Introduction to SEPs - Reuven Ramaty High Energy Solar ...

Introduction to SEPs - Reuven Ramaty High Energy Solar ...

Introduction to SEPs Christina Cohen Caltech Outline What are SEPs? And why do we care? How are the measured? on the ground in space What is the SEP history? pre-1997 post 1997 What is new and exciting about SEPs? in my humble opinion..... What are SEPs? Solar Energetic Particles Solar = assumed to originate at the Sun Energetic = historically above a few hundred keV/nuc Particles = ions (mostly H, He like the Sun) + electrons

Seen as increases in counting rates of ions (and/or electrons) of energies usually above 0.1 MeV/nucleon What measure history (old/new) excitement Why do we care about SEPs? A sample of the Sun one of the most accurately measured solar samples if we can just figure out the details of creating them and getting them here Earth effects energetic particles hitting the Earths atmosphere excite atoms and create aurora What measure history (old/new)

excitement Aurora Examples energetic particles hitting the Earths atmosphere excite atoms and create aurora What measure history (old/new) excitement Earth Radiation Belts Energetic particles are trapped in belts around the Earth Radiation hazard for Earthorbiting spacecraft What measure history (old/new)

excitement Why do we care about SEPs? A sample of the Sun one of the most accurately measured solar samples if we can just figure out the details of creating them and getting them here Earth effects energetic particles hitting the Earths atmosphere excite atoms and create aurora energetic particles contribute to the radiation belts part of geomagnetic storms which can cause black outs change in Earths magnetic field induces strong currents in power system Hydro Quebec lost power grid for 9 hours in March 1989 What measure history (old/new) excitement Why do we care about

SEPs? Spacecraft Effects Loss of data Spurious signals False alarms, noise strobes, erroneous telemetry values Phantom commands For example gain changes and attitude sensor errors Mission or sensor degradation Solar array degradation Safeholds Latchups Subsystem failure Loss of a redundant system Mission Loss What measure history (old/new) excitement How are SEPs Measured? On the ground neutron monitors (indirect measurement)

In space (since early 1960s) first measurements (scintillation and Geiger counters) dE/dx vs E technique Proportional counters Solid state detectors Time of flight E/q + dE/dx vs E (SEPICA) What measure history (old/new) excitement How are SEPs Measured? On the ground neutron monitors (indirect measurement) In space (since early 1960s) first measurements (scintillation and Geiger counters) dE/dx vs E technique Proportional counters Solid state detectors

Time of flight E/q + dE/dx vs E (SEPICA) What measure history (old/new) excitement How are SEPs Measured? dE/dx (Z/V)Z/V))2 (Z/V)MZ2/E) On the ground E dE/dx Z2Mmeasurement) neutron monitors (indirect dE/dx ~early E/ L =1960s) E/(Z/V)L0 sec ) In space (since first measurements (scintillation and Geiger counters) dE/dx vs E technique Proportional counters

Solid state detectors Time of flight E/q + dE/dx vs E (SEPICA) What measure history (old/new) excitement How are SEPs Measured? On the ground neutron monitors (indirect measurement) In space (since early 1960s) first measurements (scintillation and Geiger counters) dE/dx vs E technique Proportional counters Solid state detectors Time of flight E/q + dE/dx vs E (SEPICA) What

measure history (old/new) excitement How are SEPs Measured? On the ground neutron monitors (indirect measurement) In space (since early 1960s) first measurements (scintillation and Geiger counters) dE/dx vs E technique Proportional counters Solid state detectors Time of flight E/q + dE/dx vs E (SEPICA) What measure history (old/new) excitement

What is the History of SEPs? (pre-1997) First detection with connection to solar flare observation - Forbush 1946 in neutron monitor Timing related to gamma ray flare 1956 (most well studied) Better in space because can see them directly - space age intensity energy spectra composition What measure Categorization history (old/new) excitement What is the History of SEPs? (pre-1997) First detection with connection to solar flare

observation - Forbush 1946 in neutron monitor Timing related to gamma ray flare 1956 (most well studied) Better in space because can see them directly - space age intensity energy spectra composition What measure Categorization history (old/new) excitement What is the History of SEPs? At the same time... (pre-1997) flares are being categorized by size, duration, emission wavelength

radio emission is being categorized flares and radio emission combined to create... Two classes of flares Impulsive Gradual What measure history (old/new) excitement What is the History of SEPs? (pre-1997) Correlations with SEP characteristics results in a 2 class SEP system: Impulsive Gradual Flare Short duration

Characterist Compact/Point Source ics Long duration Large Source Radio Characterist Type III/V ics Type II/IV 3 Particle He, e-, heavy ion SW like composition Characterist rich long duration, large, ics short duration, small, wide longitude limited longitude What measure history (old/new) excitement What is the History of SEPs?

