Coronal electron density distributions estimated
from DH type II radio bursts based on
CME nose and flank observations
Jae-Ok Lee1, Y.–J. Moon1, 2, Jin-Yi Lee2, Kyung-Sun Lee3, and R.–S. Kim4
1
School of Space Research, Kyung Hee University, Rep. of Korea
Department of Astronomy and Space Science, Kyung Hee University, Rep. of Korea
3
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
4
Korea Astronomy and Space Science, Rep. of Korea
ljoking@khu.ac.kr
2
We determine coronal electron density distributions by analyzing deca-hectometer
(DH) type II radio observations based on the two assumptions: First, the lowest
frequency of the fundamental emission lane of a DH type II radio burst is generated by
the shock formed at a CME leading edge. Second, the fundamental frequency is caused
by a CME-streamer interaction. For this, we consider 399 Wind/WAVES DH type II
radio bursts associated with SOHO/LASCO CMEs. We select 11 events satisfying the
following criteria: (1) their source longitudes are greater than 60 degree; (2) the
fundamental and second harmonic emission lanes are well identified. For the selected
events, we determine the lowest frequencies of their fundamental emission lanes and the
heights of the fastest moving leading edges of their associated CMEs. We also
determine interaction heights between CME leading edges and streamers. Coronal
electron density distributions are estimated by minimizing the root mean square error of
the heights between CME observations and DH type II radio bursts from assumed
electron density distributions. We find the following results. (1) Using the first
assumption, the estimated coronal electron density distributions at the heights between
about 3 and 20 Rs range from 2.2 to 8.8-fold Saito's coronal electron density model,
which are similar to those from metric type II radio bursts and CMEs. (2) Using the
second assumption, the electron density distributions at the heights between 3 and 10 Rs
range from 0.8 to 2.0-fold Saito's model, which are similar to those by polarized
brightness measurements.