The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
S Yashiro - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
The Astrophysical Journal, 2012Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (1000 km s −1 ) limb coronal mass ejections(CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston‐shock relationship to the observed CME’s standoff distance and electron density compression ratio, we estimated the Mach number, Alfv´ en speed, and Magnetic Field Strength in the height range 3‐15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49‐3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47‐1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfv´ en speed ranges from 259 to 982 km s −1 and the Magnetic Field Strength is in the range 6‐105mG when the standoff distance is
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (> 1000 km/s) limb CMEs which show clear shock structures in SOHO/LASCO images. By applying piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and Magnetic Field Strength in the height range 3 to 15 solar radii (Rs). Main results from this study are: (1) the standoff distance observed in solar corona is consistent with those from a magnetohydrodynamic (MHD) model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49 to 3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47 to 1.90, implying that the measured density compression ratio is likely to be underestimated due to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the Magnetic Field Strength is in the range 6 to 105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of 2, the Alfven speeds and the Magnetic Field Strengths are consistent in both methods; (5) the Magnetic Field Strengths derived from the shock parameters are similar to those of empirical models and previous estimates.
K Cho - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
The Astrophysical Journal, 2012Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (1000 km s −1 ) limb coronal mass ejections(CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston‐shock relationship to the observed CME’s standoff distance and electron density compression ratio, we estimated the Mach number, Alfv´ en speed, and Magnetic Field Strength in the height range 3‐15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49‐3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47‐1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfv´ en speed ranges from 259 to 982 km s −1 and the Magnetic Field Strength is in the range 6‐105mG when the standoff distance is
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (> 1000 km/s) limb CMEs which show clear shock structures in SOHO/LASCO images. By applying piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and Magnetic Field Strength in the height range 3 to 15 solar radii (Rs). Main results from this study are: (1) the standoff distance observed in solar corona is consistent with those from a magnetohydrodynamic (MHD) model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49 to 3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47 to 1.90, implying that the measured density compression ratio is likely to be underestimated due to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the Magnetic Field Strength is in the range 6 to 105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of 2, the Alfven speeds and the Magnetic Field Strengths are consistent in both methods; (5) the Magnetic Field Strengths derived from the shock parameters are similar to those of empirical models and previous estimates.
Roksoon Kim - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
The Astrophysical Journal, 2012Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (1000 km s −1 ) limb coronal mass ejections(CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston‐shock relationship to the observed CME’s standoff distance and electron density compression ratio, we estimated the Mach number, Alfv´ en speed, and Magnetic Field Strength in the height range 3‐15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49‐3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47‐1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfv´ en speed ranges from 259 to 982 km s −1 and the Magnetic Field Strength is in the range 6‐105mG when the standoff distance is
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (> 1000 km/s) limb CMEs which show clear shock structures in SOHO/LASCO images. By applying piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and Magnetic Field Strength in the height range 3 to 15 solar radii (Rs). Main results from this study are: (1) the standoff distance observed in solar corona is consistent with those from a magnetohydrodynamic (MHD) model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49 to 3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47 to 1.90, implying that the measured density compression ratio is likely to be underestimated due to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the Magnetic Field Strength is in the range 6 to 105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of 2, the Alfven speeds and the Magnetic Field Strengths are consistent in both methods; (5) the Magnetic Field Strengths derived from the shock parameters are similar to those of empirical models and previous estimates.
