Density and magnetic field turbulence in solar flares estimated from radio zebra observations
by M. Karlicky and L. Yasnov

2020-07-14 165 views

Solar flares are characterized by fast plasma flows. In such plasma flows owing to the Kelvin-Helmholtz instability the maqnetohydrodynamic turbulence can be generated. Although, the turbulence plays an important role in solar flares, e.g., in acceleration of particles, a knowledge about the level of  this turbulence is still very limited.  In the present study we estimate the levels of this turbulence. For this purpose we use observations of the so called zebra […]

First radio evidence of impulsive heating contribution to the quiet solar corona
by Surajit Mondal et al

2020-06-30 175 views

The solar community has been trying to understand the mechanism responsible for coronal heating for several decades now. In the past decade, a number of studies have shown that the active regions and the coronal loops are heated impulsively. However, such a consensus is yet to be reached for the quiet sun. Past searches for impulsive events in the EUV and X-ray are yet to provide conclusive evidence in favour […]

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

2020-06-09 174 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 […]

First observation of a transitioning Type II solar radio burst using the Low-Frequency Array (LOFAR)
by Nicolina Chrysaphi et al

2020-05-26 376 views

Type II solar radio bursts are believed to be excited by shock waves. They are often linked to shocks driven by solar eruptive events like Coronal Mass Ejections (CMEs) and solar flares, and are characterised by a slow drift from high to low frequencies thought to reflect the speed with which the shock propagates away from the Sun.  Shock-excited emissions that show very little or no frequency drift are known […]

Loss-cone instability modulation due to a magnetohydrodynamic sausage mode oscillation in the solar corona
by E. P. Carley et al.*

2020-05-12 141 views

Flare accelerated electrons emit light from X-rays to radio waves, which sometimes show highly regular and periodic intensity pulsations (Nakariakov et al. 2009). However, the processes that bring about these pulsations remains a hotly debated topic. The primary candidates are periodic magnetic reconnection, magnetohydrodynamic (MHD) oscillations, or some complex combination of both (Aschwanden et al. 1986, Nakariakov et al. 2006). Plasma dynamics of these processes can play out on timescales […]

Solar polarization observations at 3 and 13 mm
by J. Kallunki and M. Tornikoski

2020-04-28 230 views

Microwave solar polarization observations give us information about the magnetic field of the solar atmosphere. They are important for understanding the various solar activity phenomena and emission mechanisms related to them. Polarization properties of solar active regions have been studied previously mainly at lower radio frequencies. Here we present solar radio polarization observations that were made at Aalto University Metsähovi Radio Observatory (MRO) in Finland with the 13.7-metre radio telescope, […]

Observing onset of turbulent fast magnetic reconnection in solar microflares
by L. P. Chitta and A. Lazarian

2020-04-14 190 views

Magnetic reconnection is a key process in astrophysical and space plasmas that converts magnetic energy into other forms of energy. It drives gamma-ray bursts, solar flares, and accelerates particles. A fast reconnection is necessary to explain the explosive nature of flares and bursts. However, conditions for the onset of fast reconnection are a topic of intense debate. Simulations of magnetic reconnection in 2D have shown that the current sheet is […]

Density Fluctuations in the Solar Wind Based on Type III Radio Bursts Observed by Parker Solar Probe
by V. Krupar et al.*

2020-03-31 271 views

Type III bursts belong among the strongest radio signals routinely observed by both space-borne and ground-based instrumentations. They are generated via the plasma emission mechanism, when beams of suprathermal electrons interact with the ambient plasma triggering radio emissions at the plasma frequency (the fundamental emission) or at its second harmonic (the harmonic emission). As the electron beams propagate outward from the Sun, radio emissions are generated at progressively lower frequencies […]

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