Radio Observations of Coronal Mass Ejection Initiation and Development in the Low Solar Corona (original) (raw)
Related papers
The Coronal Mass Ejection of 1998 April 20: Direct Imaging at Radio Wavelengths
The Astrophysical Journal, 2001
We observed the fast coronal mass ejection (CME) of 1998 April 20 with the radioheliograph at Nançay, France, between 164 and 432 MHz. Spectroscopic data were obtained between 40 and 800 MHz by the spectrometer at Tremsdorf, Germany, and between 20 kHz and 14 MHz with the WAVES instrument on board the Wind spacecraft. Energetic particle data were obtained from the Wind 3D Plasma and Energetic Particle experiment. The CME was observed in white light by the Large-Angle Spectrometric COronagraph experiment on board the Solar and Heliospheric Observatory spacecraft. For the first time, the expanding CME loops are imaged directly at radio wavelengths. We show that the radio-emitting CME loops are the result of nonthermal synchrotron emission from electrons with energies of ∼0.5-5 MeV interacting with magnetic fields of ∼0.1 to a few gauss. They appear nearly simultaneously with the onset of an associated type II radio burst, shock-accelerated type III radio bursts, and the initiation of a solar energetic particle event. We suggest possible sources of the energetic electrons responsible for this "radio CME" and point out diagnostic uses for synchrotron emission from CME loops.
The Astrophysical Journal, 2010
We study the global development of the 2007 May 19 event and investigate the origin and the escape of the energetic electrons responsible for the interplanetary bursts and for the solar energetic particle event. The data analysis combines radio spectral and imaging observations with STEREO EUV observations. We also use the direction-finding capabilities on the Wind/Waves radio instrument. Electron acceleration and injections into the interplanetary medium occur with some delay after the flare. It is shown that they are related to the expansion of the coronal mass ejection and of the extreme ultraviolet imager wave. There are two accelerations at two different locations in the corona which correspond to two different electron trajectories in the interplanetary medium.
The Astrophysical Journal, 2012
It has been suggested that type II radio bursts are due to energetic electrons accelerated at coronal shocks. Radio observations, however, have poor or no spatial resolutions to pinpoint the exact acceleration locations of these electrons. In this paper, we discuss a promising approach to infer the electron acceleration location by combining radio and white light observations. The key assumption is to relate specific morphological features (e.g., spectral bumps) of the dynamic spectra of type II radio bursts to imaging features (e.g., coronal mass ejection (CME) going into a streamer) along the CME (and its driven shock) propagation. In this study, we examine the CME-streamer interaction for the solar eruption dated on 2003 November 1. The presence of spectral bump in the relevant type II radio burst is identified, which is interpreted as a natural result of the shock-radio-emitting region entering the dense streamer structure. The study is useful for further determinations of the location of type II radio burst and the associated electron acceleration by CME-driven shock.
The Astrophysical Journal
Understanding electron acceleration associated with magnetic energy release at subsecond scales presents major challenges in solar physics. Solar radio spikes observed as subsecond, narrow-bandwidth bursts with Δf/f ∼ 10−3–10−2 are indicative of a subsecond evolution of the electron distribution. We present a statistical analysis of frequency- and time-resolved imaging of individual spikes and Type IIIb striae associated with a coronal mass ejection (CME). LOFAR imaging reveals that the cotemporal (<2 s) spike and striae intensity contours almost completely overlap. On average, both burst types have a similar source size with a fast expansion at millisecond scales. The radio source centroid velocities are often superluminal and independent of frequency over 30–45 MHz. The CME perturbs the field geometry, leading to increased spike emission likely due to frequent magnetic reconnection. As the field restores itself toward the prior configuration, the observed sky-plane emission loc...
Radio evidence for shock acceleration of electrons in the solar corona
Geophysical Research Letters, 1981
A new class of kilometer wavelength solar radio bursts has been observed with the ISEE-3 Radio Astronomy Experiment. These events resemble groups of ordinary type III bursts but have some unique properties. They are very intense and have durations considerably longer than groups of type III bursts. The new class of events do not necessarily occur at the times of reported meter wavelength type III activity and therefore do not appear to be the continuation of such activity to long wavelengths. Instead they occur at the reported times of type II events, which are •nd•cat•ve of a shock wave.
Solar Physics, 2011
On 17 January 2005 two fast coronal mass ejections were recorded in close succession during a 3B/X3.8 flare. Both were accompanied by metreto-kilometre type-III groups tracing energetic electrons escaping into the interplanetary space and by decametre-to-hectometre type-II bursts attributed to CME-driven shock waves. A peculiar type-III burst observed near the intersection, on the dynamic spectrum, of the two CME fronts (at heliocentric distance 38 R ⊙ ), was associated with the interaction of the CMEs. Near-relativistic electrons observed by the EPAM experiment onboard ACE near 1 AU revealed successive particle releases that can be associated with the two flare/CME events and the low-frequency type-III burst at the time of CME interaction. Although the decametre-to-hectometre spectral signatures of the two type-III groups appeared similar, the metric radio emission reveals distinctive differences that suggest evolving acceleration regions in the corona. The role of shock acceleration is clearly established at low energies, by the type II radio emission. We compare the pros and cons of shock acceleration and acceleration in the course of magnetic reconnection for the escaping electron beams revealed by the type III bursts and the in situ measurements.
The Astrophysical Journal, 2013
Low-frequency (80 MHz) imaging and spectral (≈85-20 MHz) observations of moving type IV radio bursts associated with coronal mass ejections (CMEs) from the Sun on three different days are reported. The estimated drift speed of the bursts is in the range ≈150-500 km s −1. We find that all three bursts are most likely due to second harmonic plasma emission from the enhanced electron density in the associated white-light CMEs. The derived maximum magnetic field strength of the latter is B ≈ 4 G at a radial distance of r ≈ 1.6 R .