Addendum to: Strength of the Solar Coronal Magnetic Field – A Comparison of Independent Estimates Using Contemporaneous Radio and White-Light Observations

Abstract

This addendum uses an alternate fit for the electron density distribution $N(r)$ (see Figure 1) and estimates the coronal magnetic field using the new model. We find that the estimates of the magnetic field are in close agreement using both the models.

We have fit the $N(r)$ distribution obtained from STEREO-A/COR1 and SOHO/LASCO-C2 using a fifth-order polynomial (see Figure 1). The expression can be written as

$$\begin{aligned} N_{\text{cor}}(r) &= 1.43 \times 10^{9} r^{-5} - 1.91 \times 10^{9} r^{-4} + 1.07 \times 10^{9} r^{-3} - 2.87 \times 10^{8} r^{-2} \\ &\quad {} + 3.76 \times 10^{7} r^{-1} - 1.91 \times 10^{6} , \end{aligned}$$

(1)

where $N_{\text{cor}}(r)$ is in units of cm⁻³ and $r$ is in units of $\mathrm{R}_{\odot}$. The background coronal electron density is enhanced by a factor of 5.5 at 2.63 $\mathrm{R}_{\odot}$ during the coronal mass ejection (CME). The estimated coronal magnetic field strength ($B$) using radio data indicates that $B(r) \approx(0.51\text{\,--\,}0.48) \pm 0.02\ \mathrm{G}$ in the range $r \approx2.65\text{\, --\,}2.82\ \mathrm{R}_{\odot}$. The field strengths for STEREO-A/COR1 and SOHO/LASCO-C2 are ≈ 0.32 G at $r \approx 3.11\ \mathrm{R}_{\odot}$ and ≈ 0.12 G at $r \approx 4.40\ \mathrm{R}_{\odot}$, respectively.