1,002 research outputs found
Deciphering Solar Magnetic Activity: The (Solar) Hale Cycle Terminator of 2021
McIntosh and colleagues identified an event in the solar timeline that
appeared to play a role in how Sunspot Cycle 23 (SC23) transitioned into
Sunspot Cycle 24 (SC24). The timeframe for this transition was rapid, taking
place in as short as time as a solar rotation. M2014 inferred that the
transition observed was a critical episode for the Sun's global-scale magnetic
field that was being manifest in the spatially and temporally overlapping and
magnetic systems belonging to the Sun's 22-year (Hale) magnetic cycle. These
events have been dubbed as Hale Cycle terminations, or `terminators' for short.
Further exploration revealed a relationship between terminator separation (as a
measure of overlap in the Hale Cycles) and the upcoming sunspot cycle
amplitude. McIntosh and colleagues extrapolated upon this relationship to
identify the termination of the SC24 carrying Hale Cycle band in Mid-2020 and
inferred that this would result in a very large Sunspot Cycle 25 (SC25). This
paper presents observational analysis of the end of SC24 and the initial months
of SC25 growth following a terminator that occurred in mid-December 2021
(approximately 12/13/2021). We use the December 2021 terminator to finalize the
forecast of SC25 amplitude 184 (17 with 95\% confidence, and 63 with
68\% confidence). Finally, we use other terminator-related superposed epoch
analyses to project the timing of SC25 maxima in late 2023 to mid 2024.Comment: 16 pages, 10 figures - Submitted to Frontier
Observations Supporting the Role of Magnetoconvection in Energy Supply to the Quiescent Solar Atmosphere
Identifying the two physical mechanisms behind the production and sustenance
of the quiescent solar corona and solar wind poses two of the outstanding
problems in solar physics today. We present analysis of spectroscopic
observations from the Solar and Heliospheric Observatory that are consistent
with a single physical mechanism being responsible for a significant portion of
the heat supplied to the lower solar corona and the initial acceleration of the
solar wind; the ubiquitous action of magnetoconvection-driven reprocessing and
exchange reconnection of the Sun's magnetic field on the supergranular scale.
We deduce that while the net magnetic flux on the scale of a supergranule
controls the injection rate of mass and energy into the transition region
plasma it is the global magnetic topology of the plasma that dictates whether
the released ejecta provides thermal input to the quiet solar corona or becomes
a tributary that feeds the solar wind.Comment: 34 pages, 13 figures - In press Astrophysical Journal (Jan 1 2007
Brief for the United States as Amicus Curiae in Support of Neither Party
Amicus ("friend of the court") brief written by the United States in support of neither party in AMP v. Myriad Genetics (No. 2010-1406)
Evaluation of a Group Administered 24-Hour Recall Method for Dietary Assessment
A group administered 24-hour food recall was developed by the Expanded Food and Nutrition Education Program of Texas to expedite dietary assessment of clients. The study reported here evaluated the group recall and an individual recall method. Data for one meal collected with the use of dietary recalls, either group of individual, were compared to observational data. Results suggest that the group recall may be at least as effective as the individual recall to estimate dietary intakes of subjects. The group recall method could be used by programs such as EFNEP to simplify and expedite dietary assessment of clients
Brief for the United States as Amicus Curiae in Support of Neither Party
Amicus ("friend of the court") brief written by the United States in support of neither party in AMP v. Myriad Genetics (No. 2010-1406)
Simple Magnetic Flux Balance as an Indicator of Neon VIII Doppler Velocity Partitioning in an Equatorial Coronal Hole
We present a novel investigation into the relationship between simple
estimates of magnetic flux balance and the Ne VIII Doppler velocity
partitioning of a large equatorial coronal hole observed by the Solar
Ultraviolet Measurements of Emitted Radiation spectrometer (SUMER) on the Solar
and Heliospheric Observatory (SOHO) in November 1999. We demonstrate that a
considerable fraction of the large scale Doppler velocity pattern in the
coronal hole can be qualitatively described by simple measures of the local
magnetic field conditions, i.e., the relative unbalance of magnetic polarities
and the radial distance required to balance local flux concentrations with
those of opposite polarity.Comment: To appear ApJL (June
A Tale Of Two Spicules: The Impact of Spicules on the Magnetic Chromosphere
We use high-resolution observations of the Sun in Ca II H 3968 A from the
Solar Optical Telescope on Hinode to show that there are at least two types of
spicules that dominate the structure of the magnetic solar chromosphere. Both
types are tied to the relentless magnetoconvective driving in the photosphere,
but have very different dynamic properties. ``Type-I'' spicules are driven by
shock waves that form when global oscillations and convective flows leak into
the upper atmosphere along magnetic field lines on 3-7 minute timescales.
``Type-II'' spicules are much more dynamic: they form rapidly (in ~10s), are
very thin (<200km wide), have lifetimes of 10-150s (at any one height) and seem
to be rapidly heated to (at least) transition region temperatures, sending
material through the chromosphere at speeds of order 50-150 km/s. The
properties of Type II spicules suggest a formation process that is a
consequence of magnetic reconnection, typically in the vicinity of magnetic
flux concentrations in plage and network. Both types of spicules are observed
to carry Alfven waves with significant amplitudes of order 20 km/s.Comment: 8 pages, 5 figures, accepted for Hinode special issue of PAS
The Post-Eruptive Evolution of a Coronal Dimming
We discuss the post-eruptive evolution of a "coronal dimming" based on
observations of the EUV corona from the Solar and Heliospheric Observatory and
the Transition Region and Coronal Explorer. This discussion highlights the
roles played by magnetoconvection-driven magnetic reconnection and the global
magnetic environment of the plasma in the "filling" and apparent motion of the
region following the eruption of a coronal mass ejection (CME). A crucial
element in our understanding of the dimming region evolution is developed by
monitoring the disappearance and reappearance of bright TRACE "moss" around the
active region giving rise to the CME. We interpret the change in the TRACE moss
as a proxy of the changing coronal magnetic field topology behind the CME
front. We infer that the change in global magnetic topology also results in a
shift of energy balance in the process responsible for the production of the
moss emission while the coronal magnetic topology evolves from closed, to open
and back to closed again because, following the eruption, the moss reforms
around the active region in almost exactly its pre-event configuration. As a
result of the moss evolution, combining our discussion with recent
spectroscopic results of an equatorial coronal hole, we suggest that the
interchangeable use of the term "transient coronal hole" to describe a coronal
dimming is more than just a simple coincidence.Comment: In Press ApJ [May 2007] - 15 pages, 5 figures, 7 movies that are
available upon request [contact author
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