How are storm time injections different from nonstorm time injections?

Dy, Lee; Hwang, Ja Young; Es, Lee; Min, Kyoung‐Wook; Han, W.; Nam, UW

doi:10.1016/j.jastp.2004.07.034

Cited by 5 publications

(5 citation statements)

References 10 publications

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“…The substorm injection usually occurs in the energy range from a few tens of keV (typically ~50 keV) up to a few hundreds of keV (rarely 300–400 keV, depending on particle species, level of the geomagnetic state, and substorm intensity, etc.) [e.g., Reeves , ; Lee et al ., , and references therein]. The energy range that the convection covers also depends on its intensity, but that of a normal intensity usually brings earthward the particles of a much lower energy than the lower cutoff energy for the substorm injection.…”

Section: Summary and Discussionmentioning

confidence: 99%

Long‐term loss and re‐formation of the outer radiation belt

et al. 2013

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[1] The Earth's outer radiation belt is known to vary often and significantly on various time scales. In this study, we have used the data of various instruments onboard the THEMIS spacecraft to study long-term changes of the outer radiation belt electrons around the year 2009. We find that the entire outer belt became extremely weak for nearly a year and was practically lost a few times, each time lasting~20 days up to~2 months, before eventually re-forming. This was revealed at a wide energy range from several tens of keV to up to 719 keV, which was covered by the THEMIS spacecraft measurements. The loss of the outer belt was associated with extremely weak solar wind conditions, i.e., low interplanetary magnetic field magnitude and slow solar wind speed. In particular, this set greatly reduced magnetospheric convection and/or injections for a prolonged time interval, which led to a large expansion of the plasmasphere, even beyond geosynchronous altitude and thus invading the majority of the typical outer belt territory for the same prolonged time interval. Consequently, preexisting electrons inside the plasmasphere had enough time to be lost into the atmosphere gradually over a time scale of several days without being supplied with fresh electrons from the plasma sheet under the same reduced convection and/or injections. Plasmaspheric hiss waves with an amplitude of up to a few tens of pT persisted to exist during the gradual decay periods, implying that they are likely responsible for the continual loss of the electrons inside the plasmasphere. A complete re-formation of the outer belt to full intensity was then realized over an interval of a few months. During the re-formation process, the magnetospheric convection and/or injections increased, which led to a gradual increase of whistler chorus wave activity, contraction of the plasmasphere, and supply of the plasma sheet electrons at high L shells. This set first an outward increasing profile of the phase space density, which eventually developed into a profile with a peak at low L of~5 over a time scale of 1-2 days. In this latter stage, a local acceleration at low L shells is found to be clearly needed although the radial diffusion process can contribute to some extent, in particular, for particles with a low first adiabatic invariant value.

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Section: Summary and Discussionmentioning

confidence: 99%

Long‐term loss and re‐formation of the outer radiation belt

et al. 2013

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“…Birn et al [2000] found that electrons are mainly accelerated by both betatron and Fermi acceleration mechanisms, while ions behave nonadiabatically and get accelerated by the cross-tail electric field based on test particle orbit computations. Lee et al [2004] reported that the average flux enhancement of ion injections tends to be bigger at higher-energy channels than at lower-energy channels, whereas electron injections exhibit the opposite tendency as can be seen in the energy-spectral dependence of flux enhancements. They argued that different spatial distributions of the source populations can be a possible reason responsible for the difference in the flux enhancement between protons and electrons.…”

Section: Discussionmentioning

confidence: 94%

Spectral characteristics of the plasma dispersionless injection during the storm recovery phase on 11 March 1998

