Table Of ContentGM01012_CH01.qxd 11/8/06 11:33 AM Page i
Geophysical Monograph Series
Including
IUGG Volumes
Maurice Ewing Volumes
Mineral Physics Volumes
GM01012_CH01.qxd 11/8/06 11:33 AM Page ii
Geophysical Monograph Series
128 Hawaiian Volcanoes: Deep Underwater Perspectives 148 Mid-Ocean Ridges: Hydrothermal Interactions
Eiichi Takahashi, Peter W. Lipman, Michael O. Garcia, Between the Lithosphere and Oceans
Jiro Naka, and Shigeo Aramaki (Eds.) Christopher R. German, Jian Lin, and Lindsay M.
129 Environmental Mechanics: Water, Mass and Energy Parson (Eds.)
Transfer in the Biosphere Peter A. C. Raats, David 149 Continent-Ocean Interactions Within East Asian
Smiles, and Arthur W. Warrick (Eds.) Marginal Seas Peter Clift, Wolfgang Kuhnt, Pinxian
130 Atmospheres in the Solar System: Comparative Wang, and Dennis Hayes (Eds.)
Aeronomy Michael Mendillo, Andrew Nagy, 150 The State of the Planet: Frontiers and Challenges
and J. H. Waite (Eds.) inGeophysics Robert Stephen John Sparks
131 The Ostracoda: Applications in Quaternary Research and Christopher John Hawkesworth (Eds.)
Jonathan A. Holmes and Allan R. Chivas (Eds.) 151 The Cenozoic Southern Ocean: Tectonics,
132 Mountain Building in the Uralides Pangea to the Sedimentation, and Climate Change Between Australia
Present Dennis Brown, Christopher Juhlin, and and Antarctica Neville Exon, James P. Kennett,
Victor Puchkov (Eds.) and Mitchell Malone (Eds.)
133 Earth’s Low-Latitude Boundary Layer Patrick T. Newell 152 Sea Salt Aerosol Production:Mechanisms, Methods,
and Terry Onsage (Eds.) Measurements, and Models Ernie R. Lewis and
134 The North Atlantic Oscillation: Climatic Significance Stephen E. Schwartz
and Environmental Impact James W. Hurrell, Yochanan
153 Ecosystems and Land Use Change Ruth S. DeFries,
Kushnir, Geir Ottersen, and Martin Visbeck (Eds.)
Gregory P. Anser, and Richard A. Houghton (Eds.)
135 Prediction in Geomorphology Peter R. Wilcock
154 The Rocky Mountain Region—An Evolving
and Richard M. Iverson (Eds.)
Lithosphere: Tectonics, Geochemistry, and Geophysics
136 The Central Atlantic Magmatic Province: Insights from
Karl E. Karlstrom and G. Randy Keller (Eds.)
Fragments of Pangea W. Hames, J. G. McHone,
155 The Inner Magnetosphere: Physics and Modeling
P. Renne, and C. Ruppel (Eds.)
Tuija I. Pulkkinen, Nikolai A. Tsyganenko, and Reiner
137 Earth’s Climate and Orbital Eccentricity: The Marine
H. W. Friedel (Eds.)
Isotope Stage 11 Question André W. Droxler, Richard
156 Particle Acceleration in Astrophysical Plasmas:
Z. Poore, and Lloyd H. Burckle (Eds.)
Geospace and Beyond Dennis Gallagher, James Horwitz,
138 Inside the Subduction Factory John Eiler (Ed.)
Joseph Perez, Robert Preece, and John Quenby (Eds.)
139 Volcanism and the Earth’s Atmosphere Alan Robock
157 Seismic Earth: Array Analysis of Broadband
and Clive Oppenheimer (Eds.)
Seismograms Alan Levander and Guust Nolet(Eds.)
140 Explosive Subaqueous Volcanism James D. L. White,
158 The Nordic Seas: An Integrated Perspective Helge
John L. Smellie, and David A. Clague (Eds.)
Drage, Trond Dokken, Tore Furevik, Rüdiger Gerdes,
141 Solar Variability and Its Effects on Climate Judit M.
and Wolfgang Berger (Eds.)
Pap and Peter Fox (Eds.)
