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Overview of the 2018 August 20 eruptions from remote‐sensing solar disc imagery. (a) Pre‐eruptive configuration on the solar disc. The erupting S‐shaped structure (“S”) and filament (“F”), as well as the two nearby coronal holes (“CH1” and “CH2”) are labeled. (b) and (d) Zoomed‐in images of the erupting sigmoid (CME1) and filament (CME2), respectively. (c) and (e) Base‐difference images of the sigmoid and filament eruptions, respectively, with magnetogram data saturated to ±100 G overlaid (red = positive, blue = negative). The approximate eruption footpoints are indicated with green circles in both panels.
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The activity of the Sun alternates between a solar minimum and a solar maximum, the former corresponding to a period of “quieter” status of the heliosphere. During solar minimum, it is in principle more straightforward to follow eruptive events and solar wind structures from their birth at the Sun throughout their interplanetary journey. In this pa...
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Citations
... Coronal mass ejections (CMEs) are large-scale solar eruptions associated with massive amounts of plasma expulsion and release of enormous energy. In the solar system, CMEs play an important part in shaping the interplanetary space environment, driving the variations in space weather around Earth and other planets (e.g., Gopalswamy 2016;Palmerio et al. 2022). CMEs also occur on other stars (stellar CMEs). ...
Stellar coronal mass ejections (CMEs) from host stars are an important factor that affects the habitability of exoplanets. Although their solar counterparts have been well observed for decades, it is still very difficult to find solid evidence of stellar CMEs. Using the spectral line profile asymmetry caused by the Doppler shift of erupting plasma, several stellar CME candidates have been identified from spectral lines formed at chromospheric or transition region temperatures of the stars. However, a successful detection of stellar CME signals based on the profile asymmetries of coronal lines is still lacking. It is unclear whether we can detect such signals. Here we construct an analytical model for CMEs on solar-type stars and derive an expression of stellar extreme-ultraviolet (EUV) line profiles during CME eruptions. For different instrumental parameters, exposure times, CME propagation directions, and stellar activity levels, we synthesized the corresponding line profiles of Fe ix λ 171.07 and Fe xv λ 284.16. Further investigations provide constraints on the instrumental requirements for successful detection and characterization of stellar CMEs. Our results show that it is possible to detect stellar CME signals and infer their velocities based on spectral profile asymmetries using an EUV spectrometer with a moderate spectral resolution and signal-to-noise ratio. Our work provides important references for the design of future EUV spectrometers for stellar CME detection and the development of observation strategies.
... This led to an ICME observed at Mercury as a very organized structure becoming complex at 1 au. Palmerio et al. (2022) investigated a CME observed at Earth that missed Mars owing to the interaction with a high-speed stream, causing deflection and rotation. If any interaction happened for the current event, it would affect the CME for a much shorter period than in previous studies mentioned. ...
The relationship between CME properties in the corona and their interplanetary counterparts is not well understood. Until recently, a wide spatial gap existed between the two regions, which prevented us from disentangling the spatial and temporal evolution of CMEs. NASA’s Parker Solar Probe (PSP) has imaged multiple CMEs since its launch in 2018, but these events either intercepted the spacecraft far from the corona or completely missed it. Here we describe one of the first CMEs observed simultaneously by remote sensing and in situ instruments, and compare the corresponding measured properties, such as orientation, cross section diameter, density, and speed. The CME encounter occurred on 2022 June 2, while PSP was around 14 solar radii from the Sun center. We reconstruct the CME with forward modeling and determine its morphology and kinematics. The reconstruction suggests that PSP misses the CME apex but encounters its flank. The encounter time matches the period when the PSP in situ measurements indicate the passage of a CME. We also reconstruct the flux rope diameter and orientation using the in situ magnetic field measurements. The results are consistent with the CME reconstruction from imaging data. The close agreement between remote sensing and in situ analyses suggests that discrepancies found in past studies are more likely associated with the CME temporal evolution. We also find that the magnetic field of the CME flank extrapolated to 1 au is well below the average solar wind background and likely indistinguishable from it. This point could explain past events where the CMEs' interplanetary counterparts were not identified.
... Streams of fast solar wind emanating from these regions, especially from the equatorial coronal hole (outlined in orange in Figure 4)-could have expedited the propagation of the CMEs, resulting in earlier-than-expected Earth arrivals. It is well known that the push "from behind" exerted by a HSS can result in acceleration and compression, and sometimes in enhanced geoeffectiveness, of a preceding CME (e.g., Palmerio et al., 2022;Y. Wang et al., 2016). ...
