8 research outputs found
An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles
The extreme solar and SEP event of 20 January 2005 is analyzed from two
perspectives. Firstly, we study features of the main phase of the flare, when
the strongest emissions from microwaves up to 200 MeV gamma-rays were observed.
Secondly, we relate our results to a long-standing controversy on the origin of
SEPs arriving at Earth, i.e., acceleration in flares, or shocks ahead of CMEs.
All emissions from microwaves up to 2.22 MeV line gamma-rays during the main
flare phase originated within a compact structure located just above sunspot
umbrae. A huge radio burst with a frequency maximum at 30 GHz was observed,
indicating the presence of a large number of energetic electrons in strong
magnetic fields. Thus, protons and electrons responsible for flare emissions
during its main phase were accelerated within the magnetic field of the active
region. The leading, impulsive parts of the GLE, and highest-energy gamma-rays
identified with pi^0-decay emission, are similar and correspond in time. The
origin of the pi^0-decay gamma-rays is argued to be the same as that of lower
energy emissions. We estimate the sky-plane speed of the CME to be 2000-2600
km/s, i.e., high, but of the same order as preceding non-GLE-related CMEs from
the same active region. Hence, the flare itself rather than the CME appears to
determine the extreme nature of this event. We conclude that the acceleration,
at least, to sub-relativistic energies, of electrons and protons, responsible
for both the flare emissions and the leading spike of SEP/GLE by 07 UT, are
likely to have occurred simultaneously within the flare region. We do not rule
out a probable contribution from particles accelerated in the CME-driven shock
for the leading GLE spike, which seemed to dominate later on.Comment: 34 pages, 14 Postscript figures. Solar Physics, accepted. A typo
corrected. The original publication is available at
http://www.springerlink.co
A Long-Term Decrease of the Mid-Size Segmentation Lengths Observed in the He ii (30.4 nm) Solar EUV Emission
Variability of Solar Five-Minute Oscillations in the Corona as Observed by the Extreme Ultraviolet Spectrophotometer (ESP) on the Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment (SDO/EVE)
Resolving Differences in Absolute Irradiance Measurements Between the SOHO/CELIAS/SEM and the SDO/EVE
A Change in the Solar He ii EUV Global Network Structure as an Indicator of the Geo-Effectiveness of Solar Minima
35th International Cosmic Ray Conference, ICRC, The Astroparticle Physics Conference
We performed an analysis of high-energy particle emission from the Sun in two extreme solar particle events observed even with ground-based neutron monitors (NMs). We model particle transport and interactions from near-Sun source through the solar wind and the Earth's magne-tosphere and atmosphere in order to make a deep analysis of the events. The time profile of the proton source at the Sun is deduced and compared with observed electromagnetic emissions. Several complementary to each other data sets are studied jointly with the broadband dynamic radio spectra EUV images as well as other data available for both events. We find a common scenario for both eruptions including the flare's dual impulsive phase the coronal mass ejection (CME)-launch-associated burst and the late low-frequency type III radio bursts at the time of the relativistic proton injection into the interplanetary medium. The analysis supports the idea that the two considered events start with emission of relativistic protons previously accelerated during the flare and CME launch then trapped in large-scale magnetic loops and later released by the expanding CME.</p
Origin of two extreme solar particle events
Abstract
We performed an analysis of high-energy particle emission from the Sun in two extreme solar particle events observed even with ground-based neutron monitors (NMs). We model particle transport and interactions from near-Sun source through the solar wind and the Earth’s magnetosphere and atmosphere in order to make a deep analysis of the events. The time profile of the proton source at the Sun is deduced and compared with observed electromagnetic emissions. Several complementary to each other data sets are studied jointly with the broadband dynamic radio spectra, EUV images as well as other data available for both events. We find a common scenario for both eruptions, including the flare’s dual impulsive phase, the coronal mass ejection (CME)-launch-associated burst and the late low-frequency type III radio bursts at the time of the relativistic proton injection into the interplanetary medium. The analysis supports the idea that the two considered events start with emission of relativistic protons previously accelerated during the flare and CME launch, then trapped in large-scale magnetic loops and later released by the expanding CME