scholarly journals A homogeneous aa index: 2. Hemispheric asymmetries and the equinoctial variation

2018 ◽  
Vol 8 ◽  
pp. A58 ◽  
Author(s):  
Mike Lockwood ◽  
Ivan D. Finch ◽  
Aude Chambodut ◽  
Luke A. Barnard ◽  
Mathew J. Owens ◽  
...  
Keyword(s):  
Activity Index ◽  
Auroral Oval ◽  
Time Of Day ◽  
Hemispheric Asymmetries ◽  
Index 2 ◽  
The Difference ◽  
Time Of Year ◽  
Annual Means ◽  
Geomagnetic Activity Index ◽  
Aa Index

Paper 1 (Lockwood et al., 2018) generated annual means of a new version of the aa geomagnetic activity index which includes corrections for secular drift in the geographic coordinates of the auroral oval, thereby resolving the difference between the centennial-scale change in the northern and southern hemisphere indices, aaN and aaS. However, other hemispheric asymmetries in the aa index remain: in particular, the distributions of 3-hourly aaN and aaS values are different and the correlation between them is not high on this timescale (r = 0.66). In the present paper, a location-dependant station sensitivity model is developed using the am index (derived from a much more extensive network of stations in both hemispheres) and used to reduce the difference between the hemispheric aa indices and improve their correlation (to r = 0.79) by generating corrected 3-hourly hemispheric indices, aaHN and aaHS, which also include the secular drift corrections detailed in Paper 1. These are combined into a new, “homogeneous” aa index, aaH. It is shown that aaH, unlike aa, reveals the “equinoctial”-like time-of-day/time-of-year pattern that is found for the am index.

scholarly journals A homogeneous aa index: 1. Secular variation

2018 ◽  
Vol 8 ◽  
pp. A53 ◽  
Author(s):  
Mike Lockwood ◽  
Aude Chambodut ◽  
Luke A. Barnard ◽  
Mathew J. Owens ◽  
Ellen Clarke ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Angular Separation ◽  
Auroral Oval ◽  
Secular Change ◽  
Independent Data ◽  
Scale Factors ◽  
Before And After ◽  
Time Of Year ◽  
Vital Resource ◽  
Aa Index

Originally complied for 1868–1967 and subsequently continued so that it now covers 150 years, the aa index has become a vital resource for studying space climate change. However, there have been debates about the inter-calibration of data from the different stations. In addition, the effects of secular change in the geomagnetic field have not previously been allowed for. As a result, the components of the “classical” aa index for the southern and northern hemispheres (aa S and aa N) have drifted apart. We here separately correct both aa S and aa N for both these effects using the same method as used to generate the classic aa values but allowing δ, the minimum angular separation of each station from a nominal auroral oval, to vary as calculated using the IGRF-12 and gufm1 models of the intrinsic geomagnetic field. Our approach is to correct the quantized a K -values for each station, originally scaled on the assumption that δ values are constant, with time-dependent scale factors that allow for the drift in δ. This requires revisiting the intercalibration of successive stations used in making the aa S and aa N composites. These intercalibrations are defined using independent data and daily averages from 11 years before and after each station change and it is shown that they depend on the time of year. This procedure produces new homogenized hemispheric aa indices, aa HS and aa HN, which show centennial-scale changes that are in very close agreement. Calibration problems with the classic aa index are shown to have arisen from drifts in δ combined with simpler corrections which gave an incorrect temporal variation and underestimate the rise in aa during the 20th century by about 15%.

ASSOCIATION BETWEEN VARIATIONS OF SOLAR WIND PARAMETERS AND GEOMAGNETIC ACTIVITY INDEX Ap IN 2003 - 2005

2011 ◽  
Vol 2 (3) ◽  
pp. 205-210 ◽  
Author(s):  
Igor Savel'evich Fal'kovich ◽  
M. R. Olyak ◽  
Nikolai Nikolaevich Kalinichenko ◽  
I. N. Bubnov
Keyword(s):  
Solar Wind ◽  
Geomagnetic Activity ◽  
Activity Index ◽  
Solar Wind Parameters ◽  
Geomagnetic Activity Index

