Are high-intensity long-duration continuous AE activity (HILDCAA) events substorm expansion events?

Tsurutani, B. T.; González, W. D.; Guarnieri, F. L.; Kamide, Y.; Zhou, X.; Arballo, J. K.

doi:10.1016/j.jastp.2003.08.015

Cited by 113 publications

(115 citation statements)

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“…The ASY-H index (Sugiura and Chapman, 1960) is a proxy for auroral-related activity and describes the partial ring current asymmetry during geomagnetically disturbed conditions. (Tsurutani and Gonzalez, 1987) with maximum values at the leading/peak edges of HSSs (or at CIRs) (Tsurutani et al, 2004a). In the MGA interval of 2009 we observe maximum AE values decrease to ∼800 to 1200 (especially around DOY 100 to 170).…”

Section: Discussionmentioning

confidence: 75%

“…It was shown that AE increases in HILDCAAs and substorms are poorly correlated (Tsurutani et al, 2004a(Tsurutani et al, , 2006c, and can transfer large amounts of energy to the auroral region , thus efficiently starting the DD. Low and equatorial ionosphere studies performed during HSS intervals have shown complex longitudinal dependence of DD electric fields Sobral et al, 2006;de Siqueira et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

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Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

et al. 2013

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We study solar wind–ionosphere coupling through the late declining phase/solar minimum and geomagnetic minimum phases during the last solar cycle (SC23) – 2008 and 2009. This interval was characterized by sequences of high-speed solar wind streams (HSSs). The concomitant geomagnetic response was moderate geomagnetic storms and high-intensity, long-duration continuous auroral activity (HILDCAA) events. The JPL Global Ionospheric Map (GIM) software and the GPS total electron content (TEC) database were used to calculate the vertical TEC (VTEC) and estimate daily averaged values in separate latitude and local time ranges. Our results show distinct low- and mid-latitude VTEC responses to HSSs during this interval, with the low-latitude daytime daily averaged values increasing by up to 33 TECU (annual average of ~20 TECU) near local noon (12:00 to 14:00 LT) in 2008. In 2009 during the minimum geomagnetic activity (MGA) interval, the response to HSSs was a maximum of ~30 TECU increases with a slightly lower average value than in 2008. There was a weak nighttime ionospheric response to the HSSs. A well-studied solar cycle declining phase interval, 10–22 October 2003, was analyzed for comparative purposes, with daytime low-latitude VTEC peak values of up to ~58 TECU (event average of ~55 TECU). The ionospheric VTEC changes during 2008–2009 were similar but ~60% less intense on average. There is an evidence of correlations of filtered daily averaged VTEC data with Ap index and solar wind speed. We use the infrared NO and CO2 emission data obtained with SABER on TIMED as a proxy for the radiation balance of the thermosphere. It is shown that infrared emissions increase during HSS events possibly due to increased energy input into the auroral region associated with HILDCAAs. The 2008–2009 HSS intervals were ~85% less intense than the 2003 early declining phase event, with annual averages of daily infrared NO emission power of ~ 3.3 × 1010 W and 2.7 × 1010 W in 2008 and 2009, respectively. The roles of disturbance dynamos caused by high-latitude winds (due to particle precipitation and Joule heating in the auroral zones) and of prompt penetrating electric fields (PPEFs) in the solar wind–ionosphere coupling during these intervals are discussed. A correlation between geoeffective interplanetary electric field components and HSS intervals is shown. Both PPEF and disturbance dynamo mechanisms could play important roles in solar wind–ionosphere coupling during prolonged (up to days) external driving within HILDCAA intervals

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

et al. 2013

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“…Several studies regarding this topic have been published and some also show the low-latitude responses (Tsurutani et al, 2004bSobral et al, 2006;Koga et al, 2011). Tsurutani and Gonzalez (1987) proposed some empirical definitions in order to establish the HILDCAA occurrence: (a) AE index must reach peaks greater than or equal to 1000 nT sometime during the event, (b) the event must have a duration of at least 2 days, (c) AE never drops below 200 nT for more than 2 h at a time, and (d) the auroral activity occurs outside the main phase of magnetic storms.…”

Section: P M De Siqueira Negreti Et Al: Total Electron Content Resmentioning

confidence: 99%

“…Tsurutani and Gonzalez (1987) proposed some empirical definitions in order to establish the HILDCAA occurrence: (a) AE index must reach peaks greater than or equal to 1000 nT sometime during the event, (b) the event must have a duration of at least 2 days, (c) AE never drops below 200 nT for more than 2 h at a time, and (d) the auroral activity occurs outside the main phase of magnetic storms. Tsurutani et al (2004b) argued that the original criteria set for HILDCAA events was arbitrary and extreme criteria were also imposed to illustrate the phenomena. They state that HILDCAAs may occur even if one or more of these criteria are not followed.…”

Section: P M De Siqueira Negreti Et Al: Total Electron Content Resmentioning

confidence: 99%

“…HILDCAAs are caused by corotating high-speed solar streams (HSSs) emanating from coronal holes which are more frequent during the declining phase of the solar cycle (Tsurutani et al, 1995). Additionally, the interaction between HSSs and slower-speed streams (near the ecliptic plane) is responsible for creating regions of intense magnetic field called "corotating interaction regions" or CIRs (Tsurutani et al, 2004b, and references therein). The impingement of CIRs at the magnetosphere can cause CIR-induced geomagnetic storms of weak to moderate intensity, which are followed by HILDCAAs periods (days to weeks) when elevated levels of the ring current are observed (Dst).…”

