Fifty Years of 3He-Rich Events

Charge Ratio ◽

Radio Bursts ◽

Closed Loops ◽

The early 1970s saw a new and surprising feature in the composition of solar energetic particles (SEPs), resonant enhancements up to 10,000-fold in the ratio 3He/4He that could even make 3He dominant over H in rare events. It was soon learned that these events also had enhancements in the abundances of heavier elements, such as a factor of ∼10 enhancements in Fe/O, which was later seen to be part of a smooth increase in enhancements vs. mass-to-charge ratio A/Q from H to Pb, rising by a factor of ∼1000. These events were also associated with streaming 10–100 keV electrons that produce type III radio bursts. In recent years we have found these “impulsive” SEP events to be accelerated in islands of magnetic reconnection from plasma temperatures of 2–3 MK on open field lines in solar jets. Similar reconnection on closed loops traps the energy of the particles to produce hot (>10 MK), bright flares. Sometimes impulsive SEP intensities are boosted by shock waves when the jets launch fast coronal mass ejections. No single theory yet explains both the sharp resonance in 3He and the smooth increase up to heavier elements; two processes seem to occur. Sometimes the efficient acceleration even exhausts the rare 3He in the source region, limiting its fluence.

The Evolution of Research on Abundances of Solar Energetic Particles

Universe ◽

10.3390/universe7080292 ◽

2021 ◽

Vol 7 (8) ◽

pp. 292

Author(s):

Donald V. Reames

Keyword(s):

Shock Waves ◽

Power Laws ◽

Energetic Particles ◽

Charge Ratio ◽

Particle Interactions ◽

Solar Cosmic Rays ◽

Element Abundances ◽

Resonant Wave ◽

Sixty years of study of energetic particle abundances have made a major contribution to our understanding of the physics of solar energetic particles (SEPs) or solar cosmic rays. An early surprise was the observation in small SEP events of huge enhancements in the isotope 3He from resonant wave–particle interactions, and the subsequent observation of accompanying enhancements of heavy ions, later found to increase 1000-fold as a steep power of the mass-to-charge ratio A/Q, right across the elements from H to Pb. These “impulsive” SEP events have been related to magnetic reconnection on open field lines in solar jets; similar processes occur on closed loops in flares, but those SEPs are trapped and dissipate their energy in heat and light. After early controversy, it was established that particles in the large “gradual” SEP events are accelerated at shock waves driven by wide, fast coronal mass ejections (CMEs) that expand broadly. On average, gradual SEP events give us a measure of element abundances in the solar corona, which differ from those in the photosphere as a classic function of the first ionization potential (FIP) of the elements, distinguishing ions and neutrals. Departures from the average in gradual SEPs are also power laws in A/Q, and fits of this dependence can determine Q values and thus estimate source plasma temperatures. Complications arise when shock waves reaccelerate residual ions from the impulsive events, but excess protons and the extent of abundance variations help to resolve these processes. Yet, specific questions about SEP abundances remain.

Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles

10.5194/egusphere-egu21-3719 ◽

2021 ◽

Author(s):

David Ruffolo ◽

Rohit Chhiber ◽

William H. Matthaeus ◽

Arcadi V. Usmanov ◽

Paisan Tooprakai ◽

...

Keyword(s):

Magnetic Field ◽

Random Walk ◽

Field Line ◽

Large Scale ◽

Transport Model ◽

Source Region ◽

Science Research ◽

Energetic Particles ◽

<p>The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles (SEPs) propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. We develop a formalism in which the differential equation describing the field line random walk contains both effects due to localized magnetic displacements and a non-stochastic contribution from the large-scale expansion. We use this formalism together with a global magnetohydrodynamic simulation of the inner-heliospheric solar wind, which includes a turbulence transport model, to estimate the diffusive spreading of magnetic field lines that originate in different regions of the solar atmosphere. We first use this model to quantify field line spreading at 1 au, starting from a localized solar source region, and find rms angular spreads of about 20 &#8211; 60 degrees. In the second instance, we use the model to estimate the size of the source regions from which field lines observed at 1 au may have originated, thus quantifying the uncertainty in calculations of magnetic connectivity; the angular uncertainty is estimated to be about 20 degrees. Finally, we estimate the filamentation distance, i.e., the heliocentric distance up to which field lines originating in magnetic islands can remain strongly trapped in filamentary structures. We emphasize the key role of slab-like fluctuations in the transition from filamentary to more diffusive transport at greater heliocentric distances. This research has been supported in part by grant RTA6280002 from Thailand Science Research and Innovation and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165). &#160;MLG acknowledges support from the Parker Solar Probe FIELDS MAG team. &#160;Additional support is acknowledged from the&#160; NASA LWS program&#160; (NNX17AB79G) and the HSR program (80NSSC18K1210 & 80NSSC18K1648).</p>

Element Abundances of Solar Energetic Particles and the Photosphere, the Corona, and the Solar Wind

