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

2016-11-15 742 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.*

2016-11-01 798 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.*

2016-10-18 893 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 […]

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

2016-10-04 926 views

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.*

2016-09-27 553 views

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 1,348 views

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

2016-09-06 983 views

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 1,025 views

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 […]

1 9 10 11 12 13 14