Statistical nature of geomagnetic storms

Yokoyama, Noboru; Kamide, Y.

doi:10.1029/97ja00903

Cited by 115 publications

(157 citation statements)

References 33 publications

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“…Their average duration is shorter than typically observed [Yokoyama and Kamide, 1997], primarily because numerical difficulties prevented us from modeling longer time periods with the RCM-E. With the test particle tracing code, we can calculate the contributions of different sources as a function of storm intensity. Figure 8a shows that the total plasma energy inside geosynchronous orbit and that contributed by bubbles are well correlated with Dst index.…”

Section: Results From 20 Idealized Stormsmentioning

confidence: 99%

On the contribution of plasma sheet bubbles to the storm time ring current

et al. 2015

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Particle injections occur frequently inside 10 Re during geomagnetic storms. They are commonly associated with bursty bulk flows or plasma sheet bubbles transported from the tail to the inner magnetosphere. Although observations and theoretical arguments have suggested that they may have an important role in storm time dynamics, this assertion has not been addressed quantitatively. In this paper, we investigate which process is dominant for the storm time ring current buildup: large‐scale enhanced convection or localized bubble injections. We use the Rice Convection Model‐Equilibrium (RCM‐E) to model a series of idealized storm main phases. The boundary conditions at 14–15 Re on the nightside are adjusted to randomly inject bubbles to a degree roughly consistent with observed statistical properties. A test particle tracing technique is then used to identify the source of the ring current plasma. We find that the contribution of plasma sheet bubbles to the ring current energy increases from ~20% for weak storms to ~50% for moderate storms and levels off at ~61% for intense storms, while the contribution of trapped particles decreases from ~60% for weak storms to ~30% for moderate and ~21% for intense storms. The contribution of nonbubble plasma sheet flux tubes remains ~20% on average regardless of the storm intensity. Consistent with previous RCM and RCM‐E simulations, our results show that the mechanisms for plasma sheet bubbles enhancing the ring current energy are (1) the deep penetration of bubbles and (2) the bulk plasma pushed ahead of bubbles. Both the bubbles and the plasma pushed ahead typically contain larger distribution functions than those in the inner magnetosphere at quiet times. An integrated effect of those individual bubble injections is the gradual enhancement of the storm time ring current. We also make two predictions testable against observations. First, fluctuations over a time scale of 5–20 min in the plasma distributions and electric field can be seen in the central ring current region for the storm main phase. We find that the plasma pressure and the electric field EY there vary over about 10%–30% and 50%–300% of the background values, respectively. Second, the maximum plasma pressure and magnetic field depression in the central ring current region during the main phase are well correlated with the Dst index.

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Section: Results From 20 Idealized Stormsmentioning

confidence: 99%

On the contribution of plasma sheet bubbles to the storm time ring current

et al. 2015

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“…Observational studies [e.g., Tsurutani et al, 1988; Yokoyama and Kamide, 1997; Kamide et al, 1998] show that especially intense magnetic storms (e.g., those during which Dst attains values < -toe nT) are often associated with two distinct intervals of large southward IMF Bz and with two distinct intervals of increasingly negative Dst indicating that a second ring-current enhance-fomia [e.g., Kamide et al, 1997], suggested that perhaps the ring current enhancement attained during the first stage of a double-dip storm provides a necessary seed population for the more intense ring current to be attained during the second enhancement. If so, then it seems that a double-dip storm would inherently attain a stronger ring current than a comparable single-dip storm.…”

Section: Introductionmentioning

confidence: 99%

Stormtime ring‐current formation: A comparison between single‐and double‐dip model storms with similar transport characteristics