Atoms ◽

10.3390/atoms7040104 ◽

2019 ◽

Vol 7 (4) ◽

pp. 104 ◽

Cited By ~ 2

Author(s):

Donald V. Reames

Keyword(s):

Solar Wind ◽

Shock Waves ◽

Solar Corona ◽

Plasma Temperature ◽

Energetic Particles ◽

Charge Ratio ◽

Ambient Plasma ◽

Element Abundances ◽

Resonant Wave

From a turbulent history, the study of the abundances of elements in solar energetic particles (SEPs) has grown into an extensive field that probes the solar corona and physical processes of SEP acceleration and transport. Underlying SEPs are the abundances of the solar corona, which differ from photospheric abundances as a function of the first ionization potentials (FIPs) of the elements. The FIP-dependence of SEPs also differs from that of the solar wind; each has a different magnetic environment, where low-FIP ions and high-FIP neutral atoms rise toward the corona. Two major sources generate SEPs: The small “impulsive” SEP events are associated with magnetic reconnection in solar jets that produce 1000-fold enhancements from H to Pb as a function of mass-to-charge ratio A/Q, and also 1000-fold enhancements in 3He/4He that are produced by resonant wave-particle interactions. In large “gradual” events, SEPs are accelerated at shock waves that are driven out from the Sun by wide, fast coronal mass ejections (CMEs). A/Q dependence of ion transport allows us to estimate Q and hence the source plasma temperature T. Weaker shock waves favor the reacceleration of suprathermal ions accumulated from earlier impulsive SEP events, along with protons from the ambient plasma. In strong shocks, the ambient plasma dominates. Ions from impulsive sources have T ≈ 3 MK; those from ambient coronal plasma have T = 1 – 2 MK. These FIP- and A/Q-dependences explore complex new interactions in the corona and in SEP sources.

Reconnection on Open Field Lines Ahead of Coronal Mass Ejections

The High Latitude Heliosphere ◽

10.1007/978-94-011-0167-7_23 ◽

1995 ◽

pp. 129-132

Author(s):

D. J. McComas ◽

J. T. Gosling ◽

C. M. Hammond ◽

M. B. Moldwin ◽

J. L. Phillips ◽

...

Keyword(s):

Open Field ◽

Coronal Mass Ejections ◽

MHD simulations of the transition of magnetic reconnection from closed to open field lines

Journal of Geophysical Research Atmospheres ◽

10.1029/95ja02857 ◽

1996 ◽

Vol 101 (A5) ◽

pp. 10805-10816 ◽

Cited By ~ 31

Author(s):

Michael Hesse ◽

Joachim Birn ◽

Daniel N. Baker ◽

James A. Slavin

Keyword(s):

Magnetic Reconnection ◽

Open Field ◽

Mhd Simulations ◽

Secondary Magnetic Reconnection at Earth’s Flank Magnetopause

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.740560 ◽

2021 ◽

Vol 8 ◽

Author(s):

B. B. Tang ◽

W. Y. Li ◽

C. Wang ◽

Yu. V. Khotyaintsev ◽

D. B. Graham ◽

...

Keyword(s):

Solar Wind ◽

Magnetic Reconnection ◽

Open Field ◽

Global Scale ◽

Diffusion Region ◽

Magnetic Shear ◽

Magnetospheric Multiscale ◽

Field Lines ◽

Secondary Ion ◽

Magnetospheric Field

We report local secondary magnetic reconnection at Earth’s flank magnetopause by using the Magnetospheric Multiscale observations. This reconnection is found at the magnetopause boundary with a large magnetic shear between closed magnetospheric field lines and the open field lines generated by the primary magnetopause reconnection at large scales. Evidence of this secondary reconnection are presented, which include a secondary ion jet and the encounter of the electron diffusion region. Thus the observed secondary reconnection indicates a cross-scale process from a global scale to an electron scale. As the aurora brightening is also observed at the morning ionosphere, the present secondary reconnection suggests a new pathway for the entry of the solar wind into geospace, providing an important modification to the classic Dungey cycle.

Impulsive SEP Events (and Flares)

Solar Energetic Particles - Lecture Notes in Physics ◽

10.1007/978-3-030-66402-2_4 ◽

2021 ◽

pp. 71-95

Author(s):

Donald V. Reames

Keyword(s):

Magnetic Reconnection ◽

Gamma Ray ◽

Active Regions ◽

Energetic Particles ◽

Charge Ratio ◽

Direct Access ◽

Particle Interactions ◽

Element Abundances ◽

Resonant Wave ◽

Abstract3He-rich, Fe-rich, and enriched in elements with Z > 50, the abundances of solar energetic particles (SEPs) from the small impulsive SEP events stand out as luminaries in our study. The 3He is enhanced by resonant wave-particle interactions. Element abundances increase 1000-fold as the ~3.6 power of the mass-to-charge ratio A/Q from He to heavy elements like Au or Pb, enhanced during acceleration in islands of magnetic reconnection in solar jets, and probably also in flares. This power-law of enhancement vs. A/Q implies Q determined by a source temperature of 2.5–3.2 MK, typical of jets from solar active regions where these impulsive SEPs occur. However, a few small events are unusual; several have suppressed 4He, and rarely, a few very small events with steep spectra have elements N or S greatly enhanced, perhaps by the same resonant-wave mechanism that enhances 3He. Which mechanism will dominate? The impulsive SEP events we see are associated with narrow CMEs, from solar jets where magnetic reconnection on open field lines gives energetic particles and CMEs direct access to space. Gamma-ray lines tell us that the same acceleration physics may occur in flares.

