32 research outputs found
Abundances of Suprathermal Heavy Ions in CIRs during the Minimum of Solar Cycle 23
In this paper we examine the elemental composition of the 0.1-1 MeV/nucleon
interplanetary heavy ions from H to Fe in corotating interaction regions (CIRs)
measured by the SIT (Suprathermal Ion Telescope) instrument. We use
observations taken on board the STEREO spacecraft from January 2007 through
December 2010, which included the unusually long solar minimum following solar
cycle 23. During this period instruments on STEREO observed more than 50 CIR
events making it possible to investigate CIR ion abundances during solar
minimum conditions with unprecedented high statistics. The observations reveal
annual variations of relative ion abundances in the CIRs during the 2007-2008
period as indicated by the He/H, He/O and Fe/O elemental ratios. We discuss
possible causes of the variability in terms of the helium focusing cone passage
and heliolatitude dependence. The year 2009 was very quiet in CIR event
activity. In 2010 the elemental composition in CIRs were influenced by sporadic
solar energetic particle (SEP) events. The 2010 He/H and He/O abundance ratios
in CIRs show large event to event variations with values resembling the
SEP-like composition. This finding points out that the suprathermal SEPs could
be the source population for CIR acceleration.Comment: accepted for publication in Solar Physic
Energy spectra of 3He-rich solar energetic particles associated with coronal waves
In addition to their anomalous abundances, 3He-rich solar energetic particles
(SEPs) show puzzling energy spectral shapes varying from rounded forms to power
laws where the later are characteristics of shock acceleration. Solar sources
of these particles have been often associated with jets and narrow CMEs, which
are the signatures of magnetic reconnection involving open field. Recent
reports on new associations with large-scale EUV waves bring new insights on
acceleration and transport of 3He-rich SEPs in the corona. We examined energy
spectra for 32 3He-rich SEP events observed by ACE at L1 near solar minimum in
2007-2010 and compared the spectral shapes with solar flare signatures obtained
from STEREO EUV images. We found the events with jets or brightenings tend to
be associated with rounded spectra and the events with coronal waves with power
laws. This suggests that coronal waves may be related to the unknown second
stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs.Comment: Presented at 15th Annual International Astrophysics Conference "The
Science of Ed Stone". Accepted for publication in Journal of Physics:
Conference Serie
Interpretation of increased energetic particle flux measurements by SEPT aboard the STEREO spacecraft and contamination
Context. Interplanetary (IP) shocks are known to be accelerators of energetic
charged particles observed in-situ in the heliosphere. However, the
acceleration of near-relativistic electrons by shocks in the interplanetary
medium is often questioned. On 9 August 2011 a Corotating Interaction Region
(CIR) passed STEREO B (STB) that resulted in a flux increase in the electron
and ion channels of the Solar Electron and Proton Telescope (SEPT). Because
electron measurements in the few keV to several 100 keV range rely on the
so-called magnet foil technique, which is utilized by SEPT, ions can contribute
to the electron channels. Aims. We aim to investigate whether the flux increase
in the electron channels of SEPT during the CIR event on 9 August 2011 is
caused by ion contamination only. Methods. We compute the SEPT response
functions for protons and helium utilizing an updated GEANT4 model of SEPT. The
CIR energetic particle ion spectra for protons and helium are assumed to follow
a Band function in energy per nucleon with a constant helium to proton ratio.
Results. Our analysis leads to a helium to proton ratio of 16.9% and a proton
flux following a Band function with the parameters /
(cm2 s sr MeV/nuc.), keV/nuc. and spectral indices of and which are in good agreement with measurements by
the Suprathermal Ion Telescope (SIT) aboard STB. Conclusions. Since our results
explain the SEPT measurements, we conclude that no significant amount of
electrons were accelerated between keV and keV by the CIR
BBMRI-ERIC Negotiator:Implementing Efficient Access to Biobanks
Various biological resources, such as biobanks and disease-specific registries, have become indispensable resources to better understand the epidemiology and biological mechanisms of disease and are fundamental for advancing medical research. Nevertheless, biobanks and similar resources still face significant challenges to become more findable and accessible by users on both national and global scales. One of the main challenges for users is to find relevant resources using cataloging and search services such as the BBMRI-ERIC Directory, operated by European Research Infrastructure on Biobanking and Biomolecular Resources (BBMRI-ERIC), as these often do not contain the information needed by the researchers to decide if the resource has relevant material/data; these resources are only weakly characterized. Hence, the researcher is typically left with too many resources to explore and investigate. In addition, resources often have complex procedures for accessing holdings, particularly for depletable biological materials. This article focuses on designing a system for effective negotiation of access to holdings, in which a researcher can approach many resources simultaneously, while giving each resource team the ability to implement their own mechanisms to check if the material/data are available and to decide if access should be provided. The BBMRI-ERIC has developed and implemented an access and negotiation tool called the BBMRI-ERIC Negotiator. The Negotiator enables access negotiation to more than 600 biobanks from the BBMRI-ERIC Directory and other discovery services such as GBA/BBMRI-ERIC Locator or RD-Connect Finder. This article summarizes the principles that guided the design of the tool, the terminology used and underlying data model, request workflows, authentication and authorization mechanism(s), and the mechanisms and monitoring processes to stimulate the desired behavior of the resources: to effectively deliver access to biological material and data