solar energetic particles (SEP)

A possible new scenario for widespread solar energetic particle events by Nina Dresing et al.

2023-09-12

A long-standing problem in solar energetic particle (SEP) studies is to pinpoint their source regions at the Sun. Potential contributions by both the flare and CME-driven shocks complicate the analysis. A certain type of SEP events shows very wide particle spreads up to all around the Sun. The mechanisms proposed so far to generate these widespread events are a very wide SEP injection region, likely a shock, or strong perpendicular […]

Langmuir wave motion observed in the most intense radio sources in the sky
by H. Reid and E. Kontar

2021-08-31

The Sun routinely produces energetic electrons in its outer atmosphere that subsequently travel through interplanetary space. These electron beams generate Langmuir waves in the background plasma, producing type III radio bursts that are the brightest radio sources in the sky (Suzuki & Dulk, 1985). These solar radio bursts also provide a unique opportunity to understand particle acceleration and transport which is important for our prediction of extreme space weather events […]

Spectral Structures of Type II Solar Radio Bursts and Solar Energetic Particles
by K. Iwai

2020-03-03

Solar eruptive phenomena, such as flares and coronal mass ejections (CMEs), generate high-energy particles called solar energetic particles (SEPs). Severe SEP events sometimes cause satellite anomalies and radiation exposure to humans in space. Hence, understanding and forecasting SEPs is an important issue in space weather. Type II solar radio bursts are nonthermal radio emissions with negative frequency drift observed between the metric and kilometric frequency range. They are thought to […]

Solar Physics with the Square Kilometre Array
by A. Nindos et al.*

2019-08-13

Although solar physics is one of the most mature branches of astrophysics, the Sun confronts us with a large number of outstanding problems that are fundamental in nature.  These problems include the determination of the structure and dynamics of the solar atmosphere, the magnetic field evolution in the chromosphere and corona, coronal heating, the physics of impulsive energy release, energetic particle acceleration and transport, the physics of coronal mass ejections […]

Non-radial propagation of energetic electrons in solar corona by A. Klassen et al.

2018-10-16

STEREO and near-Earth multi-spacecraft observations of solar energetic particle (SEP) events have revealed that some events show quite unexpected intensity distributions at 1 AU (Dresing et al. 2012, Lario et al. 2013). They can be much broader (circumsolar) (Gómez-Herrero et al. 2015), non-symmetric, and sometimes irregular showing so-called finger distribution (Klassen et al. 2016). It had been suggested that these non-symmetric and irregular distributions, among others, may result from non-radial […]

Size distributions of solar proton events and their asso-ciated soft X-ray flares based on the maximum likelihood estimator
by E.W. Cliver and E. D’Huys

2018-09-18

It has been known for some time that the size distributions of solar radio bursts and soft X-ray (SXR) flares have steeper power-law slopes (~1.8) than those (~1.2) of solar energetic proton (SEP) events. Hudson (1978) suggested three possibilities for this difference: (1) proton flares are fundamentally different from ordinary flares; (2) proton flares represent the large end of the total energy distribution of ordinary flares; and (3) proton flare […]

Synergy of stochastic and systematic energization of plasmas during turbulent reconnection
by Th. Pisokas, L. Vlahos and H. Isliker

2018-02-06

In the current literature the acceleration of particles during solar flares is attributed to either weak turbulence or to large scale Unstable Current Sheet (UCS). The way UCS drive weak turbulence in a separated volume on the loop top or inside the loops below the UCS was never been presented in detail. During the last thirty years the plasma physics community developed the concept of turbulent reconnection. This concept went unnoticed […]

Critical Fluctuations in Beam-Plasma Systems and Solar Type III Radio Bursts
by G. Thejappa and R. J. MacDowall

2017-12-05

The type III radio bursts are the most intense radio emissions from the sun. In Figure 1, we present a typical type III burst observed by the STEREO spacecraft. Ginzburg and Zheleznyakov (1958) were the first to suggest that Langmuir waves excited by the solar flare accelerated electrons are the source of these bursts. The in situ detection of electron beams and Langmuir waves in association with type III bursts […]

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