6 research outputs found
Case studies of multi-day 3He-rich solar energetic particle periods
Context. Impulsive solar energetic particle events in the inner heliosphere
show the long-lasting enrichment of 3He. Aims. We study the source regions of
long-lasting 3He-rich solar energetic particle (SEP) events Methods. We located
the responsible open magnetic field regions, we combined potential field source
surface extrapolations (PFSS) with the Parker spiral, and compared the magnetic
field of the identified source regions with in situ magnetic fields. The
candidate open field regions are active region plages. The activity was
examined by using extreme ultraviolet (EUV) images from the Solar Dynamics
Observatory (SDO) and STEREO together with radio observations from STEREO and
WIND. Results. Multi-day periods of 3He-rich SEP events are associated with ion
production in single active region. Small flares or coronal jets are their
responsible solar sources. We also find that the 3He enrichment may depend on
the occurrence rate of coronal jets.Comment: 7page, 4 figure
Association of 3He-Rich Solar Energetic Particles with Large-Scale Coronal Waves
Small 3He-rich solar energetic particle (SEP) events have been commonly
associated with extreme-ultraviolet (EUV) jets and narrow coronal mass
ejections (CMEs) which are believed to be the signatures of magnetic
reconnection involving field lines open to interplanetary space. The elemental
and isotopic fractionation in these events are thought to be caused by
processes confined to the flare sites. In this study we identify 32 3He-rich
SEP events observed by the Advanced Composition Explorer near the Earth during
the solar minimum period 2007-2010 and examine their solar sources with the
high resolution Solar Terrestrial Relations Observatory (STEREO) EUV images.
Leading the Earth, STEREO-A provided for the first time a direct view on
3He-rich flares, which are generally located on the Sun's western hemisphere.
Surprisingly, we find that about half of the 3He-rich SEP events in this survey
are associated with large-scale EUV coronal waves. An examination of the wave
front propagation, the source-flare distribution and the coronal magnetic field
connections suggests that the EUV waves may affect the injection of 3He-rich
SEPs into interplanetary space.Comment: accepted for publication in The Astrophysical Journa
3He-Rich Solar Energetic Particles in Helical Jets on the Sun
Particle acceleration in stellar flares is ubiquitous in the Universe,
however, our Sun is the only astrophysical object where energetic particles and
their source flares can both be observed. The acceleration mechanism in solar
flares, tremendously enhancing (up to a factor of ten thousand) rare elements
like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we
present some of the most intense 3He- and Fe-rich solar energetic particle
events ever reported. The events were accompanied by non-relativistic electron
events and type III radio bursts. The corresponding high-resolution,
extreme-ultraviolet imaging observations have revealed for the first time a
helical structure in the source flare with a jet-like shape. The helical jets
originated in relatively small, compact active regions, located at the coronal
hole boundary. A mini-filament at the base of the jet appears to trigger these
events. The events were observed with the two Solar Terrestrial Relations
Observatories STEREO on the backside of the Sun, during the period of increased
solar activity in 2014. The helical jets may be a distinct feature of these
intense events that is related to the production of high 3He and Fe
enrichments.Comment: accepted for publication in The Astrophysical Journa
Solar Energetic Particles (SEP) and Galactic Cosmic Rays (GCR) as tracers of solar wind conditions near Saturn: event lists and applications
The lack of an upstream solar wind monitor poses a major challenge to any study that investigates the influence of the solar wind on the configuration and the dynamics of Saturnâs magnetosphere. Here we show how Cassini MIMI/LEMMS observations of Solar Energetic Particle (SEP) and Galactic Cosmic Ray (GCR) transients, that are both linked to energetic processes in the heliosphere such us Interplanetary Coronal Mass Ejections (ICMEs) and Corotating Interaction Regions (CIRs), can be used to trace enhanced solar wind conditions at Saturnâs distance. SEP protons can be easily distinguished from magnetospheric ions, particularly at the MeV energy range. Many SEPs are also accompanied by strong GCR Forbush Decreases. GCRs are detectable as a low count-rate noise signal in a large number of LEMMS channels. As SEPs and GCRs can easily penetrate into the outer and middle magnetosphere, they can be monitored continuously, even when Cassini is not situated in the solar wind. A survey of the MIMI/LEMMS dataset between 2004 and 2016 resulted in the identification of 46 SEP events. Most events last more than two weeks and have their lowest occurrence rate around the extended solar minimum between 2008 and 2010, suggesting that they are associated to ICMEs rather than CIRs, which are the main source of activity during the declining phase and the minimum of the solar cycle. We also list of 17 time periods (âŻ>⯠50 days each) where GCRs show a clear solar periodicity (âŻâŒâŻ13 or 26 days). The 13-day period that derives from two CIRs per solar rotation dominates over the 26-day period in only one of the 17 cases catalogued. This interval belongs to the second half of 2008 when expansions of Saturnâs electron radiation belts were previously reported to show a similar periodicity. That observation not only links the variability of Saturnâs electron belts to solar wind processes, but also indicates that the source of the observed periodicity in GCRs may be local. In this case GCR measurements can be used to provide the phase of CIRs at Saturn. We further demonstrate the utility of our survey results by determining that: (a) Magnetospheric convection induced by solar wind disturbances associated with SEPs is a necessary driver for the formation of transient radiation belts that were observed throughout Saturnâs magnetosphere on several occasions during 2005 and on day 105 of 2012. (b) An enhanced solar wind perturbation period that is connected to an SEP of day 332/2013 was the definite source of a strong magnetospheric compression which led to open flux loading in the magnetotail. Finally, we propose how the event lists can define the basis for single case studies or statistical investigations on how Saturn and its moons (particularly Titan) respond to extreme solar wind conditions or on the transport of SEPs and GCRs in the heliosphere
Moderate geomagnetic storm (21-22 January 2005) triggered by an outstanding coronal mass ejection viewed via energetic neutral atoms
Firefly: The Case for a Holistic Understanding of the Global Structure and Dynamics of the Sun and the Heliosphere
This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere