scholarly journals Relative contribution of electrons to the stormtime total ring current energy content

2005 ◽  
Vol 32 (3) ◽  
Author(s):  
S. Liu
Keyword(s):  
Ring Current ◽  
Energy Content ◽  
Relative Contribution ◽  
Current Energy

The Impacts of Substorms on the Ring Current

2020 ◽  
Author(s):  
Jasmine Sandhu ◽  
Jonathan Rae ◽  
Maria-Theresia Walach ◽  
Clare Watt ◽  
Mervyn Freeman ◽  
...  
Keyword(s):  
Ring Current ◽  
Energy Content ◽  
Wave Activity ◽  
Time Asymmetry ◽  
Inner Magnetosphere ◽  
H Index ◽  
Current Population ◽  
Emic Wave ◽  
The Impact ◽  
Current Energy

<p>Substorms are a highly dynamic process that results in the global redistribution of energy within the magnetosphere. The occurrence of a substorm can provide the inner magnetosphere with hot ions and consequently intensify the ring current population. However, substorms are a highly variable phenomenon that can occur as an isolated event or as part of a sequence. In this study we investigate how substorms shape the energy content, anisotropy, and storm time behaviour of the ring current population.</p><p>Using ion observations (H+, O+, and He+) from the RBSPICE and HOPE instruments onboard the Van Allen Probes, we quantify how the total ring current energy content and ring current anisotropy changes during the substorm process. A statistical analysis demonstrates the impact of a typical substorm energises the ring current by 12% on average. The features of the energy enhancement correlate well with the expected properties of particle injections into the inner magnetosphere, and large enhancements in the O+ contribution to the energy content suggest important compositional variations.</p><p>Analysis also shows that the ring current ions experience significant isotropisation following substorm onset. Although previously attributed to enhanced EMIC wave activity, a consideration of different drivers of the isotropisation identifies that although EMIC wave activity plays a role, the properties of the injected and convected population is the dominant driver.</p><p>Finally, we explore the storm time variations of the ring current, revealing important information on the role of substorms in storm dynamics. A superposed epoch analysis of ring current energy content shows large enhancements particularly in the premidnight sector during the main phase, and a reduction in both local time asymmetry and intensity during the recovery phase. A comparison with estimated energy content using the Sym-H index was conducted. In agreement with previous results, the Sym-H index significantly overestimates energy content. A new finding is an observed temporal discrepancy, where estimates maximise ~ 12 hours earlier than the in-situ observations. We assert that an observed enhancement in substorm activity coincident with the Sym-H recovery is responsible. The results highlight the drawbacks of ring current indices and emphasise the impacts of substorms on the ring current population.</p>

On the ring current energy injection rate

1983 ◽  
Vol 31 (8) ◽  
pp. 901-911 ◽  
Author(s):  
L.C. Lee ◽  
G. Corrick ◽  
S.-I. Akasofu
Keyword(s):  
Ring Current ◽  
Injection Rate ◽  
Current Energy

scholarly journals The ring current: a short biography

2012 ◽  
Vol 3 (2) ◽  
pp. 131-142 ◽  
Author(s):  
A. Egeland ◽  
W. J. Burke
Keyword(s):  
Magnetic Field ◽  
Ring Current ◽  
Energy Content ◽  
Spectral Characteristics ◽  
Direct Access ◽  
Sufficient Evidence ◽  
Mass Spectrometers ◽  
Before And After ◽  
Magnetic Signatures ◽  
Collective Plasma