Section: P M De Siqueira Negreti Et Al: Total Electron Content Resmentioning

confidence: 99%

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Total electron content responses to HILDCAAs and geomagnetic storms over South America

2017

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Abstract. Total electron content (TEC) is extensively used to monitor the ionospheric behavior under geomagnetically quiet and disturbed conditions. This subject is of greatest importance for space weather applications. Under disturbed conditions the two main sources of electric fields, which are responsible for changes in the plasma drifts and for current perturbations, are the short-lived prompt penetration electric fields (PPEFs) and the longer-lasting ionospheric disturbance dynamo (DD) electric fields. Both mechanisms modulate the TEC around the globe and the equatorial ionization anomaly (EIA) at low latitudes. In this work we computed vertical absolute TEC over the low latitude of South America. The analysis was performed considering HILDCAA (high-intensity, long-duration, continuous auroral electrojet (AE) activity) events and geomagnetic storms. The characteristics of stormtime TEC and HILDCAA-associated TEC will be presented and discussed. For both case studies presented in this work (March and August 2013) the HILDCAA event follows a geomagnetic storm, and then a global scenario of geomagnetic disturbances will be discussed. Solar wind parameters, geomagnetic indices, O / N 2 ratios retrieved by GUVI instrument onboard the TIMED satellite and TEC observations will be analyzed and discussed. Data from the RBMC/IBGE (Brazil) and IGS GNSS networks were used to calculate TEC over South America. We show that a HILDCAA event may generate larger TEC differences compared to the TEC observed during the main phase of the precedent geomagnetic storm; thus, a HILDCAA event may be more effective for ionospheric response in comparison to moderate geomagnetic storms, considering the seasonal conditions. During the August HILDCAA event, TEC enhancements from ∼ 25 to 80 % (compared to quiet time) were observed. These enhancements are much higher than the quiet-time variability observed in the ionosphere. We show that ionosphere is quite sensitive to solar wind forcing and considering the events studied here, this was the most important source of ionospheric responses. Furthermore, the most important source of TEC changes were the long-lasting PPEFs observed on August 2013, during the HILDCAA event. The importance of this study relies on the peculiarity of the region analyzed characterized by high declination angle and ionospheric gradients which are responsible for creating a complex response during disturbed periods.

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An MHD simulation study of the dynamics of the 8–9 March 2008 CIR‐/HSS‐driven geomagnetic storm

2014

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We have carried out a global magnetohydrodynamic (MHD) simulation of a geomagnetic storm initiated by a corotating interaction region followed by a high-speed solar wind (HSS) stream that occurred on 8-9 March 2008. The event began with the arrival of a corotating interaction region (CIR) at~0720 UT on 8 March. The stream interface arrived at Earth at~1830 UT on 8 March, and the arrival of a second density enhancement (a second CIR) at~0140 UT on 9 March resulted in the main phase of the storm, with a peak Dst of À97 nT at 0600 UT on 9 March. Our MHD simulation of the event, spanning the interval of 0400 UT on 8 March to 0800 UT on 9 March, shows that the arrival of the first CIR changes the configuration of the magnetotail, and that after a strong substorm at~1230 UT on 8 March, the tail evolves into a churning state in which the magnetic topology and flow structure of the magnetotail are never steady. In addition, we find that increases in ring current energy density show a nearly one-to-one correspondence to periods of V x B z > 0 (southward interplanetary magnetic field (IMF)). More importantly, we find that the ring current energy density in the MHD simulation shows a nearly linear response to increases in solar wind dynamic pressure, but only for the northward IMF intervals during the initial phase of the event, from 0400 UT to 1800 UT on 8 March. IntroductionThe largest disturbances affecting the Earth's magnetosphere-ionosphere system are geomagnetic storms, primarily driven by the strong coupling of the interplanetary magnetic field (IMF) to the magnetospheric field. Storms can be caused either by a coronal mass ejection (CME), an immense expanding mass of plasma that erupts from the Sun and evolves into an interplanetary CME (ICME), or a corotating interaction region (CIR) forming at the leading edge of a high-speed stream (HSS) of plasma originating at coronal holes [Tsurutani et al., 1995]. The dynamic pressure sunward of an interplanetary shock suddenly compresses the Earth's magnetosphere. At the Earth's surface, this can be detected as a sudden impulse (SI+) or an increase in the horizontal component of the Earth's magnetic field. If southward interplanetary magnetic fields are present at or behind the shock (in either the sheath or the ICME proper), they will cause a magnetic storm through the process of magnetic reconnection with the Earth's magnetopause fields [Dungey, 1961]. If there are no southward IMFs, there will not be a magnetic storm. Joselyn and Tsurutani [1990] suggest that the shock compression be called an SI+, and the terms "SSC" and "initial phase" be dropped from usage. The storm onset will then be defined as the start of the storm main phase. CIR/HSS and CME events include complex combinations of pressure pulses and strong northward or southward magnetic fields. Corotating interaction regions form when solar wind streams with different velocities align in the radial direction. Density pileup occurs when a high-speed stream of the solar wind, emanating from polar coronal...

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Are high-intensity long-duration continuous AE activity (HILDCAA) events substorm expansion events?

Cited by 113 publications

References 20 publications

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

Total electron content responses to HILDCAAs and geomagnetic storms over South America

An MHD simulation study of the dynamics of the 8–9 March 2008 CIR‐/HSS‐driven geomagnetic storm

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