Fast CME caused by the eruption of a quiescent prominence
by V. Grechnev and I. Kuzmenko

2020-06-09 187 views

CMEs can be the sources of space-weather disturbances. Shock waves expanding ahead of fast CMEs and associated flares are the probable sources of energetic protons. Two categories of CMEs have traditionally been identified depending on the presence of conspicuous chromospheric emissions during their development. Flare-associated CMEs erupt from active regions, carry stronger magnetic fields, can reach higher speeds and cause stronger space-weather disturbances. Non-flare-associated CMEs develop in eruptions of large […]

Split-Band Feature of a Solar Flare Termination Shock
by Chen et al

2019-11-12 268 views

In many space and astrophysical plasma contexts, shocks are considered as one of the most important mechanisms for accelerating charged particles up to relativistic speeds. Different types of shocks are present on the Sun. One of the most well-known types is shocks driven by coronal mass ejections (see, e.g., Morosan et al. 2019, and recent CESRA Nuggets by Mancuso et al., Chrysaphi et al., Zucca et al.). There is another […]

3D reconstruction of CME-driven shock-streamer interaction as a coronal magnetic field diagnostics
by S. Mancuso et al.*

2019-06-04 330 views

Coronal Mass Ejections (CMEs) expelled from the Sun can drive shocks that accelerate electrons which, in turn, produce electrostatic oscillations called Langmuir waves. These waves are then converted into escaping e.m. radiation, known as type II solar radio bursts, emitted near the fundamental and/or harmonic of the local electron plasma frequency. As shocks propagate outward from the Sun to regions of lower plasma density, type IIs appear in dynamic spectra […]

Coronal Mass Ejection-driven Type II solar radio burst structure with LOFAR and radio-wave scattering
by Nicolina Chrysaphi et al.*

2019-01-29 580 views

Coronal Mass Ejections (CMEs) are often viewed as the major drivers of space weather disturbances in the Sun-Earth system. Shocks driven by CMEs can excite radio emissions characterised by a slow frequency drift across dynamic spectra. These radio emissions are known as Type II solar radio bursts and can consist of two bands with a frequency ratio of 1:2. Each of these bands can split into two thinner sub-bands, a […]

Shock location and CME 3-D reconstruction of a solar type II radio burst with LOFAR
by P. Zucca et al.*

2018-10-30 358 views

Type II radio bursts are the result of shocks in the solar atmosphere and they can be observed ranging from sub-metric to kilometric wavelengths (~400 MHz to ~0.4 MHz). Coronal mass ejections initiate most of the metric type II (m-type II) bursts. The region of a CME responsible for driving the shock might be different for each event and has not yet been comprehensively identified. Multiple scenarios have been suggested, […]

Fragmented radio emission reveals a shock passing through solar active region loops
by Silja Pohjolainen, Jens Pomoell and Rami Vainio

2008-09-02 1,022 views

Shocks and type II bursts Radio type II bursts are observed in association with flares and coronal mass ejections (CMEs). Metric type II bursts can be observed in dynamic radio spectra as slowly drifting emission lanes, with drift rates approximately 0.1 — 1.0 MHz/s. The start frequency of metric type II bursts is usually at about 100 — 200 MHz. The mechanism behind the bursts is generally assumed to be […]

Coronal shock waves: tracking down the drivers for radio emission
by Silja Pohjolainen

2006-09-21 158 views

In the solar corona, shocks are formed when the speed of a disturbance exceeds the local magnetosonic (Alfvén) speed. At low atmospheric heights, above high-density active regions, the Alfvén velocity can drop down to a few hundred km/s, but it then rises steadily to a global maximum of about 1000 km/s near the heliocentric height of 3.5 R (see calculations in Warmuth & Mann 2005). At heights above 1.5 R […]