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Height of Shock Formation in the Solar Corona Inferred from Observations of Type II Radio Bursts and Coronal Mass EjectionsEmploying coronagraphic and EUV observations close to the solar surface made by the Solar Terrestrial Relations Observatory (STEREO) mission, we determined the heliocentric distance of coronal mass ejections (CMEs) at the starting time of associated metric type II bursts. We used the wave diameter and leading edge methods and measured the CME heights for a set of 32 metric type II bursts from solar cycle 24. We minimized the projection effects by making the measurements from a view that is roughly orthogonal to the direction of the ejection. We also chose image frames close to the onset times of the type II bursts, so no extrapolation was necessary. We found that the CMEs were located in the heliocentric distance range from 1.20 to 1.93 solar radii (Rs), with mean and median values of 1.43 and 1.38 Rs, respectively. We conclusively find that the shock formation can occur at heights substantially below 1.5 Rs. In a few cases, the CME height at type II onset was close to 2 Rs. In these cases, the starting frequency of the type II bursts was very low, in the range 25-40 MHz, which confirms that the shock can also form at larger heights. The starting frequencies of metric type II bursts have a weak correlation with the measured CME/shock heights and are consistent with the rapid decline of density with height in the inner corona.
Document ID
20150019780
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Gopalswamy, N.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Xie, H.
(Catholic Univ. of America Washington, DC, United States)
Makela, P.
(Catholic Univ. of America Washington, DC, United States)
Yashiro, S.
(Catholic Univ. of America Washington, DC, United States)
Akiyama, S.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Uddin, W.
(Aryabhatta Research Inst. of Observational Sciences Nainital, India)
Srivastava, A. K.
(Aryabhatta Research Inst. of Observational Sciences Nainital, India)
Joshi, N. C.
(Aryabhatta Research Inst. of Observational Sciences Nainital, India)
Chandra, R.
(Kumaun Univ. Nainital, India)
Manoharan, P. K.
(Tata Inst. of Fundamental Research Ootacamund, India)
Date Acquired
October 27, 2015
Publication Date
January 17, 2013
Publication Information
Publication: Advances in Space Research
Publisher: Elsevier
Volume: 51
Issue: 11
ISSN: 0273-1177
Subject Category
Solar Physics
Report/Patent Number
GSFC-E-DAA-TN26684
Funding Number(s)
CONTRACT_GRANT: NNG11PL10A
Distribution Limits
Public
Copyright
Other
Keywords
EUV
STEREO

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