Timescale separation in the solar wind‐magnetosphere coupling during St. Patrick's Day storms in 2013 and 2015

Abstract

In this work, we present a case study of the relevant timescales responsible for coupling between the changes of the solar wind and interplanetary magnetic field (IMF) conditions and the magnetospheric dynamics during the St. Patrick's Day Geomagnetic Storms in 2013 and 2015. We investigate the behavior of the interplanetary magnetic field (IMF) component Bz, the Perreault‐Akasofu coupling function and the AE, AL, AU, SYM‐H, and ASY‐H geomagnetic indices at different timescales by using the empirical mode decomposition (EMD) method and the delayed mutual information (DMI). The EMD, indeed, allows to extract the intrinsic oscillations (modes) present into the different data sets, while the DMI, which provides a measure of the total amount of the linear and nonlinear shared information (correlation degree), allows to investigate the relevance of the different timescales in the solar wind‐magnetosphere coupling. The results clearly indicate the existence of a relevant timescale separation in the solar wind‐magnetosphere coupling. Indeed, while fluctuations at long timescales (τ > 200 min) show a large degree of correlation between solar wind parameters and magnetospheric dynamics proxies, at short timescales (τ < 200 min) this direct link is missing. This result suggests that fluctuations at timescales lower than 200 min, although triggered by changes of the interplanetary conditions, are mainly dominated by internal processes and are not directly driven by solar wind/IMF. Conversely, the magnetospheric dynamics in response to the solar wind/IMF driver at timescales longer than 200 min resembles the changes observed in the solar wind/IMF features. Finally, these results can be useful for Space Weather forecasting.

Revisiting Ionosphere‐Thermosphere Responses to Solar Wind Driving in Superstorms of November 2003 and 2004

“…In the magnetospheric dynamics, both directly solar wind‐driven processes and internal processes originated from the magnetotail can occur at the timescales of ≤1–3 h (Alberti et al, ; Consolini & de Michelis, ; Kamide & Kokubun, ). Moreover, Alberti et al () in their study of two strong storms found a larger degree of correlation between the solar wind parameters and magnetospheric indices at long timescales (>200 min) as compared to shorter timescales. A separate study is needed to understand how these findings affect the magnetosphere‐IT coupling.…”

Recurrence‐Based Quantification of Dynamical Complexity in the Earth's Magnetosphere at Geospace Storm Timescales

“…Moreover, Balasis et al (2006Balasis et al ( , 2018 demonstrated the existence of two different regimes in the magnetospheric dynamics associated with the prestorm activity and magnetic storms, respectively, a picture that is compatible with the occurrence of a phase transition. Another intense point of research is the inherent separation of timescales between internal and externally driven/triggered processes (e.g., Alberti et al, 2017;Consolini & De Michelis, 2005;Kamide & Kokobun, 1996;Tsurutani et al, 1990). Low-dimensional dynamics, self-organized criticality (Consolini, 1997;Chapman et al, 1998;Uritsky & Pudovkin, 1998;Uritsky et al, 2006) and phase transitions offer different perspectives on geomagnetic activity, all of which need to be taken into account to obtain a coherent global picture of the underlying dynamical processes.…”

Ionospheric Response to the St. Patrick's Day Space Weather Events in March 2012, 2013, and 2015 at Southern Low and Middle Latitudes

“…The interplanetary parameters and solar wind conditions associated with the 17–18 March 2015 storm have been presented by several researchers (e.g., Alberti et al, ; Guerrero et al, ; Marubashi et al, ; Verkhoglyadova et al, ; Wu et al, ). The IMF B Z variation during 16–19 March 2015 (Figure c) shows two southward turnings of IMF B Z with the second one strong (< −15 nT) and of longer duration (>10 hr).…”

“…The interplanetary parameters and solar wind conditions associated with the 17-18 March 2015 storm have been presented by several researchers (e.g., Alberti et al, 2017;Guerrero et al, 2017;Marubashi et al, 2016;Verkhoglyadova et al, 2016;Wu et al, 2016). (1) There occurred an intense storm on 15 July 2012 that developed in two steps with the first step (main phase onset) commencing at about 06:40 UT and giving a minimum Dst index of −128 nT at~09 UT on 15 July.…”