss...10..568B
We have simulated magneto-convection near the solar surface
with two topologies: (1) an initial vertical field; and (2) a
horizontal field carried in with the fluid entering at the base
of the computational domain. We report results on the interaction
of convection and magnetic fields. An MPEG video is viewable at:
http://www.pa.msu.edu/~steinr/images/bhoriz.mpg The MPEG video is also
included on the CS10 CD ROM.
---------------------------------------------------------
Title: Heat Transport in the Convective Zone and Deviations from
the Mixing Length Models
Authors: Georgobiani, D.; Kuhn, J. R.; Nordlund, AA.; Stein, R. F.
1998ESASP.418..771G Altcode: 1998soho....6..771G
For several decades, the heat transport in the solar convective
zone has been thought to be isotropic. Attempts to describe it in
terms of the mixing length theory seemed to be quite successful. In
contradiction with such an idealized picture, recent numerical
and observational data have demonstrated a highly non-isotropic,
inhomogeneous structure of the convective zone. This work presents the
results of calculations of the thermal conductivity in the convective
zone, using the numerical model of Stein-Nordlund. Thermal conductivity
is assumed to be a 3D tensor. Its vertical and horizontal diagonal
components differ in magnitudes for each given depth. Moreover, the
horizontal component stays negative, while increasing with depth. Both
features are naturally explained by the physical properties of the
solar convective zone. Implications for global questions of solar
convection are considered.
---------------------------------------------------------
Title: Near-surface constraints on the structure of stellar convection
zones
Authors: Trampedach, R.; Christensen-Dalsgaard, J.; Nordlund, A.;
Stein, R.
1997ASSL..225...73T Altcode: 1997scor.proc...73T
By simulating the convection in the upper layers of six different stars
and matching these simulations to 1D-mixing length models using the
same input physics, we have been able to infer the behaviour of the
mixing-length parameter, $\alpha$, as the stellar parameters changes.
---------------------------------------------------------
Title: Sound speed variations near the photosphere due to entropy
perturbations in 3d numerical experiments
Authors: Georgobiani, D.; Kuhn, J. R.; Stein, R. F.
1997ASSL..225..127G Altcode: 1997scor.proc..127G
Results on how the temperature distribution near the solar photosphere
is altered by perturbing the entropy of rising fluid in the convection
zone several megameters below the surface, are presented. Effects on
the emergent intensity and implications for helioseismic observations
are described.
---------------------------------------------------------
Title: Stellar Convection; general properties
Authors: Nordlund, A.; Stein, R.
1997ASSL..225...79N Altcode: 1997scor.proc...79N
We review the properties of stellar convection zones, in
particular with respect to issues of relevance to helio- and
astero-seismology. Convection is responsible both for establishing
the one-dimensional average structure on top of which the waves are
propagating and for maintaining large amplitude three-dimensional
fluctuations that interact with the wave mode fluctuations. We discuss
qualitative and quantitative aspects of these interactions on the
background of numerical simulations of convection. We conclude that
the average properties obtained from numerical simulations are quite
robust and that the main uncertainties in applying these results to
helio- and astero-seismology lie in evaluating the effects of the
convective fluctuations on the wave propagation. One of the main
structure effects is the elevation of the photosphere caused by the
turbulent pressure. An important wave-convection interaction effect
is the contribution of the fluctuations in the turbulent pressure to
the effective gamma of the turbulent gas.
---------------------------------------------------------
Title: Dynamic Behavior of the Solar Atmosphere
Authors: Stein, R. F.; Carlsson, M.
1997ASSL..225..261S Altcode: 1997scor.proc..261S
We have studied the dynamics of acoustic and MHD waves in the
solar atmosphere using a one-dimensional, non-LTE, radiation
magneto-hydrodynamic code, with 6 level model atoms for hydrogen and
singly ionized calcium. We drive waves by a piston through an initial
atmosphere in radiative equilibrium. We report on the effects of
radiative energy loss on the waves, the effects of shocks on line
formation, and the behavior of typical diagnostics in a dynamic
atmosphere.
---------------------------------------------------------
Title: Formation of Solar Calcium H and K Bright Grains
Authors: Carlsson, Mats; Stein, Robert F.
1997ApJ...481..500C Altcode:
We have simulated the generation of Ca II H<SUB>2V</SUB> bright
grains by acoustic shocks. We employ a one-dimensional, non-LTE
radiation-hydrodynamic code, with six-level model atoms for hydrogen
and singly ionized calcium. We drive acoustic waves through a stratified
radiative equilibrium atmosphere by a piston, whose velocity is chosen
to match the Doppler shift observed in the Fe I 396.68 nm line in
the H line wing, formed at about 260 km above τ<SUB>500</SUB> =
1. <P />The simulations closely match the observed behavior of Ca
II H<SUB>2V</SUB> bright grains down to the level of individual
grains. The bright grains are produced by shocks near 1 Mm above
τ<SUB>500</SUB> = 1. Shocks in the mid-chromosphere produce a large
source function (and therefore high emissivity) because the density
is high enough for collisions to couple the Ca II populations to the
local conditions. The asymmetry of the line profile is due to velocity
gradients near 1 Mm. Material motion Doppler-shifts the frequency at
which atoms emit and absorb photons, so the maximum opacity is located
at--and the absorption profile is symmetric about--the local fluid
velocity, which is shifted to the blue behind shocks. The optical
depth depends upon the velocity structure higher up. Shocks propagate
generally into downflowing material, so there is little matter above
to absorb the Doppler-shifted radiation. The corresponding red peak
is absent because of small opacity at the source function maximum and
large optical depth due to overlying material. The bright grains are
produced primarily by waves from the photosphere that are slightly
above the acoustic cutoff frequency. The precise time and strength
of a grain depend upon the interference between these waves near the
acoustic cutoff frequency and higher frequency waves. When waves near
the acoustic cutoff frequency are weak, then higher frequency waves
may produce grains. The “5 minute” trapped p-mode oscillations are
not the source of the grains, although they can slightly modify the
behavior of higher frequency waves.
---------------------------------------------------------
Title: Solar Convection: Comparison of Numerical Simulations and
Mixing-Length Theory
Authors: Abbett, William P.; Beaver, Michelle; Davids, Barry;
Georgobiani, Dali; Rathbun, Pamela; Stein, Robert F.
1997ApJ...480..395A Altcode:
We compare the results of realistic numerical simulations of convection
in the superadiabatic layer near the solar surface with the predictions
of mixing-length theory. We find that the peak values of such quantities
as the temperature gradient, the temperature fluctuations, and the
velocity fluctuations, as well as the entropy jump in the simulation,
can be reproduced by mixing-length theory for a ratio of mixing length
to pressure scale height α ~ 1.5. However, local mixing-length theory
neither reproduces the profiles of these variables with depth nor allows
penetration of convective motions into the overlying stable photosphere.
---------------------------------------------------------
Title: Chromospheric Dynamics - What Can Be Learnt from Numerical
Simulations
Authors: Carlsson, M.; Stein, R. F.
1997LNP...489..159C Altcode: 1997shpp.conf..159C
Observations of the solar chromosphere are often interpreted using
methods derived from static modeling (e.g., the Vernazza et al. 1981
model atmospheres and work based on such models) or linear theory
(e.g., phase relations). Recent numerical simulations have shown that
such an analysis can be very misleading. It is found that enhanced
chromospheric emission, which corresponds to an outwardly increasing
semi-empirical temperature structure, can be produced by wave motions
without any increase in the mean gas temperature. Thus, despite
long held beliefs, the Sun may not have a classical chromosphere
in magnetic field free internetwork regions. This dynamic picture
is consistent with observations in CO lines and the calcium H and
K bright grains. More opaque lines, on the other hand, seem to show
emission all of the time. This indicates the existence of a hotter,
magnetic, component that increases in importance with height.
---------------------------------------------------------
Title: The nonlinear evolution of a single mode of the magnetic
shearing instability
Authors: Torkelsson, U.; Ogilvie, G. I.; Brandernburg, A.; Nordlund,
Å.; Stein, R. F.
1997LNP...487..135T Altcode: 1997adna.conf..135T
We simulate in one dimension the magnetic shearing instability for
a vertical magnetic field penetrating a Keplerian accretion disc. An
initial equilibrium state is perturbed by adding a single eigenmode of
the shearing instability and the subsequent evolution is followed into
the nonlinear regime. Assuming that the perturbation is the most rapidly
growing eigenmode, the linear theory remains applicable until the
magnetic pressure perturbation is strong enough to induce significant
deviations from the original density. If the initial perturbation is
not the fastest growing mode, the faster growing modes will appear
after some time.
---------------------------------------------------------
Title: Magnetohydrodynamic Turbulence in Accretion Discs: Towards
More Realistic Models
Authors: Torkelsson, U.; Brandenburg, A.; Nordlund, A.; Stein, R. F.
1997ASPC..121..210T Altcode: 1997apro.conf..210T; 1997IAUCo.163..210T
No abstract at ADS
---------------------------------------------------------
Title: Numerical Simulations Can Lead to New Insights
Authors: Stein, Robert F.; Carlsson, Mats; Nordlund, Ake
1997ASPC..123...72S Altcode: 1997taca.conf...72S
No abstract at ADS
---------------------------------------------------------
Title: The non-magnetic solar chromosphere.
