Energetic electrons generated during solar flares
by Gottfried Mann

2016-11-22 1,167 views

The Sun is an active star. It manifests not only in everybody’s well-known Sun spots with the related 11-year cycle. This activity manifests not only as the well-known sun spot phenomenon with a related 11-year cycle, but also in flares, coronal mass ejections (CMEs), and solar energetic particle (SEP) events. Thus, the Sun is a giant particle accelerator. Basically, a flare occurs as a local enhancement of the Sun’s emission of […]

Solar Type III Radio Bursts: Directivity Characteristics
by G. Thejappa and R. J. MacDowall

2016-11-15 760 views

Type III radio bursts are a group of fast drifting radio emissions associated with solar flares [see also previous CESRA highlights on type III bursts here and here]. These radio emissions are believed to be excited at the fundamental and second harmonic of the electron plasma frequency, by the electron beam excited Langmuir waves through a mechanism called the plasma mechanism. This mechanism attributes the dipole and quadrupole beam patterns for the fundamental and harmonic emissions. […]

Multiwavelength study of 20 jets that emanate from the periphery of active regions
by Sargam M. Mulay et al.*

2016-11-01 804 views

Solar jets are transient phenomena observed in the solar atmosphere. They appear as sharp-edged, impulsive, and collimated flows of plasma that move outwards with a bright spot at the footpoint, which forms an ‘inverted-Y’ topology of magnetic field lines. They are observed throughout the atmosphere i.e. in the photosphere (Hα, Ca II K surges), chromosphere (UV), transition region (EUV) and corona (X-ray). Jets can occur in different environments such as coronal holes (CHs; Young & […]

Decameter type III bursts with changing frequency drift-rate signs
by V. Melnik et al.*

2016-10-18 903 views

We discuss properties of type III bursts that change the sign of their drift rate from negative to positive and vice versa. Moreover, these bursts may change the sign of their drift rates more than once. These particular type III bursts were observed simultaneously by the radio telescopes UTR-2, URAN-2, and NDA in the frequency range 8-41 MHz. The negative drift rates of these bursts are similar to those of […]

Particle Acceleration and heating by turbulent reconnection
by L. Vlahos, T. Pisokas, H. Isliker, V. Tsiolis and A. Anastasiadis

2016-08-09 416 views

Fermi (1949) introduced a fundamental stochastic process to solve the problem of particle energization (heating and/or acceleration) in space and astrophysical plasmas. The initial idea of Fermi with randomly moving scatterers (magnetic clouds), was soon replaced with a spectrum of low amplitude (δΒ/Β<<1) waves and termed particle acceleration by MHD (weak) turbulence. In the other extreme, isolated turbulent shock waves or isolated unstable current sheets (UCS) were studied. The regime […]

Radio emission and relativistic proton acceleration in the large solar particle event of 20 Jan 2005
by Karl-Ludwig Klein and Sophie Masson

2015-01-16 276 views

Energetic particle acceleration Enhanced fluxes of solar energetic particles (SEP) – so-called SEP events – result from processes of explosive energy conversion in the corona, notably flares and coronal mass ejections. The highest energies of solar energetic nucleons detected in space or through gamma-ray emission in the solar atmosphere are in the GeV range. Where and how the particles are accelerated is still controversial. The most debated candidate processes are […]

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