Evidence of Multiple Reconnection Lines at the Magnetopause from Cusp Observations

Recent global hybrid simulations investigated the formation of flux transfer events (FTEs) and their convection and interaction with the cusp. Based on these simulations, we have analyzed several Polar cusp crossings in the Northern Hemisphere to search for the signature of such FTEs in the energy distribution of downward precipitating ions: precipitating ion beams at different energies parallel to the ambient magnetic field and overlapping in time. Overlapping ion distributions in the cusp are usually attributed to a combination of variable ion acceleration during the magnetopause crossing together with the time-of-flight effect from the entry point to the observing satellite. Most "step up" ion cusp structures (steps in the ion energy dispersions) only overlap for the populations with large pitch angles and not for the parallel streaming populations. Such cusp structures are the signatures predicted by the pulsed reconnection model, where the reconnection rate at the magnetopause decreased to zero, physically separating convecting flux tubes and their parallel streaming ions. However, several Polar cusp events discussed in this study also show an energy overlap for parallel-streaming precipitating ions. This condition might be caused by reopening an already reconnected field line, forming a magnetic island (flux rope) at the magnetopause similar to that reported in global MHD and Hybrid simulation

PRIME: a probabilistic neural network approach to solar wind propagation from L1

Introduction: For the last several decades, continuous monitoring of the solar wind has been carried out by spacecraft at the first Earth-Sun Lagrange point (L1). Due to computational expense or model limitations, those data often must be propagated to some point closer to the Earth in order to be usable by those studying the interaction between Earth’s magnetosphere and the solar wind. The current most widely used tool to propagate measurements from L1 (roughly 235 RE upstream) to Earth is the planar propagation method, which includes a number of known limitations. Motivated by these limitations, this study introduces a new algorithm called the Probabilistic Regressor for Input to the Magnetosphere Estimation (PRIME).Methods: PRIME is based on a novel probabilistic recurrent neural network architecture, and is capable of incorporating solar wind time history from L1 monitors to generate predictions of near-Earth solar wind as well as estimate uncertainties for those predictions.Results: A statistical validation shows PRIME’s predictions better match MMS magnetic field and plasma measurements just upstream of the bow shock than measurements from Wind propagated to MMS with a minimum variance analysis-based planar propagation technique. PRIME’s continuous rank probability score (CRPS) is 0.214σ on average across all parameters, compared to the minimum variance algorithm’s CRPS of 0.350σ. PRIME’s performance improvement over minimum variance is dramatic in plasma parameters, with an improvement in CRPS from 2.155 cm−3 to 0.850 cm−3 in number density and 16.15 km/s to 9.226 km/s in flow velocity VX GSE.Discussion: Case studies of particularly difficult to predict or extreme conditions are presented to illustrate the benefits and limitations of PRIME. PRIME’s uncertainties are shown to provide reasonably reliable predictions of the probability of particular solar wind conditions occurring.Conclusion: PRIME offers a simple solution to common limitations of solar wind propagation algorithms by generating accurate predictions of the solar wind at Earth with physically meaningful uncertainties attached

Comparison Between Vortices Created and Evolving During Fixed and Dynamic Solar Wind Conditions

We employ Magnetohydrodynamic (MHD) simulations to examine the creation and evolution of plasma vortices within the Earth's magnetosphere for steady solar wind plasma conditions. Very few vortices form during intervals of such solar wind conditions. Those that do remain in fixed positions for long periods (often hours) and exhibit rotation axes that point primarily in the x or y direction, parallel (or antiparallel) to the local magnetospheric magnetic field direction. Occasionally, the orientation of the axes rotates from the x direction to another direction. We compare our results with simulations previously done for unsteady solar wind conditions. By contrast, these vortices that form during intervals of varying solar wind conditions exhibit durations ranging from seconds (in the case of those with axes in the x or y direction) to minutes (in the case of those with axes in the z direction) and convect antisunward. The local-time dependent sense of rotation seen in these previously reported vortices suggests an interpretation in terms of the Kelvin-Helmholtz instability. For steady conditions, the biggest vortices developed on the dayside (about 6R(E) in diameter), had their rotation axes aligned with the y direction and had the longest periods of duration. We attribute these vortices to the flows set up by reconnection on the high latitude magnetopause during intervals of northward Interplanetary Magnetic Field (IMF) orientation. This is the first time that vortices due to high-latitude reconnection have been visualized. The model also successfully predicts the principal characteristics of previously reported plasma vortices within the magnetosphere, namely their dimension, flow velocities, and durations

Seven Sisters: a mission to study fundamental plasma physical processes in the solar wind and a pathfinder to advance space weather prediction

This paper summarizes the Seven Sisters solar wind mission concept and the outstanding science questions motivating the mission science objectives. The Seven Sisters mission includes seven individual spacecraft designed to uncover fundamental physical processes in the solar wind and provides up to ≈ 2 days of advanced space weather warnings for 550 Earth days during the mission. The mission will collect critical measurements of the thermal and suprathermal plasma and magnetic fields, utilizing, for the first time, Venus–Sun Lagrange points. The multi-spacecraft configuration makes it possible to distinguish between spatial and temporal changes, define gradients, and quantify cross-scale transport in solar wind structures. Seven Sisters will determine the 3-D structure of the solar wind and its transient phenomena and their evolution in the inner heliosphere. Data from the Seven Sisters mission will allow the identification of physical processes and the quantification of the relative contribution of different mechanisms responsible for suprathermal particle energization in the solar wind

On the need for International Solar Terrestrial Program Next (ISTPNext)

AGS-1845151 - National science foundation; national science foundationhttps://hal.science/hal-04289274/documentPublished versio