Long-duration high-energy proton events observed by GOES in October 1989

Anttila, Anu-Hanna; Kocharov, L. G.; Torsti, J.; Vainio, R.

doi:10.1007/s005850050662

Cited by 3 publications

(14 citation statements)

References 27 publications

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“…7), analyzed earlier by Anttila et al (1998), in Table 1. It is noteworthy that the parameters by themselves do not tell us a lot about the nature of the events.…”

Section: Resultsmentioning

confidence: 99%

“…Also the charge states of energetic Fe ions are similar to coronal plasma, not solar wind (Boberg et al, 1996). A recent study by Klein et al (1999) gives evidence that the initial pre-acceleration up to $1 MeV close to the Sun suggested by Tan et al (1989) and Anttila et al (1998) takes place behind the CME.…”

Section: Introductionmentioning

confidence: 87%

“…The model for deconvolution of the spectrum in the source is the same as presented by Anttila et al (1998). We adopted the following parametrization (Ellison and Ramaty, 1985) for the proton source function of the injection:…”

Section: The Modelmentioning

confidence: 99%

“…The injection energy E 1 was selected to be 0.5 MeV (see Anttila et al, 1998). The cut-o energy E 0 and normalization factor N 0 are ®tting parameters.…”

Section: The Modelmentioning

confidence: 99%

“…We obtained values k r (1 GV) = 0.37 AU for the April 7 event and k r (1 GV) = 0.15 AU for the May 12 event. The best ®t for the observed intensity at 1 AU was then obtained by convoluting the Monte Carlo simulated IP transport Green's function with the source function q(E,t) (Torsti et al, 1996;Anttila et al, 1998).…”

Section: The Modelmentioning

confidence: 99%

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ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997

Anttila

Sahla

2000

Ann. Geophys.

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Abstract. Two Earth-directed coronal mass ejections (CMEs), which were most e ective in energetic ($1± 50 MeV) particle acceleration during the ®rst 18 months since the Solar and Heliospheric Observatory (SOHO) launch, occurred on April 7 and May 12, 1997. In the analysis of these events we have deconvoluted the injection spectrum of energetic protons by using the method described by Anttila et al. In order to apply the method developed earlier for data of a rotating satellite (Geostationary Operational Environmental Satellites, GOES), we ®rst had to develop a method to calculate the omnidirectional energetic particle intensities from the observations of Energetic and Relativistic Nuclei and Electrons (ERNE), which is an energetic particle detector onboard the three-axis stabilized SOHO spacecraft. The omnidirectional intensities are calculated by ®tting an exponential pitch angle distribution from directional information of energetic protons observed by ERNE. The results of the analysis show that, compared to a much faster and more intensive CMEs observed during the previous solar maximum, the acceleration e ciency decreases fast when the shock propagates outward from the Sun. The particles injected at distances <0.5 AU from the Sun dominate the particle¯ux during the whole period, when the shock propagates to the site of the spacecraft. The main portion of particles injected by the shock during its propagation further outward from the Sun are trapped around the shock, and are seen as an intensity increase at the time of the shock passage.

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“…7), analyzed earlier by Anttila et al (1998), in Table 1. It is noteworthy that the parameters by themselves do not tell us a lot about the nature of the events.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 87%

Section: The Modelmentioning

confidence: 99%

“…The injection energy E 1 was selected to be 0.5 MeV (see Anttila et al, 1998). The cut-o energy E 0 and normalization factor N 0 are ®tting parameters.…”

Section: The Modelmentioning

confidence: 99%

Section: The Modelmentioning

confidence: 99%

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ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997

Anttila

Sahla

2000

Ann. Geophys.

