• Không có kết quả nào được tìm thấy

Donald V. Reames - Solar Energetic Particles

N/A
N/A
Nguyễn Gia Hào

Academic year: 2023

Chia sẻ "Donald V. Reames - Solar Energetic Particles"

Copied!
233
0
0

Loading.... (view fulltext now)

Văn bản

Solar energetic particles (SEPs) come as bursts of high-energy particles from the direction of the Sun that last for hours or sometimes days. In this chapter, we introduce properties of SEPs after reviewing some properties of the solar and interplanetary environment in which they exist.

The Structure of the Sun

Within the tachocline, which lies at the bottom of the convective zone, the Sun rotates (from east to west) as a rigid body, but throughout the convective zone, the Sun rotates differently, faster at the equator than at the poles. Azimuthal surfaces of constant rotational speed run radially through the convection zone and form conical shells around the axis of rotation that extend inward only to the tachocline and not to the peak at the center of the Sun.

The Solar Magnetic Field

Coronal holes, often seen near the poles, are regions of open magnetic field lines that extend into the outer heliosphere and are stretched by the plasma of the solar wind. This usually defines the "top" of the corona and usually occurs near 2 RS, where it is ~ 106 cm3.

Figure 1.2 shows an image of the Sun in ultraviolet (UV) light taken by the Atmospheric Imaging Assembly (AIA) on the NASA spacecraft Solar Dynamics Observatory (SDO; https://sdo.gsfc.nasa.gov/)
Figure 1.2 shows an image of the Sun in ultraviolet (UV) light taken by the Atmospheric Imaging Assembly (AIA) on the NASA spacecraft Solar Dynamics Observatory (SDO; https://sdo.gsfc.nasa.gov/)

Coronal Mass Ejections (CMEs)

However, CMEs and the solar wind drag some of the field lines far into the outer heliosphere. However, βP increases with height in the corona and when βP>1, the plasma is no longer trapped in magnetic loops; it can spread out into space and pull magnetic fields outward into the solar wind.

Interplanetary Space

Solar Energetic Particles

  • Time Duration
  • Abundances
  • The Solar Cycle
  • Relativistic Kinematics

The abundances of elements and isotopes were powerful indicators of the origin, acceleration and transport of SEPs. It differs from abundances in the photosphere by a factor that depends on the first ionization potential (FIP) of the element as shown in Fig.1.6 and listed in Table 1.1 (Reames 1995,2014).

Table 1.1 lists the photospheric (Asplund et al. 2009) and the reference SEP (Reames 1995, 2014, 2020) abundances that we can use
Table 1.1 lists the photospheric (Asplund et al. 2009) and the reference SEP (Reames 1995, 2014, 2020) abundances that we can use

What Do We “ See ” at the Sun?

Reames, D.V.: ​​The "FIP effect" and the origin of solar particles and the solar wind. arXiv Reames, D.V.: ​​Four Different Pathways to Element Abundance in Solar Particles. Schmelz, J.T., Reames, D.V., von Steiger, R., Basu, S.: Composition of the solar corona, solar wind and solar particles.

The First SEPs

Solar Radio Bursts and Electrons

This differed from the large proton events in which the associated electrons were mainly relativistic. For type III bursts, frequencies drift rapidly, produced by 10–100 keV electrons streaming from the Sun; frequencies in type II bursts drift outward from a source moving at the speed (~1000 km s1) of a shock wave.

The Spatial Distribution

  • Lateral Diffusion and the Birdcage Model
  • Large Scale Shock Acceleration and CMEs
  • The Longitude Distribution
  • Scatter-Free Events
  • Field-Line Random Walk

Does ambient turbulence in the interplanetary medium cause pitch-angle scattering of the particles emanating from the Sun? In Fig.2.4 this contributes to the longitude distribution of the impulsive events shown in the right panel.

Fig. 2.2 Variation of the appearance of typical SEP events is shown as viewed from three solar longitudes (see text; after Reames 1999 # Springer; see also Cane et al
Fig. 2.2 Variation of the appearance of typical SEP events is shown as viewed from three solar longitudes (see text; after Reames 1999 # Springer; see also Cane et al

Shock Theory

If this process continues indefinitely, it can lead to a power law spectrum where power depends on shock compression ratio. However, there is no stronger collaboration effect; shock acceleration occurs within a modest number of proton gyro radii of the shock, and CME-powered shocks crossing each other spend negligible time at such a small separation.