Authors: Carlsson, M.; Stein, R. F.
1997smf..conf...59C Altcode:
The authors summarize recent results form self-consistent non-LTE
radiation hydrodynamics simulations of the propagation of acoustic
waves through the non-magnetic solar chromosphere. References to more
detailed write-ups of the work are given.
---------------------------------------------------------
Title: Supercomputer windows into the solar convection zone
Authors: Nordlund, Å.; Stein, R. F.; Brandenburg, A.
1996BASI...24..261N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Accounting for the Solar Acoustic and Luminosity Variations
from the Deep Convection Zone
Authors: Kuhn, J. R.; Stein, R. F.
1996ApJ...463L.117K Altcode:
Recent helioseismic observations (Duvall et al.) have demonstrated
how new data analysis techniques can determine local changes in the
acoustic properties beneath the photosphere. The recent results provide
compelling evidence of a latitudinal sound speed variation. Using
results from numerical simulations, we show here how this acoustic
variation has the correct form and amplitude needed to account for
the previously observed solar photometric changes. In this picture,
both the acoustic and irradiance changes may be caused by magnetically
induced entropy fluctuations near the base of the solar convection zone.
---------------------------------------------------------
Title: Sound Speed Variations Near the Photosphere due to Entropy
Perturbations in 3D Numerical Experiments
Authors: Georgobiani, D.; Kuhn, J. R.; Stein, R. F.
1996AAS...188.6910G Altcode: 1996BAAS...28..937G
Results on how the temperature distribution near the solar photosphere
is altered by perturbing the entropy of fluid in the convection zone
several megameters below the surface are presented. Effects on the
emergent intensity and implications for helioseismic observations
are described.
---------------------------------------------------------
Title: The Disk Accretion Rate for Dynamo-generated Turbulence
Authors: Brandenburg, Axel; Nordlund, Ake; Stein, Robert F.;
Torkelsson, Ulf
1996ApJ...458L..45B Altcode:
Dynamo-generated turbulence is simulated in a modified shearing
box approximation that removes scale invariance and allows finite
accretion rates for a given distance from the central object. The
effective Shakura-Sunyaev viscosity parameter, alpha SS, is estimated
in three different ways using the resulting mass accretion rate, the
heating rate, and the horizontal components of the Maxwell and Reynolds
stress tensors. The results are still resolution dependent: doubling
the resolution leads to 1.4--1.6 times larger values for the viscosity
parameter. For 63 x 127 x 64 meshpoints we find that alpha SS = 0.007.
---------------------------------------------------------
Title: Stellar/Solar Convection Simulations
Authors: Stein, Robert F.
1996STIN...9671199S Altcode:
The primary objective is to understand convection in the solar
envelope: its role in transporting energy and angular momentum, in
generating the solar magnetic field, in providing energy to heat the
solar chromosphere and corona, in exciting p-mode oscillations and
in modifying their resonant frequencies. A secondary objective is
to elucidate the interaction between convection, magnetic fields and
shear flow in accretion disks.
---------------------------------------------------------
Title: Solar chromospheric dynamics - Results from numerical
simulations
Authors: Carlsson, M.; Stein, R. F.
1996ASPC..109..119C Altcode: 1996csss....9..119C
No abstract at ADS
---------------------------------------------------------
Title: Large classes and quality instruction: the "interrupted
lecture".
Authors: Hufnagel, B.; Hawley, S. L.; Stein, R.; Wilhelm, R.
1996BAAS...28.1203H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic structures in a dynamo simulation
Authors: Brandenburg, A.; Jennings, R. L.; Nordlund, Å.; Rieutord,
M.; Stein, R. F.; Tuominen, I.
1996JFM...306..325B Altcode:
We use three-dimensional simulations to study compressible convection
in a rotating frame with magnetic fields and overshoot into surrounding
stable layers. The, initially weak, magnetic field is amplified and
maintained by dynamo action and becomes organized into flux tubes
that are wrapped around vortex tubes. We also observe vortex buoyancy
which causes upward flows in the cores of extended downdraughts. An
analysis of the angles between various vector fields shows that there
is a tendency for the magnetic field to be parallel or antiparallel
to the vorticity vector, especially when the magnetic field is
strong. The magnetic energy spectrum has a short inertial range with
a slope compatible with k(+1/3) during the early growth phase of the
dynamo. During the saturated state the slope is compatible with k(-1). A
simple analysis based on various characteristic timescales and energy
transfer rates highlights important qualitative ideas regarding the
energy budget of hydromagnetic dynamos.
---------------------------------------------------------
Title: The Turbulent Viscosity in Accretion Discs
Authors: Torkelsson, U.; Brandenburg, A.; Nordlund, Å.; Stein, R. F.
1996ApL&C..34..383T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamo-generated turbulence in disks: value and variability
of alpha.
Authors: Brandenburg, A.; Nordlund, Å.; Stein, R. F.; Torkelsson, U.
1996bpad.conf..285B Altcode: 1996pada.conf..285B
Dynamo-generated turbulence seems to be a universal mechanism for
angular momentum transport in accretion disks. The authors discuss the
resulting value of the viscosity parameter alpha and emphasize that this
value is in general not constant. Alpha varies with the magnetic field
strength which, in turn, can vary in an approximately cyclic manner. The
authors also show that the stress does not vary significantly with
depth, even though the density drops by a factor of about 30.
---------------------------------------------------------
Title: Dynamo-generated Turbulence and Large-Scale Magnetic Fields
in a Keplerian Shear Flow
Authors: Brandenburg, Axel; Nordlund, Ake; Stein, Robert F.;
Torkelsson, Ulf
1995ApJ...446..741B Altcode:
The nonlinear evolution of magnetized Keplerian shear flows is
simulated in a local, three-dimensional model, including the effects
of compressibility and stratification. Supersonic flows are initially
generated by the Balbus-Hawley magnetic shear instability. The
resulting flows regenerate a turbulent magnetic field which, in
turn, reinforces the turbulence. Thus, the system acts like a dynamo
that generates its own turbulence. However, unlike usual dynamos,
the magnetic energy exceeds the kinetic energy of the turbulence by
a factor of 3-10. By assuming the field to be vertical on the outer
(upper and lower) surfaces we do not constrain the horizontal magnetic
flux. Indeed, a large-scale toroidal magnetic field is generated,
mostly in the form of toroidal flux tubes with lengths comparable
to the toroidal extent of the box. This large-scale field is mainly
of even (i.e., quadrupolar) parity with respect to the midplane and
changes direction on a timescale of ∼30 orbits, in a possibly cyclic
manner. The effective Shakura-Sunyaev alpha viscosity parameter is
between 0.001 and 0.005, and the contribution from the Maxwell stress
is ∼3-7 times larger than the contribution from the Reynolds stress.
---------------------------------------------------------
Title: Does a Nonmagnetic Solar Chromosphere Exist?
Authors: Carlsson, Mats; Stein, Robert F.
1995ApJ...440L..29C Altcode: 1994astro.ph.11036C
Enhanced chromospheric emission which corresponds to an outwardly
increasing semiempirical temperature structure can be produced by
wave motion without any increase in the mean gas temperture. Hence,
the sun may not have a classical chromosphere in magnetic field
free internetwork regions. Other significant differences between the
properties of dynamic and static atmospheres should be considered when
analyzing chromospheric observations.
---------------------------------------------------------
Title: Convection; Significance for Stellar Structure and Evolution
Authors: Nordlund, A.; Stein, R. F.
1995LIACo..32...75N Altcode: 1995sews.book...75N
No abstract at ADS
---------------------------------------------------------
Title: Dynamo Generated Turbulence in Discs
Authors: Brandenburg, A.; Nordlund, Å.; Stein, R. F.; Torkelsson, U.
1995LNP...462..385B Altcode: 1995ssst.conf..385B
The magnetic shear instability appears to be a workable mechanism
for generating turbulence in accretion discs. The magnetic field,
in turn, is generated by a dynamo process that taps energy from the
Keplerian shear flow. Large scale magnetic fields are generated, whose
strength is comparable with, or in excess of, the turbulent kinetic
energy. Such models enable us to investigate the detailed nature
of turbulence in discs. We discuss in particular the possibility of
generating convection, where the heat source is viscous and magnetic
heating in the bulk of the disc.
---------------------------------------------------------
Title: No Magnetic Field - No Chromosphere (Abstract only)
Authors: Carlsson, M.; Stein, R.
1995itsa.conf..325C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Modeling of the Solar Convection Zone
Authors: Basu, S.; Bercik, D. J.; Nordlund, A.; Stein, R. F.
1994AAS...185.4402B Altcode: 1994BAAS...26Q1377B
We present results from a simulation of a 6 x 6 x 3 Mm region
of the upper solar convection zone at twice the resolution (25 km
horizontally and 15-35 km vertically) of our previous calculation. We
compare identical times at the two resolutions to show the effect on
downdrafts and other properties of convection.
---------------------------------------------------------
Title: On Sound Generation by Turbulent Convection: A New Look at
Old Results
Authors: Musielak, Z. E.; Rosner, R.; Stein, R. F.; Ulmschneider, P.