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ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997

Anttila

Sahla

2000

Annales Geophysicae

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View full text Add to dashboard Cite

Two Earth-directed coronal mass ejections (CMEs), which were most eective in energetic ($1± 50 MeV) particle acceleration during the ®rst 18 months since the Solar and Heliospheric Observatory (SOHO) launch, occurred on April 7 and May 12, 1997. In the analysis of these events we have deconvoluted the injection spectrum of energetic protons by using the method described by Anttila et al. In order to apply the method developed earlier for data of a rotating satellite (Geostationary Operational Environmental Satellites, GOES), we ®rst had to develop a method to calculate the omnidirectional energetic particle intensities from the observations of Energetic and Relativistic Nuclei and Electrons (ERNE), which is an energetic particle detector onboard the three-axis stabilized SOHO spacecraft. The omnidirectional intensities are calculated by ®tting an exponential pitch angle distribution from directional information of energetic protons observed by ERNE. The results of the analysis show that, compared to a much faster and more intensive CMEs observed during the previous solar maximum, the acceleration eciency decreases fast when the shock propagates outward from the Sun. The particles injected at distances <0.5 AU from the Sun dominate the particle¯ux during the whole period, when the shock propagates to the site of the spacecraft. The main portion of particles injected by the shock during its propagation further outward from the Sun are trapped around the shock, and are seen as an intensity increase at the time of the shock passage.

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Concurrent solar and corotating interaction region particle events in August 1996

Torsti¹,

Anttila²,

Sahla³

1999

J. Geophys. Res.

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Abstract. The energetic particle telescope ERNE onboard SOHO registered a continuous particle flux enhancement during August 7-18, 1996. The particle event was limited in the low energy range from 1.6 to 8 MeV during the first week of the event. It originated from a corotating interaction region (CIR). At 1630 UT on August 13, an additional new flux of energetic particles emerged with maximum energies above 50 MeV. The southwest directed coronal mass ejection (CME) is the most probable source of the high energy particles. Our spectral analysis revealed a two-component structure with a hard Bessel-type spectrum (c•T -0.02) of the CME-injected particles and a soft power law spectrum (index s -4.0) of CIR particles from 1630 UT till 1000 UT on August 14. In the following 3 hours the intensities above 3 MeV decreased more than 10-fold. During the plateau-type intensity maximum phase the intensities remained almost isotropic in the wide ERNE/HED view cone. We claim that the reason for the drop was that the direct connection to the CME was lost but the connection to the CIR was still maintained. The flux of > 12 MeV protons still prevailing in interplanetary space had probably been injected earlier by the CME-associated event in its very early phase in the solar atmosphere, and trapped there between the CIR and the Sun. The spectrum of these protons was of power form and very hard, s • 1.9. During August 15, the high-energy part hardened further, s • 1.1. At the same time, the intensities increased, leading to a second intensity maximum during the first half of August 16. Finally, on August 18, a disconnection from the CIR took place in all energy channels. IntroductionIn 1996, only five periods of energetic particle enhancements above 13 MeV were registered by the Energetic and Relativistic Nuclei and Electrons (ERNE) experiment (a description of the instrument is given by Torsti et al. [1995]) onboard the Solar and Heliospheric Observatory (SOHO). Exceptionally low energetic particle fluxes were observed in events in 1996 as compared to fluxes during two previous solar minimum periods in 1976 and 1986 [Torsti et al., 1997]. During quiet times in 1996, as manifested in the exceptionally low activity of particle acceleration, a uniquely undisturbed interplanetary environment was provided for the study of particle events of solar and interplanetary origin. In addition, the large geometric factor of the ERNE High Energy Detector (HED), about 10 times larger than in particle sensors flown in the 1970s and 1980s, is a new tool to study the appearance and variation of minor particle fluxes in more detail than was possible earlier.Among the particle events in 1996 which started on July 9 and 12, August 13, November 26, and December 24, the August event was the most special. The ERNE high-energy proton channels (13-50 MeV) did not rise above the background until 6 days after the onset of flux enhancement in the lowenergy channels, 1.6-6 MeV. In this range, the intensities remained above the background level during the long p...

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Long-duration high-energy proton events observed by GOES in October 1989

Cited by 3 publications

References 27 publications

ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997

ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997

ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997

Concurrent solar and corotating interaction region particle events in August 1996

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