AKR disappearance during magnetic storms

Morioka, A.; Miyoshi, Y.; Seki, Takeshi; Tsuchiya, F.; Misawa, Hiroaki; Oya, Hiroshi; Matsumoto, Hiroshi; Hashimoto, K.; Mukai, T.; Yumoto, K.; Nagatsuma, Tsutomu

doi:10.1029/2002ja009796

Cited by 13 publications

(17 citation statements)

References 27 publications

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“…A close relationship between AKR disappearances [ Morioka et al , 2003; Seki et al , 2005] and the electron density enhancements in and near the nightside auroral zone was demonstrated in the present study. In situ observations of the AKR source region above 3400 km altitude indicated that the electron densities in the AKR source region were of the order of 1 cm −3 or less [ Calvert , 1981; Perraut et al , 1990; Hilgers et al , 1991; Ergun et al , 1998].…”

Section: Discussionsupporting

confidence: 85%

Temporal variations and spatial extent of the electron density enhancements in the polar magnetosphere during geomagnetic storms

et al. 2010

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[1] In order to understand temporal variations and spatial distributions of plasma density enhancements in the polar magnetosphere during geomagnetic storms, nearly simultaneous observations of storm time electron densities in the polar magnetosphere by the Akebono satellite and ion upflows in the polar ionosphere by the DMSP satellites were investigated. Akebono observations show that the electron densities were highest (>100 cm −3 at ∼9000 km altitude) from the main to early recovery phases of geomagnetic storms. The regions of enhanced electron density were not localized but widely spread in the polar magnetosphere. Coordinated observations by the DMSP satellites detected ion upflows with large fluxes (∼10 10 /cm 2 /s) in and near the cusp, when the electron density enhancements were observed by the Akebono satellite. This result indicates that the storm time electron density enhancements are caused by cleft ion fountain mechanisms from the polar ionosphere. Very low-energy component (<13 eV) of the cleft ion fountain drifted deep into the polar cap, and increased the plasma densities in a wide region of the polar cap and auroral zone. A large amount of the very low-energy plasma may flow out through the polar magnetosphere during the main phase of geomagnetic storms.

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Section: Discussionsupporting

confidence: 85%

Temporal variations and spatial extent of the electron density enhancements in the polar magnetosphere during geomagnetic storms

et al. 2010

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“…Observing these amplitudes of squared wavelet coefficients, it can be concluded that the FACs are highly perturbed at high latitudes, where high‐frequency signals are dominant. This fact actually confirms the already known concept by Morioka et al []. They concluded that at higher latitudes high‐frequency signals play dominant role to characterize the penetration of charged particles and the energy injection phenomena, whereas at lower latitudes high‐frequency signal attenuates by coupling processes.…”

Section: Dwt Analysissupporting

confidence: 90%

Study of field‐aligned current (FAC), interplanetary electric field component (E_y), interplanetary magnetic field component (B_z), and northward (x) and eastward (y) components of geomagnetic field during supersubstorm

Adhikari¹,

Dahal

Chapagain

2017

Earth and Space Science

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A dominant process by which energy and momentum are transported from the magnetosphere to the ionosphere is known as field‐aligned current (FAC). It is enhanced during magnetic reconnection and explosive energy release at a substorm. In this paper, we studied FAC, interplanetary electric field component (Ey), interplanetary magnetic field component (Bz), and northward (x) and eastward (y) components of geomagnetic field during three events of supersubstorm occurred on 24 November 2001, 21 January 2005, and 24 August 2005. Large‐scale FAC, supposed to be produced during supersubstorm (SSS), has potentiality to cause blackout on Earth. We examined temporal variations of the x and y components of high‐latitude geomagnetic field during SSS, which is attributed to the FACs. We shall report the characteristics of high‐latitude northward and eastward components of geomagnetic field variation during the growth phase of SSS by the implementation of discrete wavelet transform (DWT) and cross‐correlation analysis. Among three examples of SSS events, the highest peak value of FAC was estimated to be ~19 μAm−2. This is shore up with the prediction made by Parks (1991) and Stasiewicz et al. (1998) that the FACs may vary from a few tens to several hundred μAm−2. Although this peak value of FACs for SSS event is much higher than the average FACs associated with regular substorms or magnetic storms, it is expedient and can be expect for SSS events which might be due to very high density solar wind plasma parcels (PPs) triggering the SSS events. In all events, during growth phase, the FAC increases to extremely high level and the geomagnetic northward component decreases to extremely low level. This represents a strong positive correlation between FAC and geomagnetic northward component. The DWT analysis accounts that the highest amplitude of the wavelet coefficients indicates singularities present in FAC during SSS event. But the amplitude of squared wavelet coefficient is found to be different from each other, which might be due to the solar wind PPs of different density triggering the SSS events. The cross‐correlation analysis suggests that the perturbation on geomagnetic northward component at high latitude during SSS strongly correlates with the fluctuation pattern of FAC density. Hence, the FAC is the primary sources for the eastward‐westward magnetic field perturbations at high latitude.

