By coupling a solar surface flux transport model with an extrapolation of the heliospheric field, we simulate the evolution of the Sun's open magnetic flux and the heliospheric current sheet (HCS) based on observational data of sunspot groups since 1976. The results are consistent with measurements of the interplanetary magnetic field near Earth and with the tilt angle of the HCS as derived from extrapolation of the observed solar surface field. This opens the possibility for an improved reconstruction of the Sun's open flux and the HCS into the past on the basis of empirical sunspot data.
Coronal Mass Ejection and Heliospheric Current Sheet Interaction Causing a Long-Duration Magnetic Field Sector Transition
Institute of Physics, University of Graz（格拉茨大学物理研究所）；Department of Physics, University of Helsinki（赫尔辛基大学物理系）；Department of Physics and Astronomy, University of Turku（图尔库大学物理与天文学系）；Hvar Observatory, Faculty of Geodesy, University of Zagreb（萨格勒布大学大地测量学院赫瓦尔天文台）
The effects of the heliospheric current sheet (HCS) on the evolution of Alfvénic turbulence in the solar wind are studied using MHD simulations incorporating the expanding-box-model (EBM). The simulations show that near the HCS, the Alfvénicity of the turbulence decreases as manifested by lower normalized cross helicity and larger excess of magnetic energy. The numerical results are supported by a superposed-epoch analysis using OMNI data, which shows that the normalized cross helicity decreases inside the plasma sheet surrounding HCS, and the excess of magnetic energy is significantly enhance…
There are many difficulties associated with forecasting high-energy solar particle events at Earth. One issue is understanding why some large solar eruptive events trigger ground level enhancement (GLE) events and others do not. In this work we perform 3D test particle simulations of a set of historic GLEs to understand more about what causes these powerful events. Particular focus is given to studying how the heliospheric current sheet (HCS) affects high-energy proton transport through the heliosphere following an event. Analysis of $\geq$M7.0 flares between 1976$-$2020 shows that active regi…
Context. Solar Orbiter and PSP jointly observed the solar wind for the first time in June 2020, capturing data from very different solar wind streams, calm and Alfvénic wind as well as many dynamic structures. Aims. The aim here is to understand the origin and characteristics of the highly dynamic solar wind observed by the two probes, in particular in the vicinity of the heliospheric current sheet (HCS). Methods. We analyse the plasma data obtained by PSP and Solar Orbiter in situ during the month of June 2020. We use the Alfvén-wave turbulence MHD solar wind model WindPredict-AW, and perform…
The Role of Magnetic Reconnection in Energizing Protons and Heavier Ions at the Heliospheric Current Sheet
West Virginia University（西弗吉尼亚大学）；University of Hawai’i at Mānoa（夏威夷大学马诺阿分校）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；New Mexico Consortium（新墨西哥联盟）；University of Wisconsin-Madison（威斯康星大学麦迪逊分校）
Parker Solar Probe Observations of Compound Reconnection Exhaust Boundaries and Mirror-Mode Structures in the Near-Sun Heliospheric Current Sheet
Space Sciences Laboratory, University of California, Berkeley（加州大学伯克利分校空间科学实验室）；Department of Physics and Astronomy, Dartmouth College（达特茅斯学院物理与天文学系）；Department of Climate and Space Sciences and Engineering, University of Michigan（密歇根大学气候与空间科学与工程系）；Earth, Planetary and Space Sciences, and Institute of Geophysics and Space Physics, University of California, Los Angeles（加州大学洛杉矶分校地球、行星与空间科学及地球物理与空间物理研究所）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体物理科学系）
Ion-Scale Current Sheets Embedded in Reconnection Jet Shear Layer of the Near-Sun Heliospheric Current Sheet
Chungbuk National University（忠北国立大学）；University of California, Berkeley（加州大学伯克利分校）；New Mexico Consortium（新墨西哥联盟）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）
We present observations of >10-100 keV/nucleon suprathermal (ST) H, He, O, and Fe ions associated with crossings of the heliospheric current sheet (HCS) at radial distances <0.1 au from the Sun. Our key findings are: 1) very few heavy ions are detected during the 1st full crossing, the heavy ion intensities are reduced during the 2nd partial crossing and peak just after the 2nd crossing; 2) ion arrival times exhibit no velocity dispersion; 3) He pitch-angle distributions track the magnetic field polarity reversal and show up to ~10:1 anti-sunward, field-aligned flows and beams closer to the HC…
Magnetic clouds (MCs) are flux-rope magnetic structures forming a subset of solar coronal mass ejections which have significant space weather impacts. The geoeffectiveness of MCs depends on their properties which evolve during their interplanetary passage. Based on an analysis of observations spanning two solar cycles we establish that MCs interacting with the ambient solar wind magnetic field (i.e., heliospheric open flux) lose a substantial amount of their initial magnetic flux via magnetic reconnection, which in some cases, reduce their geoeffectiveness. We find a linear correlation between…
Strong Prevalence of Hammerhead Velocity Distributions Close to the Heliospheric Current Sheet
Center for Astrophysics — Harvard & Smithsonian（哈佛-史密森天体物理中心）；NASA, Goddard Space Flight Center（美国国家航空航天局戈达德太空飞行中心）；GPHI, University of Maryland, Baltimore County（马里兰大学巴尔的摩县分校GPHI）；Space Sciences Laboratory, University of California, Berkeley（加州大学伯克利分校空间科学实验室）
This White Paper argues for the urgent need for the multi-vantage/multi-point observations of the Sun and the heliosphere in the framework of six (6) key science objectives. We further emphasize the critical importance of 5D-``space'': three spatial, one temporal and the magnetic field components. The importance of such observations cannot be overstated both for scientific research and the operational space weather forecast.
We investigate the source eruption, propagation and expansion characteristics, and heliospheric impacts of the 2020 November 29 coronal mass ejection (CME) and associated shock, using remote sensing and in situ observations from multiple spacecraft. A potential--field source--surface model is employed to examine the coronal magnetic fields surrounding the source region. The CME and associated shock are tracked from the early stage to the outer corona using extreme ultraviolet and white light observations. Forward models are applied to determine the structures and kinematics of the CME and the …
Solar cycle (SC) 24 has come to an end by the end of 2019, providing information on two full cycles to understand the manifestations of SC 24, the smallest cycle in the Space Age that has resulted in a weak heliospheric state indicated by the reduced pressure. The backreaction of the heliospheric state is to make the coronal mass ejections (CMEs) appear physically bigger than in SC 23, but their magnetic content has been diluted resulting in a lower geoeffectiveness. The heliospheric magnetic field is also lower in SC 24, leading to the dearth of high-energy solar energetic particle (SEP) even…
Investigating the heliospheric evolution and consequences of Coronal mass ejections (CMEs) is critical to understanding the solar-terrestrial relationship. For the first time, Heliospheric Imagers (HIs) onboard STEREO, providing multiple views of CMEs in the heliosphere, observed the vast and crucial observational gap between the Sun and the Earth. Using J-maps constructed from coronagraphs (CORs) and HIs observations, we continuously tracked different density enhanced features of CMEs. We implemented several reconstruction methods to estimate the three-dimensional (3D) kinematics of CMEs duri…
