2,675 research outputs found
BiSON data preparation: A correction for differential extinction and the weighted averaging of contemporaneous data
The Birmingham Solar Oscillations Network (BiSON) has provided high-quality
high-cadence observations from as far back in time as 1978. These data must be
calibrated from the raw observations into radial velocity and the quality of
the calibration has a large impact on the signal-to-noise ratio of the final
time series. The aim of this work is to maximise the potential science that can
be performed with the BiSON data set by optimising the calibration procedure.
To achieve better levels of signal-to-noise ratio we perform two key steps in
the calibration process: we attempt a correction for terrestrial atmospheric
differential extinction; and the resulting improvement in the calibration
allows us to perform weighted averaging of contemporaneous data from different
BiSON stations. The improvements listed produce significant improvement in the
signal-to-noise ratio of the BiSON frequency-power spectrum across all
frequency ranges. The reduction of noise in the power spectrum will allow
future work to provide greater constraint on changes in the oscillation
spectrum with solar activity. In addition, the analysis of the low-frequency
region suggests we have achieved a noise level that may allow us to improve
estimates of the upper limit of g-mode amplitudes.Comment: Accepted for publication in MNRAS; 10 pages, 7 figure
Reliability of P mode event classification using contemporaneous BiSON and GOLF observations
We carried out a comparison of the signals seen in contemporaneous BiSON and
GOLF data sets. Both instruments perform Doppler shift velocity measurements in
integrated sunlight, although BiSON perform measurements from the two wings of
potassium absorption line and GOLF from one wing of the NaD1 line.
Discrepancies between the two datasets have been observed. We show,in fact,
that the relative power depends on the wing in which GOLF data observes. During
the blue wing period, the relative power is much higher than in BiSON datasets,
while a good agreement has been observed during the red period.Comment: 7 pages, HELAS II: Helioseismology, Asteroseismology, and MHD
Connections, conference proceedin
Evaluating Doppel’s impact on Anxiety and Focus amongst adults with ADHD
Attention Deficit Hyperactivity Disorder (ADHD) is the most commonly diagnosed psychiatric disorder in children. Amongst adults, it is often underdiagnosed and associated with comorbidities including anxiety. This study presents a trial evaluating the efficacy of Doppel, a wrist-worn wearable that provides vibrations linked to one’s heart rate to improve symptoms of anxiety and poor focus amongst young adults with ADHD. Young adults (aged 18–25) used either an active or comparator Doppel for 8 weeks, completing measures of anxiety and focus at baseline, 4 weeks, and 8 weeks. Participants in both groups experienced a reduction in anxiety and an increase in focus across the trial duration. No superiority for vibrations linked to one’s heart rate was found. Whilst the current study cannot determine a specific mechanism of action, the findings provide some promising initial evidence as to the potential for direct-to-consumer digital health products to be useful in symptom management amongst young adults with ADHD
Aerodynamic Interference on Finned Slender Body
Aerodynamic interference can occur between high-speed slender bodies when in close proximity. A complex flowfield develops where shock and expansion waves from a generator body impinge upon the adjacent receiver body and modify its aerodynamic characteristics in comparison to the isolated case. The aim of this research is to quantify and understand the multibody interference effects that arise between a finned slender body and a second disturbance generator body. A parametric wind tunnel study was performed in which the effects of the receiver incidence and axial stagger were considered. Computational fluid dynamic simulations showed good agreement with the measurements, and these were used in the interpretation of the experimental results. The overall interference loads for a given multibody configuration were found to be a complex function of the pressure footprints from the compression and expansion waves emanating from the generator body as well as the flow pitch induced by the generator shockwave. These induced interference loads change sign as the shock impingement location moves aft over the receiver and in some cases cause the receiver body to become statically unstable. Overall, the observed interference effects can modify the subsequent body trajectories and may increase the likelihood of a collision
Performance of the Birmingham Solar-Oscillations Network (BiSON)
The Birmingham Solar-Oscillations Network (BiSON) has been operating with a
full complement of six stations since 1992. Over 20 years later, we look back
on the network history. The meta-data from the sites have been analysed to
assess performance in terms of site insolation, with a brief look at the
challenges that have been encountered over the years. We explain how the
international community can gain easy access to the ever-growing dataset
produced by the network, and finally look to the future of the network and the
potential impact of nearly 25 years of technology miniaturisation.Comment: 31 pages, 19 figures. Accepted by Solar Physics: 2015 October 20.
