Enhancement of optical aurora triggered by the solar wind negative pressure impulse (SI<sup>−</sup>)

Sato, Natsuo; Murata, Y.; Yamagishi, Hisakazu; Yukimatu, A. S.; Kikuchi, Masayuki; Watanabe, Masakazu; Makita, Kazuo; Yang, Huigen; Liu, Ruiyuan; Rich, F. J.

doi:10.1029/2000gl003742

Cited by 24 publications

(28 citation statements)

References 13 publications

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“…The observation of auroral disturbances during sudden expansion of the magnetosphere is not uncommon. For example, Sato et al [2001] associate an optical auroral enhancement with a negative solar wind pressure impulse. Their results showed field line resonance, which resulted in upward and downward field‐aligned currents.…”

Section: Discussionmentioning

confidence: 99%

HF radar observation of field‐aligned currents associated with quiet time transient flow bursts in the magnetosphere

Munsami¹,

Pinnock

Rodger

2002

Journal of Geophysical Research: Space Physics

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.[1] The present study reveals the ionospheric signature of low level near-Earth flow burst activity in the central plasma sheet during a relatively quiet magnetosphere. Flow bursts were observed by Geotail in the near-Earth plasma sheet at (X = À17 R E , Y = À6 R E ) GSM , between 0300 and 0400 UT on 9 March 1997. Simultaneous observations of the solar wind conditions by the Wind satellite located 235 R E upstream, and of the southern auroral ionosphere, by the Sanae-Halley Super Dual Auroral Radar Network (SuperDARN) HF radar pair, offered a unique opportunity to investigate both the solar wind trigger and the related auroral ionospheric signature of these flow bursts. Although the prevailing solar wind conditions conformed to that expected for a quiescent magnetosphere, the solar wind dynamic pressure showed stepwise decreases, which gave rise to a near instantaneous observation of tailward flow bursts. Also, peak values in the local potential variation associated with the ionospheric convection during the quiet solar wind conditions exceeded 10 kV and therefore are not associated with viscous processes. We believe that the drop in solar wind pressure may have allowed the magnetosphere to relax into a lower metastable energy configuration. The associated reconfiguration of the magnetotail allows for the release or redistribution of stored magnetic energy, via magnetic reconnection, with the consequent observation of tailward flow bursts. The observations of earthward flow bursts, however, are thought to be a natural bimodal response of the magnetosphere to solar wind variations. Concurrent with these flow bursts in the magnetotail, we observed the development of convection vortices near the conjugate midnight auroral ionosphere, which are consistent with the flow of field-aligned currents. The spatial structure and the temporal locale of the convection vortices are suggestive of a small substorm current wedge.

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Section: Discussionmentioning

confidence: 99%

HF radar observation of field‐aligned currents associated with quiet time transient flow bursts in the magnetosphere

Munsami¹,

Pinnock

Rodger

2002

Journal of Geophysical Research: Space Physics

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“…Liou et al (2006) investigated 13 sudden decreases of the dynamic pressure from Polar Ultraviolet Imager (UVI) and found that globally both the auroral luminosity as well as the average energy of precipitating electrons decrease as a response. They noted that the result is not in contradiction with Sato et al (2001) as in some cases local brightenings did occur also in the global UVI pictures. Liou et al (2006) speculated that the decrease of the global luminosity may be explained by an adiabatic expansion and reduction of the mirror ratio of the precipitating electrons, while possibly induction electric fields and Fermi acceleration effects would be the cause of the decreasing energy of the loss cone electrons.…”

Section: Introductionmentioning

confidence: 86%

“…Lukianova (2003) and Stauning and Troshichev (2008) found that for negative pressure steps the temporal evolution of the polar cap index (PCI) is consistent with transient convection vortices that divert ChapmanFerraro currents from the magnetopause to the polar cap ionosphere. In a case study, Sato et al (2001) found that the local auroral brightness as measured by an all-sky-camera can increase after a negative pressure impulse. Liou et al (2006) investigated 13 sudden decreases of the dynamic pressure from Polar Ultraviolet Imager (UVI) and found that globally both the auroral luminosity as well as the average energy of precipitating electrons decrease as a response.…”

