Alfvénicity-related Long Recovery Phases of Geomagnetic Storms: A Space Weather Perspective

Telloni, Daniele; D’Amicis, R.; Bruno, R.; Perrone, D.; Sorriso‐Valvo, L.; Raghav, Anil; Choraghe, Komal

doi:10.3847/1538-4357/ac071f

Cited by 18 publications

(14 citation statements)

References 56 publications

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“…High-intensity long-duration continuous AE activities (HILDCAAs) are the effects of Alfvén wave trains in the IMF (Tsurutani & Gonzalez 1987). Alfvénic fluctuations are associated with repetitive substorms (Lee et al 2006) and inferred to extend the recovery phase of geomagnetic storms (Tsurutani et al 2011;Raghav et al 2018;Telloni et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Geoeffectiveness of Interplanetary Alfvén Waves. I. Magnetopause Magnetic Reconnection and Directly Driven Substorms

Dai¹,

Han

Wang³

et al. 2023

ApJ

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In particular during the descending phase of the solar cycle, Alfvén waves in the high-speed solar wind streams are a major form of interplanetary disturbances. The fluctuating southward interplanetary magnetic field (IMF) of Alfvén waves has been suggested to induce geomagnetic activities through intermittent magnetic reconnection at the magnetopause. In this study, we provide in situ observational evidence for dayside magnetopause reconnection induced by such interplanetary Alfvén waves. Using multipoint conjunction observations, we show that the IMF B z from interplanetary Alfvén waves is transmitted through and amplified by the Earth’s bow shock. Associated with the intensified southward B z to the magnetopause, in situ signatures of magnetic reconnection are detected. Repetitively, interplanetary Alfvén waves transmit the intensified B z to the magnetosheath, leading to intervals of large magnetic shear angles across the magnetopause and magnetopause reconnection. Such intervals are promptly followed by hundreds of nanoTesla (nT) increases in the auroral electrojet indices (AE and AU) within 10–20 minutes. These observations are confirmed in multiple events in corotating interaction region-driven geomagnetic storms. To put the observations into context, we propose a phenomenological model of a strongly driven substorm. The substorm electrojet is linked to the enhanced magnetopause reconnection in the short timescale of re-establishing the ionosphere electric field and the two-cell convection. These results provide insights on the temporal patterns of solar wind magnetosphere–ionosphere coupling, especially during the descending phase of the solar cycle.

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Section: Introductionmentioning

confidence: 99%

Geoeffectiveness of Interplanetary Alfvén Waves. I. Magnetopause Magnetic Reconnection and Directly Driven Substorms

Dai¹,

Han

Wang³

et al. 2023

ApJ

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“…This can be of importance for certain phenomena in the heliosphere, particularly in situ ations where high cross-helicity winds interact with low cross-helicity plasmas, such as the magnetosphere. Recently, a causal link has been found between the longer duration of the recovery phase of geomagnetic storms and the arrival of solar wind streams with large cross helicity after the solar drivers of the storms (Telloni et al 2021). The need for more time for the cross-helicity cascade to fully develop in the magnetosphere could be related to the longer period needed by the magnetosphere to recover its properties prior to the arrival of the solar driver.…”

Section: Discussionmentioning

confidence: 99%

Quantification of the Cross-helicity Turbulent Cascade in Compressible MHD Simulations

Montagud-Camps

Hellinger

Verdini

et al. 2022

ApJ

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In plasma turbulence, energy and cross helicity are transferred across scales at a constant rate as a consequence of nonlinear interactions. In incompressible magnetohydrodynamics (MHD), the energy cascade rate of both quantities can be computed by means of the temporal evolution of second-order structure functions, known as Karman–Howarth–Monin (KHM) equations. In the present work, we derive the KHM equation to compute the energy cascade rate of cross helicity in compressible MHD. Using three-dimensional direct numerical simulations, we validate the equation and use it to measure the cross-helicity turbulence properties. Our results show a slower development of the cross-helicity cascade with respect to the energy one and the presence of inverse cascades of energy and cross helicity at large scales when in the presence of a strong mean field. We propose the relation of these phenomena with the longer duration of geomagnetic storms after the arrival of solar winds with large cross helicity and the observation of patchy inertial ranges displaying positive and negative cascade rates for certain solar wind intervals.

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“…Repetitive substorms are reported to occur every ∼1-4 hr, associated with northward turnings of the Alfvénic IMF (Lee et al 2006). Continuous Alfvén waves are inferred to extend the recovery phase of geomagnetic storms (Tsurutani et al 2011;Raghav et al 2018;Telloni et al 2021).…”

Section: Introductionmentioning

confidence: 98%

Geoeffectiveness of Interplanetary Alfvén Waves. II. Spectral Characteristics and Geomagnetic Responses

Han

Dai²,

Yao

et al. 2023

ApJ

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Using multipoint observations over 10 yr near 1 au, we investigate the spectra (5 minutes to 2 hr) of interplanetary Alfvén waves and the responses in the geomagnetic activities. We compute the two-point correlations of the wave magnetic field between the ACE and the THEMIS spacecraft, which are separated by ∼200 Earth radius (R E) in the solar wind. Alfvén waves associated with high two-point correlations exhibit steep spectra (spectra index ∼−1.63). Such Alfvén waves occur mostly in slow-speed streams. By contrast, Alfvén waves with low two-point correlations exhibit flatter spectra (spectra index ∼−1.51) with a relative enhancement of power above 2 × 10−4 Hz. The occurrence of Alfvén waves with low two-point correlations is more equally distributed between high-speed and low-speed streams. In general, interplanetary Alfvén waves show correlations with moderate geomagnetic responses in symmetric ring-current intensity, SuperMAG electrojet (SME), and Kp indices. Statistical analyses indicate that the Alfvén waves with flat spectra correspond to stronger responses in the geomagnetic indices than those with steep spectra, suggesting the importance of the tens of minutes (30–90 minutes) Alfvénic power spectra in the generation of SME/Auroral Electrojets. These observations may shed light on the response of the magnetosphere to fluctuating interplanetary magnetic field B z .

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Alfvénicity-related Long Recovery Phases of Geomagnetic Storms: A Space Weather Perspective

Cited by 18 publications

References 56 publications

Geoeffectiveness of Interplanetary Alfvén Waves. I. Magnetopause Magnetic Reconnection and Directly Driven Substorms

Geoeffectiveness of Interplanetary Alfvén Waves. I. Magnetopause Magnetic Reconnection and Directly Driven Substorms

Quantification of the Cross-helicity Turbulent Cascade in Compressible MHD Simulations

Geoeffectiveness of Interplanetary Alfvén Waves. II. Spectral Characteristics and Geomagnetic Responses

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