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“…This fact, actually, confirms the already known concepts that at higher latitudes the penetration of charged particles and the energy injection are characterized by phenomena that involve high-frequency signals; while at lower latitudes coupling processes do exist that attenuate high-frequency signals (Morioka et al 2003).…”

Section: Resultssupporting

confidence: 75%

Wavelet analysis applied to magnetograms: Singularity detections related to geomagnetic storms

Mendes

Domingues

Costa

et al. 2005

Journal of Atmospheric and Solar-Terrestrial Physics

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When the interplanetary magnetic field carried by the solar wind opposes to the Earth's intrinsic magnetic field, a substantial transfer of energy into the terrestrial magnetosphere takes place. If this condition persists for several hours, the magnetosphere becomes very disturbed. As a result at mid-to low latitudes a ring current starts to develop and at high latitudes ionospheric currents (electrojet and field-aligned currents) dominate. The ring current provides the geomagnetic conditions for magnetic storms to be settled down. Wavelet analysis is becoming a common tool since they allow the decomposition of data, functions or operators into different frequency or scale components. Accordingly, wavelet transforms seem to be good tools to "zoom in" short-lived high frequency phenomena such as discontinuities ("shocks") in signals and transient structures. In this work the remarkable ability of wavelets to highlight the singularities associated with discontinuities present in the horizontal component of the Earth magnetic field is explored. Magnetograms obtained at five magnetic stations for two geomagnetic storms have been analyzed by a Daubechies orthogonal wavelet transform decomposition. The wavelet coefficient magnitudes at three levels have been studied. In both cases, the physical discontinuities in the horizontal component of the geomagnetic field are clearly detected by means of these coefficients identifying the disturbed interval related to geomagnetic storms. Wavelet analysis has proved to be a useful tool in the identification of the geomagnetic storms just using non-processed data.

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AKR disappearance during magnetic storms

Cited by 13 publications

References 27 publications

Temporal variations and spatial extent of the electron density enhancements in the polar magnetosphere during geomagnetic storms

Temporal variations and spatial extent of the electron density enhancements in the polar magnetosphere during geomagnetic storms

Study of field‐aligned current (FAC), interplanetary electric field component (E_y), interplanetary magnetic field component (B_z), and northward (x) and eastward (y) components of geomagnetic field during supersubstorm

Wavelet analysis applied to magnetograms: Singularity detections related to geomagnetic storms

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AKR disappearance during magnetic storms

Cited by 13 publications

References 27 publications

Temporal variations and spatial extent of the electron density enhancements in the polar magnetosphere during geomagnetic storms

Temporal variations and spatial extent of the electron density enhancements in the polar magnetosphere during geomagnetic storms

Study of field‐aligned current (FAC), interplanetary electric field component (Ey), interplanetary magnetic field component (Bz), and northward (x) and eastward (y) components of geomagnetic field during supersubstorm

Wavelet analysis applied to magnetograms: Singularity detections related to geomagnetic storms

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Study of field‐aligned current (FAC), interplanetary electric field component (E_y), interplanetary magnetic field component (B_z), and northward (x) and eastward (y) components of geomagnetic field during supersubstorm