Chen¹,

Lyons²,

Schulz³

2000

J. Geophys. Res.

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Abstract. Intense magnetic storms often develop in two stages such that a second ring current enhancement begins before the first ring current enhancement has recovered to the prestorm level. Since Dst traces of such storms exhibit two dips, we refer to these as double-dip storms. Here we compare double-and single-dip storms with similar convective and diffusive transport characteristics for effectiveness at forming the proton ring current. Our model storms consist of superposition of almost randomly occurring impulses in the convection electric field. We have synthesized a hypothetical double-dip storm consisting of a moderate 6-hour storm, followed by a 3-hour quiet interval and then by a more intense 15-hour storm, for a total duration of 24 hours. For comparison, we consider a single-dip model storm with an unmodulated 24-hour main phase during which the root-mean-square enhancement of the cross-tail potential drop is made equal to the timeweighted rms enhancement for the double-dip model storm. This leads to comparable timeaveraged diffusion coefficients for our single-and double-dip model storms. The mean enhancement of the cross-tail potential drop of the two storms are also comparable. When the stormtime proton plasma sheet distribution, the source of ring current protons, is left unchanged from its quiet (prestorm) level, we find little difference in proton energy content per unit R (which is geocentric distance normalized by RE) between our double-and single-dip model storms. The protonenergy content of the magnetosphere is roughly increased by a factor of 2.5 by either model storm under this scenario, in which the overall amount of stormtime transport, whether convective or diffusive, is nearly the same for the double-and single-dip model storms. As in our earlier work, we require here an enhanced stormtime plasma sheet population (in addition to enhanced particle transport) in order to achieve (for example) the 20-fold increase in IDstl characteristic of a large storm. Only when we invoke a two-stage stormtime enhancement of the boundary (plasma sheet) phase space density in combination with the two-stage enhancement in particle transport, our double-dip model storm does show a much larger total energy content than our single-dip model storm with a one-stage enhancement of the boundary spectrum. This suggests that plasma sheet preconditioning may be important for the development of especially intense storms.

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“…Figure 13 shows the results of a superposed epoch analyses by Yokoyama and Kamide (1997) and Kamide et al (1998b), for an examination of single storms and double storms. The top panel gives the AL index for single and double storm events.…”

Section: Multiple Magnetic Stormsmentioning

confidence: 99%

“…In that "classic" statistical study, they identified magnetic storms on the basis of the existence of SSCs, thus excluding the so-called gradual storms. In more recent studies, Taylor et al (1994), Loewe and Prölss (1997), and Yokoyama and Kamide (1997) have conducted statistical studies of geomagnetic storms in which Dst variations were compared with auroral electrojet activity, as well as with their interplanetary causes. These studies followed essentially the same approach as Sugiura and Chapman, where the variability in duration for different storms was obscured in their averaging process.…”

Section: Two-step Growth In the Ring Currentmentioning

confidence: 99%

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Space Storms and Space Weather Hazards

Daglis¹

2001

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Subject Terms Report Classification unclassified Classification of this page unclassified Classification of Abstract unclassified Limitation of Abstract UU Number of Pages 486REPORT DOCUMENTATION PAGE Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, -to review recent spacecraft measurements that have provided new insight into the dynamics and effects of space storms; -to review space weather hazards associated with space storms and pertinent to the operation of technological systems in space and on ground;-to discuss and assess methods of space weather forecasting, as well as national and international initiatives towards an efficient development of space climatology.Space weather, the invisible but nevertheless effective result of solar activity and solar-terrestrial coupling, has affected the operations of communication systems since the appearance of telegraph in the 19th century, though as an unknown trouble factor. Nowadays, the effects of space weather affect in various ways all communication modes, from cable to wireless to space-based systems. Moreover, space weather hazards include malfunction or even permanent damage of power distribution grids and of telecommunication, navigation and surveillance satellites, disturbances of over-the-horizon (OTH) radar, HF, VHF and UHF communications, surveying and navigation systems that use Global Positioning System (GPS) satellites, surveillance (optical and radar), and satellite tracking. Space weather influences on the Earth's weather and climate is still a developing topic. Little is known concerning the biological effects of space weather, especially regarding astronauts.This Institute could not be timelier. Space Weather, which has been defined as "conditions on the sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-and ground-based technological systems and can endanger human life", encompasses a broad range of phenomena impacting both space science and technology. The effects of Space Weather, while present throughout the solar cycle, gain particular prominence around the peak of the 11-year sunspot activity; the maximum of cycle 23 occurred in summer 2000.The fact that this ASI on Space Weather was held in Europe is particularly appropriate. European countries host a considerable repository of knowledge and world-class facilities in this field. Nevertheless, while Space Weather activities in c...

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Statistical nature of geomagnetic storms

Cited by 115 publications

References 33 publications

On the contribution of plasma sheet bubbles to the storm time ring current

On the contribution of plasma sheet bubbles to the storm time ring current

Stormtime ring‐current formation: A comparison between single‐and double‐dip model storms with similar transport characteristics

Space Storms and Space Weather Hazards

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