Element Abundances

First Ionization Potential (FIP) and Powers of A/Q

It also became apparent that there were other abundance increases, such as Fe/O, which was about 10 times larger than in the solar wind (e.g. Gloeckler et al. 1975). The next generation of measurements of 3He-rich events (Figure 2.6) led to their association with non-relativistic electron events (Reames et al. 1985) and with type III radio bursts (Reames and Stone 1986).

Fig. 2.6 Intensities of 3 He and electrons of various energies (upper panels) show velocity dispersion (i.e
Fig. 2.6 Intensities of 3 He and electrons of various energies (upper panels) show velocity dispersion (i.e

The Seed Population for Shocks

We will see that in most cases these ESP peaks represent coronal environmental material, although suprathermal ions may also contribute. 2005) found that in two otherwise similar large SEP events, the energy dependence of Fe/C above ~10 MeV amu1 suddenly increased in one event and decreased in the other, as shown in the left panel of Fig. The right panel shows hypothetical spectra of two sources of suprathermal ions where different injection thresholds will yield different abundance ratios (Tylka et al.2005).

Fig. 2.7 The mass distribution of He is shown directly (solid – left scale) and with an expanded scale (open – right scale) to show
Fig. 2.7 The mass distribution of He is shown directly (solid – left scale) and with an expanded scale (open – right scale) to show

Ionization States

For further studies of the dependence of spectral refraction, of the power-law dependence of Q/A and the variation with shock geometry, see Li et al. Recent studies of the A/Q dependence in gradual SEP events (Reames2016) have found that most of these events (69%) have source-plasma temperatures of 1.6 MK, consistent with the acceleration of the ambient coronal plasma shock (see Sect. 5.6).

Disappearing-Filament Events

Only 24% of the events have active region temperatures of 2.5–3.2 MK and thus include dominant enhancements due to impulsive suprathermal seed ions. Thus, the properties of the SEP are controlled by those of the CME and the shock.

Fig. 2.11 Intensities vs. time are shown for the
Fig. 2.11 Intensities vs. time are shown for the

Wave Generation and the Streaming Limit

The controversy raised by Gosling's (1993) paper led to an invited discussion of three alternative perspectives in Eoswhere Hudson (1995) argued that the term. While the broadening of the term "flare" has some philosophical merit, it is important for SEP studies to distinguish a point-source flare, or now, a localized jet, from the source of acceleration in a broad, solar-extending CME. . pushed shock wave, especially when they involve different physical mechanisms.

SEP – CME Correlation

Of course, the "peak intensity" is in fact a strong function of longitude, as expected from Fig. 2.2 (see also Fig. 5.16), as is the speed of the shock driven by the CME; these factors contribute to the spread of the measurement, which, as we will see, can be reduced by using the measurements of several spacecraft in a single SEP event (see Fig. has greatly improved the CME-SEP relationship by modeling the full 3D geometry of shock waves using the three coronagraph images from SOHO/LASCO and STEREO A and B. Much of the remaining scattering must be due to differences in particle transport conditions that scatter the particles in space and give time variations and delays in reaching peak intensities .

SEPs Actually Cause Flares, Not the Reverse

Reames, D.V., Cliver, E.W., Kahler, S.W.: Abundance enhancements in impulsive solar energetic particle events with associated coronal mass ejections. Reames, D.V., Cliver, E.W., Kahler, S.W.: Variations in abundance enhancements in impulsive solar energetic particle events and related CMEs and flares.

SEP Onset Times

This may be the width of the source shock surface above closed loops that was once erroneously referred to as the "rapid propagation region". Surely there are a few GLEs where only the SPR timing would allow some sort of (unspecified) acceleration at the time of the associated flare.

Fig. 3.2 A comparison is shown of timing in two impulsive (left) and two gradual (right) SEP events
Fig. 3.2 A comparison is shown of timing in two impulsive (left) and two gradual (right) SEP events

Realistic Shock-SEP Timing and Correlations

The mean abundances of the elements in gradual events, relative to those in Fig. Reames, D.V.: ​​The "FIP Effect" and the Origin of Solar Energetic Particles and of the Solar Wind.

