[en] Understanding coronal mass ejection (CME) energetics and dynamics has been a long-standing problem, and although previous observational estimates have been made, such studies have been hindered by large uncertainties in CME mass. Here, the two vantage points of the Solar Terrestrial Relations Observatory (STEREO) COR1 and COR2 coronagraphs were used to accurately estimate the mass of the 2008 December 12 CME. Acceleration estimates derived from the position of the CME front in three dimensions were combined with the mass estimates to calculate the magnitude of the kinetic energy and driving force at different stages of the CME evolution. The CME asymptotically approaches a mass of 3.4 ± 1.0 × 10¹⁵ g beyond ∼10 R_☉. The kinetic energy shows an initial rise toward 6.3 ± 3.7 × 10²⁹ erg at ∼3 R_☉, beyond which it rises steadily to 4.2 ± 2.5 × 10³⁰ erg at ∼18 R_☉. The dynamics are described by an early phase of strong acceleration, dominated by a force of peak magnitude of 3.4 ± 2.2 × 10¹⁴ N at ∼3 R_☉, after which a force of 3.8 ± 5.4 × 10¹³ N takes effect between ∼7 and 18 R_☉. These results are consistent with magnetic (Lorentz) forces acting at heliocentric distances of ∼<7 R_☉, while solar wind drag forces dominate at larger distances (∼>7 R_☉).

[en] A common feature of electromagnetic emission from solar flares is the presence of intensity pulsations that vary as a function of time. Known as quasi-periodic pulsations (QPPs), these variations in flux appear to include periodic components and characteristic timescales. Here, we analyze a GOES M3.7 class flare exhibiting pronounced QPPs across a broad band of wavelengths using imaging and time series analysis. We identify QPPs in the time series of X-ray, low-frequency radio, and extreme ultraviolet (EUV) wavelengths using wavelet analysis, and localize the region of the flare site from which the QPPs originate via X-ray and EUV imaging. It was found that the pulsations within the 171 Å, 1600 Å, soft X-ray, and hard X-ray light curves yielded similar periods of ${122}_{-<!--\; ???\; -->22}^{+26}$ s, ${131}_{-<!--\; ???\; -->27}^{+36}$ s, ${123}_{-<!--\; ???\; -->26}^{+11}$ s, and ${137}_{-<!--\; ???\; -->56}^{+49}$ s, respectively, indicating a common progenitor. The low-frequency radio emission at 2.5 MHz contained a longer period of ∼231 s. Imaging analysis indicates that the location of the X-ray and EUV pulsations originates from a hard X-ray footpoint linked to a system of nearby open magnetic field lines. Our results suggest that intermittent particle acceleration, likely due to “bursty” magnetic reconnection, is responsible for the QPPs. The precipitating electrons accelerated toward the chromosphere produce the X-ray and EUV pulsations, while the escaping electrons result in low-frequency radio pulses in the form of type III radio bursts. The modulation of the reconnection process, resulting in episodic particle acceleration, explains the presence of these QPPs across the entire spatial range of flaring emission.

[en] As the most energetic eruptions in the solar system, coronal mass ejections (CMEs) can produce shock waves at both their front and flanks as they erupt from the Sun into the heliosphere. However, the amount of energy produced in these eruptions, and the proportion of their energy required to produce the waves, is not well characterized. Here we use observations of a solar eruption from 2014 February 25 to estimate the energy budget of an erupting CME and the globally propagating ''EIT wave'' produced by the rapid expansion of the CME flanks in the low solar corona. The ''EIT wave'' is shown using a combination of radio spectra and extreme ultraviolet images to be a shock front with a Mach number greater than one. Its initial energy is then calculated using the Sedov-Taylor blast-wave approximation, which provides an approximation for a shock front propagating through a region of variable density. This approach provides an initial energy estimate of ≈2.8 × 10³¹ erg to produce the ''EIT wave'', which is approximately 10% the kinetic energy of the associated CME (shown to be ≈2.5 × 10³² erg). These results indicate that the energy of the ''EIT wave'' may be significant and must be considered when estimating the total energy budget of solar eruptions

