Community of European Solar Radio Astronomers – Page 27

Propagation of Coronal Mass Ejections: Aerodynamic Drag
by Nishtha Sachdeva and Prasad Subramanian

2016-10-04

Coronal Mass Ejections (CMEs) are hot, massive blobs of plasma and magnetic fields that erupt from the Sun, and are sometimes Earth-directed. Depending on their speed and mass these transients can strongly effect the space weather, causing geomagnetic storms and damage to space bound technologies. It is therefore imperative to understand the CME kinematics and propagation dynamics. Close to the Sun, CMEs are governed by Lorentz Forces, while they are […]

Diagnostics of the acceleration modulation process based on quasi-periodic variations of flare emission
by Kupriyanova et al.*

2016-09-27

Quasi-periodic pulsations (QPPs) with the characteristic time scales from a few seconds up to tens of minutes are frequently seen in the time profiles of solar and stellar flare emission (Nakariakov et al., 2016 ). Among all the possibilities of QPPs explanation, two reasons are discussed more actively: magnetohydrodynamic (MHD) oscillations in plasma waveguides and periodic reconnection. A solar flare showing clear quasi-periodic pulsations in X-rays, microwaves and followed by […]

An Analysis of Interplanetary Solar Radio Emissions Associated with a Coronal Mass Ejection
by V. Krupar et al.*

2016-09-13

Type II and type III bursts are generated, via the plasma emission mechanism, when beams of suprathermal electrons interact with the ambient plasma generating radio emissions at the plasma frequency fp (the fundamental emission) or at its second harmonic 2fp (the harmonic emission) [see also previous CESRA highlights here and here]. As the electron beams propagate outward from the Sun, radio emissions are generated at progressively lower frequencies corresponding to […]

High resolution observations of radio noise storms in the solar corona
by Prasad Subramanian and Claude Mercier

2016-09-06

The solar corona is a well known site for particle acceleration – examples range from spectacular large flares to the hard-to-observe nanoflares that are now a leading candidate for coronal heating. We focus here on radio noise storms, which are very commonplace instances of small electron acceleration episodes. Noise storm sources are relatively small (less than 1 arcmin) and vary over timescales shorter than a second. There can often be […]

On the thermal nature of 140 GHz emission from the 4 July 2012 solar flare
by Yuriy Tsap et al.*

2016-08-30

The nature of the solar flare sub-THz emission (Kaufmann, 2012) with a positive spectral slope at 200-400 GHz is still not clear [see also previous CESRA highlight]. Some authors associate this emission with thermal bremsstrahlung, while other suggest it is associated with different, non-thermal mechanisms (see Fleishman & Kontar, 2010; Krucker et al., 2013). There are two serious disadvantages of the existing approaches. First, there is a lack of observations in […]

Bright 30 THz impulsive solar bursts
by Pierre Kaufmann et al.*

2016-08-23

Impulsive 30 THz continuum bursts have been recently observed in solar flares, utilizing small telescopes with a unique and relatively simple optical setup concept (Kaufmann et al. 2015). The most intense burst was observed together with a GOES X2 class event on October 27, 2014, also detected at two sub-THz frequencies, RHESSI X-rays and SDO/HMI and EUV. It exhibits strikingly good correlation in time and in space with white light […]

Decameter U-burst Harmonic Pair from a High Loop
by Dorovskyy, Melnik, Konovalenko, Bubnov , Gridin, Shevchuk, Rucker, Poedts and Panchenko

2016-08-16

We discuss the results of recent observations of a solar U-burst harmonic pair in the frequency range 10-70 MHz, performed by the radio telescope UTR-2 and the recently built first section of the new Giant Ukrainian Radio Telescope (GURT) (see Dorovskyy et al. 2015). A considerably extended frequency range of the new telescope makes the detection of harmonically connected pairs much more probable. In particular, we focus on interpreting the time delay […]

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

2016-08-09

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 […]

« 1 … 25 26 27 28 29 30 »