Section: Introductionmentioning

confidence: 99%

On the response of ionospheric electrojets to solar wind discontinuities

et al. 2009

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Abstract. We investigate the ionospheric response to solar wind discontinuities as detected by the IE index computed from IMAGE ground magnetometers. The solar wind discontinuities include both sudden increases as well as decreases of the solar wind dynamic pressure, recorded by the SWEPAM instrument of the ACE spacecraft during the period 1998-2004. In our statistical study, we identify four categories of events: 1) sudden increases of the dynamic pressure with a simultaneous increase of the interplanetary magnetic field (IMF) magnitude; 2) sudden increases of the dynamic pressure accompanied with a simultaneous decrease of the IMF; 3) sudden decreases of the dynamic pressure accompanied with a sudden increase of the IMF; and 4) sudden decreases of the dynamic pressure with relatively steady IMF. We perform a superposed epoch analysis for the four event categories to distinguish the ionospheric response. We find that the IE index increases/decreases in response to the solar wind dynamic pressure increases/decreases regardless of the simultaneous change in the IMF or the amount of estimated input energy. We investigate the magnitude of the ionospheric response according to the IMF north-south direction, the dynamic pressure step size as well as the pressure level prior the dynamic pressure change. We find that the ionospheric result is augmented for larger pressure steps, while the prior IMF has a role only in some of the event categories. We also perform global MHD simulation runs to investigate the ionospheric dissipation rate during such solar wind discontinuities, and find that the simulation results are in good qualitative accordance with the observational statistical results.

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“…The effect of negative impulses should not be ignored. For example, Sato et al [16] firstly studied the responses of aurora activities to negative impulses and found that aurora activities enhanced dramatically during the presence of the negative impulse. They proposed that FLRs were excited by the negative impulses; the electrons were accelerated by the upstream field aligned current associated with the FLRs in the polar region, causing the intensification of the aurora activities.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of magnetospheric ULF waves excited by positive and negative impulses of solar wind dynamic pressure

Zhang

Zong

Yang

et al. 2009

Sci. China Ser. E-Technol. Sci.

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The sources of ultra low frequency (ULF) waves in the magnetosphere are generally believed to be either the external solar wind perturbations or the internal plasma instabilities. When a sudden impulse of the solar wind dynamic pressure impinges on the magnetopause, ULF waves might be excited and thus the solar wind energy is transported into the earth's magnetosphere. In this paper, we study the ULF waves excited by different kinds of sudden solar wind pressure impulses through an MHD simulation. We primarily focus on the responses of the earth's magnetosphere to positive/negative impulses of solar wind dynamic pressure, and positive-negative impulse pairs. The simulation results show that the ULF waves excited by positive and negative impulse have the same amplitude and frequency, with 180° difference in phase, if the amplitude and durations of the input impulses are the same. In addition, it is found that field line resonances (FLRs) occur at certain L-shell regions of the earth's magnetosphere after the impact of different positive-negative impulse pairs, which appear to be related to the duration of the impulses and the time interval between the sequential impulses. Another result is that the energy from the solar wind could be transported deeper into the inner magnetosphere by an impulse pair than by a single pulse impact. The results presented in this paper could help us to better understand how energy is transported from solar wind to the earth's magnetosphere via ULF waves. Also, these results provide some new clues to understanding of how energetic particles in the inner magnetosphere response to different kinds of solar wind pressure impulse impacts including interplanetary shocks.positive and negative impulses of solar wind dynamic pressure, ULF waves, field line resonances (FLRs)

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Enhancement of optical aurora triggered by the solar wind negative pressure impulse (SI⁻)

Cited by 24 publications

References 13 publications

HF radar observation of field‐aligned currents associated with quiet time transient flow bursts in the magnetosphere

HF radar observation of field‐aligned currents associated with quiet time transient flow bursts in the magnetosphere

On the response of ionospheric electrojets to solar wind discontinuities

Numerical simulation of magnetospheric ULF waves excited by positive and negative impulses of solar wind dynamic pressure

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Enhancement of optical aurora triggered by the solar wind negative pressure impulse (SI−)

Cited by 24 publications

References 13 publications

HF radar observation of field‐aligned currents associated with quiet time transient flow bursts in the magnetosphere

HF radar observation of field‐aligned currents associated with quiet time transient flow bursts in the magnetosphere

On the response of ionospheric electrojets to solar wind discontinuities

Numerical simulation of magnetospheric ULF waves excited by positive and negative impulses of solar wind dynamic pressure

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Enhancement of optical aurora triggered by the solar wind negative pressure impulse (SI⁻)