scholarly journals Understanding the Origins of Problem Geomagnetic Storms Associated with “Stealth” Coronal Mass Ejections

2021 ◽  
Vol 217 (8) ◽  
Author(s):  
Nariaki V. Nitta ◽  
Tamitha Mulligan ◽  
Emilia K. J. Kilpua ◽  
Benjamin J. Lynch ◽  
Marilena Mierla ◽  
...  
Keyword(s):  
Solar Activity ◽  
Coronal Mass Ejections ◽  
Geomagnetic Storms ◽  
Active Regions ◽  
The Sun ◽  
Interplanetary Coronal Mass Ejections ◽  
Source Regions ◽  
Solar Eruptions ◽  
Cycle 24 ◽  
Mass Ejection

AbstractGeomagnetic storms are an important aspect of space weather and can result in significant impacts on space- and ground-based assets. The majority of strong storms are associated with the passage of interplanetary coronal mass ejections (ICMEs) in the near-Earth environment. In many cases, these ICMEs can be traced back unambiguously to a specific coronal mass ejection (CME) and solar activity on the frontside of the Sun. Hence, predicting the arrival of ICMEs at Earth from routine observations of CMEs and solar activity currently makes a major contribution to the forecasting of geomagnetic storms. However, it is clear that some ICMEs, which may also cause enhanced geomagnetic activity, cannot be traced back to an observed CME, or, if the CME is identified, its origin may be elusive or ambiguous in coronal images. Such CMEs have been termed “stealth CMEs”. In this review, we focus on these “problem” geomagnetic storms in the sense that the solar/CME precursors are enigmatic and stealthy. We start by reviewing evidence for stealth CMEs discussed in past studies. We then identify several moderate to strong geomagnetic storms (minimum Dst $< -50$ < − 50  nT) in solar cycle 24 for which the related solar sources and/or CMEs are unclear and apparently stealthy. We discuss the solar and in situ circumstances of these events and identify several scenarios that may account for their elusive solar signatures. These range from observational limitations (e.g., a coronagraph near Earth may not detect an incoming CME if it is diffuse and not wide enough) to the possibility that there is a class of mass ejections from the Sun that have only weak or hard-to-observe coronal signatures. In particular, some of these sources are only clearly revealed by considering the evolution of coronal structures over longer time intervals than is usually considered. We also review a variety of numerical modelling approaches that attempt to advance our understanding of the origins and consequences of stealthy solar eruptions with geoeffective potential. Specifically, we discuss magnetofrictional modelling of the energisation of stealth CME source regions and magnetohydrodynamic modelling of the physical processes that generate stealth CME or CME-like eruptions, typically from higher altitudes in the solar corona than CMEs from active regions or extended filament channels.

scholarly journals The spatial relationship between active regions and coronal holes and the occurrence of intense geomagnetic storms throughout the solar activity cycle

1998 ◽  
Vol 16 (1) ◽  
pp. 49-54 ◽  
Author(s):  
S. Bravo ◽  
J. A. L. Cruz-Abeyro ◽  
D. Rojas
Keyword(s):  
Solar Activity ◽  
Coronal Mass Ejections ◽  
Geomagnetic Storms ◽  
Coronal Holes ◽  
Spatial Relationship ◽  
Active Regions ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Frequency Of Occurrence ◽  
Sunspot Maximum

Abstract. We study the annual frequency of occurrence of intense geomagnetic storms (Dst < –100 nT) throughout the solar activity cycle for the last three cycles and find that it shows different structures. In cycles 20 and 22 it peaks during the ascending phase, near sunspot maximum. During cycle 21, however, there is one peak in the ascending phase and a second, higher, peak in the descending phase separated by a minimum of storm occurrence during 1980, the sunspot maximum. We compare the solar cycle distribution of storms with the corresponding evolution of coronal mass ejections and flares. We find that, as the frequency of occurrence of coronal mass ejections seems to follow very closely the evolution of the sunspot number, it does not reproduce the storm profiles. The temporal distribution of flares varies from that of sunspots and is more in agreement with the distribution of intense geomagnetic storms, but flares show a maximum at every sunspot maximum and cannot then explain the small number of intense storms in 1980. In a previous study we demonstrated that, in most cases, the occurrence of intense geomagnetic storms is associated with a flaring event in an active region located near a coronal hole. In this work we study the spatial relationship between active regions and coronal holes for solar cycles 21 and 22 and find that it also shows different temporal evolution in each cycle in accordance with the occurrence of strong geomagnetic storms; although there were many active regions during 1980, most of the time they were far from coronal holes. We analyse in detail the situation for the intense geomagnetic storms in 1980 and show that, in every case, they were associated with a flare in one of the few active regions adjacent to a coronal hole.