Gradual What measure (pre-1997) Impulsive history (old/new) excitement What is the History of SEPs? (pre-1997) All SEPs created by flares slight problem with longitude distribution of gradual events ideas of storage, cross-field transport, lots of scattering in the interplanetary medium (not happy about this) Not a good correlation between interacting protons and SEP protons (SMM allowed gamma-ray measurements in space 1980)

Enter Skylab and CME observations (1978) high correlation (96%) between gradual flares and CMEs CMEs can drive shocks and shocks can accelerate particles What measure history (old/new) excitement What is the History of SEPs? (pre-1997) Nice things about CME-shock acceleration for gradual SEP events CME angular size close to longitude distribution of gradual SEP events Solves the cross-field transport problem Correlation between CME size/speed and SEP size Found a gradual SEP event with no flare but with CME Found CMEs did not occur with impulsive SEP events

Long acceleration in the IPM explained long duration of gradual SEP events (compared to short impulsive) What measure history (old/new) excitement What is the History of SEPs? (pre-1997) Nice things about CME-shock acceleration for gradual SEP events CME angular size close to longitude distribution of gradual SEP events Solves the cross-field transport problem Correlation between CME size/speed and SEP size Found a gradual SEP event with no flare but with CME Found CMEs did not occur with impulsive SEP events Long acceleration in the IPM explained long duration of gradual SEP events (compared to short impulsive)

What measure history (old/new) excitement What is the History of SEPs? (pre-1997) Paradigm Shift Had 1 acceleration mechanism for all SEP events Now have two independent acceleration mechanisms CME-driven shock acceleration => Gradual SEP events Impulsive flare acceleration => Impulsive SEP events

Reames 1999 What measure history (old/new) excitement What is the History of SEPs? (pre-1997) Flurry of activity in SEP studies to define characteristics of two classes (1980s) Impulsive Klecker et al. 1984 finds charge state difference Mason et al. 1986 finds systematic composition difference Reames explains charge and composition characteristics in terms of low altitude What measure

history (old/new) excitement What is the History of SEPs? (pre-1997) Flurry of activity in SEP studies to define characteristics of two classes (1980s) Impulsive Klecker et al. 1984 finds charge state difference Mason et al. 1986 finds systematic composition difference Reames explains charge and composition characteristics in terms of low altitude What measure history (old/new) excitement What is the History of SEPs?

(pre-1997) Flurry of activity in SEP studies to define characteristics of two classes (1980s) Impulsive Klecker et al. 1984 finds charge state difference Mason et al. 1986 finds systematic composition difference Reames explains charge and composition characteristics in terms of low altitude What measure history (old/new) excitement What is the History of SEPs? (pre-1997) Gradual All flare material is like impulsive SEP material but gradual SEP material looks

like the solar wind composition charge states Roll offs of spectra consistent with diffusion from shock region What measure history (old/new) excitement What is the History of SEPs? (pre-1997) Gradual All flare material is like impulsive SEP material but gradual SEP material looks like the solar wind composition charge states

Roll offs of spectra consistent with diffusion from shock region What measure history (old/new) excitement What is the History of SEPs? (pre-1997) The 1990s standard 2 class system table Two Groups => Impulsive Flare acceleratio n Gradual Shock acceleratio

n He/4He ~1 ~0.0005 Fe/O ~1 ~0.1 QFe ~20 ~14 Duration Hours Days X-rays

Impulsive Gradual 3 Coronagrap h What Reames 1999 Big Point to remember: the two classes are exclusive Flare particles in gradual events do not escape into the -CME (96%) IPM because of closed field lines behind the CME measure history (old/new) excitement What is the History of SEPs? (pre-1997)

The 1990s standard 2 class system table Two Groups => Impulsive Flare acceleratio n Gradual Shock acceleratio n He/4He ~1 ~0.0005 Fe/O ~1 ~0.1

