Publications

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: On 2000 September 12-14 the Energetic and Relativistic Nuclei and Electron (ERNE) instrument on the Solar and Heliospheric Observatory (SOHO) observed a gradual solar energetic particle (SEP) event associated with Halo CME and M class solar flare from the South West hemisphere. Production of 20-90 MeV protons lasted for 160-137 hr respectively. The analysis of the intensity-time profile, 4 He/p-Fe/O ratios and anisotropy flux suggested that this event is combined with a second eruption associated with a Halo CME from the North East hemisphere and that the shock wave of the first CME was an efficient accelerator for∼20 MeV protons during only the first 8 hr after the launch. According to our calculation of the angle Θ Bn between the shock normal and the direction of the upstream magnetic field, shock parameters such as speed, compression ratio and Mach number, this shock seems to be gradually slowed down, weakened, and became transparent for the protons produced by the second eruption behind the previous CME or the protons of the second CME may have access to field lines that curve around the first CME structure
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report here on two proton energetic particle events observed by the Energetic and Relativistic Nuclei and Electron (ERNE) instrument on the Solar and Heliospheri-cal Observatory (SOHO). Both events were impulsive (SEP) events with intensities of > 10 −3 cm −2 sr −1 s −1 MeV −1 at an energy range of tens of MeVs and were associated with CMEs of angular widths < 60 • and linear speed of > 800 kms −1 . In one of the events there was no associated solar flare, which indicates that the first injected protons were completely due to the associated CME and in the second event the associated solar flare was an impulsive M1.1 class flare and the calculated first injection time for protons of en-ergies ∼ 36 MeV and propagating along 1.2 AU path length, was close to the liftoff time of the CME. These observations are inconsistent with the view presented in some studies that narrow fast CME are not associated with SEP events.
    Astrophysics and Space Sciences Transactions 01/2012; 8(1):1-5.
  • Source
    H Allawi, W Al-Ramdhan, A Al-Sawad
    [Show abstract] [Hide abstract]
    ABSTRACT: We analyzed 25 solar energetic particle events, with energies ∼ 1 − 100 MeV, observed with ERNE instrument onboard Solar and Heliospheric Observatory (SOHO) and found that all of the solar energetic particlse were associated with coronal mass ejections, observed with LASCO/SOHO. The observational data suggests that the associated coronal mass ejections were located at lower heliocentric altitudes during the time of maximum intensity of the high energy protons than those during the time of maximum intensity of lower energy protons. This might indicate that the upper limit of maximum acceleration by the shock waves decreases earlier as we go higher in the proton energy level.
    17th Young Scientists' Conference on Astronomy and Space Physics, held in Kyiv, Ukraine, April 26 - May 1, 2010; 01/2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report new evidence on energetic protons penetrating previous shock wave. We have chosen four Multi Eruption Solar Energetic Particle (MESEP) events from the list presented by Al-Sawad 2007, and observed by Energetic and Relativistic Nuclei and Electron (ERNE) instrument on the Solar and Heliospheric Observatory (SOHO). Two events were studied in details, the event of 2001 October 19-21, which was in association with two X1.6/2B solar flares and halo CMEs separated by ~15 hours and the event of 2000 April 04, which was associated with two CMEs separated by ~8 hours. The other two new MESEP events were on 2000 February 17-19 and 2005 August 22-25. The first event was associated with two CMEs. The first halo CME was associated with M 1.3 solar flare at S29E07 Halpha location from the NOAA AR 8827, and with metric and later D-H type II radio bursts, indicating a formation of shock wave, which was later passed near the Earth's orbit and registered, by SOHO, ACE and Wind spacecrafts. The second CME erupted from the south-west after ~13 hours. The second event was associated with two halo CMEs separated by ~16 and erupted from same NOAA AR 10798 in association with M class solar flares. The first halo was in association with metric type II but both were in association with D-H type II. In both events the first CME was decelerating and both events can be classified as gradual SEP events. Our analysis for proton flux anisotropy data, He/P ratio and possible velocity dispersion in the second peak of the intensity-time profile are related to the second CME in both events. This suggests that the energetic protons > 10 MeV penetrate the first shock waves associated with first CMEs in order to reach 1 AU and thus, these observations indicate that capability of interplanetary shock to accelerate high-energy protons gradually declines as shock travels from near the Sun to beyond 1~AU.
    AGU Fall Meeting Abstracts. 12/2009;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: On 2001 October 19-21 the Energetic and Relativistic Nuclei and Electron (ERNE) instrument on the Solar and Heliospheric Observatory (SOHO) observed two gradual solar energetic particle (SEP) events separated by 15 h, in association with two X1.6/2B solar flares and halo coronal mass ejections (CMEs). The observational data suggest that the second acceleration of ~10-100 MeV protons occurred behind the first CME and the previous CME was not an obstacle for new particles to directly reach 1 AU. The proton flux anisotropy data support the idea that the particle production significantly declined in about 10 h after the shock wave started, while the prolonged temporal profile of the solar energetic particle event was due to a slow transport of previously accelerated particles in the interplanetary space. These observations call into question the view that in all gradual events high-energy particles are continuously produced at a CME bow shock as it travels from near the Sun to beyond 1 AU.