159 Inner Magnetosphere Interactions: New Perspectives
142 Disturbances in Geospace: The Storm-Substorm
From Imaging James Burch, Michael Schulz, and
Relationship A. Surjalal Sharma, Yohsuke Kamide,
Harlan Spence (Eds.)
and Gurbax S. Lakhima (Eds.)
160 Earth’s Deep Mantle: Structure, Composition, and
143 Mt. Etna:Volcano Laboratory Alessandro Bonaccorso,
Evolution Robert D. van der Hilst, Jay D. Bass,
Sonia Calvari, Mauro Coltelli, Ciro Del Negro,
Jan Matas, and Jeannot Trampert (Eds.)
and Susanna Falsaperla (Eds.)
144 The Subseafloor Biosphere at Mid-Ocean Ridges 161 Circulation in the Gulf of Mexico: Observations and
William S. D. Wilcock, Edward F. DeLong, Deborah S. Models Wilton Sturges and Alexis Lugo-Fernandez
Kelley, John A. Baross, and S. Craig Cary (Eds.) (Eds.)
145 Timescales of the Paleomagnetic Field James E. T. 162 Dynamics of Fluids and Transport Through Fractured
Channell, Dennis V. Kent, William Lowrie, and Joseph Rock Boris Faybishenko, Paul A. Witherspoon, and
G. Meert (Eds.) John Gale (Eds.)
146 The Extreme Proterozoic: Geology, Geochemistry, 163 Remote Sensing of Northern Hydrology: Measuring
and Climate Gregory S. Jenkins, Mark A. S. McMenamin, Environmental Change Claude R. Duguay and Alain
Christopher P. McKay, and Linda Sohl (Eds.) Pietroniro (Eds.)
147 Earth’s Climate: The Ocean–Atmosphere Interaction 164 Archean Geodynamics and Environments
Chunzai Wang,Shang-Ping Xie,and James Keith Benn, Jean-Claude Mareschal, and Kent C. Condie
A. Carton (Eds.) (Eds.)
GM01012_CH01.qxd 11/8/06 11:33 AM Page iii
Geophysical Monograph 165
Solar Eruptions and
Energetic Particles
Natchimuthukonar Gopalswamy
Richard Mewaldt
Jarmo Torsti
Editors
American Geophysical Union
Washington, DC
GM01012_CH01.qxd 11/8/06 11:33 AM Page iv
Published under the aegis of the AGU Books Board
Jean-Louis Bougeret, Chair; Gray E. Bebout, Cassandra G. Fesen, Carl T. Friedrichs, Ralf R. Haese, W. Berry Lyons,
Kenneth R. Minschwaner, Andrew Nyblade, Darrell Strobel, and Chunzai Wang, members.
Library of Congress Cataloging-in-Publication Data
Solar eruptions and energetic particles / Natchimuthukonar Gopalswamy, Richard
Mewaldt, Jarmo Torsti, editors.
p. cm. -- (Geophysical monograph ; 165)
Includes bibliographical references and index.
ISBN-13: 978-0-87590-430-6 (alk. paper)
ISBN-10: 0-87590-430-0 (alk. paper)
1. Coronal mass ejections. 2. Solar energetic particles. 3. Solar activity. I.
Gopalswamy, N. II. Mewaldt, R. A. III. Torsti, Jarmo.
QB529.S623 2006
523.7'5--dc22
2006022105
ISBN-13: 978-0-87590-430-6 (alk. paper)
ISBN-10: 0-87590-430-0 (alk. paper)
ISSN 0065-8448
Copyright 2006 by the American Geophysical Union
2000 Florida Avenue, N.W.
Washington, DC 20009
Figures, tables and short excerpts may be reprinted in scientific books and journals if the source is properly cited.
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commercial purposes requires permission from the American Geophysical Union.
Printed in the United States of America.
