The largest geomagnetic storms of solar cycle 24 so far occurred on 2015 March 17 and June 22 with $D_{\rm st}$ minima $-223$ $-195$ nT, respectively. Both the show a multi-step development. We examine plasma magnetic field characteristics driving coronal mass ejections (CMEs) in connection development storms. A particular effort is to reconstruct situ structure using Grad-Shafranov technique compare reconstruction results observations, which gives larger spatial perspective source...

On 2012 September 30–October 1 the Earth underwent a two-step geomagnetic storm. We examine Sun-to-Earth characteristics of coronal mass ejections (CMEs) responsible for storm with combined heliospheric imaging and in situ observations. The first CME, which occurred on 25, is slow event shows an acceleration followed by nearly invariant speed whole Sun–Earth space. second event, launched from Sun 27, exhibits quick acceleration, then rapid deceleration, finally constant speed, typical...

As a follow-up study on Sun-to-Earth propagation of fast coronal mass ejections (CMEs), we examine the characteristics slow CMEs combining heliospheric imaging and in situ observations. Three events particular interest, 2010 June 16, 2011 March 25 2012 September CMEs, are selected for this study. We compare with intermediate-speed events, obtain key results complementing attempt \citet{liu13} to create general picture CME propagation: (1) typical can be approximately described by two phases,...

The coronal heating problem remains one of the most challenging questions in solar physics. energy driving is widely understood to be associated with convective motions below photosphere. Recent high-resolution observations reveal that photospheric magnetic fields quiet Sun undergo complex and rapid evolution. These dynamics are expected reflected field. Motivated by these insights, our research aims explore relationship between heating. By combining from Solar Orbiter SDO a field...

We study the role of coronal magnetic field configuration an active region (AR) in determining propagation direction a mass ejection (CME). The CME occurred AR 11944 (S09W01) near disk center on 2014 January 7 and was associated with X1.2 flare. A new reconstruction procedure based polarimetric technique is adopted, which shows that changed its by around 28° latitude within 2.5 43° longitude 6.5 respect to source region. This significant non-radial motion consistent finding Möstl et al. use...

The transition between the supersonic solar wind and subsonic heliosheath, termination shock (TS), was observed by Voyager 2 (V2) on 2007 August 31-September 1 at a distance of 84 AU from Sun. data reveal multiple crossings complex, quasi-perpendicular supercritical shock. These experimental are starting point for more sophisticated analysis that includes computer modeling in presence pickup ions (PUIs). here, we present two-dimensional (2-D) particle-in-cell (PIC) simulations TS including...

An unexpected strong geomagnetic storm occurred on 2018 August 26, which was caused by a slow coronal mass ejection (CME) from gradual eruption of large quiet-region filament. We investigate the and propagation characteristics this CME in relation to with remote sensing situ observations. Coronal magnetic fields around filament are extrapolated compared EUV determine direction tilt angle flux rope near Sun using graduated cylindrical shell (GCS) model Sun-to-Earth kinematics wide-angle...

We examine two successive flare eruptions (X5.4 and X1.3) on 2012 March 7 in the NOAA active region 11429 investigate magnetic field reconfiguration associated with eruptions. Using an advanced non-linear force-free extrapolation method based SDO/HMI vector magnetograms, we obtain a stepwise decrease free energy during eruptions, which is roughly 20%–30% of pre-flare phase. also calculate helicity suggest that changes sign injection rate might be Through investigation evolution, find...

Abstract We investigate a global extreme-ultraviolet (EUV) wave associated with coronal mass ejection (CME)-driven shock on 2017 September 10. The EUV is transmitted by north- and south-polar holes (CHs), which observed the Solar Dynamics Observatory ( SDO ) Terrestrial Relations A STEREO-A from opposite sides of Sun. obtain key findings how interacts multiple structures, its connection CME-driven shock: (1) still connected that incurvated to Sun, after has reached side eruption; (2) south...

Abstract Electron dynamics at low-Mach-number collisionless shocks are investigated by using two-dimensional electromagnetic particle-in-cell simulations with various shock normal angles. We found: (1) The reflected ions and incident electrons the front provide an effective mechanism for quasi-electrostatic wave generation due to charge-separation. A fraction of can be effectively trapped accelerated leading edge foot. (2) At quasi-perpendicular shocks, electron trapping reflection is...