1994ApJ...423..474M Altcode:
We have revisited the problem of acoustic wave generation by turbulent
convection in stellar atmospheres. The theory of aerodynamically
generated sound, originally developed by Lighthill and later modified
by Stein to include the effects of stratification, has been used
to estimate the acoustic wave energy flux generated in solar and
stellar convection zones. We correct the earlier computations by
incorporating an improved description of the spatial and temporal
spectrum of the turbulent convection. We show the dependence of the
resulting wave fluxes on the nature of the turbulence, and compute the
wave energy spectra and wave energy fluxes generated in the Sun on
the basis of a mixing-length model of the solar convection zone. In
contrast to the previous results, we show that the acoustic energy
generation does not depend very sensitively on the turbulent energy
spectrum. However, typical total acoustic fluxes of order F<SUB>A</SUB>
= 5 x 10<SUP>7</SUP> ergs/sq cm/s with a peak of the acoustic frequency
spectrum near omega = 100 mHz are found to be comparable to those
previously calculated. The acoustic flux turns out to be strongly
dependent on the solar model, scaling with the mixing-length parameter
alpha as alpha<SUP>3.8</SUP>. The computed fluxes most likely constitute
a lower limit on the acoustic energy produced in the solar convection
zone if recent convection simulations suggesting the presence of shocks
near the upper layers of the convection zone apply to the Sun.
---------------------------------------------------------
Title: Magnetoconvection and magnetoturbulence
Authors: Nordlund, Å.; Galsgaard, K.; Stein, R. F.
1994ASIC..433..471N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Numerical Simulations of Magnetic Reconnection in 3-D
Authors: Stein, Robert; Galsgaard, Klaus; Nordlund, Aake
1994ASPC...68..210S Altcode: 1994sare.conf..210S
No abstract at ADS
---------------------------------------------------------
Title: Subphotospheric Convection
Authors: Stein, R. F.; Nordlund, A.
1994IAUS..154..225S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radiation shock dynamics in the solar chromosphere - results
of numerical simulations
Authors: Carlsson, M.; Stein, R. F.
1994chdy.conf...47C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Calcium II phase relations and chromospheric dynamics
Authors: Skartlien, R.; Carlsson, M.; Stein, R. F.
1994chdy.conf...79S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A New Description of the Solar Five-Minute Oscillation
Authors: Leibacher, J.; Stein, R. F.
1994snft.book..400L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ionization Effects in Three-dimensional Solar Granulation
Simulations
Authors: Rast, Mark P.; Nordlund, Ake; Stein, Robert F.; Toomre, Juri
1993ApJ...408L..53R Altcode:
These numerical studies show that ionization influences both the
transport and dynamical properties of compressible convection
near the surface of the Sun. About two-thirds of the enthalpy
transported by convective motions in the region of partial hydrogen
ionization is carried as latent heat. The role of fast downflow
plumes in total convective transport is substantially elevated
by this contribution. Instability of the thermal boundary layer
is strongly enhanced by temperature sensitive variations in the
radiative properties of the fluid, and this provides a mechanism for
plume initiation and cell fragmentation in the surface layers. As
the plumes descend, temperature fluctuations and associated buoyancy
forces are maintained because of the increased specific heat of the
partially ionized material. This can result is supersonic vertical
flows. At greater depths, ionization effects diminish, and the plumes
are decelerated by significant entrainment of surrounding fluid.
---------------------------------------------------------
Title: Ionization Effects on Solar Granulation Dynamics
Authors: Rast, M. P.; Nordlund, A.; Stein, R. F.; Toomre, J.
1993ASPC...42...57R Altcode: 1993gong.conf...57R
No abstract at ADS
---------------------------------------------------------
Title: Rotational effects on convection simulated at different
latitudes
Authors: Pulkkinen, Pentti; Tuominen, Ilkka; Brandenburg, Axel;
Nordlund, Ake; Stein, Robert F.
1993A&A...267..265P Altcode:
We simulate numerically convection inside the solar convection
zone under the influence of rotation at different latitudes. The
computational domain is a small rectangular box with stress-free upper
and lower boundaries, and with periodicity assumed in the lateral
directions. We study the transport of angular momentum, which is
important for the generation of differential rotation. The sign and
the latitudinal dependence of the horizontal Reynolds stress component
turn out to be in good agreement with correlation measurements of
sunspot proper motions and with predictions from the theory of the
Lambda effect. We also investigate the other components of the Reynolds
stress as well as the eddy heat flux tensor, both of which are needed
in mean field models of differential rotation.
---------------------------------------------------------
Title: Non-LTE radiating shocks and the formation of Ca II lines in
the solar chromosphere.
Authors: Carlsson, M.; Stein, R. F.
1993wpst.conf...21C Altcode:
The authors present self-consistent solutions of the time dependent
one-dimensional equations of non-LTE radiation-hydrodynamics in solar
chromospheric conditions. The vertical propagation of acoustic waves
is calculated.
---------------------------------------------------------
Title: Evolution of a magnetic flux tube in two-dimensional
penetrative convection
Authors: Jennings, R. L.; Brandenburg, A.; Nordlund, A.; Stein, R. F.
1992MNRAS.259..465J Altcode:
Highly supercritical compressible convection is simulated in a
two-dimensional domain in which the upper half is unstable to convection
while the lower half is stably stratified. This configuration is
an idealization of the layers near the base of the solar convection
zone. Once the turbulent flow is well developed, a toroidal magnetic
field B<SUB>tor</SUB> is introduced to the stable layer. The field's
evolution is governed by an advection-diffusion-type equation, and
the Lorentz force does not significantly affect the flow. After many
turnover times the field is stratified such that the absolute value
of B<SUB>tor/rho</SUB> is approximately constant in the convective
layer, where rho is density, while in the stable layer this ratio
decreases linearly with depth. Consequently most of the magnetic flux
is stored in the overshoot layer. The inclusion of rotation leads
to travelling waves which transport magnetic flux latitudinally in a
manner reminiscent of the migrations seen during the solar cycle.
---------------------------------------------------------
Title: Non-LTE Radiating Acoustic Shocks and CA II K2V Bright Points
Authors: Carlsson, Mats; Stein, Robert F.
1992ApJ...397L..59C Altcode:
We present, for the first time, a self-consistent solution of the
time-dependent 1D equations of non-LTE radiation hydrodynamics in
solar chromospheric conditions. The vertical propagation of sinusoidal
acoustic waves with periods of 30, 180, and 300 s is calculated. We
find that departures from LTE and ionization recombination determine
the temperature profiles of the shocks that develop. In LTE almost all
the thermal energy goes into ionization, so the temperature rise is very
small. In non-LTE, the finite transition rates delay the ionization to
behind the shock front. The compression thus goes into thermal energy at
the shock front leading to a high temperature amplitude. Further behind
the shock front, the delayed ionization removes energy from the thermal
pool, which reduces the temperature, producing a temperature spike. The
180 s waves reproduce the observed temporal changes in the calcium K
line profiles quite well. The observed wing brightening pattern, the
violet/red peak asymmetry and the observed line center behavior are
all well reproduced. The short-period waves and the 5 minute period
waves fail especially in reproducing the observed behavior of the wings.
---------------------------------------------------------
Title: Dynamo Action in Stratified Convection with Overshoot
Authors: Nordlund, Ake; Brandenburg, Axel; Jennings, Richard L.;
Rieutord, Michel; Ruokolainen, Juha; Stein, Robert F.; Tuominen, Ilkka
1992ApJ...392..647N Altcode:
Results are presented from direct simulations of turbulent compressible
hydromagnetic convection above a stable overshoot layer. Spontaneous
dynamo action occurs followed by saturation, with most of the generated
magnetic field appearing as coherent flux tubes in the vicinity
of strong downdrafts, where both the generation and destruction of
magnetic field is most vigorous. Whether or not this field is amplified
depends on the sizes of the magnetic Reynolds and magnetic Prandtl
numbers. Joule dissipation is balanced mainly by the work done against
the magnetic curvature force. It is this curvature force which is also
responsible for the saturation of the dynamo.
---------------------------------------------------------
Title: CA II K2V Bright Grains Formed by Acoustic Waves
Authors: Carlsson, M.; Stein, R.
1992ASPC...26..515C Altcode: 1992csss....7..515C
No abstract at ADS
---------------------------------------------------------
Title: Magnet Convection (Invited Review)
Authors: Stein, R. F.; Brandenburg, A.; Nordlund, A.
1992ASPC...26..148S Altcode: 1992csss....7..148S
No abstract at ADS
---------------------------------------------------------
Title: Convection and Its Influence on Oscillations
Authors: Stein, Robert F.; Nordlund, Åke
1991LNP...388..195S Altcode: 1991ctsm.conf..195S
We investigate the interaction between p-mode oscillations and
convection using a realistic, three-dimensional simulation of the
upper solar convection zone. P-mode oscillations are excited at the
eigenfrequencies of the simulation volume. Their frequency is different
than that found from one-dimensional mixing length models. Their
resonant cavity becomes larger when overshooting into the photosphere
is possible, which lowers the mode frequencies, while interaction with
the inhomogeneities in the sound speed and the motions generated by the
convection tends to raise the mode frequencies. The modes are excited
stochastically by non-adiabatic fluctuations in the gas pressure caused
by the switch from convective to radiative energy transport at the
solar surface.