GM01012_CH01.qxd 11/8/06 11:33 AM Page v
CONTENTS
Overview
Preface
Natchimuthukonar Gopalswamy, Richard Mewaldt, and Jarmo Torsti.................................................... ix
Solar Eruptions and Energetic Particles: An Introduction
N. Gopalswamy, R. Mewaldt, and J. Torsti............................................................................................. 1
AHistorical Perspective on Coronal Mass Ejections
R. A. Howard......................................................................................................................................... 7
Solar Energetic Particles and Coronal Mass Ejections: APerspective
J. R. Jokipii............................................................................................................................................. 15
Coronal Mass Ejections
Observational Properties of Coronal Mass Ejections
S. W. Kahler........................................................................................................................................... 21
ABroad Perspective on Automated CME Tracking: Towards Higher Level Space Weather Forecasting
Eva Robbrecht and David Berghmans.................................................................................................... 33
Initiation of Coronal Mass Ejections
Ronald L. Moore and Alphonse C. Sterling............................................................................................ 43
Magnetic Helicity and Coronal Mass Ejections
A. Nindos............................................................................................................................................... 59
Bursting the Solar Bubble: The Flare-Coronal Mass Ejection Relationship
Richard Harrison.................................................................................................................................... 73
Models of Solar Eruptions: Recent Advances From Theory and Simulations
Ilia I. Roussev and Igor V. Sokolov......................................................................................................... 89
Solar Energetic Particles
Solar Energetic Particles: An Overview
Tycho von Rosenvinge and Hilary V. Cane............................................................................................103
The Source Material for Large Solar Energetic Particle Events
R. A. Mewaldt, C. M. S. Cohen, and G. M. Mason................................................................................115
GM01012_CH01.qxd 11/8/06 11:33 AM Page vi
Observations of Energy-Dependent Charge States in Solar Energetic Particles
M. A. Popecki.......................................................................................................................................127
Modeling the Energy-Dependent Charge States of Solar Energetic Particles
Leon Kocharov......................................................................................................................................137
Solar Energetic Particle Composition
Berndt Klecker.......................................................................................................................................147
Flares and Energetic Particles
Radiative Diagnoses of Energetic Particles
A. L. MacKinnon...................................................................................................................................157
Gamma Radiation From Flare-Accelerated Particles Impacting the Sun
Gerald H. Share and Ronald J. Murphy.................................................................................................177
Particle Acceleration in Solar Flares and Escape Into Interplanetary Space
Markus J. Aschwanden..........................................................................................................................189
Solar Energetic Electrons, X-rays, and Radio Bursts
R. P. Lin.................................................................................................................................................199
CME-Driven Shocks and SEPs in the Heliosphere
Coronal Mass Ejections and Type II Radio Bursts
Nat Gopalswamy..................................................................................................................................207
EIT Waves and Coronal Shock Waves
G. Mann................................................................................................................................................221
Radio Bursts and Solar Energetic Particle Events
K.-L. Klein.............................................................................................................................................233
Diffusive Ion Acceleration by CME-Driven Shocks
Martin A. Lee........................................................................................................................................245
Acceleration of SEPs: Role of CME-Associated Shocks and Turbulence
R. Vainio...............................................................................................................................................253
Spectral and Compositional Characteristics of Gradual and Impulsive Solar Energetic Particle Events
Allan J. Tylka and Martin A. Lee............................................................................................................263
Observations of Energetic Storm Particles: An Overview
Christina M. S. Cohen...........................................................................................................................275
Fifty Years of Ground Level Solar Particle Event Observations
C. Lopate...............................................................................................................................................283
GM01012_CH01.qxd 11/8/06 11:33 AM Page vii
The Propagation of Solar Energetic Particles in the Interplanetary Medium
Wolfgang Dröge....................................................................................................................................297
Radial and Latitudinal Variations of the Energetic Particle Response to ICMEs
David Lario...........................................................................................................................................309
KET Ulysses Observations of SEPin and out of the Ecliptic
Alexei Struminsky and Bernd Heber......................................................................................................321
Space Weather
Geoeffective Coronal Mass Ejections and Energetic Particles
Eino Valtonen........................................................................................................................................335
The Creation of New Ion Radiation Belts Associated With Solar Energetic Particle Events and
Interplanetary Shocks
J. E. Mazur, J. B. Blake, P. L. Slocum, M. K. Hudson, and G. M. Mason................................................345
Energetic Particles in the Magnetosphere and Their Relationship to Solar Wind Drivers
I. Roth, M. K. Hudson, B. T. Kress, and K. L. Perry................................................................................353
Space Weather Challenges Intrinsic to the Human Exploration of Space
Ronald E. Turner....................................................................................................................................367
Space Weather: From Solar Eruptions to Magnetospheric Storms
Hannu E. J. Koskinen and K. Emilia J. Huttunen....................................................................................375
GM01012_CH02.qxd 11/8/06 11:36 AM Page 1
Solar Eruptions and Energetic Particles: An Introduction
N. Gopalswamy1, R. Mewaldt2, and J. Torsti3
This introductory article highlights current issues concerning two related
phenomena involving mass emission from the Sun: solar eruptions and solar
energetic particles. A brief outline of the chapters is provided indicating how the
current issues are addressed in the monograph. The sections in this introduction
roughly group the chapters dealing with coronal mass ejections (CMEs), solar
energetic particles (SEPs), shocks, and space weather. The concluding remarks
include a brief summary of outstanding issues that drive current and future
research on CMEs and SEPs.