    Astronomy and Astrophysics 04/2009; 497:L1-L4. · 5.08 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on four multi-eruption solar energetic particle (SEP) events observed by Energetic and Relativistic Nuclei and Electron (ERNE) instru-ment on the Solar and Heliospheric Observatory (SOHO). All the events were gradual (SEP) events associated with two solar eruptions. One event was observed on 2001 October 19–21, in association with two X1.6/2B solar flares and halo coronal mass ejections (CMEs) separated by ∼15 hours. The event observed on 2000 April 04–06 was associated with two CMEs separated by ∼8 hours. The two other events were observed on 2000 February 17–19, in association with two CMEs separated by ∼13 hours, and on 2000 September 12–14, associated with two CMEs separated by ∼5 hours. We had analyzed the first two events in detail and found a second peak in 10–100 MeV protons associated with changes in proton flux anisotropy, energy spectrum and in He/p ratio. The observational data suggests that the second acceleration of 10–100 MeV protons occurred behind the first CME and the previous CME was not an obstacle for the new particles to directly access 1 AU in both events. The proton flux anisotropy data support the idea that the particle production significantly declined in about 10 hours after the first eruption, while the prolonged temporal profiles of the solar energetic particle events were due to a slow transport of previously accelerated particles in the interplanetary space.
    31st ICRC; 01/2009
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: On 2000 April 4-6 the Energetic and Relativistic Nuclei and Electron particle telescope on the Solar and Heliospheric Observatory spacecraft observed a major solar energetic particle (SEP) event associated with two coronal mass ejections (CMEs) separated by approximately 8 hr. The first CME was accompanied by a low-frequency type II radio burst observed by the WAVES receivers on the Wind spacecraft. Analysis of the high-precision measurements of the ~20 MeV proton flux anisotropy, model fitting of the type II dynamic spectrum, and SEP transport modeling support the idea that the shock wave of the first CME was an efficient accelerator for ~20 MeV protons during only the first 6 hr after the launch. This shock gradually slowed down, weakened, and became transparent for the protons produced by the second eruption behind the previous CME. The main production of SEPs due to the two successive eruptions continued together for 12 hr. The near-Earth SEP event was additionally amplified by the SEP mirroring in the interplanetary magnetic field draping at the edge of an old CME beyond the Earth's orbit, which made the SEP intensity-time profiles more prolonged than would be expected based on the assumption of SEP transport in the standard solar wind.
    The Astrophysical Journal 01/2009; 700:L51--L55. · 6.73 Impact Factor
  • Source
    Amjad Al-Sawad
    [Show abstract] [Hide abstract]
    ABSTRACT: A combination of many Solar energetic particle (SEP) events, each one of which is associated with a single eruption, can create one complex intensity-time profile, that will result in masking the observation of the first injected particles detected near Earth for each participated eruption. We defined such SEP events as Multi Eruption Solar Energetic Particle (MESEP) events. We have investigated the intensity-time profile of 333 solar energetic particle events during the operation time of SOHO mission and studied the associative solar eruptions (CMEs and solar flare) from the starting time of each event till the end. We found that most of the events have multi eruption phenomena which might or might not affect the intensity-time profile. We found that it is possible to know the real effect of some of the eruptions during the whole duration of the event, even if their effect as masked by the first eruption, by studying the widest possible energy range, the $^4He/P$ ratio and the anisotropy.
    01/2008;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We examined solar energetic particle (SEP) events from May 1996 through April 2000 that showed evidence for two peaks of intensity, separated by 3-24 hours, in the energy range ~1-20 MeV, observed with the Energetic and Relativistic Nuclei and Electron instrument (ERNE) onboard Solar and Heliospheric Observatory (SOHO). Of 88 clear SEP events observed, 18 exhibited such double peaks, with more than factor of two dips between the peaks in the energy range up to at least 8 MeV. Second peaks were examined in terms of velocity dispersion and change of 4He/p abundance ratio. Three events showed both velocity dispersion and abundance change, four events just an abundance change, and four showed velocity dispersion and no abundance change. We discuss how these different properties may reflect acceleration processes near the Sun and in the interplanetary medium. In the remaining seven events with neither velocity dispersion nor abundance change, we suggest that the second peak was a spatial feature caused by interplanetary magnetic field structures.
    Journal of Geophysical Research Atmospheres 10/2006; 111:10-+. · 3.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have developed an interactive program which shows the solar energetic particle (SEP) intensity-time profile as observed by SOHO/ERNE, simultaneously with the associated coronal mass ejection in optical imaging movies taken by LASCO coronagraph, soft X-ray by YOHKOH, ultraviolet by EIT, DH radio emission by WAVE/Wind, and the H$\alpha$ location for the solar flare and spectral radio emission from the journal of geophysical data. The whole set of data will provide increased scientific knowledge on the solar energetic particle events and the solar phenomena associated with them, because in this program one can see easily the temporal associations of each phenomenon during the evolution of the particle intensity. The (SEP) intensity-time profile will give a clear view to detect the velocity dispersion in the events, if it exists. The ERNE data are commented in order to follow of phenomena associated with changes of the intensity-time profiles. We introduce this set of data as an index for the ERNE/SOHO solar energetic particle events. The interactive program is applied for statistical, correlative study of SEP events observed on board SOHO.
    08/2006;

22 Following View all

15 Followers View all