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Understanding CME and associated shock in the solar corona by merging multi wavelengths observation  

Pietro Zucca   Submitted: 2014-09-17 02:33

Using multi-wavelength imaging observations, in EUV, white light and radio, and radio spectral data over a large frequency range, we analyzed the triggering and development of a complex eruptive event. This one includes two components, an eruptive jet and a CME which interact during more than 30 min, and can be considered as physically linked. This was an unusual event. The jet is generated above a typical complex magnetic configuration which has been investigated in many former studies related to the build-up of eruptive jets; this configuration includes fan-field lines originating from a corona null point above a parasitic polarity, which is embedded in one polarity region of large Active Region (AR). The initiation and development of the CME, observed first in EUV, does not show usual signatures. In this case, the eruptive jet is the main actor of this event. The CME appears first as a simple loop system which becomes destabilized by magnetic reconnection between the outer part of the jet and the ambient medium. The progression of the CME is closely associated with the occurrence of two successive types II bursts from distinct origin. An important part of this study is the first radio type II burst for which the joint spectral and imaging observations allowed: i) to follow, step by step, the evolution of the spectrum and of the trajectory of the radio burst, in relationship with the CME evolution; ii) to obtain, without introducing an electronic density model, the B-field and the Alfvén speed.

Authors: Pietro Zucca, Monique Pick, Pascal Demoulin, Alain Kerdraon, Alain Lecacheux, Peter T. Gallagher
Projects:

Publication Status: Accepted
Last Modified: 2014-09-17 13:06
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The formation heights of coronal shocks from 2D density and Alfvén speed maps  

Pietro Zucca   Submitted: 2014-03-20 04:15

Super-Alfvénic shock waves associated with coronal mass ejections (CMEs) can produce radio emission known as Type II bursts. In the absence of direct imaging, accurate estimates of coronal electron densities, magnetic field strengths and Alfvén speeds are required in order to calculate the kinematics of shocks. To date, 1D radial models have been used, but these are not appropriate for shocks propagating in non-radial directions. Here, we study a coronal shock wave associated with a CME and Type II radio burst using 2D electron density and Alfvén speed maps to determine the locations that shocks are excited as the CME expands through the corona. Coronal density maps were obtained from emission measures derived from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) and polarized brightness measurements from the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). Alfvén speed maps were calculated using these density maps and magnetic field extrapolations from the Helioseismic and Magnetic Imager (SDO/HMI). The computed density and Alfvén speed maps were then used to calculate the shock kinematics in non-radial directions. Using the kinematics of the Type II burst and associated shock, we find our observations to be consistent with the formation of a shock located at the CME flanks where the Alfvén speed has a local minimum. 1D density models are not appropriate for shocks that propagate non-radially along the flanks of a CME. Rather, the 2D density, magnetic field and Alfvén speed maps described here give a more accurate method for determining the fundamental properties of shocks and their relation to CMEs.

Authors: Pietro Zucca, Eoin P. Carley, D. Shaun Bloomfield, Peter T. Gallagher
Projects: SDO-AIA

Publication Status: Accepted
Last Modified: 2014-03-20 15:28
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Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory  

Pietro Zucca   Submitted: 2012-04-04 07:19

The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53 05'38.9'', 7 55'12.7'') in 2010 to study solar radio bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low- frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range 10-870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range 10-400 MHz are obtained with 4 sweeps per second over 600 channels. Here, we describe the RSTO solar radio spectrometer set-up, and present dynamic spectra of a sample of Type II, III and IV radio bursts. In particular, we describe fine- scale structure observed in Type II bursts, including band splitting and rapidly varying herringbone features.

Authors: P. Zucca, E. P. Carley, J. McCauley, P. T. Gallagher, C. Monstein, R. T. J. McAteer
Projects:

Publication Status: Accepted
Last Modified: 2012-04-17 06:32
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Understanding CME and associated shock in the solar corona by merging multi wavelengths observation
The formation heights of coronal shocks from 2D density and Alfv?n speed maps
Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory

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