Coronal phenomena at the release of solar energetic electron events

Klein, Karl‐Ludwig; Krucker, S.; Trottet, G.; Hoang, S.

doi:10.1051/0004-6361:20041258

Cited by 77 publications

(61 citation statements)

References 49 publications

(72 reference statements)

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“…Here a fraction F h of electrons are heated from T e to T h (>T e ) over a typical region (δt, δx) centered at (t h , x h ). Based on observations (Aschwanden 2002;Klein et al 2005), we choose F h = 10 −5 , T h = 25 MK, t h = 50 ms, δt = 2 ms, x h = 0.405 Gm, and δx = 1 Mm. Other simulation parameters are as in Li et al (2008a).…”

Section: Simulation Resultsmentioning

confidence: 99%

Imprints of coronal temperature disturbances on type III bursts

Cairns

Robinson

2010

A&A

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The electron temperature T e and ion temperature T i in the corona vary with time and location, due to transient and persistent activity on the Sun. The effects of spatially localized disturbances in T e and T i on coronal type III radio bursts are simulated. The disturbances are superimposed on monotonically varying temperature backgrounds and arise from spatially confined solar activity, Qualitatively and quantitatively different imprints are found on the curve of the maximum flux versus frequency of type III bursts, because of the disturbances in T e and T i . The results indicate that nonthermal coronal type III bursts offer a new tool to probe and distinguish between spatially localized structures of T e and T i along the paths of type III beams. Furthermore, localized temperature disturbances may be responsible for some fine structures in type III bursts, e.g., striae in type IIIb bursts in the presence of multiple, localized temperature disturbances.

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Section: Simulation Resultsmentioning

confidence: 99%

Imprints of coronal temperature disturbances on type III bursts

Cairns

Robinson

2010

A&A

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“…Rouillard et al 2012). The radio emission has a rich diagnostic potential on the location and temporal evolution of the particle release processes from the corona into the interplanetary medium, and it often reveals a complex, multi-impulsive or quasi-continuous structure (Maia & Pick 2004;Klein et al 2005).…”

Section: Introductionmentioning

confidence: 99%

“…In some cases, this can be an incomplete sample of the electrons accelerated during a solar event, as not all of them may have access to interplanetary space (Krucker et al 2007;Klein et al 2010), and those which do have access may be injected into several coronal structures (Klein et al 2005). Open magnetic flux tubes expand rapidly and cover several tens of degrees in longitude on the source surface, and some of these open field lines are found to connect the parent active region to the footpoint of the nominal Parker spiral, even when the parent active region is as far as 50…”

Section: Introductionmentioning

confidence: 99%

Release timescales of solar energetic particles in the low corona

Agueda

Klein

Vilmer

et al. 2014

A&A

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Aims. We present a systematic study of the timing and duration of the release processes of near-relativistic (NR; >50 keV) electrons in the low corona. Methods. We analyze seven well-observed events using in situ measurements by both the ACE and Wind spacecraft and context electromagnetic observations in soft X-rays, radio, hard X-rays and white light. We make use of velocity dispersion analysis to estimate the release time of the first arriving electrons and compare with the results obtained by using a simulation-based approach, taking interplanetary transport effects into account to unfold the NR electron release time history from in situ measurements. Results. The NR electrons observed in interplanetary space appear to be released during either short (<30 min) or long (>2 h) periods. The observation of NR electron events showing beamed pitch-angle distributions (PADs) during several hours is the clearest observational signature of sustained release in the corona. On the other hand, the in situ observation of PADs isotropizing in less than a couple of hours is a clear signature of a prompt release of electrons in the low corona. Short release episodes appear to originate in solar flares, in coincidence with the timing of the observed type III radio bursts. Magnetic connectivity plays an important role. Only type III radio bursts reaching the local plasma line measured at 1 AU are found to be related with an associated release episode in the low corona. Other type III bursts may also have a release of NR electrons associated with them, but these electrons do not reach L1. Long release episodes appear associated with signatures of long acceleration processes in the low corona (long decay of the soft X-ray emission, type IV radio bursts, and time-extended microwave emission). Type II radio bursts are reported for most of the events and do not provide a clear discrimination between short and long release timescales.

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“…Observational studies have suggested that most NR electron events result from flares (Kahler 2007). But other mechanisms, such as magnetic restructuring in the aftermath of CMEs (Maia & Pick 2004;Klein et al 2005) or acceleration at shocks driven by fast (>1000 km s −1 ) CMEs (Simnett et al 2002), have also been proposed as mechanisms for producing NR electrons. These associations are based on the observational comparison between the timing of solar event phenomena and the inferred electron injection time.…”

Section: Introductionmentioning

confidence: 99%

Modeling solar near-relativistic electron events

Agueda

Lario

Vainio

et al. 2009

A&A

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Context. Solar near-relativistic electrons (>30 keV) are observed as discrete events in the inner heliosphere following different types of solar transient activity. Several mechanisms have been proposed for the production of these electrons. One candidate is related to solar flare activity. Other candidates include shocks driven by fast coronal mass ejections (CMEs) or processes of magnetic reconnection in the aftermath of CMEs. Aims. We study eleven near-relativistic (NR) electron events observed by the Advanced Composition Explorer (ACE) between 1998 and 2005 with the aim of estimating the roles played by solar flares, CME-driven shocks, and processes of magnetic restructuring in the aftermath of the CMEs in the injection of NR electrons. The main goal is to infer the underlying injection profile from particle observations at 1 AU, as well as the interplanetary transport conditions. Methods. We used Monte Carlo simulations to model the transport of particles along the interplanetary magnetic field. By taking the angular response of the LEFS60 telescope of the EPAM instrument onboard ACE into account, we were able to deconvolve the transport effects from the observed intensities, and thus infer the solar injection profile. Results. In this set of events, we have identified two types of injection episodes: short (<15 min) and time-extended (>1 h). Short injection episodes seem to be associated with the flare processes and/or the reconnection phenomena in the aftermath of the CME, while time-extended episodes seem to be consistent with injection from CME-driven shocks. Conclusions. We find that there is no single scenario that operates in all the events. The interplanetary propagation of NR electrons can occur both under strong scattering and under almost scatter-free propagation conditions and several injection phases (related to flares and/or CMEs) are possible.

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Coronal phenomena at the release of solar energetic electron events

Cited by 77 publications

References 49 publications

Imprints of coronal temperature disturbances on type III bursts

Imprints of coronal temperature disturbances on type III bursts

Release timescales of solar energetic particles in the low corona

Modeling solar near-relativistic electron events

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