---------------------------------------------------------
Title: Granulation: Non-adiabatic Patterns and Shocks
Authors: Nordlund, Åke; Stein, Robert F.
1991LNP...388..141N Altcode: 1991ctsm.conf..141N
We present, in graphical form, some results from numerical simulations
of the solar granulation. We compare synthetic granulation images with
observations of the solar granulation, and illustrate the corresponding
pressure and velocity fields. In particular, the non-adiabatic part
of the pressure fluctuation, which is a major source of stochastic
excitation of P-modes, is shown.
---------------------------------------------------------
Title: The Role of Overshoot in Solar Activity - a Direct Simulation
of the Dynamo
Authors: Brandenburg, A.; Jennings, R. L.; Nordlund, Å.; Stein,
R. F.; Tuominen, I.
1991LNP...380...86B Altcode: 1991IAUCo.130...86B; 1991sacs.coll...86B
We investigate convective overshoot in a layer of electrically
conducting fluid. The radiative conductivity is assumed to be larger
in the lower part of the layer which makes it stable to convective
motions, yet penetrative convection from the upper layer can occur. The
numerical resolution is 633 gridpoints. We observe a dynamo effect for
magnetic Reynolds numbers around one thousand when a magnetic seed
field is rapidly concentrated to form flux tubes. Later the average
magnetic field is expelled from the convectively unstable regions,
but it accumulates in the interface between the convection zone and
the radiative interior.
---------------------------------------------------------
Title: Magnetic Tubes in Overshooting Compressible Convection
Authors: Jennings, R. L.; Brandenburg, A.; Nordlund, Å.; Stein,
R. F.; Tuominen, I.
1991LNP...380...92J Altcode: 1991sacs.coll...92J; 1991IAUCo.130...92J
A magnetic tube is introduced into turbulent compressible penetrative
convection. After being strongly advected, most of the magnetic flux
is stored in the overshoot region. With rotation there are meridional
travelling waves.
---------------------------------------------------------
Title: Convection and p-modes.
Authors: Nordlund, Å.; Stein, R. F.
1991dsoo.conf...37N Altcode:
An introductory overview of the qualitative properties of convection
and p modes in solar type stars is followed by a discussion of how to
obtain a meaningful separation between "wave-motion" and "convection" in
a strongly inhomogeneous medium. For radial waves, a natural separation
is obtained by using certain weighted averages, in a "pseudo-Lagrangian"
coordinate system in which there is no net vertical mass flux. Three
principal influences of the convection on the wave modes are identified:
Frequency shifts due to coherent perturbations in phase with "restoring
force" terms in the wave equations, linear damping or growth due to
coherent perturbations 90 degrees out of phase with restoring force
terms, and stochastic excitation due to incoherent perturbations of
the wave equations. In addition, convection influences p-modes by
cavity changes: i.e., changes of the size of the resonant cavity due
to changes in the mean structure. Numerical illustrations of these
effects are given, using results from supercomputer simulations of
the interaction of solar convection with p-modes.
---------------------------------------------------------
Title: Recent development in solar convection theory.
Authors: Chan, Kwing L.; Nordlund, A.; Steffen, Matthias; Stein, R. F.
1991sia..book..223C Altcode:
In recent years, the theory of solar (and stellar) convection has
made fundamental advances due to the increasing cost effectiveness of
supercomputers and the constant improvement of numerical techniques. It
is expected that the numerical approach will become a dominant trend
for the future. The authors report on these new advances. References
to theoretical studies on phenomena related to solar convection are
compiled. The authors then discuss three numerical studies of solar
convection in greater detail, so as to provide the readers with some
general understanding of the numerical techniques being used and
the results obtained: The discussion starts with a two-dimensional
study of the spectroscopic properties of solar granules. While the
two-dimensional limitation is severely detrimental to some important
hydrodynamical processes, it is both economical and able to provide some
initial understanding of the gross features of solar convection. Next
they discuss the testing of the well-known mixing-length theory with
three-dimensional numerical experiments. An example is also given of
applying the numerically gained knowledge to analytical study, in this
case the behavior of compressible convection as a heat engine. The
third case describes a realistic, three-dimensional simulation of
solar granulation; many observational features of solar granules
are faithfully reproduced. It is the most sophisticated numerical
calculation of this sort today.
---------------------------------------------------------
Title: Magnetoacoustic Waves and Their Generation by Convection
(With 15 Figures)
Authors: Stein, R. F.; Nordlund, Å.
1991mcch.conf..386S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Rotational Effects on Reynolds Stresses in the Solar
Convection Zone
Authors: Pulkkinen, P.; Tuominen, I.; Brandenburg, A.; Nordlund, Å.;
Stein, R. F.
1991LNP...380...98P Altcode: 1991IAUCo.130...98P; 1991sacs.coll...98P
Three-dimensional hydrodynamic simulations are carried out in a
rectangular box. The angle between gravity and rotation axis is kept
as an external parameter in order to study the latitude-dependence
of convection. Special attention is given to the horizontal Reynolds
stress and the -effect (Rüdiger, 1989). The results of the simulations
are compared with observations and theory and a good agreement is found.
---------------------------------------------------------
Title: Dynamics of an Radiative Transfer in Inhomogeneous Media
Authors: Nordlund, A.; Stein, R. F.
1991ASIC..341..263N Altcode: 1991sabc.conf..263N
No abstract at ADS
---------------------------------------------------------
Title: Shock Amplification by Radiation (With 1 Figure)
Authors: Carlsson, M.; Stein, R.
1991mcch.conf..366C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: 3-D simulation of turbulent cyclonic magneto-convection.
Authors: Brandenburg, A.; Tuominen, I.; Nordlund, A.; Pulkkinen, P.;
Stein, R. F.
1990A&A...232..277B Altcode:
Results are presented of a simulation of turbulent three-dimensional
magnetic convection under the influence of rotation in a fluid layer
whose depth is about 1 pressure-scale hight. The approach is similar
to that of Meneguzzi and Pouquet (1989), except for the assumptions
that the fluid is a compressible conducting gas and there is a
vanishing horizontal magnetic field at the boundaries. The results
demonstrate that topological effects may be of great importance for
MHD convection. It is shown that, as a consequence of topological
effects, anisotropies of the alpha-effect can play a dominant role. In
particular, the sign of alpha(V) can be opposite to that expected from
a first-order smoothing approach.
---------------------------------------------------------
Title: 3-D simulations of solar and stellar convection and
magnetoconvection
Authors: Nordlund, Å.; Stein, R. F.
1990CoPhC..59..119N Altcode:
We present the key components of a 3-D code designed for simulating
the hydrodynamics and magnetohydrodynamics of stellar atmospheres
and envelopes. Some particular properties of the code are: (1) the
ability to handle strong stratification (extensive simulations with
bottom/top pressure ratios of 3×10<SUP>4</SUP> have been performed,
and simulations with pressure ratios of 5×10<SUP>6</SUP> are being
initiated); (2) a detailed treatment of the radiating surface; (3) a
functional form of the subgrid-scale diffusion designed to minimize
the influence on resolved motions; (4) boundary conditions open
to flows. The top boundary allows the transmission of short period
waves, while the bottom boundary condition was designed to enforce a
displacement node for radial pressure modes.
---------------------------------------------------------
Title: Turbulent diffusivities derived from simulations.
Authors: Brandenburg, A.; Nordlund, Å.; Pulkkinen, P.; Stein, R. F.;
Tuominen, I.
1990fas..conf....1B Altcode:
By employing direct simulations of turbulent magneto-convection the
authors determine the turbulent diffusivities, such as the turbulent
magnetic diffusivity, the eddy viscosity and the turbulent heat
conductivity.
---------------------------------------------------------
Title: Solar Magnetoconvection
Authors: Nordlund, Å.; Stein, R. F.
1990IAUS..138..191N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Non-LTE radiative hydrodynamic interactions in the solar
chromosphere.
Authors: Carlsson, M.; Stein, R.
1990ppst.conf..177C Altcode:
Strong, optically thick lines from iron and from ionized calcium and
magnesium dominate the radiative losses of the solar chromosphere. This
radiative loss cannot be approximated in the optically thin limit or
by a grey approximation. In order to properly calculate the effects
of waves in the chromosphere it is necessary to solve simultaneously
the equations of hydrodynamics, radiative transfer and statistical
equilibrium. Efficient methods in radiative transfer are here being
combined with a treatment of the dynamical equations capable of
resolving shocks. The authors present the first results showing that
radiative hydrodynamic interactions may have a significant effect on
the heating by acoustic waves.
---------------------------------------------------------
Title: Driving and Damping of Oscillations
Authors: Stein, Robert F.; Nordlund, Åke
1990LNP...367...93S Altcode: 1990psss.conf...93S
We have simulated the upper 2.5 Mm of the solar convection zone using
a realistic, three-dimensional, compressible, hydrodynamic computer
code. P-mode oscillations are excited at the eigenfrequencies of the
simulation volume. We have calculated the time averages of the work
terms in the kinetic energy equation, using the internal energy equation
to evaluate the fluctuations in the gas pressure. This calculation
shows that the modes are excited near the surface by the divergence
of the convective flux and damped by the divergence of the radiative
flux. The fundamental mode is also spuriously driven at the lower
boundary, by density and turbulent pressure fluctuations induced when
downward plunging convective plumes pass through the lower boundary
of the simulation.
