scholarly journals Another way of deriving the ring current decay time during disturbed periods

1995 ◽  
Vol 38 (2) ◽  
Author(s):  
M. M. Zossi de Artigas ◽  
J. R. Manzano
Keyword(s):  
Ring Current ◽  
Coupling Parameter ◽  
Life Time ◽  
Recovery Phase ◽  
Main Phase ◽  
Physical Analysis ◽  
Inner Magnetosphere ◽  
Current Decay ◽  
The Many ◽  
Energy Dissipated

Coupling parameter, E, and the total energy dissipated by the magnetosphere, UT, are determined for six disturbed periods, following three known criteria for UT computation. It is observed that UT exceeds E for Dst < -90 nT, for alI models. Differences between models reside on the estimated valnes for the particles' life time il1 the equatorial ring current. The values of TR, used in the models, are small during the main phase of the di."turbance, in disagreement with the charge exchange life time of the majority species, H+ and O'-. Based on this conclusion, a different criterion to calculate TR is proposed, differentiating the different stages of the perturbation. TR is calculated, for the main phase of the storm, from the rate of energy deposition estimation, Q, in the ring current. For Dst recovery phase, the vallles are obtained from a ring current decay law computation. The UTvu calculated, physically more coherent with the processes occurring during the event, is now smaller than expected. In this sense, it is understood that the power generated by the solar wind-magnetosphere dy- namo, should also be distributed in the inner magnetosphere, auroral zones and equatorial ring current, as in the outer magnetosphere, plasmoids in the tail shot in antisolar direction. A further adjustment of E, with the Chapman-Ferraro distance, 10' variable, has been made. Although the reslllts, improve the estimation of E, they are sti!l smaller than UT, except UTNU, for some disturbed periods. This result indicates the uncertainty in the computation of the input energy, by using the many expressions proposed in the literature, which are always presented as laws proportional to a given group of parameters, with an unknown factor of proportionality, which deserves more detailed physical analysis.

MLT Dependence of Contribution of Charge Exchange Loss to the Storm Time Ring Current Decay: Van Allen Probes Observations

2020 ◽  
Author(s):  
Songyan Li ◽  
Hao Luo
Keyword(s):  
Charge Exchange ◽  
Ring Current ◽  
Radial Distance ◽  
Recovery Phase ◽  
Local Times ◽  
Loss Mechanism ◽  
Exchange Effect ◽  
Current Decay ◽  
Van Allen Probes ◽  
Level 3

&lt;p&gt;Much evidence has indicated that charge exchange with the neutral atoms is an important loss mechanism of the ring current ions, especially during the slow recovery phase of a geomagnetic storm. Most of the studies, however, were focused on the global effect of the charge exchange on the ring current decay. The effect on different magnetic local times and L shells has not been achieved. In this study, based on the in-situ energetic ion data (Level 3) from RBSPICE onboard two Van Allen Probes, we study the contribution of the charge exchange, calculated from the differential flux of ions, to the local ring current decay at different magnetic local times and radial distance. Results indicate that the charge exchange effect on the ring current decay shows clear MLT and L dependence. Our study provides important information of spatial distribution of the ring current loss evolution, which could be as a reference during the ring current modeling.&lt;/p&gt;

scholarly journals Are our ideas about <i>Dst</i> correct?

1999 ◽  
Vol 17 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A. Grafe
Keyword(s):  
Geomagnetic Field ◽  
Ring Current ◽  
Recovery Phase ◽  
Main Phase ◽  
Local Times ◽  
Moderate Intensity ◽  
Start Time ◽  
Low Latitude ◽  
Magnetospheric Configuration And Dynamics ◽  
Phase Asymmetry