First online: 2015 December 7. Open Acces
Changes in the sensitivity of solar p-mode frequency shifts to activity over three solar cycles
Low-degree solar p-mode observations from the long-lived Birmingham Solar
Oscillations Network (BiSON) stretch back further than any other single
helioseismic data set. Results from BiSON have suggested that the response of
the mode frequency to solar activity levels may be different in different
cycles. In order to check whether such changes can also be seen at higher
degrees, we compare the response of medium-degree solar p-modes to activity
levels across three solar cycles using data from Big Bear Solar Observatory
(BBSO), Global Oscillation Network Group (GONG), Michelson Doppler Imager (MDI)
and Helioseismic and Magnetic Imager (HMI), by examining the shifts in the mode
frequencies and their sensitivity to solar activity levels. We compare these
shifts and sensitivities with those from radial modes from BiSON. We find that
the medium-degree data show small but significant systematic differences
between the cycles, with solar cycle 24 showing a frequency shift about 10 per
cent larger than cycle 23 for the same change in activity as determined by the
10.7 cm radio flux. This may support the idea that there have been changes in
the magnetic properties of the shallow subsurface layers of the Sun that have
the strongest influence on the frequency shifts.Comment: 6 pages, 3 figures, accepted by MNRAS 3rd July 201
Why should we correct reported pulsation frequencies for stellar line-of-sight Doppler velocity shifts?
In the age of Kepler and Corot, extended observations have provided estimates
of stellar pulsation frequencies that have achieved new levels of precision,
regularly exceeding fractional levels of a few parts in . These high
levels of precision now in principle exceed the point where one can ignore the
Doppler shift of pulsation frequencies caused by the motion of a star relative
to the observer. We present a correction for these Doppler shifts and use
previously published pulsation frequencies to demonstrate the significance of
the effect. We suggest that reported pulsation frequencies should be routinely
corrected for stellar line-of-sight velocity Doppler shifts, or if a
line-of-sight velocity estimate is not available, the frame of reference in
which the frequencies are reported should be clearly stated.Comment: 5 pages, 1 figure, accepted for publication in MNRAS Letter
Decarbonising universities: Case study of the University of Exeter’s green strategy plans based on analysing its energy demand in 2012–2020
This is the final version. Available on open access from MDPI via the DOI in this record. This study investigates the carbon footprint of the University of Exeter by analysing its
energy consumption between 2012 and 2020 to assess its current standing in the process of achieving
carbon neutrality. The study then explores the possible methods of reaching this target in line with
the University of Exeter’s Environment & Climate Emergency Policy Statement. The leading part of
the statement is as follows: “All Campus activities/operations shall have a carbon net zero impact
and or result in environmental gain by 2030 and aims to be carbon net zero by 2050 (accounting for
all associated activities and Scope 3 footprint)”. Using methods of energy consumption reduction, a
new carbon footprint for Scope 1 and 2 emissions was calculated for the year 2030, which included
phasing out oil and gas and swapping out inefficient systems, such as old heating or lighting. This
reduced the emissions from 17.24 ktCO2e to 3.34 ktCO2e also greatly helped by the reduction in
electricity grid conversion factors. The remaining emissions would be reduced further to net zero by
on site solar and offsite wind investment
A thorough analysis of the short- and mid-term activity-related variations in the solar acoustic frequencies
The frequencies of the solar acoustic oscillations vary over the activity
cycle. The variations in other activity proxies are found to be well correlated
with the variations in the acoustic frequencies. However, each proxy has a
slightly different time behaviour. Our goal is to characterize the differences
between the time behaviour of the frequency shifts and of two other activity
proxies, namely, the area covered by sunspots and the 10.7cm flux. We define a
new observable that is particularly sensitive to the short-term frequency
variations. We then compare the observable when computed from model frequency
shifts and from observed frequency shifts obtained with the Global Oscillation
Network Group (GONG) for cycle 23. Our analysis shows that on the shortest
time-scales the variations in the frequency shifts seen in the GONG
observations are strongly correlated with the variations in the area covered by
sunspots. However, a significant loss of correlation is still found. We verify
that the times when the frequency shifts and the sunspot area do not vary in a
similar way tend to coincide with the times of the maxima of the quasi-biennial
variations seen in the solar seismic data. A similar analysis of the relation
between the 10.7cm flux and the frequency shifts reveals that the short-time
variations in the frequency shifts follow even more closely those of the 10.7cm
flux than those of the sunspot area. However, a loss of correlation between
frequency shifts and 10.7cm flux variations is still found around the same
times.Comment: 7 pages, 6 figures, accepted for publication in MNRA
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