---------------------------------------------------------
Title: Topology of Convection beneath the Solar Surface
Authors: Stein, R. F.; Nordlund, A.
1989ApJ...342L..95S Altcode:
It is shown that the topology of convection beneath the solar surface
is dominated by effects of stratification. Convection in a strongly
stratified medium has: (1) gentle expanding structureless warm upflows
and (2) strong converging filamentary cool downdrafts. The horizontal
flow topology is cellular, with a hierarchy of cell sizes. The small
density scale height in the surface layers forces the formation of
the solar granulation, which is a shallow surface phenomenon. Deeper
layers support successively larger cells. The downflows of small cells
close to the surface merge into filamentary downdrafts of larger cells
at greater depths, and this process is likely to continue through most
of the convection zone. Radiative cooling at the surface provides the
entropy-deficient material which drives the circulation.
---------------------------------------------------------
Title: Convection and Waves
Authors: Stein, R. F.; Nordlund, Å.; Kuhn, J. R.
1989ASIC..263..381S Altcode: 1989ssg..conf..381S
No abstract at ADS
---------------------------------------------------------
Title: Simulating Magnetoconvection
Authors: Nordlund, Å.; Stein, R. F.
1989ASIC..263..453N Altcode: 1989ssg..conf..453N
No abstract at ADS
---------------------------------------------------------
Title: Convection and p-mode oscillations.
Authors: Stein, R. F.; Nordlund, A.; Kuhn, J. R.
1988ESASP.286..529S Altcode: 1988ssls.rept..529S
The authors have simulated the upper 2.5 Mm of the solar convection
zone using a three-dimensional, compressible, hydrodynamic computer
code. Preliminary results show that convection excites p-mode
oscillations. The frequencies of the modes in the numerical simulation
agree well with the eigenfrequencies of our computational box calculated
for the time averaged mean atmosphere. The agreement is excellent at low
frequencies, and diverges at higher frequencies in a manner similar to
the difference between observed and theoretical frequencies for the sun.
---------------------------------------------------------
Title: What Does the Sun Look Like Beneath the Surface?
Authors: Nordlund, A.; Stein, R. F.
1988BAAS...20..702N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Can Progressive Acoustic Waves Interact with Evanescent
P-Modes in the Solar Chromosphere
Authors: Bohn, H. U.; Stein, R. F.
1985tphr.conf..331B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Non-Magnetic Motions in the Photosphere and Chromosphere
Authors: Stein, R. F.
1985tphr.conf...48S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamical behavior of a theoretical chromosphere model.
Authors: Bohn, H. U.; Stein, R. F.
1985cdm..proc..228B Altcode:
Time dependent calculations of a solar chromosphere model perturbed by
a spectrum of short period acoustic waves superimposed on the observed
power spectrum of five minute oscillations are presented. The resulting
data is analyzed by Fourier techniques and discussed in terms of
nonlinear interaction of various modes.
---------------------------------------------------------
Title: Can progressive acoustic waves interact with evanescent
p-modes in the solar chromosphere?
Authors: Bohn, H. U.; Stein, R. F.
1985MPARp.212..331B Altcode:
To study the interaction of acoustic waves with the solar five minute
oscillations calculations of a dynamical chromosphere model are used
and the results interpreted by Fourier analysis to be compatible with
modern observational techniques.
---------------------------------------------------------
Title: Mechanisms for chromospheric heating.
Authors: Stein, R. F.
1985cdm..proc..213S Altcode:
A nonthermal energy source is required to heat the solar chromosphere
and corona. A survey is made of the properties of waves that propagate
along magnetic flux tubes, which may transport the needed energy
from the convection zone to the chromosphere. It is next explored
how convective motions can generate those waves. Finally, various
mechanisms by which these waves may develop small scale structures
and dissipate via viscosity and resistivity are discussed.
---------------------------------------------------------
Title: Non-magnetic motions in the photosphere and chromosphere.
Authors: Stein, R. F.
1985MPARp.212...48S Altcode:
The author discusses four major problems in the area of solar
atmospheric dynamics: the coupling of convective to atmospheric motions,
the transport of energy from the convection zone to the chromosphere
and corona, the nature of the motions that produce the non-thermal line
broadening, and the nature and location of the dissipation mechanisms
that heat the chromosphere and corona.
---------------------------------------------------------
Title: MHD waves and turbulence in the sun and interplanetary medium.
Authors: Barnes, A.; Goldstein, M.; Hollweg, J.; Mariska, J.;
Matthaeus, W.; Smith, C.; Smith, E.; Stein, R.; Withbroe, G.; Woo, R.
1984NASRP1120....4B Altcode:
Contents: Introduction. Global oscillations of the sun. Observations
related to waves or turbulence in the solar atmosphere. Local waves
in the solar atmosphere: theoretical considerations. Interplanetary
hydromagnetic fluctuations. Recent studies of the interplanetary plasma
based on turbulence theory. Effects of waves and turbulence of the
solar wind.
---------------------------------------------------------
Title: The dynamics of the Venus ionosphere 1. A simulation of the
solar wind compression of the upper dayside ionosphere
Authors: Wolff, R. S.; Stein, R. F.; Taylor, H. A., Jr.
1982JGR....87.8118W Altcode:
The effects of the solar wind compression of the dayside Venus
ionosphere are simulated numerically. The initial ionosphere is assumed
to be in pressure equilibrium with the (shocked) solar wind at the upper
boundary of the ionosphere. Composition, densities, and temperatures
of ions and electrons in the ionosphere are chosen in accordance with
Pioneer Venus data. A spherically symmetric Lagrangian hydrodynamic code
using a two-fluid model of the ionosphere consisting of 0<SUP>+</SUP>
and electrons is employed to simulate the effects on the ionosphere of
rapid changes in solar wind pressure. Sudden increases in solar wind
pressure are found to generate shock waves in the ions that propagate
from the ionopause downward into the ionosphere with velocities as high
as 5 km/s. The effect of shock waves on ionospheric density profiles
is dramatic with distinct `ledges' developing in the ionosphere at
the shock front. Comparison of density profiles from our simulation
with select Pioneer Venus ion mass spectrometer data suggest possible
agreement between shock produced ionospheric ledges resulting from
rapid solar wind compression and observed ionospheric ledges.
---------------------------------------------------------
Title: The dynamics of the Venus ionosphere II. The effects of the
time scale of the solar wind dynamic pressure variations
Authors: Stein, R. F.; Wolff, R. S.
1982Icar...51..296S Altcode:
The effects on the upper dayside Venus ionosphere of a slow increase
in solar wind dynamic pressure are simulated numerically with a
1-dimensional (spherically symmetric) Lagrangian hydrodynamical
code. The simulation is started with an extended ionosphere in pressure
equilibrium with the solar wind at the ionopause. The pressure at the
ionopause is gradually increased to five times the initial pressure
with rise times of 5, 15, and 30 min. It is found that, for rise times
greater than about 10 min, the compression of the ionopause is nearly
adiabatic, with the ionopause moving downward at velocities of ∼1-2
km/sec until it reaches a maximally compressed states, at which time
the motion reverses. For short rise times the compression produces a
shock wave similar to that occuring in the case of a sudden increase
in pressure. The global implications of these processes are discussed
within the context of Pioneer Venus observations and future theoretical
work on this problem is outlined.
---------------------------------------------------------
Title: Solar atmospheric dynamics. II - Nonlinear models of the
photospheric and chromospheric oscillations
Authors: Leibacher, J.; Gouttebroze, P.; Stein, R. F.
1982ApJ...258..393L Altcode:
The one-dimensional, nonlinear dynamics of the solar atmosphere is
investigated, and models of the observed photospheric (300 s) and
chromospheric (200 s) oscillations are described. These are resonances
of acoustic wave cavities formed by the variation of the temperature
and ionization between the subphotospheric, hydrogen convection zone
and the chromosphere-corona transition region. The dependence of
the oscillations upon the excitation and boundary conditions leads
to the conclusion that for the observed amplitudes, the modes are
independently excited and, as trapped modes, transport little if any
mechanical flux. In the upper photosphere and lower chromosphere,
where the two modes have comparable energy density, interference
between them leads to apparent vertical phase delays which might be
interpreted as evidence of an energy flux.
---------------------------------------------------------
Title: Chromospheric and coronal heating mechanisms.
Authors: Leibacher, J.; Stein, R. F.
1982SAOSR.392A..23L Altcode: 1982csss....2...23L
Dissipation mechanisms in the chromosphere were examined. The problem
of a heat flux from a cool region of the star to a hot region of the
star, which violates our second law of thermodynamics is discussed. It
is suggested that this is caused by a nonthermal energy flux. While
convection transports the thermal flux, a very small percentage is
converted into a nonthermal flux. The major part of the outgoing
convective energy is turned back into the radiation field which
gets decoupled from the star when the star becomes transparent and
the radiant energy escapes to space. The small nonthermal flux is
transmitted upwards and becomes the dominant energy flux still coupled
to the star. The importance of recycling of energy via advection and
conduction is emphasized.