Effect of time of day, time of year, and life history strategy on time budgeting in juvenile Atlantic salmon, Salmo salar

1999 ◽  
Vol 56 (12) ◽  
pp. 2397-2403 ◽  
Author(s):  
Sveinn K Valdimarsson ◽  
Neil B Metcalfe
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Life History Strategy ◽  
Time Of Day ◽  
Life History Strategies ◽  
Foraging Efficiency ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Time Of Year

Traditionally, behavioural studies on juvenile Atlantic salmon, Salmo salar, have been conducted during the day in summer. It is known that Atlantic salmon become nocturnal in winter, but very little is known about their behaviour at that time. Therefore, observations in a seminatural stream were carried out during the day and night, from February to June, comparing diel and seasonal differences in behaviour between fish adopting alternative life history strategies. The results showed a general trend for more activity in spring than in winter, and the fish were found to be foraging at surprisingly low light levels. There were differences in relative feeding rate between the life history strategies; the early migrant fish foraged mostly during the day whereas the delayed migrant fish did more foraging at night. There is some evidence that the early migrant fish made fewer feeding attempts over the winter, which is surprising, since they grow faster over that period. This suggests differences in foraging efficiency, which could contribute to the separation into these two life history strategies.

Phase-advance shifts of human circadian pacemaker are accelerated by daytime physical exercise

2001 ◽  
Vol 281 (1) ◽  
pp. R197-R205 ◽  
Author(s):  
Toshihiko Miyazaki ◽  
Satoko Hashimoto ◽  
Satoru Masubuchi ◽  
Sato Honma ◽  
Ken-Ichi Honma
Keyword(s):  
Physical Exercise ◽  
Single Pulse ◽  
Time Of Day ◽  
Phase Advance ◽  
Circadian Pacemaker ◽  
Light Conditions ◽  
Melatonin Rhythm ◽  
Dim Light ◽  
The Difference ◽  
Isolation Facility

Effects of forced sleep-wake schedules with and without physical exercise were examined on the human circadian pacemaker under dim light conditions. Subjects spent 15 days in an isolation facility separately without knowing the time of day and followed a forced sleep-wake schedule of a 23 h 40-min period for 12 cycles, and physical exercise was imposed twice per waking period for 2 h each with bicycle- or rowing-type ergometers. As a result, plasma melatonin rhythm was significantly phase advanced with physical exercise, whereas it was not changed without exercise. The difference in phase was already significant 6 days after the start of exercise. The amplitude of melatonin rhythm was not affected. A single pulse of physical exercise in the afternoon or at midnight significantly phase delayed the melatonin rhythms when compared with the prepulse phase, but the amount of phase shift was not different from that observed in the sedentary controls. These findings indicate that physical exercise accelerates phase-advance shifts of the human circadian pacemaker associated with the forced sleep-wake schedule.

scholarly journals Investigation of monthly variations in the efficiencies of photovoltaics due to sunrise and sunset times

2020 ◽  
Vol 18 (1) ◽  
pp. 310
Author(s):  
Armstrong O. Njok ◽  
Julie C. Ogbulezie ◽  
Manoj Kumar Panjwani ◽  
Raja Masood Larik
Keyword(s):  
Relative Humidity ◽  
Solar Energy ◽  
Electrical Energy ◽  
Time Of Day ◽  
Peak Efficiency ◽  
Pv Module ◽  
Average Relative Humidity ◽  
The Difference ◽  
Monthly Variations ◽  
Different Levels

<p>The effect of time of day and month on the efficient conversion of solar energy to electrical energy using a polycrystalline (PV) module in calabar was studied. A KT-908 precision digital hygrometer and thermometer, and a M890C+ digital multimeter were used in the process. Results obtained shows that photovoltaic produce different levels of peak efficiencies at different times of the day for different months due to the difference in sunrise and sunset times for the months. The results also indicated that photovoltaics will be more efficient in months with low average relative humidity couple with low panel temperature. A peak efficiency of 77% at 12:30 in the month of April was observed before dropping to 73% at 12:00 in the month of May, indicating that there might be further drop in efficiency as we proceed further into the year. Results also show that photovoltaics are more efficient before noon in the month of May than in April while the reverse will be observed in the afternoon. </p>

scholarly journals Road lighting density and brightness linked with increased cycling rates after-dark

