Polarization Plot

From a pair of 17GHz and 34GHz images, spectrum distribution can be obtained. It is used for judging the emission mechanism and/or deriving the power-law index of non-thermal elecrons. The derived variable is $\alpha$ whose definition is

$$F_{\nu} \propto {\nu}^{\alpha}$$

Since available frequencies for NoRH are only two, the actual derivation is

$${\alpha} = {\log{(F_{\nu}^{34{\rm GHz}}/F_{\nu}^{17{\rm GHz}})} \over \log{({34{\rm GHz}}/{17{\rm GHz}})}}$$

By using a pair of images of 17 GHz and 34 GHz with the same field of view
IDL> file='./ips990828_005642' $<$CR$>$
IDL> norh_rd_img,file,indexs,datas $<$CR$>$
IDL> fi17=norh_tb2flux(dataa,indexa,/intensity) $<$CR$>$
IDL> fv17=norh_tb2flux(datas,indexs,/intensity) $<$CR$>$
IDL> norh_polariz,indexa,fi17,indexs,fv17,indexp,pol,mvdp $<$CR$>$
pol is an array of $r_{c}$. mvdp is an array including the values of unity (1) for valid data or zero (0) for non-valid data. indexp is an index correspoinding to data pol. For easy plot (Fig 3)
IDL> norh_plot,indexa,dataa,indexp,pol,mvdp $<$CR$>$
For preparing to overplot with other instrumental data, change the data format to SolarSoftware map.
IDL> norh_index2map,indexp,pol*mvdp,mappol $<$CR$>$
IDL> plot_map,mappol,/cont,levels=[-0.8,-0.4,-0.2,0.2,0.4,0.8] $<$CR$>$