Spectrum Distribution

図 4: Spectrum Distribution (gray scale), $T_{b}^{\rm 17GHz}=1{\rm MK}$ (contour of thick line), and circular polarization degree (contour of thin line)

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='./ipa990828_005642' $<$CR$>$
IDL> norh_rd_img,file,indexa,dataa $<$CR$>$
IDL> file='./ipz990828_005642' $<$CR$>$
IDL> norh_rd_img,file,indexz,dataz $<$CR$>$
IDL> fi17=norh_tb2flux(dataa,indexa,/intensity) $<$CR$>$
IDL> fi34=norh_tb2flux(dataz,indexz,/intensity) $<$CR$>$
IDL> norh_convol,indexz,indexa,fi17,indexa_c,fi17_c $<$CR$>$
IDL> norh_convol,indexa,indexz,fi34,indexz_c,fi34_c $<$CR$>$
IDL> norh_alpha,indexa_c,fi17_c,indexz_c,fi34_c ,indexal,alpha,mvda $<$CR$>$
alpha is the power law index of spectrum $\alpha$. mvda is an array including the values of unity (1) for valid data or zero (0) for non-valid data. indexal is an index correspoinding to data alpha. For easy plot (Fig 4)
IDL> norh_plot_alpha,indexal,alpha,mvda,indexp,pol,mvdp,indexa,dataa $<$CR$>$
For preparing to overplot with other instrumental data, change the data format to SolarSoftware map.
IDL> norh_index2map,indexal,alpha*mvda,mapalpha $<$CR$>$
IDL> plot_map,mapalpha,dmin=-4,dmax=2 $<$CR$>$