Abstract
Spatially averaged intensity profiles of the chromospheric Na I D and Ca II infrared lines exhibit a pronounced red asymmetry in their cores with bisectors in the shape of an inverse 
. This shape stands in stark contrast to the regular shape of photospheric spectral line bisectors, which on average exhibit a blue shift as a result of the asymmetry in surface area subtended by convective upflows over downflows. The nature of the inverse chromospheric shape is investigated by comparing spatially averaged profiles of the Na I D and Ca II infrared lines with mean profiles computed through three-dimensional snapshots of a hydrodynamic convection simulation and a one-dimensional simulation of chromospheric radiation hydrodynamics. In part the red asymmetry is the result of the asymmetry in time the atmosphere spends in downward motion compared to upward motion when it is traversed by acoustic shocks. Profiles from convection simulations without shocks suggest that convective motions play a limited role in shaping the chromospheric line asymmetry. Further simulations that include effects of both convection and shock wave formation are needed to reach a definitive conclusion on the origin of the inverse- shaped bisectors.
Export citation and abstract BibTeX RIS
References
- Asensio Ramos, A., Trujillo Bueno, J., Carlsson, M., & Cernicharo, J. 2003, ApJL, 588, 61
- Asplund, M., Ludwig, H.-G., Nordlund, Å., & Stein, R. F. 2000a, A&A, 359, 669
- Asplund, M., Nordlund, Å., Trampedach, R., Allende Prieto, C., & Stein, R. F. 2000b, A&A, 359, 729
- Auer, L., Fabiani Bendicho, P., & Trujillo Bueno, J. 1994, A&A, 292, 599
- Brault, J. W. 1978, in Future Solar Optical Observations Needs and Constraints, ed. G. Godoli (Florence: Baccini & Chiappi), 33
- Brault, J. W. 1993, in Selected Papers on Instrumentation in Astronomy, ed. W. Livingston & B. J. Thompson (Bellingham: SPIE), 273
- Bruls, J. H. M. J., & Rutten, R. J. 1992, A&A, 265, 257
- Carlsson, M., Judge, P. G., & Wilhelm, K. 1997, ApJL, 486, 63
- Carlsson, M., & Stein, R. F. 1997, ApJ, 481, 500
- Carlsson, M., & Stein, R. F. 1999, in AIP Conf. Proc. 471, Solar Wind Nine, ed. S. R. Habbal et al. (New York: AIP), 23
- Carlsson, M., & Stein, R. F. 2002, ApJ, 572, 626
- Dravins, D. 1987a, A&A, 172, 200
- Dravins, D. 1987b, A&A, 172, 211
- Dravins, D., & Nordlund, Å. 1990, A&A, 228, 203
- Dupree, A. K., Penn, M. J., & Jones, H. P. 1996, ApJL, 467, 121
- Fossum, A., & Carlsson, M. 2004, in Proc. SOHO 13—Waves, Oscillations, and Small-Scale Transient Events in the Solar Atmosphere: A Joint View from SOHO and TRACE (ESA SP-547), ed. H. Lacoste (Noordwijk: ESA), 125
- Grevesse, N., & Anders, E. 1991, in Solar Interior and Atmosphere, ed. A. Cox, W. Livingston, & M. Matthews (Tucson: Univ. Arizona Press), 1227
- Harvey, J. 2005, Poster presented at American Geophysical Union Spring 2005 Joint Assembly (SP41B-05; Washington: AGU)
- McIntosh, S. W., & Judge, P. G. 2001, ApJ, 561, 420
- Nordlund, Å. 1982, A&A, 107, 1
- Peter, H., & Judge, P. G. 1999, ApJ, 522, 1148
- Rammacher, W., & Ulmschneider, P. 1992, A&A, 253, 586
- Rybicki, G. B., & Hummer, D. G. 1991, A&A, 245, 171
- Rybicki, G. B., & Hummer, D. G. 1992, A&A, 262, 209
- Skartlien, R. 2000, ApJ, 536, 465
- Skartlien, R., Stein, R. F., & Nordlund, Å. 2000, ApJ, 541, 468
- Stein, R. F., & Nordlund, Å. 1998, ApJ, 499, 914
- Uitenbroek, H. 1989, A&A, 213, 360
- Uitenbroek, H. 2000, ApJ, 536, 481
- Uitenbroek, H. 2001, ApJ, 557, 389
- Uitenbroek, H. 2002, ApJ, 565, 1312
- Uitenbroek, H. 2003, ApJ, 592, 1225
- Uitenbroek, H., & Bruls, J. H. M. J. 1992, A&A, 265, 268
- von Uexkuell, M., & Kneer, F. 1995, A&A, 294, 252
- Wikstøl, Ø., Hansteen, V. H., Carlsson, M., & Judge, P. G. 2000, ApJ, 531, 1150
Citations
-
Simulations of the Mg II k and Ca II 8542 lines from an AlfvÉn Wave-heated Flare Chromosphere
Graham S. Kerr et al. 2016 The Astrophysical Journal 827 101 -
Emergence of Granular-sized Magnetic Bubbles through the Solar Atmosphere. II. Non-LTE Chromospheric Diagnostics and Inversions
Jaime de la Cruz Rodríguez et al. 2015 The Astrophysical Journal 810 145 -
The Effect of Isotopic Splitting on the Bisector and Inversions of the Solar Ca II 854.2 nm Line
Jorrit Leenaarts et al. 2014 The Astrophysical Journal Letters 784 L17 -
Multi-dimensional Radiative Transfer to Analyze Hanle Effect in Ca II K Line at 3933 Å
L. S. Anusha and K. N. Nagendra 2013 The Astrophysical Journal 767 108 -
Ca II 854.2 nm Bisectors and Circumfacular Regions
A. Pietarila and J. W. Harvey 2013 The Astrophysical Journal 764 153 -
The Formation of the Hα Line in the Solar Chromosphere
J. Leenaarts et al. 2012 The Astrophysical Journal 749 136 -
Solar Cycle Variation in Sun-as-a-star Ca II 854.2 nm Bisectors
A. Pietarila and W. Livingston 2011 The Astrophysical Journal 736 114 -
Three-Dimensional Non-LTE Radiative Transfer Computation of the CA 8542 Infrared Line From a Radiation-MHD Simulation
J. Leenaarts et al. 2009 The Astrophysical Journal Letters 694 L128 -
3D radiative transfer in stellar atmospheres
M Carlsson 2008 Physica Scripta 2008 014012 -
Spectroscopic Measurements of Dynamic Fibrils in the Ca II λ8662 Line
Øystein Langangen et al. 2008 The Astrophysical Journal 673 1194