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Register a new userCME development in the corona and interplanetary medium: A multi-wavelength approach
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This review focuses on the so called three-part CMEs which essentially represent the standard picture of a CME eruption. It is shown how the multi-wavelength observations obtained in the last decade, especially those with high cadence, have validated the early models and contributed to their evolution. These observations cover a broad spectral range including the EUV, white-light, and radio domains.
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One of the major unsolved problems in Solar Physics is that of CME initiation. In this paper, we have studied the initiation of a flare associated CME which occurred on 2010 November 03 using multi-wavelength observations recorded by Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) and Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We report an observation of an inflow structure initially in 304~{AA} and in 1600~{AA} images, a few seconds later. This inflow strucure was detected as one of the legs of the CME. We also observed a non-thermal compact source concurrent and near co-spatial with the brightening and movement of the inflow structure. The appearance of this compact non-thermal source, brightening and movement of the inflow structure and the subsequent outward movement of the CME structure in the corona led us to conclude that the CME initiation was caused by magnetic reconnection.
We present Spitzer Space Telescope IRAC and MIPS observations of a 0.85 deg^2 field including the Corona Australis (CrA) star-forming region. At a distance of 130 pc, CrA is one of the closest regions known to be actively forming stars, particularly within its embedded association, the Coronet. Using the Spitzer data, we identify 51 young stellar objects (YSOs) in CrA which include sources in the well-studied Coronet cluster as well as distributed throughout the molecular cloud. Twelve of the YSOs discussed are new candidates, one of which is located in the Coronet. Known YSOs retrieved from the literature are also added to the list, and a total of 116 candidate YSOs in CrA are compiled. Based on these YSO candidates, the star formation rate is computed to be 12 M_o Myr^-1, similar to that of the Lupus clouds. A clustering analysis was also performed, finding that the main cluster core, consisting of 68 members, is elongated (having an aspect ratio of 2.36), with a circular radius of 0.59 pc and mean surface density of 150 pc^-2. In addition, we analyze outflows and jets in CrA by means of new CO and H_2 data. We present 1.3 mm interferometric continuum observations made with the Submillimeter Array (SMA) covering R CrA, IRS 5, IRS 7, and IRAS 18595-3712 (IRAS 32). We also present multi-epoch H_2 maps and detect jets and outflows, study their proper motions, and identify exciting sources. The Spitzer and ISAAC/VLT observations of IRAS 32 show a bipolar precessing jet, which drives a CO (2-1) outflow detected in the SMA observations. There is also clear evidence for a parsec-scale precessing outflow, E-W oriented, and originating in the SMA 2 region, likely driven by SMA 2 or IRS 7A.
Identifying the source of the material within coronal mass ejections (CMEs) and understanding CME onset mechanisms are fundamental issues in solar and space physics. Parameters relating to plasma composition, such as charge states and He abundance (ahe), may be different for plasmas originating from differing processes or regions on the Sun. Thus, it is crucial to examine the relationship between in-situ measurements of CME composition and activity on the Sun. We study the CME that erupted on 2014 September 10, in association with an X1.6 flare, by analyzing AIA imaging and IRIS spectroscopic observations and its in-situ signatures detected by Wind and ACE. We find that during the slow expansion and intensity increase of the sigmoid, plasma temperatures of 9 MK, and higher, first appear at the footpoints of the sigmoid, associated with chromospheric brightening. Then the high-temperature region extends along the sigmoid. IRIS observations confirm that this extension is caused by transportation of hot plasma upflow. Our results show that chromospheric material can be heated to 9 MK, and above, by chromospheric evaporation at the sigmoid footpoints before flare onset. The heated chromospheric material can transport into the sigmoidal structure and supply mass to the CME. The aforementioned CME mass supply scenario provides a reasonable explanation for the detection of high charge states and elevated ahe in the associated ICME. The observations also demonstrate that the quasi-steady evolution in the precursor phase is dominated by magnetic reconnection between the rising flux rope and the overlying magnetic field structure.
During solar flares a large amount of electrons with energies greater than 20 keV is generated with a production rate of typically $10^{36}$ s$^{-1}$. A part of them is able to propagate along open magnetic field lines through the corona into interplanetary space. During their travel they emit radio radiation which is observed as type III radio bursts in the frequency range from 100 MHz down to 10 kHz by the WAVES radio spectrometer aboard the spacecraft WIND, for instance. From the drift rates of these bursts in dynamic radio spectra the radial propagation velocity $V_r$ of the type III burst exciting electrons is derived by employing a newly developed density model of the heliosphere. Calculations show that the radio radiation is emitted by electrons with different $V_r$ and therefore by different electrons of the initially produced electron distribution.
The eruption of a large quiescent prominence on 17 August 2013 and associated coronal mass ejection (CME) were observed from different vantage points by Solar Dynamics Observatory (SDO), Solar-Terrestrial Relations Observatory (STEREO), and Solar and Heliospheric Observatory (SOHO). Screening of the quiet Sun by the prominence produced an isolated negative microwave burst. We estimated parameters of the erupting prominence from a model of radio absorption and measured from 304 AA images. Their variations obtained by both methods are similar and agree within a factor of two. The CME development was studied from the kinematics of the front and different components of the core and their structural changes. The results are verified using movies in which the CME expansion was compensated according to the measured kinematics. We found that the CME mass ($3.6 times 10^{15}$ g) was mainly supplied by the prominence ($approx 6 times 10^{15}$ g), while a considerable part drained back. The mass of the coronal-temperature component did not exceed $10^{15}$ g. The CME was initiated by the erupting prominence, which constituted its core and remained active. The structural and kinematical changes started in the core and propagated outward. The CME structures continued to form during expansion, which did not become self-similar up to $25 R_odot$. The aerodynamic drag was insignificant. The core formed until $4 R_odot$. Some of its components were observed to straighten and stretch forward, indicating the transformation of tangled structures of the core into a simpler flux rope, which grew and filled the cavity as the CME expanded.
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