Plain Language Summary
Human society is becoming increasingly dependent on satellites at Low Earth Orbit (LEO) which cater to Earth observations, telecommunications, navigation and defense needs. The impact of space weather–changing environmental conditions in space governed by the Sun–at Low Earth Orbits is only beginning to be appreciated. The loss of an unprecedented number of Starlink satellites after their launch on 3 February 2022, which was attributed to space weather, is a case in point. Surprisingly, solar magnetic storms and space weather conditions around the time of the launch of the Starlink satellites were quite modest, making it challenging to establish physical causality. Here we utilize a multipronged approach based on observations of solar magnetic storms, near‐Earth environmental conditions and novel computer simulations to establish causality between the prevailing space environmental conditions at LEO and the loss of the satellites. Our comprehensive analysis reveals that the loss of the satellites was due to a combination of factors including prevalent space weather conditions, an insertion at a relatively high‐density LEO and possibly enhanced drag due to orientation changes of the satellites accentuated by a relatively high drag to inertia ratio.
... While this work showcases some of the difficulties associated with this particular class of events, the CME studied here featured some specific characteristics that made it "problematic": It was exceptionally extended as well as highly asymmetric (and thus difficult to model in its entirety), it was slow, and it had no significant Earth-directed component (at least according to estimates from remote-sensing imagery). Furthermore, its related space weather effects were likely intensified by the fact that it traveled through a flow of high-speed solar wind-that CME interaction with fast streams can lead to enhanced geoeffectiveness has been shown both via observational (e.g., Nitta et al. 2021;Palmerio et al. 2022b) and modeling (e.g., Kay et al. 2022) studies. Our work demonstrated two viable ways as to how to model cases in which the "problematic" status can be attributed to an extended and/or asymmetric structure of the CME, i.e., either via modeling only the Earth-directed (or observer-of-interest-directed) component or via constructing the whole CME from separate parts. ...
We present observations and modeling results of the propagation and impact at Earth of a high-latitude, extended filament channel eruption that commenced on 2015 July 9. The coronal mass ejection (CME) that resulted from the filament eruption was associated with a moderate disturbance at Earth. This event could be classified as a so-called “problem storm” because it lacked the usual solar signatures that are characteristic of large, energetic, Earth-directed CMEs that often result in significant geoeffective impacts. We use solar observations to constrain the initial parameters and therefore to model the propagation of the 2015 July 9 eruption from the solar corona up to Earth using 3D magnetohydrodynamic heliospheric simulations with three different configurations of the modeled CME. We find the best match between observed and modeled arrival at Earth for the simulation run that features a toroidal flux rope structure of the CME ejecta, but caution that different approaches may be more or less useful depending on the CME–observer geometry when evaluating the space weather impact of eruptions that are extreme in terms of their large size and high degree of asymmetry. We discuss our results in the context of both advancing our understanding of the physics of CME evolution and future improvements to space weather forecasting.
... In particular, a complex nest of active regions dominates this area in May and June of 2019. These regions were responsible for many of the CMEs that occurred during the WHPI interval (Palmerio et al., 2022) . ...
The McIntosh Archive consists of four solar cycles (SC20–23) of synoptic maps of solar features (magnetic polarities, coronal holes, filaments, sunspots, plage) that were produced by Patrick McIntosh and his cartographers. In this paper we present the full Archive for the first time and find a hemispheric pattern of coronal hole polarity reflecting the Hale sunspot polarity pattern. In addition, we present a supplemental set of related maps created for the 2019–2020 solar minimum in support of the Whole Heliosphere and Planetary Interactions (WHPI) interval. To facilitate this addition, we cross calibrate EUV and He‐I 10,830 Å coronal holes and study differences between the WHPI solar minimum and the earlier minima in the main Archive. We find, first, that the visibility of coronal holes in EUV introduces a bias toward larger counts of low‐latitude coronal holes near solar minimum. However, the estimated lifetimes (in Carrington Rotations) of coronal hole complexes are unaffected by this fragmentation, and we find the longest‐lived low‐latitude coronal holes occurred during the 2008–2009 solar minimum, with 2019–2020 solar minimum lifetimes not far behind. In this way, we consider the large‐scale organization of solar magnetic fields between solar minima and study each solar minimum in the context of its solar cycle.