1. OVERVIEW charged particles in the upstream medium to very high
energies. Even sub-Alfvenic CMEs interact with the solar
The Sun loses mass in three different ways: the Solar wind resulting in momentum exchange described by the
Wind, Coronal Mass Ejections (CMEs), and Solar Energetic aerodynamic drag. Thus, the three types of mass emissions
Particles (SEPs). These phenomena are signatures of solar are not independent. Even the flare process is not indepen-
variability from the matter point of view; electromagnetic dent: Almost all CMEs are associated with flares, which
radiation in the form of quiescent and flare emissions repre- accelerate electrons and ions that flow towards the Sun and
sents the other major variability. The mass emissions from away from the Sun producing electromagnetic radiation at
the Sun also signal fundamental physical processes such as various wavelengths and injecting flare-heated plasmas into
acceleration of plasmas to high energies, magnetic field the CMEs. Flares are also associated with the smaller and
reconnection and interaction between large-scale plasma more frequent SEPevents, known as impulsive SEP events.
structures. Fast solar wind originates from the open field It is thought that impulsive SEP events can provide seed
regions on the Sun known as coronal holes while CMEs particles for CME-driven shocks causing an interesting mix
originate from the closed field regions such as active regions of SEP compositions and charge states. Studies of these
and filament regions. The interplanetary plasma is the solar mass outflows from the Sun are also of significant practical
wind, and the propagation of CMEs through this plasma importance: they can cause severe space weather effects
represents interaction between them. CMEs often attain such as disruption of power systems on Earth, and can pose
super-Alfvenic speeds in the magnetized coronal and radiation hazards to our space travelers and spacecraft
interplanetary plasmas and hence are bound to drive fast systems. Various chapters in this volume provide a review of
mode shocks, which in turn are known to accelerate the the current status of our understanding of these energetic
phenomena, the underlying physics, and why humans care
about them.
The concept of mass leaving the Sun was contemplated
1NASA Goddard Space Flight Center, Greenbelt, Maryland
well over 100 years ago from when high-speed prominence
2California Institute of Technology, Pasadena, California
eruptions from the Sun were observed. R.A. Howard
3University of Turku, Turku, Finland
describes the historical development culminating in the dis-
covery of CMEs in the early 1970s, and the subsequent mile-
Solar Eruptions and Energetic Particles
stones in CME research including the pre-eminent position
Geophysical Monograph Series 165
This paper is not subject to U.S. copyright. Published in 2006 by occupied by CMEs as major drivers of geospace distur-
the American Geophysical Union bances. The discovery of SEPs preceded that of CMEs
10.1029/165GM02 by three decades, when Forbush reported the first event.
1
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2 SOLAR ERUPTIONS AND ENERGETIC PARTICLES: AN INTRODUCTION
J.R. Jokipii takes us through the early observations and the flare explosion causing CMEs to flares as a byproduct of
development of a theoretical understanding of particle accel- CMEs, he points out the common cause for the explosive
eration. He points out the universal nature of the energetic emission of mass and flare radiation.
particle distribution, whether it is from the Sun or from the I. Roussev and I. Sokolov review current CME modeling
rest of the universe as cosmic rays. efforts, focusing on the flux-rope and shear-arcade models.