scholarly journals Magnetic helicity ejections and coronal activity

2012 ◽  
Vol 8 (S294) ◽  
pp. 519-530 ◽  
Author(s):  
A. Nindos
Keyword(s):  
Magnetic Field ◽  
Physical Quantity ◽  
Coronal Mass Ejections ◽  
Active Regions ◽  
Magnetic Helicity ◽  
The Sun ◽  
Coronal Activity ◽  
Solar Eruptions ◽  
Ideal Tool ◽  
The Magnetic Field

AbstractMagnetic helicity quantifies the degree of linkage and/or twistedness in the magnetic field. It is probably the only physical quantity which is approximately conserved even in resistive MHD. This makes it an ideal tool for the exploration of the physics of solar eruptions. In this article, I discuss the sources of magnetic helicity injected into active regions and I point out that coronal mass ejections (CMEs) are probably necessary to remove at least part of the excess helicity produced in the Sun. I also discuss the importance of magnetic helicity in the overall coronal evolution that may lead to eruptions.

scholarly journals Introducing the Sun and SEPs

2021 ◽  
pp. 1-18
Author(s):  
Donald V. Reames
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Solar Cycle ◽  
Differential Rotation ◽  
Coronal Mass Ejections ◽  
Energetic Particle ◽  
Solar Magnetic Field ◽  
Solar Energetic Particle ◽  
Active Regions ◽  
The Sun

AbstractThe structure of the Sun, with its energy generation and heating, creates convection and differential rotation of the outer solar plasma. This convection and rotation of the ionized plasma generates the solar magnetic field. This field and its variation spawn all of the solar activity: solar active regions, flares, jets, and coronal mass ejections (CMEs). Solar activity provides the origin and environment for both the impulsive and gradual solar energetic particle (SEP) events. This chapter introduces the background environment and basic properties of SEP events, time durations, abundances, and solar cycle variations.

scholarly journals Lessons learned from predictions of Solar Cycle 24

2020 ◽  
Vol 10 ◽  
pp. 60
Author(s):  
W. Dean Pesnell
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Coronal Mass Ejections ◽  
Sunspot Cycle ◽  
Lessons Learned ◽  
Machine Learning Techniques ◽  
Polar Regions ◽  
The Sun ◽  
Solar Cycle 24 ◽  
Cycle 24

Solar Cycle 24 has almost faded and the activity of Solar Cycle 25 is appearing. We have learned much about predicting solar activity in Solar Cycle 24, especially with the data provided by SDO and STEREO. Many advances have come in the short-term predictions of solar flares and coronal mass ejections, which have benefited from applying machine learning techniques to the new data. The arrival times of coronal mass ejections is a mid-range prediction whose accuracy has been improving, mostly due to a steady flow of data from SoHO, STEREO, and SDO. Longer term (greater than a year) predictions of solar activity have benefited from helioseismic studies of the plasma flows in the Sun. While these studies have complicated the dynamo models by introducing more complex internal flow patterns, the models should become more robust with the added information. But predictions made long before a sunspot cycle begins still rely on precursors. The success of some categories of the predictions of Solar Cycle 24 will be examined. The predictions in successful categories should be emphasized in future work. The SODA polar field precursor method, which has accurately predicted the last three cycles, is shown for Solar Cycle 25. Shape functions for the sunspot number and F10.7 are presented. What type of data is needed to better understand the polar regions of the Sun, the source of the most accurate precursor of long-term solar activity, will be discussed.

scholarly journals CMEs and Prominences and their Evolution Over the Solar Cycle

1998 ◽  
Vol 167 ◽  
pp. 463-474 ◽  
Author(s):  
David F. Webb
Keyword(s):  
Solar Cycle ◽  
Magnetic Flux ◽  
Coronal Mass Ejections ◽  
Energetic Particle ◽  
Geomagnetic Storms ◽  
The Sun ◽  
Interplanetary Shocks ◽  
X Ray ◽  
Magnetic Structures ◽  
Source Regions

AbstractCoronal mass ejections (CMEs) are an important aspect of coronal and interplanetary dynamics. They cause large geomagnetic storms and can drive transient interplanetary shocks, which in turn are a key source of energetic particle events. However, our knowledge of the origins and early development of CMEs at the Sun is limited. CMEs are most frequently associated with erupting prominences and long-enduring soft X-ray arcades, but sometimes with no observed surface activity. I review some of the well determined coronal properties of CMEs and what we know about their source regions, with emphasis on the characteristics of the associated prominences and helmet streamers. One of these characteristics is that many CMEs seem to arise from multipolar magnetic structures with multiple or kinked inversion lines. I also discuss the solar-cycle dependencies of these structures, including the role that erupting prominences and CMEs may play in the ejection of magnetic flux and helicity from the Sun.