D Utz - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Strength distribution of Magnetic bright points inferred from filtergrams and spectro polarimetric data
Astronomy and Astrophysics, 2013Co-Authors: D Utz, J Jurcak, A Hanslmeier, R Muller, Astrid M Veronig, O KuhnerAbstract:Context. Small scale Magnetic Fields can be observed on the Sun in G-band filtergrams as MBPs (Magnetic bright points) or identified in spectro-polarimetric measurements due to enhanced signals of Stokes profiles. These Magnetic Fields and their dynamics play a crucial role in understanding the coronal heating problem and also in surface dynamo models. MBPs can theoretically be described to evolve out of a patch of a solar photospheric Magnetic Field with values below the equipartition Field Strength by the so-called convective collapse model. After the collapse, the Magnetic Field of MBPs reaches a higher stable Magnetic Field level. Aims. The Magnetic Field Strength distribution of small scale Magnetic Fields as seen by MBPs is inferred. Furthermore, we want to test the model of convective collapse and the theoretically predicted stable value of about 1300 G. Methods. We used four different data sets of high-resolution Hinode/SOT observations that were recorded simultaneously with the broadband filter device (G-band, Ca II-H) and the spectro-polarimeter. To derive the Magnetic Field Strength distribution of these small scale features, the spectropolarimeter (SP) data sets were treated by the Merlin inversion code. The four data sets comprise different solar surface types: active regions (a sunspot group and a region with pores), as well as quiet Sun. Results. In all four cases the obtained Magnetic Field Strength distribution of MBPs is similar and shows peaks around 1300 G. This agrees well with the theoretical prediction of the convective collapse model. The resulting Magnetic Field Strength distribution can be fitted in each case by a model consisting of log-normal components. The important parameters, such as geometrical mean value and multiplicative standard deviation, are similar in all data sets, only the relative weighting of the components is different.
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Magnetic Field Strength distribution of Magnetic bright points inferred from filtergrams and spectro polarimetric data
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: D Utz, J Jurcak, A Hanslmeier, R Muller, Astrid M Veronig, O KuhnerAbstract:Small scale Magnetic Fields can be observed on the Sun in G-band filtergrams as MBPs (Magnetic bright points) or identified in spectro-polarimetric measurements due to enhanced signals of Stokes profiles. These Magnetic Fields and their dynamics play a crucial role in understanding the coronal heating problem and also in surface dynamo models. MBPs can theoretically be described to evolve out of a patch of a solar photospheric Magnetic Field with values below the equipartition Field Strength by the so-called convective collapse model. After the collapse, the Magnetic Field of MBPs reaches a higher stable Magnetic Field level. The Magnetic Field Strength distribution of small scale Magnetic Fields as seen by MBPs is inferred. Furthermore, we want to test the model of convective collapse and the theoretically predicted stable value of about 1300 G. We used four different data sets of high-resolution Hinode/SOT observations that were recorded simultaneously with the broadband filter device (G-band, Ca II-H) and the spectro-polarimeter. To derive the Magnetic Field Strength distribution of these small scale features, the spectropolarimeter (SP) data sets were treated by the Merlin inversion code. The four data sets comprise different solar surface types: active regions (a sunspot group and a region with pores), as well as quiet Sun. In all four cases the obtained Magnetic Field Strength distribution of MBPs is similar and shows peaks around 1300 G. This agrees well with the theoretical prediction of the convective collapse model. The resulting Magnetic Field Strength distribution can be fitted in each case by a model consisting of log-normal components. The important parameters, such as geometrical mean value and multiplicative standard deviation, are similar in all data sets, only the relative weighting of the components is different.
N Gopalswamy - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
The Astrophysical Journal, 2012Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (1000 km s −1 ) limb coronal mass ejections(CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston‐shock relationship to the observed CME’s standoff distance and electron density compression ratio, we estimated the Mach number, Alfv´ en speed, and Magnetic Field Strength in the height range 3‐15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49‐3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47‐1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfv´ en speed ranges from 259 to 982 km s −1 and the Magnetic Field Strength is in the range 6‐105mG when the standoff distance is
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Magnetic Field Strength in the upper solar corona using white light shock structures surrounding coronal mass ejections
arXiv: Solar and Stellar Astrophysics, 2011Co-Authors: Yong-jae Moon, Roksoon Kim, N Gopalswamy, K Cho, S YashiroAbstract:To measure the Magnetic Field Strength in the solar corona, we examined 10 fast (> 1000 km/s) limb CMEs which show clear shock structures in SOHO/LASCO images. By applying piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and Magnetic Field Strength in the height range 3 to 15 solar radii (Rs). Main results from this study are: (1) the standoff distance observed in solar corona is consistent with those from a magnetohydrodynamic (MHD) model and near-Earth observations; (2) the Mach number as a shock Strength is in the range 1.49 to 3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47 to 1.90, implying that the measured density compression ratio is likely to be underestimated due to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the Magnetic Field Strength is in the range 6 to 105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of 2, the Alfven speeds and the Magnetic Field Strengths are consistent in both methods; (5) the Magnetic Field Strengths derived from the shock parameters are similar to those of empirical models and previous estimates.