Major solar flares without coronal mass ejections

Proceedings of the International Astronomical Union ◽

10.1017/s174392130902941x ◽

2008 ◽

Vol 4 (S257) ◽

pp. 283-286 ◽

Cited By ~ 7

Author(s):

N. Gopalswamy ◽

S. Akiyama ◽

S. Yashiro

Keyword(s):

Open Field ◽

Coronal Mass Ejections ◽

Solar Flares ◽

Active Regions ◽

High Energy ◽

X Ray ◽

Type Iii ◽

High Energy Electrons ◽

Field Lines ◽

Microwave Bursts

AbstractWe examine the source properties of X-class soft X-ray flares that were not associated with coronal mass ejections (CMEs). All the flares were associated with intense microwave bursts implying the production of high energy electrons. However, most (85%) of the flares were not associated with metric type III bursts, even though open field lines existed in all but two of the active regions. The X-class flares seem to be truly confined because there was no material ejection (thermal or nonthermal) away from the flaring region into space.

Anomalous-plasmoid-ejection-induced secondary magnetic reconnection: modeling solar flares and coronal mass ejections by laser–plasma experiments

High Power Laser Science and Engineering ◽

10.1017/hpl.2013.2 ◽

2013 ◽

Vol 1 (1) ◽

pp. 11-16 ◽

Cited By ~ 2

Author(s):

Quanli Dong ◽

Dawei Yuan ◽

Shoujun Wang ◽

Xun Liu ◽

Yutong Li ◽

...

Keyword(s):

Magnetic Reconnection ◽

Current Sheet ◽

Coronal Mass Ejections ◽

Solar Flares ◽

Theoretical Models ◽

High Energy ◽

High Energy Density ◽

Driving Mechanism ◽

Secondary Current ◽

AbstractThe driving mechanism of solar flares and coronal mass ejections is a topic of ongoing debate, apart from the consensus that magnetic reconnection plays a key role during the impulsive process. While present solar research mostly depends on observations and theoretical models, laboratory experiments based on high-energy density facilities provide the third method for quantitatively comparing astrophysical observations and models with data achieved in experimental settings. In this article, we show laboratory modeling of solar flares and coronal mass ejections by constructing the magnetic reconnection system with two mutually approaching laser-produced plasmas circumfused of self-generated megagauss magnetic fields. Due to the Euler similarity between the laboratory and solar plasma systems, the present experiments demonstrate the morphological reproduction of flares and coronal mass ejections in solar observations in a scaled sense, and confirm the theory and model predictions about the current-sheet-born anomalous plasmoid as the initial stage of coronal mass ejections, and the behavior of moving-away plasmoid stretching the primary reconnected field lines into a secondary current sheet conjoined with two bright ridges identified as solar flares.

Radio Astronomical Tools for the Study of Solar Energetic Particles I. Correlations and Diagnostics of Impulsive Acceleration and Particle Propagation

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2020.580436 ◽

2021 ◽

Vol 7 ◽

Author(s):

Karl-Ludwig Klein

Keyword(s):

Particle Acceleration ◽

Energetic Particles ◽

Relativistic Electrons ◽

The Sun ◽

Radio Bursts ◽

Type Iii ◽

Wide Range ◽

Field Lines ◽

Impulsive Processes

Solar energetic particles (SEPs) are sporadically ejected from the Sun during flares and coronal mass ejections. They are of major astrophysical interest, because the proximity of the Sun allows for detailed multi-messenger studies. They affect space weather due to interactions with electronics, with the Earth’s atmosphere, and with humans if they leave the protective shield of the magnetosphere of the Earth. Since early studies in the 1950s, starting with particle detectors on the ground, SEP events have been related to radio bursts. Two subjects are addressed in this chapter: attempts to establish quantitative correlations between SEPs and microwave bursts produced by gyro synchrotron radiation of mildly relativistic electrons, and the information derived from type III radio bursts on impulsive processes of particle acceleration and the coronal and interplanetary propagation. Type III radio bursts produced by electron beams on open magnetic field lines have a wide range of applications, including the identification of acceleration regions, the identification of confined particle acceleration with coronal signatures, but no SEPs, and the paths that the electrons, and energetic charged particles in general, take to travel from the low corona to the Heliosphere in case they escape. Simple scenarios of coronal particle acceleration are confirmed in relatively simple and short events. But the comparison with particle transport models shows that longer and delayed acceleration episodes exist especially in large SEP events. They will be discussed in a companion chapter.