Active Regions on the Sun with Increased Flare Activity in Cycle 24

2021 ◽  
Vol 65 (6) ◽  
pp. 507-517
Author(s):  
S. A. Yazev ◽  
E. S. Isaeva ◽  
Yu. V. Ishmukhametova
Keyword(s):  
Active Regions ◽  
Flare Activity ◽  
The Sun ◽  
Cycle 24

scholarly journals Observations of flux rope formation prior to coronal mass ejections

2013 ◽  
Vol 8 (S300) ◽  
pp. 209-214 ◽  
Author(s):  
Lucie M. Green ◽  
Bernhard Kliem
Keyword(s):  
Magnetic Flux ◽  
Magnetic Structure ◽  
Solar Atmosphere ◽  
Coronal Mass Ejections ◽  
Flux Rope ◽  
Active Regions ◽  
Magnetic Configuration ◽  
Magnetic Flux Rope ◽  
Source Regions ◽  
Flux Ropes

AbstractUnderstanding the magnetic configuration of the source regions of coronal mass ejections (CMEs) is vital in order to determine the trigger and driver of these events. Observations of four CME productive active regions are presented here, which indicate that the pre-eruption magnetic configuration is that of a magnetic flux rope. The flux ropes are formed in the solar atmosphere by the process known as flux cancellation and are stable for several hours before the eruption. The observations also indicate that the magnetic structure that erupts is not the entire flux rope as initially formed, raising the question of whether the flux rope is able to undergo a partial eruption or whether it undergoes a transition in specific flux rope configuration shortly before the CME.

Numerical Short-Term Solar Activity Forecasting

2017 ◽  
Vol 13 (S335) ◽  
pp. 243-249 ◽  
Author(s):  
Huaning Wang ◽  
Yihua Yan ◽  
Han He ◽  
Xin Huang ◽  
Xinghua Dai ◽  
...  
Keyword(s):  
Solar Activity ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Magnetic Energy ◽  
Three Dimensional ◽  
Active Regions ◽  
Short Term ◽  
Solar Active Regions ◽  
Solar Eruptions ◽  
Dimensional Reconstruction

AbstractIt is well known that the energy for solar eruptions comes from magnetic fields in solar active regions. Magnetic energy storage and dissipation are regarded as important physical processes in the solar corona. With incomplete theoretical modeling for eruptions in the solar atmosphere, activity forecasting is mainly supported with statistical models. Solar observations with high temporal and spatial resolution continuously from space well describe the evolution of activities in the solar atmosphere, and combined with three dimensional reconstruction of solar magnetic fields, makes numerical short-term (within hours to days) solar activity forecasting possible. In the current report, we propose the erupting frequency and main attack direction of solar eruptions as new forecasts and present the prospects for numerical short-term solar activity forecasting based on the magnetic topological framework in solar active regions.

Prediction of upcoming grand episodes of solar activity

2018 ◽  
Vol 13 (S340) ◽  
pp. 325-326
Author(s):  
G. L. Jayalekshmi ◽  
P. R. Prince
Keyword(s):  
Solar Activity ◽  
Active Regions ◽  
Phase Changes ◽  
Activity Level ◽  
Time Interval ◽  
The Sun ◽  
Strong Magnetic Fields ◽  
Periodicity Analysis ◽  
Long Time ◽  
Grand Minima

AbstractSunspots are active regions on the surface of the Sun having strong magnetic fields. Activity level of the Sun shows long-time scale phenomena known as grand episodes-Grand maxima and Grand minima. Present study examines grand episodes shown by sunspot numbers (1090-2017), using methods of wavelet transform and sinusoidal regression. Time interval analysed includes two grand maxima and four grand minima. Interval in between grand episodes are regular oscillations. Phase changes found from periodicity analysis clearly show the presence of upcoming grand episodes. The forthcoming grand episodes are suggested to be two grand minima which are likely to occur between the years 2100-2160 and 2220-2300.

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