We use high spatial and temporal resolution observations, simultaneously obtained with the New Vacuum Solar Telescope Atmospheric Imaging Assembly (AIA) on board Dynamics Observatory, to investigate high-frequency oscillations above a sunspot umbra. A novel time--frequency analysis method, namely synchrosqueezing transform (SST), is employed represent their power spectra reconstruct signals at different solar atmospheric layers. validation study synthetic demonstrates that SST capable...

In order to have a comprehensive view of the propagation and evolution coronal mass ejections (CMEs) from Sun deep interplanetary space beyond 1 au, we carry out kinematic analysis 7 CMEs in solar cycle 23. The events are required coordinated coronagraph observations, type II radio bursts, multi-point in-situ measurements at Earth Ulysses. A graduated cylindrical shell model, an analytical model without free parameters magnetohydrodynamic used derive CME kinematics near Sun, quantify...

We study the solar energetic particle (SEP) event associated with 2012 July 23 extreme storm, for which STEREO and spacecraft at L1 provide multi-point remote sensing in situ observations. The a superfast shock extremely enhanced ejecta magnetic fields observed near 1 AU A, was caused by combination of successive coronal mass ejections (CMEs). Meanwhile, particles were near-Earth such as ACE SOHO, suggestive wide longitudinal spread AU. Combining SEP observations plasma field measurements we...

Abstract The S-shaped magnetic structure in the solar wind formed by twisting of field lines is called a switchback, whose main characteristics are reversal and significant increase radial velocity. We identify 242 switchbacks during first two encounters Parker Solar Probe. Statistics methods applied to analyze distribution rotation angle direction switchbacks. diameter estimated with minimum variance analysis (MVA) method based on assumption cylindrical tube. also make comparison between...

Propagation of coronal mass ejections (CMEs) from the Sun far into interplanetary space is not well understood due to limited observations. In this study we examine propagation characteristics two geo-effective CMEs, which occurred on 2005 May 6 and 13, respectively. Significant heliospheric consequences associated with CMEs are observed, including (ICMEs) at Earth Ulysses, shocks, a long-duration type II radio burst, intense geomagnetic storms. We use coronagraph observations SOHO/LASCO,...

We carry out two-dimensional global particle-in-cell simulations of the interaction between solar wind and a dipole field to study formation bow shock magnetosphere. A self-reforming ahead is presented by using relatively high temporal-spatial resolutions. find that (1) magnetosphere are formed reach quasi-stable state after several ion cyclotron periods, (2) under Bz southward condition undergoes self-reformation for low \b{eta}i MA. Simultaneously, magnetic reconnection in magnetotail...

Abstract We investigate the coronal and interplanetary evolution of a mass ejection (CME) launched on 2010 September 4 from source region linking two active regions (ARs), 11101 11103, using extreme ultraviolet imaging, magnetogram, white-light, in situ observations SDO , STEREO SOHO VEX Wind . A potential-field source-surface model is employed to examine configuration magnetic field surrounding region. The graduated cylindrical shell triangulation method are applied determine kinematics CME...

Experimental data from Cluster have shown that entropy density can be generated across Earth's bow shock. These new observations are a starting point for more sophisticated analysis includes computer modeling of collisionless shock using observed parameters as input. In this Letter, we present the first comparison between and particle-in-cell simulations such generation The ion heating at is dominated by phase mixing reflected directly transmitted ions, which separated incident ions....

We report on the first direct in situ measurements of a fast coronal mass ejection (CME) and shock corona, which occurred 2022 September 5. In from Parker Solar Probe (PSP) spacecraft near perihelion suggest two shocks with second one decayed, is consistent more than eruptions coronagraph images. Despite flank crossing, indicate unique features young ejecta: plasma much hotter ambient medium suggestive hot solar source, large $\beta$ implying highly non-force-free state importance thermal...

A solar active region (AR) may produce multiple notable flares during its passage across the disk. We investigate successive from flare-eruptive regions, and explore their relationship with magnetic parameters. examine six ARs in this study, each at least one major flare above X1.0. The Space-Weather HMI Active Region Patch (SHARP) is employed study to parameterize ARs. aim identify most flare-related SHARP parameters lay foundation for future practical forecasts. first evaluate correlation...