[en] Electron acceleration in the solar corona is often associated with flares and the eruption of twisted magnetic structures known as flux ropes. However, the locations and mechanisms of such particle acceleration during the flare and eruption are still subject to much investigation. Observing the exact sites of particle acceleration can help confirm how the flare and eruption are initiated and how they evolve. Here we use the Atmospheric Imaging Assembly to analyze a flare and erupting flux rope on 2014 April 18, while observations from the Nançay Radio Astronomy Facility allow us to diagnose the sites of electron acceleration during the eruption. Our analysis shows evidence of a pre-formed flux rope that slowly rises and becomes destabilized at the time of a C-class flare, plasma jet, and the escape of ≳75 keV electrons from the rope center into the corona. As the eruption proceeds, continued acceleration of electrons with energies of ∼5 keV occurs above the flux rope for a period over 5 minutes. At the flare peak, one site of electron acceleration is located close to the flare site, while another is driven by the erupting flux rope into the corona at speeds of up to 400 km s⁻¹. Energetic electrons then fill the erupting volume, eventually allowing the flux rope legs to be clearly imaged from radio sources at 150–445 MHz. Following the analysis of Joshi et al. (2015), we conclude that the sites of energetic electrons are consistent with flux rope eruption via a tether cutting or flux cancellation scenario inside a magnetic fan-spine structure. In total, our radio observations allow us to better understand the evolution of a flux rope eruption and its associated electron acceleration sites, from eruption initiation to propagation into the corona.

[en] The Sun produces highly dynamic and eruptive events that can drive shocks through the corona. These shocks can accelerate electrons, which result in plasma emission in the form of a type II radio burst. Despite the large number of type II radio burst observations, the precise origin of coronal shocks is still subject to investigation. Here, we present a well-observed solar eruptive event that occurred on 2015 October 16, focusing on a jet observed in the extreme ultraviolet by the Atmospheric Imaging Assembly (SDO/AIA), a streamer observed in white light by the Large Angle and Spectrometric Coronagraph (SOHO/LASCO), and a metric type II radio burst observed by the LOw Frequency Array (LOFAR). LOFAR interferometrically imaged the fundamental and harmonic sources of a type II radio burst and revealed that the sources did not appear to be cospatial, as would be expected from the plasma emission mechanism. We correct for the separation between the fundamental and harmonic using a model that accounts for scattering of radio waves by electron density fluctuations in a turbulent plasma. This allows us to show the type II radio sources were located ∼0.5R _⊙ above the jet and propagated at a speed of ∼1000 km s⁻¹, which was significantly faster than the jet speed of ∼200 km s⁻¹. This suggests that the type II burst was generated by a piston shock driven by the jet in the low corona.

[en] This colloquium was organized at the half-course of the French 'Sun-Earth' national programme (PNST); it was intended for all researchers and students in the domain of magnetized plasmas in solar and terrestrial environments. It also concerns solar and stellar magnetism and planetary plasmas which are at the interfaces between PNST, stellar physics and planetology. The colloquium is organized around 7 main themes: simulations and numerical tools; new missions and instrumentation (ground and space); couplings between plasma envelopes (i.e. interior/corona/solar wind, solar wind/magnetosphere, magnetosphere/ionosphere/high atmosphere); multi-scale energy transport and turbulence (i.e. Sun, solar wind, magnetospheres, ion and electronic scales, dynamo); particle acceleration mechanisms and plasma heating (i.e. corona and solar winds, magnetospheres, energetic particles); eruptive or impulsive activity in plasmas (i.e. corona, terrestrial and planetary magnetospheres); Sun-Earth relations and space meteorology (i.e. observation/forecasting of solar activity, space environment, geomagnetic conditions, irradiance variability)