The Joined-up Magnetosphere

Lockwood, Mike

doi:10.3389/fspas.2022.856188

Cited by 3 publications

(5 citation statements)

References 25 publications

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“…The findings obtained by the application of information-theoretic approaches to the geomagnetic activity indices could be possibly exploited in subsequent work by space weather experts and space physics modellers. These findings may be utilized in order to improve forecast schemes and models of the coupled solar wind-magnetosphere-ionosphere system in terms of including information on the preconditioning of the system by the existing state of the magnetosphere [53,54].…”

Section: Discussionmentioning

confidence: 99%

Investigation of Dynamical Complexity in Swarm-Derived Geomagnetic Activity Indices Using Information Theory

et al. 2023

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In 2023, the ESA’s Swarm constellation mission celebrates 10 years in orbit, offering one of the best ever surveys of the topside ionosphere. Among its achievements, it has been recently demonstrated that Swarm data can be used to derive space-based geomagnetic activity indices, similar to the standard ground-based geomagnetic indices monitoring magnetic storm and magnetospheric substorm activity. Recently, many novel concepts originating in time series analysis based on information theory have been developed, partly motivated by specific research questions linked to various domains of geosciences, including space physics. Here, we apply information theory approaches (i.e., Hurst exponent and a variety of entropy measures) to analyze the Swarm-derived magnetic indices from 2015, a year that included three out of the four most intense magnetic storm events of the previous solar cycle, including the strongest storm of solar cycle 24. We show the applicability of information theory to study the dynamical complexity of the upper atmosphere, through highlighting the temporal transition from the quiet-time to the storm-time magnetosphere, which may prove significant for space weather studies. Our results suggest that the spaceborne indices have the capacity to capture the same dynamics and behaviors, with regards to their informational content, as traditionally used ground-based ones.

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Section: Discussionmentioning

confidence: 99%

Investigation of Dynamical Complexity in Swarm-Derived Geomagnetic Activity Indices Using Information Theory

et al. 2023

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“…The effect is modest, the SD of Δθ increasing by about 1% per 1R E increase in R XY , but nevertheless present. On the other hand, Lockwood (2022b) shows that the distributions of correlations (for 1-min, 10-min and 1-h averages) between an L1 coupling functions and auroral activity indices were only degraded at R XY exceeding about 80R E . Together, these results indicate that there is very likely to be an effect of spatial averaging in the correlations between L1 craft and terrestrial space weather activity.…”

Section: The Non-equilibrium Nature Of the Magnetospherementioning

confidence: 93%

“…This condition left 65,133 usable hourly mean Φ PC values, about one third of the total obtained over 25 years. Despite not being a continuous record and despite the fact that it is only of hourly time resolution, these data are included in the present study because magnetic flux transport (i.e., voltage) is known to be a key and fundamental part of the coupling of solar wind mass, momentum and energy into the magnetosphere and Lockwood and McWilliams (2021b) and Lockwood (2022b) have shown it has a significantly different behavior to geomagnetic indices.…”

Section: Data Employedmentioning

confidence: 99%

“…factor B′ = B ⊥ sin 4 (θ/2) that is designed to be a monotonic, unipolar indicator of solar wind coupling (Lockwood and McWilliams, 2021b;Lockwood, 2022b) that peaks when the southward component is strongest. Panels D, F and H show the lagged response of magnetospheric state indicators Φ PC , SMR and SML for which the peak in average disturbance associated with the southward turning is at (t−t o ) of 1.5, 6.9 and 2.0 h, respectively.…”

Section: The Non-equilibrium Nature Of the Magnetospherementioning

confidence: 99%

“…Here we are making a somewhat different point. Because the magnetosphere is rarely, if ever, in a steady-state equilibrium, some part or all of it is always responding to prior variations in the solar wind (Lockwood, 2022b) which means the ECPC concept will always have some relevance. We here investigate this idea in relation to the observed effects of solar wind dynamic pressure on transpolar voltage and geomagnetic activity.…”

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confidence: 99%

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Magnetosphere-Ionosphere Coupling: Implications of Non-Equilibrium Conditions

Lockwood

Cowley

2022

Front. Astron. Space Sci.