QFe ~20 ~14 Duration Hours Days X-rays Impulsive Gradual 3 Coronagrap h What Reames 1999

Big Point to remember: the two classes are exclusive Flare particles in gradual events do not escape into the -CME (96%) IPM because of closed field lines behind the CME measure history (old/new) excitement What is the History of SEPs? ACE launches August 1997 (post-1997) Suite of high-tech instruments to study heavy ions in SEP events over 3 orders of magnitude in energy (.1-100 MeV/n) Elemental Composition (ULEIS+SIS) Isotopic Composition (ULEIS+SIS) Charge State Composition (SEPICA) In November 1997, ACE observes first gradual SEP events Composition does not look as it should...

What measure history (old/new) excitement What is the History of SEPs? ACE launches August 1997 (post-1997) Suite of high-tech instruments to study heavy ions in SEP events over 3 orders of magnitude in energy (.1-100 MeV/n) Elemental Composition (ULEIS+SIS) Isotopic Composition (ULEIS+SIS) Charge State Composition (SEPICA) In November 1997, ACE observes first gradual SEP events Composition does not look as it should...

What measure history (old/new) excitement What is the History of SEPs? (post-1997) Within the first year, ACE observes many more of these enriched-Fe events Composition from C-Ni looks impulsive (12-60 MeV/n) Enhancements of 3He (not at impulsive levels) SAMPEX measures charge states with geomagnetic cutoff technique At 30 MeV/n QFe is ~20 (like impulsive) QFe is energy dependent What measure

history (old/new) excitement What is the History of SEPs? (post-1997) Within the first year, ACE observes many more of these enriched-Fe events Composition from C-Ni looks impulsive (12-60 MeV/n) Enhancements of 3He (not at impulsive levels) SAMPEX measures charge states with geomagnetic cutoff technique At 30 MeV/n QFe is ~20 (like impulsive) QFe is energy dependent Leske etWhat al. measure history (old/new) excitement Cohen et al. 1999

What is the History of SEPs? (post-1997) Within the first year, ACE observes many more of these enriched-Fe events Composition from C-Ni looks impulsive (12-60 MeV/n) Enhancements of 3He (not at impulsive levels) SAMPEX measures charge states with geomagnetic cutoff technique At 30 MeV/n QFe is ~20 (like impulsive) QFe is energy dependent Moebius et al. 1999 What measure Mazur et al., 1999 history (old/new) excitement

What is the History of SEPs? (post-1997) How should we classify these events? Two Groups => Impulsive Flare acceleratio n Gradual Shock acceleratio n He/4He ~1 ~0.0005 Fe/O

~1 ~0.1 QFe ~20 ~14 Duration Hours Days X-rays Impulsive Gradual Coronagrap h --

CME (96%) 3 What measure history (old/new) excitement What is the History of SEPs? (post-1997) How should we classify these events? Two Groups => Impulsive Flare acceleratio n He/4He

~1 Fe/O ~1 ~0.1 QFe ~20 ~14 Duration Hours Days X-rays Impulsive Coronagrap h

-- 3 What measure history (old/new) Gradual Shock acceleratio n ~0.0005 Gradual CME (96%) excitement

What is the History of SEPs? (post-1997) How should we classify these events? Two Groups => Impulsive Flare acceleratio n Gradual Shock acceleratio n He/4He ~1 ~0.0005 Fe/O ~1

~0.1 ~20 ~14 Duration Hours Days X-rays Impulsive Coronagrap h -- 3 QFe What

measure history (old/new) Gradual CME (96%) excitement What is the History of SEPs? (post-1997) How should we classify these events? Two Groups => Impulsive Flare acceleratio n

He/4He ~1 3 What measure Gradual Shock acceleratio n ~0.0005 Fe/O ~1 ~0.1

QFe ~20 ~14 Duration Hours X-rays Impulsive Coronagrap h -- history (old/new) Days

Gradual CME (96%) excitement What is the History of SEPs? (post-1997) What happens when new results challenge old beliefs? Q/M effect Velocity dispersion effect Grudging acceptance into existing framework (shock acceleration) Diffusion from shock region Suprathermal flare material (small amounts from preceding flares) What measure history (old/new)

excitement What is the History of SEPs? (post-1997) What happens when new results challenge old beliefs? Q/M effect Velocity dispersion effect Grudging acceptance into existing framework (shock acceleration) Diffusion from shock region Suprathermal flare material (small amounts from preceding flares) Not always What measure history (old/new) excitement What is the History of