He¹,

Chen²,

Liu³

et al. 2012

J. Geophys. Res.

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[1] A substorm dispersionless injection event observed during the storm recovery phase on 11 March 1998 at geosynchronous orbit is carefully studied. The event shows the notable characteristics that for energetic ions the flux enhancement ratio before and after injection increases and remains elevated with increasing energy, while for energetic electrons it tends to decrease with increasing energy. In order to explain the unique injection feature, the authors propose a possible mechanism that velocity space diffusion in common to electric acceleration adjusts the particle injection state. Spectral characteristics of four different phases (pregrowth phase, the growth phase, the substorm expansion phase, and the recovery phase) have been investigated. The differential fluxes of electrons from 50 keV to 1.5 Mev and ions from 50 keV to 1.2 MeV measured by Synchronous Orbit Plasma Analyzer (SOPA) instrument onboard LANL satellite 1991-080 are found to be best fitted with the three-parameter kappa distribution function) by Levenberg-Marquardt and Universal Global Optimization methods. The evolutions of the three parameters in the above kappa distribution in different substorm phases have been depicted for both electrons and ions. In each phase, E 0 and k show an approximately linear relationship k(E 0 ) = k 0 + hE 0 . This linear relationship can be obtained by solving the velocity space diffusion equation with an initial superthermal kappa distribution. Ion and electron are found to have opposite trend of parameters k 0 and h in each phase, which indicates that the different species of particles exert different velocity space diffusion processes so that their flux enhancement ratios before and after injection are rather different. This implies that not only electric field acceleration, but also velocity space diffusion plays a very important role in the particle injection.

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“…Second, the energy dependence of substorm injection has been studied by Lee et al . [] for geosynchronous particle injections, showing that the amount of electron flux enhancement of dispersionless injection decreases with energy: the flux enhancement is largest at a few tens of keV and becomes smaller toward hundreds of keV. This should contribute to larger variance of the lower energy fluxes, making a prediction harder.…”

Section: Model Results and Interpretationmentioning

confidence: 99%

Artificial neural network prediction model for geosynchronous electron fluxes: Dependence on satellite position and particle energy

et al. 2016

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Geosynchronous satellites are often exposed to energetic electrons, the flux of which varies often to a large extent. Since the electrons can cause irreparable damage to the satellites, efforts to develop electron flux prediction models have long been made until recently. In this study, we adopt a neural network scheme to construct a prediction model for the geosynchronous electron flux in a wide energy range (40 keV to >2 MeV) and at a high time resolution (as based on 5 min resolution data). As the model inputs, we take the solar wind variables, geomagnetic indices, and geosynchronous electron fluxes themselves. We also take into account the magnetic local time (MLT) dependence of the geosynchronous electron fluxes. We use the electron data from two geosynchronous satellites, GOES 13 and 15, and apply the same neural network scheme separately to each of the GOES satellite data. We focus on the dependence of prediction capability on satellite's magnetic latitude and MLT as well as particle energy. Our model prediction works less efficiently for magnetic latitudes more away from the equator (thus for GOES 13 than for GOES 15) and for MLTs nearer to midnight than noon. The magnetic latitude dependence is most significant for an intermediate energy range (a few hundreds of keV), and the MLT dependence is largest for the lowest energy (40 keV). We interpret this based on degree of variance in the electron fluxes, which depends on magnetic latitude and MLT at geosynchronous orbit as well as particle energy. We demonstrate how substorms affect the flux variance. 10.1002/2015SW001359Key Points:• Developed model for geosynchronous electrons in a wide energy range and at high time resolution • Prediction efficiency depends on satellite's latitude and MLT and electron energy • The dependence is largely related to substorm effects on electron flux variance (2016), Artificial neural network prediction model for geosynchronous electron fluxes: Dependence on satellite position and particle energy, Space Weather, 14, 313-321,

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How are storm time injections different from nonstorm time injections?

Cited by 5 publications

References 10 publications

Long‐term loss and re‐formation of the outer radiation belt

Long‐term loss and re‐formation of the outer radiation belt

Spectral characteristics of the plasma dispersionless injection during the storm recovery phase on 11 March 1998

Artificial neural network prediction model for geosynchronous electron fluxes: Dependence on satellite position and particle energy

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