Effects from dayside magnetosphere to distant tail unleashed by a bifurcated, non-reconnecting interplanetary current sheet

Abstract

Global magnetospheric effects resulting from the passage at Earth of large-scale structures have been well studied. The effects of common and short-term features, such as discontinuities and current sheets (CSs), have not been studied in the same depth. Herein we show how a seemingly unremarkable interplanetary feature can cause widespread effects in the magnetosheath-magnetosphere system. The feature was observed by Advanced Composition Explorer inside an interplanetary coronal mass ejection on 10 January 2004. It contained 1) a magnetic field dip bounded by directional discontinuities in field and flows, occurring together with 2) a density peak in what we identify as a bifurcated, non-reconnecting current sheet. Data from an array of spacecraft in key regions of the magnetosheath/magnetosphere (Geotail, Cluster, Polar, and Defense Meteorological Satellite Program) provide context for Wind’s observations of flapping of the distant (R ∼ −226 RE) magnetotail. In particular, just before the flapping began, Wind observed a hot and tenuous plasma in a magnetic field structure with enhanced field strength, with the By and Bz components rotating in a fast tailward flow burst. Closer inspection reveals a large flux rope (plasmoid) containing lobe plasma in a tail strongly deflected and twisted by interplanetary non-radial flows and magnetic field By. We try to identify the origin of this ‘precursor to flapping’ by looking at data from the various spacecraft. Working back towards the dayside, we discover a chain of effects which we argue were set in motion by the interplanetary CS and its interaction with the bow shock. These effects include 1) a compression and dilation of the magnetosphere, 2) a local deformation of the postnoon magnetopause, and, 3) at the poleward edge of the oval in an otherwise quiet polar cap flow, a strong (3 km/s) sunward flow burst in a double vortex-like structure flanked by two sets of field-aligned currents. Clearly, an intertwined set of phenomena was occurring at the same time. We learn that multi-spacecraft analysis can give us great insight into the magnetospheric response to transient changes in the solar wind.

Multispacecraft Observations of the Simultaneous Occurrence of Magnetic Reconnection at High and Low Latitudes During the Passage of a Solar Wind Rotational Discontinuity Embedded in the April 9‐11, 2015 ICME

“…There are significantly fewer studies of the geoffectiveness of the solar wind DD than those of CMEs and CIRs. Farrugia et al (2022) observed the formation of complicated structures in the magnetotail and nightside ionosphere as a DD passes by the magnetosphere.…”

“…Farrugia et al. (2022) observed the formation of complicated structures in the magnetotail and nightside ionosphere as a DD passes by the magnetosphere.…”

“…Recently, Farrugia et al. (2022) studied the effect of a solar wind DD as it passes by the magnetosphere. The DD is embedded inside a ∼1‐day interplanetary coronal mass ejection (ICME) on 2004 January 10.…”

Comparing Information Theory Analysis With Cross‐Correlation and Minimum Variance Analysis of the Solar Wind Structures

“…Thus, SW is not a smooth, homogeneous flow, but consists of expanding flux tubes (Borovsky, 2008), IMF discontinuities and fluctuations (e.g., possibly different wavelength Alfvén and compressional waves) (Nykyri et al., 2019), 2‐D and slab turbulence (Adhikari et al., 2022), and advected SW plasma and magnetic field structures (Di Matteo et al., 2022; Viall & Borovsky, 2020; Viall et al., 2009). Recent studies showed that solar wind directional discontinuities can introduce significant perturbations to the magnetosphere and ionosphere even as the geomagnetic activities remain quiet (Farrugia et al., 2022; Wing et al., 2023).…”