9 research outputs found
Observations of an Energetically Isolated Quiet Sun Transient: Evidence of Quasi-Steady Coronal Heating
Increasing evidence for coronal heating contributions from cooler solar
atmospheric layers, notably quiet Sun (QS) conditions, challenges standard
solar atmospheric descriptions of bright transition region (TR) emission. As
such, questions to the role of dynamic QS transients in contributing to the
total coronal energy budget are elevated. Using observations from the {\it
Atmospheric Imaging Assembly} and {\it Heliosemic Magnetic Imager} on board the
{\it Solar Dynamics Observatory}, and numerical model extrapolations of coronal
magnetic fields, we investigate a dynamic QS transient energetically isolated
to the TR and extruding from a common footpoint shared with two heated loop
arcades. A non-casual relationship is established between episodic heating of
the QS transient and wide-spread magnetic field re-organization events, while
evidence is found favoring a magnetic topology typical of eruptive processes.
Quasi-steady interchange reconnection events are implicated as a source of the
transient's visibly bright radiative signature. We consider the QS transient's
temporally stable (\,35\,min) radiative nature occurs as a result of
the large-scale magnetic field geometries of the QS and/or relatively quiet
nature of the magnetic photosphere, which possibly act to inhibit energetic
buildup processes required to initiate a catastrophic eruption phase. This work
provides insight to the QS's thermodynamic and magnetic relation to eruptive
processes quasi-steadily heating a small-scale dynamic and TR transient. This
work elevates arguments of non-negligible coronal heating contributions from
cool atmospheric layers in QS conditions, and increases evidence for solar wind
mass feeding of dynamic transients therein.Comment: 13 pages, 9 figure
Constraints on the baryonic load of gamma-ray bursts using ultra-high energy cosmic rays
Ultra-high energy cosmic rays are the most extreme energetic particles
detected on Earth, however, their acceleration sites are still mysterious. We
explore the contribution of low-luminosity gamma-ray bursts to the ultra-high
energy cosmic ray flux, since they form the bulk of the nearby population. We
analyse a representative sample of these bursts detected by BeppoSAX, INTEGRAL
and Swift between 1998-2016, and find they can produce a theoretical cosmic ray
flux on Earth of at least particles
km century mol. No suppression mechanisms can reconcile
this value with the flux observed on Earth. Instead, we propose that the jet of
low-luminosity gamma-ray bursts propels only the circumburst medium - which is
accelerated to relativistic speeds - not the stellar matter. This has
implications for the baryonic load of the jet: it should be negligible compared
to the leptonic content.Comment: 5 pages, submitted to MNRA
Comparative Analysis of a Transition Region Bright Point with a Blinker and Coronal Bright Point Using Multiple EIS Emission Lines
Since their discovery twenty year ago, transition region bright points
(TRBPs) have never been observed spectroscopically. Bright point properties
have not been compared with similar transition region and coronal structures.
In this work we have investigated three transient quiet Sun brightenings
including a TRBP, a coronal BP (CBP) and a blinker. We use time-series
observations of the extreme ultraviolet emission lines of a wide range of
temperature T (log T = 5.3 - 6.4) from the EUV imaging spectrometer (EIS)
onboard the Hinode satellite. We present the EIS temperature maps and Doppler
maps, which are compared with magnetograms from the Michelson Doppler Imager
(MDI) onboard the SOHO satellite. Doppler velocities of the TR BP and blinker
are <,25 km s, which is typical of transient TR phenomena. The Dopper
velocities of the CBP were found to be < 20 km s^{-1} with exception of those
measured at log T = 6.2 where a distinct bi-directional jet is observed. From
an EM loci analysis we find evidence of single and double isothermal components
in the TRBP and CBP, respectively. TRBP and CBP loci curves are characterized
by broad distributions suggesting the existence of unresolved structure. By
comparing and contrasting the physical characteristics of the events we find
the BP phenomena are an indication of multi-scaled self similarity, given
similarities in both their underlying magnetic field configuration and
evolution in relation to EUV flux changes. In contrast, the blinker phenomena
and the TRBP are sufficiently dissimilar in their observed properties as to
constitute different event classes. Our work indicates that the measurement of
similar characteristics across multiple event types holds class-predictive
power, and is a significant step towards automated solar atmospheric
multi-class classification of unresolved transient EUV sources.Comment: 38 pages, 16 figure
QUIET-SUN NETWORK BRIGHT POINT PHENOMENA WITH SIGMOIDAL SIGNATURES
Ubiquitous solar atmospheric coronal and transition region bright points (BPs) are compact features overlying strong concentrations of magnetic flux. Here, we utilize high-cadence observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to provide the first observations of extreme ultraviolet quiet-Sun (QS) network BP activity associated with sigmoidal structuring. To our knowledge, this previously unresolved fine structure has never been associated with such small-scale QS events. This QS event precedes a bi-directional jet in a compact, low-energy, and low-temperature environment, where evidence is found in support of the typical fan-spine magnetic field topology. As in active regions and micro-sigmoids, the sigmoidal arcade is likely formed via tether-cutting reconnection and precedes peak intensity enhancements and eruptive activity. Our QS BP sigmoid provides a new class of small-scale structuring exhibiting self-organized criticality that highlights a multi-scaled self-similarity between large-scale, high-temperature coronal fields and the small-scale, lower-temperature QS network. Finally, our QS BP sigmoid elevates arguments for coronal heating contributions from cooler atmospheric layers, as this class of structure may provide evidence favoring mass, energy, and helicity injections into the heliosphere