---------------------------------------------------------
Title: Heating of stellar chromospheres when magnetic fields are
present.
Authors: Ulmschneider, P.; Stein, R. F.
1982A&A...106....9U Altcode:
Constraints on possible mechanisms of chromospheric heating are derived
from recent, semi-empirical solar models, OSO-8 observations, and the
stellar Mg II emission-line fluxes of Basri and Linsky (1979). It is
shown that the observational facts are best satisfied by a scenario
in which non-magnetic regions are heated by acoustic shock waves,
while magnetic regions are heated by slow-mode shock waves. For the
case of the high chromosphere, however, this mechanism must be either
supplemented or replaced by such alternatives as Alfven wave heating.
---------------------------------------------------------
Title: On the modal structure of the solar oscillations
Authors: Stein, R. F.
1982A&A...105..417S Altcode:
The very different frequency structure of the high and low order modes
of the observed solar oscillations is shown to be due to the difference
in their cavities. The low order mode cavities extend deep into the
solar interior, while the high order mode cavities are confined near
the surface of the Sun. As a result the vertical component of the wave
vector has a very different dependence on depth in the two cases.
---------------------------------------------------------
Title: Oscillations and pulsations.
Authors: Leibacher, J. W.; Stein, R. F.
1981NASSP.450..263L Altcode: 1981suas.nasa..263L
A theory to describe the observed photospheric 5 minute oscillations,
chromospheric 3 minute oscillations, and possible motions of the
interior with periods ranging from 40 to 160 minutes is discussed. It
is similar to the theory of nonradial stellar oscillations developed
to describe the low angluar order modes (one or two wavelengths around
a circumference); however, the solar oscillations have thousands of
wavelengths around a circumference. The properties of waves in stars,
their restoring forces, periods and wavelengths, and their propagation
and motions are discussed.
---------------------------------------------------------
Title: Wave generation.
Authors: Stein, R. F.; Leibacher, J. W.
1981NASSP.450..289S Altcode: 1981suas.nasa..289S
There are three principal kinds of wave generation mechanisms,
corresponding to each of the three conservation laws that govern fluid
motions: a changing mass flux into a stable atmosphere; convective
motion; and energy exchange between a wave and the surrounding
atmosphere. These mechanisms are applied to three kinds of waves:
acoustic, gravity, and Alfven waves. They are pure cases, distinguished
by their different restoring forces pressure for acoustic waves,
buoyancy for gravity waves, and magnetic tension for Alfven waves.
---------------------------------------------------------
Title: Stellar chromospheric and coronal heating by
magnetohydrodynamic waves.
Authors: Stein, R. F.
1981ApJ...246..966S Altcode:
An investigation is presented on the way in which the generation of
magnetohydrodynamic waves by turbulent motions in stellar convection
zones depends on the star's effective temperature, surface gravity, and
magnetic field strength. It is shown that the emitted Alfven wave flux
(and acoustic slow wave flux in a very strong magnetic field) is in
reasonable agreement with the general trend of observed chromospheric
radiative losses in stars, and with the observations of three stars for
which magnetic field strength, surface area covered by strong fields,
and radiative losses have all been measured.
---------------------------------------------------------
Title: Magneto-Acoustic-Gravity Waves on the Sun
Authors: Stein, R. F.
1981BAAS...13..860S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stellar Chromospheric Heating by Magnetohydrodynamic Waves
Authors: Stein, R. F.
1980BAAS...12..872S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar atmospheric dynamics
Authors: Stein, R. F.
1980STIN...8117974S Altcode:
We have studied the heating of the solar chromosphere and transition
region by acoustic waves. We find they are incapable of transporting
sufficient energy through the chromosphere to heat the transition
region and corona. We are developing a radiative fluid dynamic computer
code to study acoustic heating of the chromosphere and the effect of
acoustic waves on line profiles. In order to study heating by other
types of wave motions we have analyzed the wave vector surface of the
Magneto-Acoustic-Gravity Waves and are developing a 'modal' computer
code to study their propagation and dissipation.
---------------------------------------------------------
Title: Small-scale dissipative processes in stellar atmospheres.
Authors: Leibacher, J. W.; Stein, R. F.
1980HiA.....5..581L Altcode:
The outer atmospheres of stars must be heated by some non-thermal
energy flux to produce chromospheres and coronae. Processes are
discussed which convert the non-thermal energy flux of organized,
macroscopic motions into random, microscopic (thermal) motions. Recent
advances in the description of the chromosphere velocity field suggest
that the acoustic waves observed there transmit very little energy,
and hence are probably incapable of heating the upper chromosphere
and corona. The apparent failure of this long held mechanism and the
growing appreciation of the importance of strong magnetic fields in
the chromosphere and corona have led to hypotheses of heating by the
dissipation of currents (both oscillatory and quasi-steady). This
follows discoveries in laboratory and ionospheric plasmas and work on
solar flares, that instabilities can concentrate currents into thin
high current density filaments where they dissipate rapidly.
---------------------------------------------------------
Title: Mechanical energy transport
Authors: Stein, R. F.; Leibacher, J. W.
1980LNP...114..225S Altcode: 1980IAUCo..51..225S; 1980sttu.coll..225S
The properties, generation, and dissipation mechanisms of acoustic,
gravity and Alfven waves are described, whose restoring forces
are pressure, buoyancy, and magnetic tension, respectively. For
acoustic waves, generation by turbulent convective motions and by the
Eddington Valve thermal overstability is discussed, considering the
'five-minute' oscillation; dissipation is possible either by radiation
or shocks. Generation of gravity waves by penetrative convective
motions and by shear arising from supergranule motions is reviewed, and
dissipation due to wave breaking, interaction with the mean horizontal
fluid flow, and very severe radiative damping is considered. Attention
is given to Alfven wave generation by convective motions and thermal
overstability, and to dissipation by mode coupling, wave decay, current
dissipation, and particle collisions producing Joule or viscous heating.
---------------------------------------------------------
Title: Deviations from LTE in a stellar atmosphere.
Authors: Kalkofen, W.; Klein, R. I.; Stein, R. F.
1979JQSRT..21..355K Altcode:
Deviations for LTE are investigated in an atmosphere of hydrogen
atoms with one bound level, satisfying the equations of radiative,
hydrostatic, and statistical equilibrium. The departure coefficient and
the kinetic temperature as functions of the frequency dependence of the
radiative cross section are studied analytically and numerically. Near
the outer boundary of the atmosphere, the departure coefficient
is smaller than unity when the radiative cross section grows with
frequency faster than with the square of frequency; it exceeds unity
otherwise. Far from the boundary the departure coefficient tends
to exceed unity for any frequency dependence of the radiative cross
section. Overpopulation always implies that the kinetic temperature in
the statistical-equilibrium atmosphere is higher than the temperature
in the corresponding LTE atmosphere. Upper and lower bounds on the
kinetic temperature are given for an atmosphere with deviations from
LTE only in the optically shallow layers when the emergent intensity
can be described by a radiation temperature.
---------------------------------------------------------
Title: Solar atmospheric dynamics
Authors: Stein, R. F.
1978msu..rept.....S Altcode:
We have studied the heating of the solar chromosphere and corona,
and the propagation of acoustic waves through the transition region
between the chromosphere and corona. In order to place an upper limit
on the effectiveness of acoustic waves in heating, we have written
and tested a computer program to accurately calculate the propagation
and dissipation of vertically travelling acoustic waves which includes
thermal conduction and radiative transfer. In order to study heating by
other possible waves, in particular magneto-acoustic-gravity waves, we
have written and are now testing a computer program which approximately
includes horizontal motions. In order to study the effects of horizontal
inhomogeneities we have started developing a three-dimensional fluid
dynamic computer program. We have also studied the propagation of
acoustic waves through the solar transition region. We find that
waves with velocity amplitudes compatible with observations near the
temperature minimum (less than + or - 1 km/s) transmit too little
flux through the transition region (- 20,000 erg/sq. cm. -s) to heat
the corona.
---------------------------------------------------------
Title: Radiative shock dynamics. II. Hydrogen continua.
Authors: Klein, R. I.; Stein, R. F.; Kalkofen, W.
1978ApJ...220.1024K Altcode:
The interaction between radiation and a shock wave propagating
through a stellar atmosphere is investigated. Departures from local
thermodynamic equilibrium (LTE) are permitted in the first two levels
of a 10-level hydrogen atom; levels 3-10 are in LTE. A piston moving
at constant velocity into the bottom of the atmosphere drives a shock
wave. This shock produces precursor radiation that diffuses through
the gas well ahead of the shock and causes a mild luminosity flash
in the emergent Balmer and free-free radiation when it reaches the
surface. The precursor wave deposits a large amount of radiative energy
in the outer layers of the atmosphere, initiating a radiation-induced
pressure wave. The process of energy transfer from the radiation field
to the compression wave is similar to the Eddington valve mechanism
which drives stellar pulsations. Material is accelerated outward by
the radiation-induced wave; eventually it free-falls inward, hits the
quasistationary atmosphere, and forms an accretion shock. The piston
driven shock is weakened by radiative energy losses. When it reaches
the surface, the shock is invisible in the continuum radiation.