In particular they discuss the salient features and major
2. CORONAL MASS EJECTIONS weaknesses of the two models. Current observations may not
be able to discriminate between the two models. They con-
S.W. Kahler reviews the current status of CME research clude that future prospects for CME modeling are more opti-
drawing heavily from the results of analyzing more than mistic, mainly because of the opportunities the STEREO
10,000 CMEs observed by the Solar and Heliospheric mission will provide for CME theorists and modelers to
Observatory (SOHO) mission. In addition to describing the answer some of the outstanding issues on CME initiation and
physical and statistical properties of CMEs, he explains the propagation.
basic magnetic structures involved in CME initiation and sub-
sequent propagation. He points out that progress in under-
standing CMEs has been accelerated by the inner coronal 3. SEPsAND THEIR RELATION TO
imaging in X-rays, EUV and radio, but more observations are FLARES AND CMEs
needed of spectral lines that can provide information on the
physical conditions in CMEs. The outstanding issues concern The SEPs that reach Earth originate in both flares and
the magnetic field geometries and topologies of CMEs, and CME-driven shocks, and there is on-going debate as to the
the way in which CME magnetic fields reconnect to become relative roles of these processes in large SEP events. T. von
open magnetic fields inthe heliosphere. The better sensitivity Rosenvinge and H.V. Cane provide an overview of the SEP
and extended field of view of the SOHO coronagraphs have phenomenon and of our current state of understanding. They
resulted in detecting a record number of CMEs. The data size focus on the current paradigm of SEP events and suggest that
will grow even further when future coronagraphs such as on some modification is needed in the two-class (impulsive and
the STEREO mission observe CMEs with higher cadence. It gradual SEP events) picture. They conclude that our under-
is therefore necessary to develop automatic techniques for standing of the SEP and related phenomena is still not com-
CME detection. E.Robbrecht and D. Berghmansdiscuss the plete despite the extensive body of observations currently
current status of such techniques for various solar features. available.
R.L. Moore and A.C. Sterling focus on how CMEs are initi- R.A. Mewaldt,C.M.S. Cohen,and G.M. Masonprovide an
ated, especially the fast ones that significantly disturb the authoritative account of the current state of affairs in SEP
heliosphere. They identify three fundamental mechanisms physics, covering a wide range of topics related to the source
that can explain the CME initiation: (1) runaway internal material for large SEP events. They review the recent work
tether-cutting reconnection, (2) runaway external tether- on the particle sources contributing to the seed population for
cutting reconnection, and (3) ideal MHD instability. The the accelerated particles. The gradual SEP events differ in
three mechanisms may operate singly or in combination. composition from the bulk solar wind in several key respects,
Magnetograms and movies of chromospheric and coronal implying that solar wind does not supply the principal seed
features are used to tell which one or which combination of population for these events. The suprathermal pool that is
these mechanisms is the trigger for eruption. One of the accelerated by CME-driven shocks seems to be made up of
points they emphasize is the production of a flux rope as a ions from impulsive solar flares and previous gradual events,
result of the eruption. The flux-rope structure has become a CIR events, pickup ions, CME ejecta, and the suprathermal
basic entity in CME research, used extensively by CME mod- tail of the solar wind.
elers. Flux-ropes are directly observed in the interplanetary The ionic charge states of SEPs reflect the thermal history
medium as magnetic clouds. The fact that CMEs carry of the material that is accelerated and possible non-thermal
twisted magnetic structures must be related to the removal of processes that may remove electrons. Observations by ACE,
accumulated helicity in the corona, as discussed by A. SAMPEX and SOHO show that the mean charge state often
Nindos. The study of helicity in CMEs has only started increases with energy over the energy range from ~50
recently, but the importance can be felt in the hemispheric keV/nucleon to 50 MeV/nucleon. M. Popecki reviews these
dependence of chirality of filaments, helicity of active observations and discusses some of the interpretations that
regions and the handedness of interplanetary magnetic have been offered for this unexpected behavior, including
clouds. R.A. Harrison discusses the connection between mixtures of heated-flare and coronal material, and stripping
flares and CMEs. While opposing views prevail from the of electrons during the acceleration and transport of the ions.
