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Coronal electron density distributions estimated from CMEs, DH type II radio bursts, and polarized brightness measurements
Author(s) -
Lee JaeOk,
Moon Y.J.,
Lee JinYi,
Lee KyoungSun,
Kim R.S.
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2015ja022321
Subject(s) - physics , astrophysics , coronal mass ejection , brightness , shock (circulatory) , coronagraph , solar prominence , electron , solar radius , solar wind , optics , plasma , magnetic field , medicine , quantum mechanics , exoplanet , planet
We determine coronal electron density distributions (CEDDs) by analyzing decahectometric (DH) type II observations under two assumptions. DH type II bursts are generated by either (1) shocks at the leading edges of coronal mass ejections (CMEs) or (2) CME shock‐streamer interactions. Among 399 Wind/WAVES type II bursts (from 1997 to 2012) associated with SOHO/LASCO (Large Angle Spectroscopic COronagraph) CMEs, we select 11 limb events whose fundamental and second harmonic emission lanes are well identified. We determine the lowest frequencies of fundamental emission lanes and the heights of leading edges of their associated CMEs. We also determine the heights of CME shock‐streamer interaction regions. The CEDDs are estimated by minimizing the root‐mean‐square error between the heights from the CME leading edges (or CME shock‐streamer interaction regions) and DH type II bursts. We also estimate CEDDs of seven events using polarized brightness (pB) measurements. We find the following results. Under the first assumption, the average of estimated CEDDs from 3 to 20 R s is about 5‐fold Saito's model ( N Saito ( r )). Under the second assumption, the average of estimated CEDDs from 3 to 10 R s is 1.5‐fold N Saito ( r ). While the CEDDs obtained from pB measurements are significantly smaller than those based on the first assumption and CME flank regions without streamers, they are well consistent with those on the second assumption. Our results show that not only about 1‐fold N Saito ( r ) is a proper CEDD for analyzing DH type II bursts but also CME shock‐streamer interactions could be a plausible origin for generating DH type II bursts.