---------------------------------------------------------
Title: Solar atmospheric dynamics
Authors: Stein, R. F.
1977bran.rept.....S Altcode:
This study seeks to calculate the generation and propagation of
Magneto-Acoustic Gravity (M.A.G.) waves in the solar atmosphere and
their effect on the heating of the chromosphere and corona. A computer
program has been written, which is capable of integrating the equations
of motion of such waves, which are inherently three-dimensional. To
simplify the equations, without seriously distorting the nature of the
motions, we impose a fixed horizontal modal structure consisting of 6
waves propagating horizontally in a hexagonal pattern. These equations
need to be integrated in time and only one spatial direction - the
vertical. The program is currently being tested for the simpler case of
non-vertically propagating acoustic-gravity waves. We have also analyzed
Skylab UV data for evidence of acoustic pulses in the transition region
and calculated the steady state structure of the solar wind flow along
a magnetic flux tube that diverges more rapidly than vertically.
---------------------------------------------------------
Title: Radiative shock dynamics. I. The Lyman continuum.
Authors: Klein, R. I.; Stein, R. F.; Kalkofen, W.
1976ApJ...205..499K Altcode:
The paper investigates coupled non-LTE radiative transfer and nonlinear
hydrodynamics by considering a shock propagating outward through an
atmosphere of pure hydrogen in which the hydrogen atoms have one bound
level and a continuum. Self-consistent numerical solutions are obtained
for the nonlinear hydrodynamic equations, the transfer equation for
Lyman continuum radiation, and the time-dependent population equation
for atoms with one bound level plus continuum. Results are discussed
for a piston-driven shock propagating through a static atmosphere
in radiative and statistical equilibrium, with attention given
to the formation of the ionization front, the ionization contour,
and the radiation intensity at the Lyman edge. The structure of the
temperature spike developed by the shock is compared for the three
cases of adiabatic, collisional, and radiating shocks. It is shown
that the escape of recombination radiation narrows the temperature
spike at small optical depth and that low postshock densities in the
upper atmosphere reduce the three-body recombination rate and produce
a large plateau of nearly constant ionization behind the shock.
---------------------------------------------------------
Title: Solar atmospheric dynamics
Authors: Stein, R. F.; Hsieh, S. H.
1976STIN...7714974S Altcode:
This study, aimed at calculating the heating of the solar chromosphere
and corona, started with the analysis of magneto-acoustic-gravity wave
vector surfaces. To permit non-linear calculation of the excitation
and propagation of these waves the equations of motion were written
for an imposed horizontal structure -- namely six waves of the same
wavelength propagating in an hexagonal pattern.
---------------------------------------------------------
Title: Non linear dynamics of stellar atmospheres
Authors: Leibacher, J.; Stein, R. F.
1976pmas.conf...69L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Waves in the solar atmosphere. IV. Magneto-gravity and
acoustic-gravity modes.
Authors: Schwartz, R. A.; Stein, R. F.
1975ApJ...200..499S Altcode:
We consider the properties of waves in a stratified, conducting
atmosphere under the influence of an applied magnetic field. Wave normal
surfaces are exhibited for acoustic-gravity and magneto-gravity waves,
and the propagation of these modes is compared. Subject headings:
atmospheres, solar hydromagnetics solar atmospheric motions
---------------------------------------------------------
Title: Volume of Material Ejected From Major Lunar Basins:
Implications for the Depth of Excavation of Lunar Samples
Authors: Head, J. W.; Settle, M.; Stein, R.
1975LPI.....6..352H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Thermal instability in supernova shells.
Authors: McCray, R.; Stein, R. F.; Kafatos, M.
1975ApJ...196..565M Altcode:
Thermal instability in the radiative-cooling region behind a shock will
cause upstream density fluctuations to collapse into thin sheets aligned
parallel to the shock front. A linearized calculation demonstrates
the development of this instability. Thermal conduction suppresses the
development of small-scale perturbations. Estimates of the scale sizes
for the fully developed condensations agree roughly with the scale sizes
of fine structure observed in supernova shells such as the Cygnus Loop.
---------------------------------------------------------
Title: Galaxy formation from primordial turbulence.
Authors: Stein, R.
1974A&A....35...17S Altcode:
The presence of large chaotic velocities in the early universe would
generate turbulence, which would in turn produce density and pressure
fluctuations. Density fluctuations on the scale of clusters of galaxies
could be gravitationally bound, but galactic mass fluctuations would
always be unbound. Galaxies would form when unbound galactic mass
eddies, expanding faster than their bound cluster background, collided
with each other as the cluster started to recollapse. These collisions
would produce shocks and thus high density protogalaxies at the eddy
interfaces. The galaxies would form rapidly. As the cluster recollapses,
the system of galaxies would undergo a violent collective relaxation.
---------------------------------------------------------
Title: Waves in the solar atmosphere.
Authors: Stein, R. F.; Leibacher, J.
1974ARA&A..12..407S Altcode:
The wave modes in the solar atmosphere are considered, taking
into account the equations of motion, pure modes, two-force modes,
and magneto-acoustic-gravity waves. Oscillations in the quiet sun
are discussed along with models of the 'five-minute' oscillation,
oscillations in regions of strong magnetic field, and nonsinusoidal
waves. Questions regarding the generation of waves are explored,
giving attention to penetrative convection, the Lighthill mechanism,
and aspects of thermal overstability. Problems regarding the heating
of the chromosphere and the corona are also examined.
---------------------------------------------------------
Title: Waves in the Solar Atmosphere. III. The Propagation of Periodic
Wave Trains in a Gravitational Atmosphere
Authors: Stein, Robert F.; Schwartz, Robert A.
1973ApJ...186.1083S Altcode:
The validity of weak shock theory for the propagation of waves in a
gravitational atmosphere is examined by comparing its results with
those from numerical integration of the exact equations of motion. The
weak-shock approximation is not valid for periods longer than half
the acoustic cutoff. In addition, the relation between the 300-s solar
oscillation and chromospheric and coronal heating is described. Subject
headings: atmospheres, solar - shock waves - solar atmospheric motions
---------------------------------------------------------
Title: Primordial Turbulence and Galaxy Formation.
Authors: Stein, R. F.
1973BAAS....5..435S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Formation of Protostars by Thermal Instability
Authors: Stein, Robert F.; McCray, Richard; Schwarz, Joseph
1972ApJ...177L.125S Altcode:
Spherically symmetric condensations driven by thermal instabilities in
a cooling interstellar medium can produce gravitationally bound clouds,
provided that the magnetic field has been previously removed from the
gas. The resulting douds have a very small ( 1o-4 pc), high-density
( 1o12 cm-3), warm ( 100 K), stationary core, surrounded by a large (
1 pc), cool ( 10 K), infalling envelope. Their structure resembles that
of an early stage in the protostar evolution calculated by Larson. Such
objects may represent Bok globules.
---------------------------------------------------------
Title: Waves in the Solar Atmosphere. II. Large-Amplitude Acoustic
Pulse Propagation
Authors: Stein, Robert F.; Schwartz, Robert A.
1972ApJ...177..807S Altcode:
Numerical experiments are performed with vertically propagating acoustic
pulses by solving the nonlinear equations of fluid motion using a
finite-difference technique. The pulse energy, dissipation, wake, and
atmospheric heating are investigated, and the results compared with
weak- shock theory. The ratio of pulse frequency to the acoustic cutoff
frequency, N = yg/2c, is found to be a crucial parameter. Weak-shock
theory gives reasonable results for pulse widths less than 50 seconds
(w > 2N ), but greatly overestimates the pulse energy and dissipation
for longer pulses. Significant dissipation begins at the height where
the crest of a simple wave overtakes its trough. For pulses with a)
> 2 the minimum damping length is about 500 km and occurs at about
1000 km above T5000 = 1. For lower-frequency pulses the minimum damping
length is about 1000 km and occurs higher up. Until hydrogen is nearly
completely ionized, ionization and radiation keep the temperature
rise small.
---------------------------------------------------------
Title: Formation of Filaments in Fossil H II Regions
Authors: McCray, Richard; Stein, Robert F.; Schwarz, Joseph
1972ApJ...177L..75M Altcode:
Ionized filaments of temperature 1 K and density contrast 10:1 are
formed by thermal instability in a low-density optically thin medium
which cools radiatively from an initial temperature 10 K. Typical
scale lengths are 0.1/n PC. The outlying filaments of the Gum Nebula
may result from this mechanism.
---------------------------------------------------------
Title: Formation of Clouds in a Cooling Interstellar Medium
Authors: Schwarz, Joseph; McCray, Richard; Stein, Robert F.