... In addition, the optimal position for a spacecraft would be a trade-off between improved lead time and the accuracy of the prediction. For example, placing a spacecraft within Mercury's orbit would give several days lead time, but the solar wind structures seen by the spacecraft may have evolved significantly after travelling to Earth (Rodríguez-García et al., 2022;Palmerio et al., 2022). While several case studies have already shown how an upstream spacecraft can be useful in predicting the arrival time and geo-effectiveness (Lindsay et al., 1999;Rollett et al., 2014;Kubicka et al., 2016;Amerstorfer et al., 2018;Pal et al., 2023), such a concept has never been attempted in real time. ...
Coronal mass ejections (CMEs) can create significant disruption to human activities and systems on Earth, much of which can be mitigated with prior warning of the upstream solar wind conditions. However, it is currently extremely challenging to accurately predict the arrival time and internal structure of a CME from coronagraph images alone. In this study, we take advantage of a rare opportunity to use Solar Orbiter, at 0.5\,AU upstream of Earth, as an upstream solar wind monitor. We were able to use real time science quality magnetic field measurements, taken only 12 minutes earlier, to predict the arrival time of a CME prior to reaching Earth. We used measurements at Solar Orbiter to constrain an ensemble of simulation runs from the ELEvoHI model, reducing the uncertainty in arrival time from 10.4\,hours to 2.5\,hours. There was also an excellent agreement in the $B_z$ profile between Solar Orbiter and Wind spacecraft, despite being separated by 0.5\,AU and 10$^{\circ}$ longitude. Therefore, we show that it is possible to predict not only the arrival time of a CME, but the sub-structure of the magnetic field within it, over a day in advance. The opportunity to use Solar Orbiter as an upstream solar wind monitor will repeat once a year, which should further help assess the efficacy upstream in-situ measurements in real time space weather forecasting.
... Similarly, while this study provides a mosaic of the inner heliosphere, spanning from the Sun and how it sculpts the solar wind to the effects on the magnetosphere and ITM systems, other studies in this special issue target specific aspects of the interconnected heliosphere and planetary systems during this minimum period (e.g., Badman et al., 2023;Gasperini et al., 2023;Hudson et al., 2021;Lloveras et al., 2022;M. G. Mlynczak et al., 2022;Palmerio, Lee, Richardson, et al., 2022;Varela et al., 2022;Younas et al., 2022), as well as focus on comparisons between the current minimum and those from the WHI and WSM intervals (Bregou et al., 2022;Hewins et al., 2023;Luhmann et al., 2022;Riley et al., 2022). The data sets used in this study are outlined in Section 2 of this manuscript. ...
The Whole Heliosphere and Planetary Interactions initiative was established to leverage relatively quiet intervals during solar minimum to better understand the interconnectedness of the various domains in the heliosphere. This study provides an expansive mosaic of observations spanning from the Sun, through interplanetary space, to the magnetospheric response and subsequent effects on the ionosphere‐thermosphere‐mesosphere (ITM) system. To accomplish this, a diverse set of observational datasets are utilized from 2019 July 26 to October 16 (i.e., over three Carrington rotations, CR2220, CR2221, and CR2222) with connections of these observations to the more focused studies submitted to this special issue. Particularly, this study focuses on two long‐lived coronal holes and their varying impact in sculpting the heliosphere and driving of the magnetospheric system. As a result, the evolution of coronal holes, impacts on the inner heliosphere solar wind, glimpses at mesoscale solar wind variability, magnetospheric response to these evolving solar wind drivers, and resulting ITM phenomena are captured to reveal the interconnectedness of this system‐of‐systems.
... The level of participation increased with its expanded scope, encompassing Sun to solar wind to planetary magnetospheres and atmospheres. The articles accompanying this introduction Badman et al., 2023;Bregou et al., 2022;Gasperini et al., 2023;Hewins et al., 2023;Hudson et al., 2021;Lloveras et al., 2022;Luhmann et al., 2022;Mlynczak et al., 2022;Palmerio et al., 2022;Riley et al., 2022;Varela et al., 2022;Younas et al., 2022) represent the beginnings of analyses that are likely to continue for years to come. ...