Abstract. The "ring current'' grows in the inner magnetosphere during magnetic storms and contributes significantly to characteristic perturbations to the Earth's field observed at low-latitudes. This paper outlines how understanding of the ring current evolved during the half-century intervals before and after humans gained direct access to space. Its existence was first postulated in 1910 by Carl Størmer to explain the locations and equatorward migrations of aurorae under stormtime conditions. In 1917 Adolf Schmidt applied Størmer's ring-current hypothesis to explain the observed negative perturbations in the Earth's magnetic field. More than another decade would pass before Sydney Chapman and Vicenzo Ferraro argued for its necessity to explain magnetic signatures observed during the main phases of storms. Both the Størmer and Chapman–Ferraro models had difficulties explaining how solar particles entered and propagated in the magnetosphere to form the ring current. During the early 1950s Hannes Alfvén correctly argued that the ring current was a collective plasma effect, but failed to explain particle entry. The discovery of a weak but persistent interplanetary magnetic field embedded in a continuous solar wind provided James Dungey with sufficient evidence to devise the magnetic merging-reconnection model now regarded as the basis for understanding magnetospheric and auroral activity. In the mid-1960s Louis Frank showed that ions in the newly discovered plasma sheet had the energy spectral characteristics needed to explain the ring current's origin. The introduction of ion mass spectrometers on space missions during the 1970s revealed that O+ ions from the ionosphere contribute large fractions of the ring current's energy content. Precisely how cold O+ ions in the ionosphere are accelerated to ring-current energies still challenges scientific understanding.

Gender differences in substrate utilization during submaximal exercise in endurance-trained subjects

2002 ◽  
Vol 282 (2) ◽  
pp. E435-E447 ◽  
Author(s):  
Carsten Roepstorff ◽  
Charlotte H. Steffensen ◽  
Marianne Madsen ◽  
Bente Stallknecht ◽  
Inge-Lis Kanstrup ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Energy Content ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Substrate Utilization ◽  
Peak Oxygen Uptake ◽  
Submaximal Exercise ◽  
Activity Level ◽  
Relative Contribution ◽  
History Of

Substrate utilization across the leg during 90 min of bicycle exercise at 58% of peak oxygen uptake (V˙o 2 peak) was studied in seven endurance-trained males and seven endurance-trained, eumenorrheic females by applying arteriovenous catheterization, stable isotopes, and muscle biopsies. The female and male groups were matched according toV˙o 2 peak per kilogram of lean body mass, physical activity level, and training history of the subjects. All subjects consumed the same diet, well controlled in terms of nutrient composition as well as energy content, for 8 days preceding the experiment, and all females were tested in the midfollicular phase of the menstrual cycle. During exercise, respiratory exchange ratio (RER) and leg respiratory quotient (RQ) were similar in females and males. Myocellular triacylglycerol (TG) degradation was negligible in males but amounted to 12.4 ± 3.2 mmol/kg dry wt in females and corresponded to 25.0 ± 6.0 and 5.0 ± 7.3% of total oxygen uptake in females and males, respectively ( P < 0.05). Utilization of plasma fatty acids (12.0 ± 2.5 and 9.6 ± 1.5%), blood glucose (13.6 ± 1.5 and 14.3 ± 1.5%), and glycogen (48.5 ± 4.9 and 42.8 ± 2.1%) were similar in females and males. Thus, in females, measured substrate oxidation accounted for 99% of the leg oxygen uptake, whereas in males 28% of leg oxygen uptake was unaccounted for in terms of measured oxidized lipid substrates. These findings may indicate that males utilized additional lipid sources, presumably very low density lipoprotein-TG or TG located between muscle fibers. On the basis of RER and leg RQ, it is concluded that no gender difference existed in the relative contribution from carbohydrate and lipids to the oxidative metabolism across the leg during submaximal exercise at the same relative workload. However, an effect of gender appears to occur in the utilization of the different lipid sources.

scholarly journals Ring Current Energy Input and Decay

2003 ◽  
Vol 109 (1-4) ◽  
pp. 105-131 ◽  
Author(s):  
Janet U. Kozyra ◽  
Michael W. Liemohn
Keyword(s):  
Energy Input ◽  
Ring Current ◽  
Current Energy

scholarly journals Energy Content in the Stormtime Ring Current

2001 ◽  
Author(s):  
N. E. Turner ◽  
D. N. Baker ◽  
T. L. Pulkkimen ◽  
J. L. Roeder ◽  
J. F. Funnell ◽  
...  
Keyword(s):  
Ring Current ◽  
Energy Content
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