1972ApJ...175..673S Altcode:
An interstellar medium cooling from 8200 K after sudden heating (e.g.,
by soft X-rays or by low- energy cosmic rays) favors the development
of thermal . One-dimensional hydrodynamic calculations show that the
condensation process will yield interstellar clouds with densities of
100 times the intercloud density, given a small ( 10 percent) initial
density perturbation, provided the scale length X of the initial
perturbation satisfies X, < Cr,, where C is the sound speed in
the gas and r, is the radiative cooling time. The condensations reach
maximum density in a few cooling timescales. For an initially uniform
medium of density fl = 0.3 hydrogen atoms per cm3 that is 5 percent
ionized, a density perturbation of wavelength 3 pc will grow by a
factor of 100 in about 10 years, reaching a final ionized fraction
x 10- and temperature T < 20' K. The intercloud medium at this
time will have cooled to about 2000' K. In the one-dimensional case,
the final extent of the cloud will be about 0.01 pc. Cloud dimensions
more typical of those observed in the interstellar medium are a likely
result of a three-dimensional treatment of this problem. An increase in
the critical condensation wavelength , as well as higher temperatures
for the time-dependent intercloud medium, will result if cooling agents
such as C, Si, Fe, and 0 are more highly ionized than assumed in these
calculations. Soft X-rays are a plausible source of such anomalously
high ionization.
---------------------------------------------------------
Title: Thermal Condensations in Cooling Interstellar Gas.
Authors: Schwarz, J. H.; McCray, R. A.; Stein, R. F.
1971BAAS....3..472S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Reflection, Refraction, and Coupling of MHD Waves at a
Density Step
Authors: Stein, Robert F.
1971ApJS...22..419S Altcode:
The transrnission and reflection coefficients for MHD waves incident
on a density step are calculated. All three modes (fast, slow, and )
are coupled together except when the magnetic field is in the plane
of incidence or the plane of the interface. Results for arbitrary
orientations of the interface normal, the magnetic field, and the
incident wave vector are shown in a series of graphs. Strong coupling
between modes occurs for incident wave vectors nearly parallel to the
magnetic field. The fast and modes are coupled for P > F , the slow
and modes are coupled for P < P , and all three modes are coupled
for F Pg . The slow and modes are decoupled for P > P .
---------------------------------------------------------
Title: A New Description of the Solar Five-Minute Oscillation
Authors: Leibacher, J. W.; Stein, R. F.
1971ApL.....7..191L Altcode: 1970ApL.....7..191L
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric and Coronal Heating by Shock Waves
Authors: Stein, R. F.
1969cctr.conf..171S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Five-Minute Oscillation of the Solar Atmosphere
Authors: Stein, R. F.; Leibacher, J. W.
1969ApL.....3...95S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Waves in the Solar Atmosphere. I. The Acoustic Energy Flux.
Authors: Stein, Robert F.
1968ApJ...154..297S Altcode:
An extension of Lighthill's theory of aerodynamic generation of sound
to stratified atmospheres is used to calculate the upward acoustic
energy flux from the solar convection zone. The result is 2 X 1O~
ergs cm2 sec'. In addition the frequency spectrum of the emitted flux
is obtained. It rises as c~ (1 < n <2.5) above the critical
frequency w~ = 7g/2c, reaches a maximum in a few octaves, and then
falls off rapidly. Acoustic emission is very sensitive to the turbulent
velocities, and BOhm-Vitense' mixing- length theory gives only a rough
model of the solar convection zone. It is also sensitive to the high-
frequency tail of the turbulence spectrum. The form of the turbulence
energy spectrum is not known and may, in fact, depend on the emission
and absorption of acoustic waves. This lack of knowledge yields
an uncertainty in the calculated acoustic flux of about an order
of magnitude
---------------------------------------------------------
Title: Heating of the Chromosphere and Corona II.
Authors: Stein, Robert F.
1968AJS....73S..78S Altcode:
Preliminary calculations, based on the theory of chromospheric
heating previously proposed (Stein, Astron. J. 72, 321, 1967), have
been performed. First, the stability of the atmospheric structure was
considered. In the chromospheric network, where heating occurs, the gas
temperature, density, and pressure, as well as the magnetic field, are
greater than inside the cells. A magnetic field configuration with the
same polarity around the cell will support such a situation. Infinite
parallel sheets of magnetic field of the same polarity provide a simple
analytic two-dimensional model of such a field configuration. At
heights where the Alfve'n speed exceeds the sound speed the field
spreads rapidly and approaches a uniform field (at about 15 000 km in a
vacuum). The Alfve'n speed, however, increases outward only along field
lines lying within a wedge of half-angle 600, and magnetic effects
will be restricted to this wedge. Second, a preliminary analysis
of magnetohydrodynamic wave propagation was obtained by considering
reflection, refraction, and coupling at density and magnetic field
steps. Because the magnetic field spreads rapidly when the Alfven
velocity exceeds the sound speed, the high field boundary is not sharp,
and fast mode MHD waves are severely refracted. However, the filtering
of waves by a multilayer atmosphere with a uniform magnetic field shows
that the density gradient causes about 1 % of the fast mode energy to
be converted into Alfve'n waves. These travel along the field lines
dissipating energy slowly. Thus Osterbrock's (Astrophys. J. 134, 347,
1961) suggested mechanism, that Alfve'n waves carry energy up to the
corona, does indeed occur.
---------------------------------------------------------
Title: Generation of Acoustic and Gravity Waves by Turbulence in an
Isothermal Stratified Atmosphere
Authors: Stein, Robert F.
1967SoPh....2..385S Altcode:
Lighthill's method of calculating the aerodynamic emission of
sound waves in a homogeneous atmosphere is extended to calculate
the acoustic and gravity-wave emission by turbulent motions in a
stratified atmosphere. The acoustic power output is P<SUB>ac</SUB> ≈
10<SUP>3</SUP>θ<SUB>o</SUB>u<SUB>o</SUB><SUP>3</SUP>/l<SUB>o</SUB>M<SUP>5</SUP>
ergs/cm<SUP>3</SUP> sec, and the upward
gravity wave flux is F<SUB>zgr</SUB> ≈
10<SUP>2</SUP>θ<SUB>o</SUB>U<SUB>o</SUB><SUP>3</SUP>/l<SUB>o</SUB>
(l<SUB>o</SUB> ergs/cm<SUP>3</SUP> sec. Here u<SUB>0</SUB> is the
turbulence velocity scale, l<SUB>0</SUB> is its length scale, and H the
scale height at the atmosphere. M = u<SUB>0</SUB>/c<SUB>0</SUB> is the
Mach number of the turbulence. The acoustic power output is proportional
to the maximum value of the turbulence spectrum, and inversely to
its rate of falloff at high frequencies. The stratification cuts
off the acoustic emission at low Mach numbers. The gravity emission
occurs near the critical angle to the vertical θ<SUB>c</SUB> =
cos<SUP>−1</SUP>ω/ω<SUB>2</SUB>, where ω<SUB>2</SUB><SUP>2</SUP>
= (γ - 1)/γ<SUP>2</SUP> (c<SUB>0</SUB>/H), and at very short
wavelengths. It is proportional to the large wave number tail of the
turbulence spectrum. On the sun, gravity-wave emission is much more
efficient than acoustic, but can occur only from turbulent motions in
stable regions, whereas acoustic waves are produced by turbulence in
the convection zone.
---------------------------------------------------------
Title: Heating of the chromosphere and corona
Authors: Stein, R. F.
1967AJ.....72Q.321S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radiative damping of sound waves.
Authors: Stein, R. F.; Spiegel, E. A.
1967ASAJ...42..866S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagation of Waves in the Solar Atmosphere.
Authors: Stein, Robert F.
1966AJ.....71Q.181S Altcode:
The frequencies and horizontal wavenumbers at which the normal modes
(large amplitude quasi-standing waves) of the solar atmosphere occur
were calcu- lated for a semi empirical model of the region around the
temperature minimum. At high frequencies the waves are compressional,
modified by gravity, and can propagate into the upper atmosphere; at low
frequencies the waves are gravitational, modified by compressibility,
and can also propagate into the upper atmosphere. Between these two
passhands is a trap baud where the waves are completely reflected. Three
types of fundamental modes were found. The fundamental acoustic
mode has ~~8x 10~ ku sec-1 for horizontal wavelengths smaller than
1000 km and goes to a constant frequency with a width 0.05>
>0.032 sec-' for horizontal wavelengths greater than 2000 km. The
fundamental acoustic-gravity mode be- haves like an acoustic mode
for horizontal wavelengths greater than 6000 km, where it is composed
of many narrow resonances of nearly constant frequency in the range
0.032>~~>0.009 sec-1. At smaller horizontal wavelengths it narrows
and changes its behavior to that of a gravity mode with a frequency
c~~0.03 sec-1. The fundamental gravity mode has o~~7.5 x 10 k11 sec-'
at horizontal wavelengths greater than 3000 km and approaches a constant
frequency ~~0.028 sec-' at small horizontal wavelengths. The calculated
fundamental acoustic-gravity mode covers the range of frequencies and
horizontal wavelengths (0.03>~~>0.015 sec-', AH>SOOO km)
where the spectral density of the observed solar oscillations, as
calculated by Pierre Mein (Compt. Rend. 260, 1867, 1965), is large. It
was also found that the height of the maximum vertical velocity shifts
to greater altitudes as the frequency increases through the wide
acoustic-gravity fundamental mode. This might explain the observed
increase in the frequency of the oscillations with height.