SEPs? (post-1997) What happens when new results challenge old beliefs? Q/M effect Velocity dispersion effect Grudging acceptance into existing framework (shock acceleration) Diffusion from shock region Suprathermal flare material (small amounts from preceding flares) Not always What measure history (old/new) excitement What is the History of SEPs? (post-1997)

What happens when new results challenge old beliefs? Q/M effect Velocity dispersion effect Grudging acceptance into existing framework (shock acceleration) Diffusion from shock region Suprathermal flare material (small amounts from preceding flares) Not always What measure history (old/new) excitement What is the History of SEPs? (post-1997) What happens when new results challenge old beliefs? Q/M effect

Velocity dispersion effect Grudging acceptance into existing framework (shock acceleration) Diffusion from shock region Suprathermal flare material (small amounts from preceding flares) Not always What measure history (old/new) excitement What is the History of SEPs? (post-1997) What happens when new results challenge old beliefs? Q/M effect Velocity dispersion effect Grudging acceptance into existing

framework (shock acceleration) Diffusion from shock region Suprathermal flare material (small amounts from preceding flares) Not always What measure history (old/new) excitement What is New and Exciting About SEPs? How do we explain these results? Flare material in gradual events Energy dependent charge states and composition CMEs seen with impulsive SEP events Type IIIs seen with gradual SEP events gradual SEP events dont look like solar wind What

measure history (old/new) excitement What is New and Exciting About SEPs? How do we explain these results? Flare material in gradual events Energy dependent charge states and composition CMEs seen with impulsive SEP events Type IIIs seen with gradual SEP events gradual SEP events dont look like solar wind What measure history (old/new) excitement What is New and Exciting About SEPs?

How do we explain these results? Flare material in gradual events Energy dependent charge states and composition CMEs seen with impulsive SEP events Type IIIs seen with gradual SEP events gradual SEP events dont look like solar wind What measure history (old/new) excitement What is New and Exciting About SEPs? How do we explain these results? Flare material in gradual events Energy dependent charge states and composition CMEs seen with impulsive SEP events Type IIIs seen with gradual SEP events gradual SEP events dont look like solar wind

Mewaldt et al. 2000 What measure history (old/new) excitement What is New and Exciting About SEPs? Back to the big questions Are there 2 distinct classes of SEP events?? What is being accelerated? How is it being accelerated? What measure history (old/new) excitement What is New and Exciting About SEPs?

Back to the big questions Are there 2 distinct classes of SEP events?? What is being accelerated? How is it being accelerated? What measure history (old/new) excitement What is New and Exciting About SEPs? Back to the big questions Are there 2 distinct classes of SEP events?? What is being accelerated? How is it being accelerated? Probably not 2 separate classes of events What measure But 2 acceleration

mechanisms (the hard part is distinguishing them in SEP observations) history (old/new) excitement What is New and Exciting About SEPs? Two competing theories Shock orientation flare suprathermals present energy-dependent composition of the seed population perpendicular vs parallel shock difference Direct flare contribution flare particles can escape observation depends on connection to flare strength of shock size of flare What measure

history (old/new) excitement What is New and Exciting About SEPs? Two competing theories Shock orientation flare suprathermals present energy-dependent composition of the seed population perpendicular vs parallel shock difference Direct flare contribution flare particles can escape observation depends on connection to flare strength of shock size of flare Tylka et al. 2005 What measure history (old/new) excitement

What is New and Exciting About SEPs? Two competing theories Shock orientation flare suprathermals present energy-dependent composition of the seed population perpendicular vs parallel shock difference Direct flare contribution flare particles can escape observation depends on connection to flare strength of shock size of flare Cane et al. 2003 What measure history (old/new) excitement What is New and Exciting

About SEPs? Two competing theories - How to decide? Measurements at different longitudes at the STEREO same time What measure history (old/new) excitement What is New and Exciting About SEPs? Two competing theories - How to decide? Measurements at different longitudes at the same time Measurements closer to the Sun (and/or at different distances at the same time) What measure

history (old/new) excitement

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