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The response times of the coupled magnetosphere-ionosphere-thermosphere system are, on average, greater than the autocorrelation timescales of solar wind forcing. This means that the system is rarely, if ever, in equilibrium. Departures from equilibrium are a key component of the Expanding-Contracting Polar Cap (ECPC) model of convection excitation in both the magnetosphere and ionosphere, driven by the Dungey reconnection cycle of opening and re-closing magnetospheric field lines. Averaging over sufficiently long timescales reduces data to the equivalent of steady-state conditions, which hides the physical mechanisms involved and allows us to map electric fields from interplanetary space to the ionosphere–but this is not valid, either physically or generally, because of magnetic induction effects. Only for transient phenomena on sufficiently short timescales do the mechanisms associated with non-equilibrium fully manifest themselves. Nevertheless, because of both ever-changing solar wind conditions and Earth’s dipole tilt, eccentricity and rotation, the magnetosphere is always tending towards a perpetually-evolving equilibrium configuration and there are important implications of transient events for understanding the general behavior of the coupled magnetosphere-ionosphere-thermosphere system and its response to solar wind forcing. We here discuss one example: as a consequence of the importance of departures from equilibrium inherent in the ECPC model, the solar wind dynamic pressure PSW influences the magnetosphere-ionosphere convection response to the generation of open field lines by reconnection in the dayside subsolar magnetopause. We here demonstrate this effect in a statistical survey of observations and show that it is as predicted by the ECPC model and that, through it, PSW has an influence on flux transport in the magnetosphere-ionosphere system.

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Wavelet determination of magnetohydrodynamic-range power spectral exponents in solar wind turbulence seen by Parker Solar Probe

Wang,

Chapman,

Dendy

et al. 2023

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Context. The high Reynolds number solar wind flow provides a natural laboratory for the study of turbulence in situ. Parker Solar Probe samples the solar wind between 0.17 AU and 1 AU, providing an opportunity to study how turbulence evolves in the expanding solar wind. Aims. We aim to obtain estimates of the scaling exponents and scale breaks of the power spectra of magnetohydrodynamic (MHD) turbulence at sufficient precision to discriminate between Kolmogorov and Iroshnikov-Kraichnan (IK) turbulence, both within each spectrum and across multiple samples at different distances from the Sun and at different plasma β. Methods. We identified multiple long-duration intervals of uniform solar wind turbulence, sampled by PSP/FIELDS and selected to exclude coherent structures, such as pressure pulses and current sheets, and in which the primary proton population velocity varies by less than 20% of its mean value. The local value of the plasma β for these datasets spans the range 0.14 < β < 4. All selected events span spectral scales from the approximately ‘1/f’ range at low frequencies, through the MHD inertial range (IR) of turbulence, and into the kinetic range, below the ion gyrofrequency. We estimated the power spectral density (PSD) using a discrete Haar wavelet decomposition, which provides accurate estimates of the IR exponents. Results. Within 0.3 AU of the Sun, the IR exhibits two distinct ranges of scaling. The inner, high-frequency range has an exponent consistent with that of IK turbulence within uncertainties. The outer, low-frequency range is shallower, with exponents in the range from –1.44 to –1.23. Between 0.3 and 0.5 AU, the IR exponents are closer to, but steeper than, that of IK turbulence and do not coincide with the value –3/2 within uncertainties. At distances beyond 0.5 AU from the Sun, the exponents are close to, but mostly steeper than, that of Kolmogorov turbulence, –5/3: uncertainties inherent in the observed exponents exclude the value –5/3. Between these groups of spectra we find examples, at 0.26 AU and 0.61 AU, of two distinct ranges of scaling within the IR with an inner, high-frequency range with exponents ∼ − 1.4, and a low-frequency range with exponents close to the Kolmogorov value of –5/3. Conclusions. Since the PSD-estimated scaling exponents are a central predictor in turbulence theories, these results provide new insights into our understanding of the evolution of turbulence in the solar wind.

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The Joined-up Magnetosphere

Abstract: Systems science is a relatively new way of studying the magnetosphere. This perspective outlines the need for it and how it can contribute to our understanding and so give more reliable forecasts, predictions, and space weather climatologies.

Cited by 3 publications

References 25 publications

Investigation of Dynamical Complexity in Swarm-Derived Geomagnetic Activity Indices Using Information Theory

Investigation of Dynamical Complexity in Swarm-Derived Geomagnetic Activity Indices Using Information Theory

Magnetosphere-Ionosphere Coupling: Implications of Non-Equilibrium Conditions

Wavelet determination of magnetohydrodynamic-range power spectral exponents in solar wind turbulence seen by Parker Solar Probe

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