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Radial and azimuthal oscillations of halo coronal mass ejections in the Sun
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Lee, Harim, Moon, Y.-J. and Nakariakov, V. M. (2015) Radial and azimuthal oscillations of halo coronal mass ejections in the Sun. The Astrophysical Journal, 803 (1). L7. doi:10.1088/2041-8205/803/1/L7
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WRAP_9877890-px-140416-harim_apjl_vmn_130315.pdf - Accepted Version - Requires a PDF viewer. Download (4Mb) | Preview |
Official URL: http://dx.doi.org/10.1088/2041-8205/803/1/L7
Abstract
We present the first observational detection of radial and azimuthal oscillations in full halo coronal mass ejections (HCMEs). We analyze nine HCMEs well-observed by the Large Angle and Spectrometric Coronagraph (LASCO) from 2011 February to June. Using the LASCO C3 running difference images, we estimated the instantaneous apparent speeds of the HCMEs in different radial directions from the solar disk center. We find that the development of all these HCMEs is accompanied by quasi-periodic variations of the instantaneous radial velocity with the periods ranging from 24 to 48 minutes. The amplitudes of the instant speed variations reach about a half of the projected speeds. The amplitudes are found to anti-correlate with the periods and correlate with the HCME speed, indicating the nonlinear nature of the process. The oscillations have a clear azimuthal structure in the heliocentric polar coordinate system. The oscillations in seven events are found to be associated with distinct azimuthal wave modes with the azimuthal wave number m = 1 for six events and m = 2 for one event. The polarization of the oscillations in these seven HCMEs is broadly consistent with those of their position angles with the mean difference of 43°. The oscillations may be connected with natural oscillations of the plasmoids around a dynamical equilibrium, or self-oscillatory processes, e.g., the periodic shedding of Alfvénic vortices. Our results indicate the need for an advanced theory of oscillatory processes in coronal mass ejections.
| Item Type: | Journal Article | ||||||||
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| Subjects: | Q Science > QB Astronomy | ||||||||
| Divisions: | Faculty of Science > Physics | ||||||||
| Library of Congress Subject Headings (LCSH): | Coronal mass ejections, Solar oscillations | ||||||||
| Journal or Publication Title: | The Astrophysical Journal | ||||||||
| Publisher: | Institute of Physics Publishing, Inc. | ||||||||
| ISSN: | 0004-637X | ||||||||
| Official Date: | 6 April 2015 | ||||||||
| Dates: |
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| Date of first compliant deposit: | 25 April 2016 | ||||||||
| Volume: | 803 | ||||||||
| Number: | 1 | ||||||||
| Article Number: | L7 | ||||||||
| DOI: | 10.1088/2041-8205/803/1/L7 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Access rights to Published version: | Open Access | ||||||||
| Funder: | National Research Foundation of Korea (NRF), European Research Council (ERC), Science and Technology Facilities Council (Great Britain) (STFC), United States. National Aeronautics and Space Administration (NASA) | ||||||||
| Grant number: | NRF-2013R1A1A2012763 (NRF), 2013R1A1A2058409 (NRF), 321141 (ERC), ST/L000733/1 (STFC) |
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