GM01012_CH02.qxd 11/8/06 11:36 AM Page 3
GOPALSWAMY ET AL. 3
L. Kocharov presents the results of a model of the evolution shocks and to interplanetary shocks, to supernova shocks.
of the ionic charge states of Fe during acceleration and trans- CME-driven shocks accelerate both electrons and ions. The
port and discusses what can be learned from ionic charge most common signature of shock-accelerated electrons is the
state observations. B. Kleckerreviews recent observations of radio emission known as type II radio bursts, which can be
the ion charge state composition in SEP events and discusses used to track the shocks from the Sun to all the way to Earth
the implications for our understanding of different accelera- and beyond. Although an additional shock source of flare
tion scenarios. There is considerable progress in our knowl- blast waves is often assumed, N. Gopalswamy has provided
edge of the elemental and isotopic composition, energy arguments that the type II phenomenon over the entire Sun-
spectra and ionic charge states in gradual and impulsive SEP Earth distance can be explained in terms of CME-driven
events. These new results show that the classification into shocks. He uses the hierarchical relationship between CME
two distinct types of events was oversimplified, and they pro- kinetic energy and the wavelength range of type II emission,
vide important new constraints on theoretical models for SEP the weakening of evidence for CME-less type II bursts, the
acceleration and transport. realistic profile of the fast-mode speed in the corona and IP
During Solar Cycle 23 considerable progress in under- medium, and the close connection between SEP events and
standing particle acceleration in SEP events resulted from type II radio bursts to support his arguments. G. Mann
new remote-sensing observations by missions such as explores the relation between coronal shocks (inferred from
RHESSI, SOHO, TRACE and Yohkoh. Some fraction of the coronal type II bursts), Moreton waves, and EUV transient
particles accelerated in flares escape into interplanetary (IP) waves (known as EIT waves because of their detection by the
space along open field lines, while others, trapped on closed Extreme-ultraviolet Imaging Telescope (EIT) on board
field lines, interact in the chromosphere and photosphere. SOHO). He also extends the Alfven speed profile in the
A.MacKinnongives an overview of the use of X-rays, γ-rays corona to two dimensions and attributes the inability of flare-
and radio observations in obtaining direct information on generated shocks to propagate beyond the Alfven-speed
flare site fast electrons and ions. He points out that observations maximum to explain the metric type II bursts. K.-L. Klein
of the SEPs detected in the IP medium as well as the flare-site compares the particle acceleration by flares and CME-driven
populations inferred from radiative diagnostics are ultimately shocks. He calls for a much closer interrelationship between
needed to fully understand the eruptive events. G. Share flares and CMEs as sources of SEPs, rather than assuming a
presents RHESSI observations of the gamma-ray and contin- clear-cut distinction between flare-related and CME shock-
uum radiation in some of the largest solar events of this past related SEP events.
solar maximum, and reviews how these observations can be M.A. Lee and R. Vainio review the present status of the
used to study the composition and energy spectra of particles theory of accelerating energetic ions at CME-driven shocks.
accelerated in the flare, as well as the composition of the solar Although the theory can generally account for the observed
atmosphere. One puzzling result is that the proton/alpha ratio features of these events, there remain outstanding issues to be
derived from the gamma-ray data is considerably smaller than addressed, including ion injection into the acceleration
is observed with in situSEP measurements. M.J. Aschwanden process, an improved description of the wave intensity
uses data from Yohkoh, SOHO, TRACE, and CGRO to illus- excited by the accelerated particles, and injection and accel-
trate the magnetic topologies in the accelerating region, the eration at quasi-perpendicular shocks. A. Tylka and M.A. Lee
asymmetry of upward versus downward acceleration, and investigate the correlations among spectral and composi-
particle access to interplanetary space. Of particular interest tional characteristics, which serve as powerful constraints for
are the magnetic topologies that lead to reconnection between their models of SEP events (both gradual and impulsive).
open and closed field lines. Along similar lines, R.P.Linuses Starting with CME-driven shocks as the accelerator for
recent observations from Wind and RHESSI to study solar gradual SEPs, they were able to account for the correlated
electron events observed both in situat 1 AU and remotely at spectral and compositional variability in SEPs by including
radio and x-ray wavelengths. While the properties of the inter- the shock normal angle and a compound seed population as
acting and escaping electrons are correlated, the correlationis variables. On the other hand, they point out the lack of
not explained by simple models. understanding of the spectra and composition of impulsive
SEP events in terms of flare parameters, such as size, dura-
4. CME-DRIVEN SHOCKS AND tion, and magnetic topology. C.M.S. Cohenreviews research
SEPsIN THE HELIOSPHERE on energetic storm particles (ESP) events, which are same as
the SEP events but occur when the accelerating shock passes
One of the greatest successes of space physics is the theory the observing spacecraft. She provides an overview of the
of shock acceleration, which has been successfully applied to observations and theories of ESPs from their first detection
particle acceleration at shocks ranging from planetary bow to our current understanding. ESP events are testimony to the
