J/ApJ/752/126 Modeling the magnetic field in the solar corona (Yamamoto+, 2012) ================================================================================ Preprocessing magnetic fields with chromospheric longitudinal fields. Yamamoto T.T., Kusano K. =2012ApJ...752..126Y ================================================================================ ADC_Keywords: Sun ; Magnetic fields Keywords: Sun: chromosphere; Sun: photosphere; Sun: surface magnetism Abstract: Nonlinear force-free field (NLFFF) extrapolation is a powerful tool for the modeling of the magnetic field in the solar corona. However, since the photospheric magnetic field does not in general satisfy the force-free condition, some kind of processing is required to assimilate data into the model. In this paper, we report the results of new preprocessing for the NLFFF extrapolation. Through this preprocessing, we expect to obtain magnetic field data similar to those in the chromosphere. In our preprocessing, we add a new term concerning chromospheric longitudinal fields into the optimization function proposed by Wiegelmann et al (2006SoPh..233..215W). We perform a parameter survey of six free parameters to find minimum force- and torque-freeness with the simulated-annealing method. Analyzed data are a photospheric vector magnetogram of AR 10953 observed with the Hinode spectropolarimeter and a chromospheric longitudinal magnetogram observed with SOLIS spectropolarimeter. It is found that some preprocessed fields show the smallest force- and torque-freeness and are very similar to the chromospheric longitudinal fields. On the other hand, other preprocessed fields show noisy maps, although the force- and torque-freeness are of the same order. By analyzing preprocessed noisy maps in the wave number space, we found that small and large wave number components balance out on the force-free index. We also discuss our iteration limit of the simulated-annealing method and magnetic structure broadening in the chromosphere. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 47 86 Free parameter pairs -------------------------------------------------------------------------------- See also: J/ApJS/169/439 : Models of solar magnetic structures (Socas-Navarro, 2007) J/A+A/432/1063 : Analysis of inner solar corona in EUV (Lanzafame+, 2005) http://solis.nso.edu/ : National Solar Observatory NISP/SOLIS Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 2 I2 --- Num [0/85] Parameter combination number 4- 5 I2 [-] logt0 [-4/2] Log of coefficient of the initial pseudo temperature; T_init_=t0*L_init_ 7- 12 F6.4 --- dT [995/0.9995] Temperature cooling factor: new T = old T * dT 14- 15 I2 [-] logmu3 Log of coefficient of L3 17- 18 I2 [-] logmu4 Log of coefficient of L4 20- 21 I2 [-] logmu5 Log of coefficient of L5 (See equation (20)) 23- 25 I3 --- Seed [3/259] Random number seed 27 I1 --- cnv [0/1] Calculation convergence code; 1=converged 29- 37 E9.4 --- r1 Ratio of L1_init_/L1_finish_ 39- 47 E9.4 --- r5 Ratio of L5_init_/L5_finish_ -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Feb-2014