solar energetic particles (SEP)

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 […]

Small electron acceleration episodes in the solar corona
by T. James et al.

2017-11-07

Large solar flares are well known sites of prodigious particle acceleration. While these have deservedly attracted considerable attention, small episodes of electron acceleration and heating have been lately recognized as possible candidates for heating the quiet solar corona. We study the number, power and energy carried by nonthermal electrons produced by instances of small scale electron acceleration in the solar corona. Our primary focus is on small electron acceleration events […]

Predicting Flares and Solar Energetic Particle Events: The FORSPEF Tool
by A. Anastasiadis et al.*

2017-10-10

A novel operational open-access forecasting system that provides reliable forecasting and nowcasting of solar energetic particle (SEP) events, as well as forecasting of solar flares (SFs) based on precursor information, is presented. FORSPEF offers continuous forecasts and nowcasts of SFs and SEP events, up to 70◦ E/W covering practically the entire course of an active-region (AR) toward the limb (up to ~85◦). The prediction window in the forecasting scheme is […]

Exploring the potential of microwave diagnostics in SEP forecasting
by P. Zucca et al.*

2017-10-03

Solar energetic particles (SEPs), especially protons and heavy ions, may be a space-weather hazard when they impact spacecraft and the terrestrial atmosphere. Forecasting schemes have been developed, which use earlier signatures of particle acceleration to predict the arrival of solar protons and ions in the space environment of the Earth. The UMASEP (University of MAlaga Solar particle Event Predictor) scheme (Núñez 2011), forecasts the occurrence and the importance of an […]

EUV-invisible reservoir of solar energetic particles
by G. Fleishman et al.*

2017-09-19

Large-scale magnetic structures, which likely make a “bridge” between the relatively compact particle acceleration site of a flare energy release and the interplanetary medium, are of particular importance because of their potential role as an “escape route” for solar energetic particles (SEPs). Although these escape routes can sometimes be associated with jets visible in extreme ultraviolet (EUV) and/or soft X-rays (SXRs), the jet plasma must be dense enough to be […]

Particle acceleration and turbulence during a solar flare
by E.P. Kontar et al.*

2017-06-13

Particle acceleration during solar flares is a highly efficient process, in terms of both the energy (tens of percent of the released magnetic energy can be transferred to the energetic particles) and the particle number (nearly all electrons in the flaring region are accelerated). So-called stochastic acceleration (e.g., Petrosian 2012 for a review) is one of the most popular mechanisms capable of providing these characteristics. In this scenario, the magnetic […]

How Electron Beams Produce Continuous Coherent Plasma Emission
by H. Che, M. Goldstein, P. Diamond, and R. Sagdeev

2017-04-11

It is commonly accepted that energetic electron beams can produce drift frequency radio emission or Type III bursts since Ginzburg and Zhelezniakov first proposed the idea in 1958. However, the electron two-stream instability time (see reference 2) in the corona is fraction of a second, while the duration of coronal Type III bursts lasts several orders of magnitude longer. This problem is called the “Sturrock Dilemma” and remains a subject […]

Large-scale simulations of Langmuir Wave Distributions Induced by Electron Beams
by H. Reid and E. Kontar

2017-02-14

Langmuir waves that generate type III radio bursts are excited by high-energy electron beams streaming out from the corona through interplanetary space. Despite a smooth temporal distribution of electrons, the Langmuir waves are measured to occur in discrete clumps, commonly attributed to the turbulent nature of the solar wind electron density (e.g. Smith and Sime 1979, Melrose et al 1986). But how do fluctuations in the background plasma shape the […]

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