Charge exchange lifetimes for ring current ions

Smith, Paul H.; Bewtra, N. K.

doi:10.1007/bf00239804

Cited by 112 publications

(95 citation statements)

References 26 publications

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“…In the particular case of the January 2005 ring current event, the analysis of which is discussed in section 3.3, in situ ion measurements made by the RAPID particle spectrometer aboard CLUSTER [Wilken et al, 1997] [Smith and Bewtra, 1987] in the center of Channel 2 (NUADU data).…”

Section: B6 Mixed Ion Populationmentioning

confidence: 99%

Moderate geomagnetic storm (21–22 January 2005) triggered by an outstanding coronal mass ejection viewed via energetic neutral atoms

McKenna‐Lawlor

Dandouras

et al. 2010

J. Geophys. Res.

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was accompanied by a coronal mass ejection which arrived at the magnetopause at ∼1712 UT, 21 January, and produced a strong compression-pressure pulse. Enhanced magnetospheric activity was stimulated. The associated development between <1800 UT and >02.19 UT on 21-22 January, 2005 of a ring current disturbance in energetic neutral atom (ENA) data, recorded aboard both the Double Star and the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) spacecraft, is described. A magnetic storm from ∼1712 UT, 21 January, reached minimum Dst = ∼−101 nT at ∼0600 UT, 22 January, and its recovery phase endured until 27 January. ENA data indicate that the ring current experienced a deep injection of H + and O + ions at ∼1830 UT when IMF Bz was oriented southward. At this time, the ring current was strongly asymmetric, although later it became more symmetric. Bz turned northward at 1946 UT. From ∼0224 to ∼0612 UT on 22 January, Bz fluctuated such that it intermittently pointed southward (±10 nT). The moderate but extended response of the geomagnetosphere to the strong pressure pulse is explained by a slow evolution in the orientation of Bz under conditions of enhanced plasma sheet density. Modeling of dynamical parameters that represent various current systems that contributed to Dst revealed their individual characteristics. The changing geomagnetic field was also modeled. Comparisons with ENA data show that early asymmetric enhancements recorded in hydrogen and oxygen were accompanied by intensified external current systems that produced a magnetic field related compression of the magnetosphere. The gradual reduction in ring current asymmetry was complemented by the largely symmetrical configuration displayed by the corresponding, still intensified, modeled magnetic field.

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Section: B6 Mixed Ion Populationmentioning

confidence: 99%

Moderate geomagnetic storm (21–22 January 2005) triggered by an outstanding coronal mass ejection viewed via energetic neutral atoms

McKenna‐Lawlor

Dandouras

et al. 2010

J. Geophys. Res.

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“…which includes the effect of corotation (V• = 90 kV), the quiescent Volland-Stern [Volland, 1973;Stern, 1974Stern, , 1975 , where 0(t) is the unit step function (--1 for t > 0; --0 for t < 0), is a superposition of almost randomly occurring impulses that rise sharply and decay exponentially with a "lifetime" •r = 20 min. The potential drop A Vl associated with any impulse is chosen randomly from a Gaussian distribution with a 25% standard deviation.…”

Section: Simulation Modelmentioning

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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“…The percent remaining is shown as a function of energy for the two models and for three di erent pitch angles. We have used the charge exchange cross sections given by Smith and Bewtra (1978) with the neutral hydrogen geocorona model of Rairden et al (1986). H + and O + results at L = 5.75 are shown, and H + only at L = 4.25.…”

Section: Modelingmentioning

confidence: 99%

Testing electric field models using ring current ion energy spectra from the Equator-S ion composition (ESIC) instrument

et al. 1999

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Abstract. During the main and early recovery phase of a geomagnetic storm on February 18, 1998, the Equator-S ion composition instrument (ESIC) observed spectral features which typically represent the di erences in loss along the drift path in the energy range (5±15 keV/e) where the drift changes from being E´B dominated to being gradient and curvature drift dominated. We compare the expected energy spectra modeled using a Volland-Stern electric ®eld and a Weimer electric ®eld, assuming charge exchange along the drift path, with the observed energy spectra for H + and O + . We ®nd that using the Weimer electric ®eld gives much better agreement with the spectral features, and with the observed losses. Neither model, however, accurately predicts the energies of the observed minima.

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Charge exchange lifetimes for ring current ions

Cited by 112 publications

References 26 publications

Moderate geomagnetic storm (21–22 January 2005) triggered by an outstanding coronal mass ejection viewed via energetic neutral atoms

Moderate geomagnetic storm (21–22 January 2005) triggered by an outstanding coronal mass ejection viewed via energetic neutral atoms

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

Testing electric field models using ring current ion energy spectra from the Equator-S ion composition (ESIC) instrument

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