2020 ◽  
Author(s):  
Jim Uttley ◽  
Steve Fotios ◽  
Robin Lovelace
Keyword(s):  
Negative Impact ◽  
Time Of Day ◽  
Aerial Images ◽  
Minimal Amount ◽  
Night Time ◽  
Road Lighting ◽  
International Policies ◽  
Relative Brightness ◽  
Two Measures ◽  
The Difference

Cycling has a range of benefits as is recognised by national and international policies aiming to increase cycling rates. Darkness acts as a barrier to people cycling, with fewer people cycling after-dark when seasonal and time-of-day factors are accounted for. This paper explores whether road lighting can reduce the negative impact of darkness on cycling rates. Changes in cycling rates between daylight and after-dark were quantified for 48 locations in Birmingham, United Kingdom, by calculating an odds ratio. These odds ratios were compared against two measures of road lighting at each location: 1) Density of road lighting lanterns; 2) Relative brightness as estimated from night-time aerial images. Locations with no road lighting showed a significantly greater reduction in cycling after-dark compared with locations that had some lighting. A nonlinear relationship was found between relative brightness at a location at night and the reduction in cyclists after-dark. Small initial increases in brightness resulted in large reductions in the difference between cyclist numbers in daylight and after-dark, but this effect reached a plateau as brightness increased. These results suggest only a minimal amount of lighting may be sufficient to promote cycling after-dark.

scholarly journals COSTEP/SOHO observations of energetic electrons far upstream of the Earth's bow-shock

2008 ◽  
Vol 26 (4) ◽  
pp. 905-912 ◽  
Author(s):  
A. Klassen ◽  
R. Gómez-Herrero ◽  
E. Böhm ◽  
R. Müller-Mellin ◽  
B. Heber ◽  
...  
Keyword(s):  
Activity Index ◽  
Libration Point ◽  
Solar Wind Speed ◽  
Bow Shock ◽  
Close Correspondence ◽  
Solar Particle Events ◽  
Earth’S Bow Shock ◽  
Geomagnetic Activity Index ◽  
Soho Spacecraft ◽  
Event Occurrence

Abstract. We have analyzed 124 electron bursts at energies above 0.25 MeV observed with the EPHIN/COSTEP instrument onboard the SOHO spacecraft far upstream of the Earth's bow-shock at the libration point L1 from 1996 through 2005. Most of the bursts were observed during low solar activity (in 1996–1997 and in 2005) and all 124 bursts were not associated with solar particle events. It is shown that some upstream events are detected at energies above 0.7 MeV. We find that the event occurrence number shows a distinct seasonal variation with maxima around equinoxes and minima near solstices. This together with a close correspondence between the event occurrence number with maxima in solar wind speed (Vsw), geomagnetic activity index (Ap) and in the southward interplanetary magnetic field (IMF) component (Bz) indicates that the observed events can be explained in terms of leakage of magnetospheric particles during enhanced geoactivity rather than by acceleration at the Earth's bow-shock.

Analysis of an Instaneous Census Method for Heathland Birds

1983 ◽  
Vol 10 (3) ◽  
pp. 521 ◽  
Author(s):  
GH Pyke
Keyword(s):  
Frequency Distribution ◽  
Bird Species ◽  
Time Of Day ◽  
Vegetation Height ◽  
Time Of Year

Birds were censused from the top of a 2.5-m ladder positioned at the centre of circles of radius 20 m. Every 1 min the observer visually scanned one half of a circle, recording the identity of and the distance to every bird seen. This procedure was carried out for about eight scans and then repeated for the complementary semicircle. Birds tended to be repulsed from the observer and/or ladder. Consequently the census method cannot be used to estimate absolute densities. However, the frequency distribution of bird-observer distances was found to be independent of time of day, time of year, and bird species. The method can, therefore, be used at a particular location to compare different bird species and different times. Vegetation height affected the frequency distribution of bird-observer distances and so the method cannot provide accurate comparisons of bird densities in different areas. Fewer birds were seen per scan when the census was carried out 4-6 h after sunrise. The two observers in the study saw the same average number of birds per scan.

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