High-energy solar-particle events

Carmichael, H.

doi:10.1007/bf00174635

Cited by 52 publications

(20 citation statements)

References 9 publications

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“…We thereby pursue the study of individual solar relativistic proton events (called ground level events, GLEs) which suggested that relativistic protons are injected into interplanetary space well after the production of interacting energetic particles revealed by their gamma-ray and hard X-ray emission, but in time coincidence with acceleration in the middle corona (∼0.1-1 R above the photosphere, say) that shows up in decimetric and metric radio emission (Klein et al 1999;Klein & Trottet 2001). While the delay of relativistic proton injection with respect to hard X-ray, gamma-ray and microwave signatures of mildly relativistic electrons and suprathermal protons in the low solar atmosphere was known earlier (e.g., Carmichael 1962;Cliver et al 1982;Kahler 1994;Debrunner et al 1997), the connection with signatures of coronal particle acceleration at greater height, where collisional radiative signatures are inefficient due to the low ambient density, and gyrosynchrotron emission is faint because of the weak magnetic field, has only rarely been investigated (Palmer & Smerd 1972;Kocharov et al 1994;Akimov et al 1996;Klein et al 1999;Miroshnichenko et al 2000).…”

Section: Introductionmentioning

confidence: 90%

Coronal electron acceleration and relativistic proton production during the 14 July 2000 flare and CME

Klein

Trottet

Lantos

et al. 2001

A&A

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Abstract. The large solar flare of 14 July 2000 10 UT occurred in an active region near the central meridian. It was accompanied by the eruption of a filament and a rapid halo-type coronal mass ejection (CME). Large particle fluxes were detected up to relativistic energies at 1 AU. In this paper accelerated particles and plasma structures in the corona are traced using radio, X-ray, EUV and visible light observations, together with neutron monitor measurements of relativistic protons at 1 AU. Both the bulk of the radio emission at decimetric and longer waves and the escape of suprathermal electrons and relativistic protons from the Sun were delayed by 10-20 min with respect to the hard X-ray emission. Despite the delay and the association with a flare near the central meridian the neutron monitor time profile was impulsive. We show that the escape of the relativistic protons occurred in time coincident both with a coronal shock wave, which may be the bow shock of the CME, and with radio sources which trace electron acceleration and magnetic field reconfiguration in the western hemisphere. Three observations support the idea that the relativistic protons were accelerated during this reconfiguration, at heights between 0.1 and 1 R above the photosphere, and not in the flaring active region or at the bow shock of the CME: (i) the rise of the neutron monitor count rates is simultaneous with the brightening of a new continuum radio source; (ii) the duration of the continuum emission is similar to the rise time of the neutron monitor count rates; (iii) the radio source is close to the Earth-connected interplanetary magnetic field line.

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Section: Introductionmentioning

confidence: 90%

Coronal electron acceleration and relativistic proton production during the 14 July 2000 flare and CME

Klein

Trottet

Lantos

et al. 2001

A&A

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“…How is it possible that SEP from a broad range of longitudes have direct access to a given spacecraft, rather than only those particles which are accelerated close to the nominal Parker spiral? Shock-wave acceleration in a broad cone of open magnetic field lines is often offered as an explanation (Carmichael 1962;Lin 1970;Reames 1999). But EUV or X-ray images of the corona also show that the magnetic field lines in the low corona are complex.…”

Section: Introductionmentioning

confidence: 99%

Open magnetic flux tubes in the corona and the transport of solar energetic particles

Klein¹,

Krucker²,

Lointier³

et al. 2008

A&A

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We investigate how magnetic fields guide energetic particles through the corona into interplanetary space and eventually to a spacecraft near the Earth. A set of seven simple particle events is studied, where energetic electrons (30-500 keV; Wind spacecraft) or protons (5-55 MeV; SoHO) were released together with low-energy electron beams producing metric-to-kilometric type III emission. Imaging of the coronal (metre-wave) part of this emission with the Nançay Radioheliograph is used to identify the open flux tubes that guide these electrons -and by inference all particles detected at 1 AU. Open coronal field lines are also computed using potential magnetic field extrapolations, constrained by a source surface and by SoHO/MDI measurements in the photosphere (code by Schrijver and DeRosa). We find that in all events the type III radio sources lie in open flux tubes in the potential magnetic field extrapolations. The open flux tubes are rooted in small parts of the parent active region, covering a heliocentric angle of a few degrees in the photosphere. But they expand rapidly above the neighbouring closed magnetic structures and cover several tens of degrees in longitude on the source surface. Some of these open field lines are found to connect the parent active region to the footpoint of the nominal Parker spiral on the source surface, within the uncertainty of about ±10• inherent to the evaluation of its connection longitude. This is so even when the parent active region is as far as 50• away. In two cases where the coronal flux tubes point to high heliolatitudes, the detection of Langmuir waves at the Wind spacecraft in the ecliptic plane suggests that the interplanetary field lines curve down to the ecliptic before reaching 1 AU. We conclude that non-radial open flux tubes in the corona can transport particles over several tens of degrees in longitude even in simple impulsive particle events. In all events we studied, potential magnetic field models give an adequate description of these structures.

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“…We estimated also the probability of missed triggers; it was shown that for events with amplitude of increase more than 10% the probability of a missed trigger for successive 2 min NM data is smaller than 1.36 · 10 À5 (this probability decreases sufficiently with increased amplitude A of the FEP increase, as shown in Table 1). Historical ground FEP events show very fast increase of amplitude in the start of event (Dorman, 1957;Carmichael, 1962;Dorman and Miroshnichenko, 1968;Duggal, 1979;Stoker, 1994). For example, in great FEP event of February 23, 1956 amplitudes of increase in the Chicago NM were at 3.51 UT -1%, at 3.52 UT -35%, at 3.53 UT -180%, at 3.54 UT -280%.…”

Section: Discussion On the Supposed Methodsmentioning

confidence: 99%

Forecasting of radiation hazard: 1. Alerts on great FEP events beginning; probabilities of false and missed alerts; on-line determination of solar energetic particle spectrum by using spectrographic method

Дорман¹,

Pustil'Nik²,

Sternlieb³

et al. 2006

Advances in Space Research

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High-energy solar-particle events

Cited by 52 publications

References 9 publications

Coronal electron acceleration and relativistic proton production during the 14 July 2000 flare and CME

Coronal electron acceleration and relativistic proton production during the 14 July 2000 flare and CME

Open magnetic flux tubes in the corona and the transport of solar energetic particles

Forecasting of radiation hazard: 1. Alerts on great FEP events beginning; probabilities of false and missed alerts; on-line determination of solar energetic particle spectrum by using spectrographic method

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