The Whole Heliosphere and Planetary Interactions (WHPI) is an international initiative to study the most recent solar minimum and its impact on the interconnected solar‐heliospheric‐planetary system by facilitating and encouraging interdisciplinary activities. Particular WHPI science foci include the global connected structure of the heliosphere and planetary space environments/atmospheres, the origins and impacts of high‐speed solar wind streams, coronal mass ejections from Sun‐to‐Heliopause, and comparative solar minima. This is achieved through a series of coordinated observing campaigns, including Parker Solar Probe perihelia, and scientific virtual interactions including a dedicated workshop where observers and modelers gathered to discuss, compare, and combine research results. This introduction sets the scene for the WHPI interval, placing it into the context of prior initiatives and describing the overall evolution of the system between 2018 and 2020. Along with the accompanying articles, it presents a selection of key scientific results on the interconnected solar‐heliospheric‐planetary system at solar minimum.
... Winslow et al. (2021) studied the CME-SIR interaction using observations from two spacecraft having longitudinal conjunction and determined drastic changes in the ICME magnetic structure and properties of sheath due to the interaction. Palmerio et al. (2022) studied two successive ICMEs followed by HSS on their way to Earth and Mars and found out the reason for the second ICME missing Mars being the ICME's rotation and deflection due to its interaction with the HSS. Moreover, all these studies focused on understanding the complexity resulting from interacting transients and serve as an indicator for further investigations on the interacting solar events in the heliosphere. ...
From 29 January to 7 February 2022, the heliosphere was structured with large-scale interacting substructures that appeared with significant dissimilarities at distant observations separated longitudinally by ∼ 34 ° . Probing the complexity of the structured heliosphere with multi-point in situ and imaging observations by using a fleet of spacecraft has revealed many unknown facts on the dynamics of large-scale structures in the heliosphere. In this paper, we investigate a complex-structured heliosphere by analyzing the Sun, solar corona, and solar wind with remote and in situ observations aided by heliospheric modeling. We identified multiple flux ropes (FRs) associated with large expulsions of magnetized plasma-coronal mass ejections, from the same solar source in a three-day interval, an interplanetary wave shock, and a sheath in front of the FRs. In situ observations displayed a stream interaction region behind FRs formed due to the overtaking of different-speed solar winds. This high-speed stream originated from a coronal hole located southeast of the coronal mass ejection solar source. We find evidence of merging FRs, FR deflection due to the presence of the nearby coronal hole, and FR’s unalike structural appearance at distant multi-point observations obtained at 1 au. This complex-structured heliosphere resulted in multiple G1-class geomagnetic storms when interacting with Earth’s magnetosphere. Thus, the study focuses on the reconstruction of the structured heliosphere based on observations and modeling. It highlights the importance of multi-point observations in understanding the global configuration and disparity in the local nature of a structured heliosphere.
... In fact, two of the three strongest geomagnetic storms of Solar Cycle 24 (in terms of the Dst index) were due to a CME immediately followed by a HSS. These are the 17 March 2015 storm, strongest of the cycle with the Dst index reaching −234 nT (e.g., Kataoka et al., 2015), and the 26 August 2018 storm, third-strongest of the cycle with the Dst index reaching −175 nT (e.g., Palmerio et al., 2022). The second-strongest storm, on 23 June 2015 and with the Dst index reaching −198 nT, on the other hand, was driven by successive, interacting CMEs (e.g., Augusto et al., 2018). ...
Predicting space weather effects of the solar wind requires knowing the location and properties of any embedded high speed streams (HSSs) or stream interactions regions (SIRs) that form as the fast solar wind catches up to slow preceding wind. Additionally, this background solar wind affects the evolution of coronal mass ejections. We present the Mostly Empirical Operation Wind with a High Speed Stream (MEOW‐HiSS) model, which runs nearly instantaneously. This model is derived from magnetohydrodynamic (MHD) simulations of an idealized HSS emanating from a circular coronal hole. We split the MHD HSS radial profiles into small regions well‐described by simple functions (e.g., flat, linear, exponential, sinusoidal) that can be constrained using the MHD values. We then determine how the region boundaries and the constraining values change with CH area and the radial distance of the HSS front. MEOW‐HiSS only requires this area and distance to reproduce the corresponding radial profile with an error of less than 10% for most parameters. MEOW‐HiSS produces profiles at any subsequent times with almost no loss in accuracy. We compare MEOW‐HiSS results to four HSS observed in situ at 1 au. We present a method for determining MEOW‐HiSS inputs from extreme ultra‐violet images and use these values to hindcast the observed cases. We find average accuracies of 2.8 cm⁻³ in the number density (50% error over the full profile), 56.7 km/s in the radial velocity (10%), 2.2 nT in the absolute radial magnetic field (50%), 1.6 nT in the absolute longitudinal magnetic field (50%), and 7 × 10⁴ K in the temperature (50%).
