Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsh41a1896f&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #SH41A-1896
Astronomy and Astrophysics
Astrophysics
[7513] Solar Physics, Astrophysics, And Astronomy / Coronal Mass Ejections, [7514] Solar Physics, Astrophysics, And Astronomy / Energetic Particles, [7519] Solar Physics, Astrophysics, And Astronomy / Flares, [7538] Solar Physics, Astrophysics, And Astronomy / Solar Irradiance
Scientific paper
We performed a case study on the possible mechanism of GLE occurrence. For this, we considered two GLE events (GLE69 and GLE70), and scrutinized their relationships with simultaneous solar flares of different energy bands. Most of the energy bands of the flares maintain strong correlations (r≥0.8) with the GLEs. But depending only on this evidence of strong correlations, we could not precisely imply that GLEs can be caused by solar flares. So, we attempted to understand possible relativistic energies of the GLEs determined by availing the relativistic traversing time and velocities of the particles along the nominal path of Archimedean spiral magnetic field lines. Results suggest that the energy released from accelerated particles in high energy (γ-ray) solar flares might sometimes cause the GLE. Important results of this study are summarized as follows. I. The relativistic energy of GLE varies with respect to the time-lag that the more the time-lag the less is the relativistic energy of GLE. That means the farther the solar flare, the less might be effectiveness of the released energy from solar flares. On this idea, when correlated with γ-ray flares, the GLE69 has sufficient energy (~2.78 GeV) which makes us believe that it might be caused by high energy solar flares but GLE70, having much less energy (~0.35 GeV) than 1 GeV, was perhaps not caused by solar flare. II. For GLE69, averagely, during the pronounced phase (06:50 - 07:10 UT) of the type III emission burst, the emission measure was ~28.1/cm3 while the decay phase representing otherwise the type II emission burst was ~18.70/cm3. The most rapid response to particle acceleration in solar flare representing solar burst type III is visible during GLE69 occurrence. It gives a sense that the high energy solar flare associated with type III burst presumably accelerated particles which consequently caused the GLE69. III. For GLE70, averagely, during the intensive phase (02:30-3:00 UT) of the type III emission burst, the emission measure was ~12.60/cm3 while the decay phase representing otherwise the type II emission burst was ~12.03/cm3. Thus, the speed (1773 km/s) of radio burst type II concomitant CME, emission measure (12.03/cm3) and image structure demonstrates that the released energy from the particle accelerations in CME-driven shock front is the possible mechanism for causing GLE70. From this study it is quite clear that GLE maintains the highest correlations with solar flares. But the highest correlations do not imply unambiguously that GLE can be caused by solar flare. The main criterion is to cognize the relativistic energy of the GLE particle. The released energy from the accelerated particles in solar flare maintaining the lowest time-lag can raise possible relativistic energy of GLE ≥1 GeV. This sort of solar flare can be considered as the reason of the GLE occurrence.
Dorman Lev I.
Firoz Kazi A.
Islam Jamal N.
Kudela Karel
Moon YaeEun
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