Abstract. The idea of two separate storm time ring currents, a symmetric and an asymmetric one has accepted since the 1960s. The existence of a symmetric equatorial ring current was concluded from Dst. However, the asymmetric development of the low-latitude geomagnetic disturbance field during storms lead to the assumption of the real existence of an asymmetric ring current. I think it is time to inquire whether this conception is correct. Thus, I have investigated the development of the low-latitude geomagnetic field during all the magnetic local times under disturbed and quiet conditions. The storm on February 6–9, 1986 and a statistical analysis of many storms has shown that the asymmetry does not vanish during the storm recovery phase. The ratio between the recovery phase asymmetry and the main phase asymmetry is low only for powerful storms. Storms of moderate intensity show the opposite. The global picture of the field evolution of the February storm shows clear differences at different local times. For instance the main phase and recovery phase start time does not coincide with Dst. Also the ring current decay is not the same at different local times. Therefore, Dst gives an incorrect picture of the field development. Moreover, asymmetry does not disappear during international quiet days as the investigation of the low-latitude geomagnetic field shows. Considering all these observations, I think we must revise our ideas about the ring current. In my opinion only one ring current exists and this is an asymmetric one. This asymmetry increases during storms and develops rather fast to more or less symmetric conditions. However, in no case is it justified to conclude from Dst that a symmetric ring current exists.Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; storms and substorms)

Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm

1994 ◽  
Vol 12 (7) ◽  
pp. 602-611 ◽  
Author(s):  
Y. I. Feldstein ◽  
A. E. Levitin ◽  
S. A. Golyshev ◽  
L. A. Dremukhina ◽  
U. B. Vestchezerova ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Ring Current ◽  
Recovery Phase ◽  
Main Phase ◽  
Storm Main Phase ◽  
Low Latitudes ◽  
Solar Wind Parameters ◽  
Magnetic Field Variations ◽  
Current Magnetic Field

Abstract. The relationship between the auroral electrojet indices (AE) and the ring current magnetic field (DR) was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'). To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE') which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence) of saturation for minimum (maximum) AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY) was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF Bz variations than the symmetric ring current. ASY increases (decreases) faster during the main phase (the recovery phase) than DR. The magnetic field decay at low latitudes in the recovery phase occurs faster in the afternoon sector than at dusk.

scholarly journals Radial diffusion modeling with empirical lifetimes: comparison with CRRES observations

2005 ◽  
Vol 23 (4) ◽  
pp. 1467-1471 ◽  
Author(s):  
Y. Y. Shprits ◽  
R. M. Thorne ◽  
G. D. Reeves ◽  
R. Friedel
Keyword(s):  
Diffusion Model ◽  
Radiation Effects ◽  
Outer Zone ◽  
Recovery Phase ◽  
Decay Rates ◽  
Radial Diffusion ◽  
Main Phase ◽  
Relativistic Electrons ◽  
Storm Main Phase ◽  
Order Of Magnitude

Abstract. A time dependent radial diffusion model is used to quantify the competing effects of inward radial diffusion and losses on the distribution of the outer zone relativistic electrons. The rate of radial diffusion is parameterized by Kp with the loss time as an adjustable parameter. Comparison with HEEF data taken over 500 Combined Release and Radiation Effects Satellite (CRRES) orbits indicates that 1-MeV electron lifetimes near the peak of the outer zone are less than a day during the storm main phase and few days under less disturbed conditions. These values are comparable to independent estimates of the storm time loss rate due to scattering by EMIC waves and chorus emission, and also provide an acceptable representation of electron decay rates following the storm time injection. Although our radial diffusion model, with data derived lifetimes, is able to simulate many features of the variability of outer zone fluxes and predicts fluxes within one order of magnitude accuracy for most of the storms and L values, it fails to reproduce the magnitude of flux changes and the gradual build up of fluxes observed during the recovery phase of many storms. To address these differences future modeling should include an additional local acceleration source and also attempt to simulate the pronounced loss of electrons during the main phase of certain storms.

scholarly journals The ionospheric storm studies: further development of the mapping technique

1996 ◽  
Vol 39 (4) ◽  
Author(s):  
I. Kutiev ◽  
T. Samardjiev ◽  
P. A. Bradley ◽  
M. I. Dick ◽  
L. R. Cander
Keyword(s):  
Magnetic Storm ◽  
Recovery Phase ◽  
Main Phase ◽  
Mapping Technique ◽  
Ionospheric Storm ◽  
Further Development

The technique of using instantaneous maps for ionospheric storm studies is further developed. Integral parameters are introduced characterizing the main features of each map. These parameters are the net volumes of ?f0F2, ?M(3000)F2and their gradients. The magnetic storm 1-2 March, 1982 was considered and it was found that before the storm commencement and in recovery phase the Net Gradient (NG) is directed steadily to the East, while in the main phase it turns southward. NG shows where the changes of the F-layer come from. The net volume of ?f0F2 (NF) correlates well with Dst and AE indices.

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