Fig. 3.7 The left panel shows H and He in the large GLE of September 29, 1989 (Lovell et al.
Fig. 3.7 The left panel shows H and He in the large GLE of September 29, 1989 (Lovell et al.

Injection Pro fi les

High-Energy Spectra and Spectral Knees

In any case, none of the 16 GLEs showed evidence of high-energy spectral enhancement that could suggest the existence of a new source that could dominate higher energies. Tylka and Dietrich (2009) have used the stiffness of the geomagnetic discontinuity at neutron monitoring stations to develop integral stiffness spectra, using data from the worldwide neutron monitoring network for 53 GLEs.

Intensity Dropouts and Compact Sources

Subsequent observations (Chollet and Giacalone 2011) showed that the boundaries between flux tubes with and without SEPs were extremely sharp. Differences in the scattering in some magnetic flux tubes can have a particularly strong influence on the intensities and angular distributions of non-relativistic electrons.

Abundances

These profound sudden changes in particle intensity mostly occur when differently coupled flux tubes are sampled within a passing CME, as measured by multiple spacecraft in the 2006 December 14 SEP event (von Rosenvinge et al. 2009). In the following chapters (Sections 4.6 and 5.6), we will see that the pattern of dependence of the stepwise abundance increase on A/Q ions leads to the determination of the value of Q and the associated temperature of the source plasma T.

Electrons

Type II emission from the shock nose and flanks can be distinguished because the nose is farther from the Sun, at lower, and therefore lower frequency; the frequencies can be correlated with the coronagraph image. Electron acceleration at the quasi-parallel nose of a shock probably occurs because real shocks are not flat but very complex structures, varying in space and time.

Fig. 3.9 The panels each show peak 0.5-MeV electron intensity vs. peak 10-MeV proton intensity.
Fig. 3.9 The panels each show peak 0.5-MeV electron intensity vs. peak 10-MeV proton intensity.

Why Not Flares?

Modern instruments allow measurement of the reconnection magnetic flux, and a recent database contains reconnection fluxes for 3137 solar-flare band events (Kazachenko et al. 2017). The observed properties of SEPs in space are not compatible with such hot flare plasma and closed fields do not simply open to release them.

SEPs as Probes

Kahler, S.W., Reames, D.V.: ​​Panagsukisok kadagiti magnetiko a topolohia dagiti magnetiko nga ulep babaen dagiti solar nga enerhia a partikula. Rouillard, A., Sheeley Jr., N.R., Tylka, A., Vourlidas, A., Ng, C.K., Rakowski, C., Cohen, C.M.S., Mewaldt, R.A., Mason, G.M., al., D. : Dagiti longitudinal a tagikua ti maysa a nasikap a pasamak ti partikulo ti init a naimbestigaan babaen ti panangusar iti moderno a solar imaging.

Figure 3.12 uses separate incident and re fl ected electron onset times to determine the release times and pathlengths for each, and also shows He ions, with no re fl ected beam (Tan et al
Figure 3.12 uses separate incident and re fl ected electron onset times to determine the release times and pathlengths for each, and also shows He ions, with no re fl ected beam (Tan et al

Selecting Impulsive Events

A more recent version of the bimodal abundance survey is the two-dimensional histogram shown in Fig. Time periods near coordinates (1, 1) in fig. 4.1 occurs during large gradual SEP events for which the normalization was chosen.

Sample Impulsive Events

Fe/O is stored for a 19-year period, and this time we have the luxury of requiring 20% ​​accuracy to prevent excessive dispersion of the distributions. The peak near (6, 3) in the figure represents impulsive events, but the Ne/O value was not actually used for the selection of candidate periods to define impulsive SEP events.

Energy Dependence

Of course, it is still true that gradual events occupy many more 8-hour periods, and lower intensity impulsive events are less likely to reach 20%.

Abundances for Z 26

Average element enhancements from 4He to Fe were summarized by Reames as shown in Figure 4.6.

Fig. 4.3 Spectra of 3 He, 4 He, O and Fe are shown in the (a) 9 September 1998 and the (b) 21 March 1999 events (Mason et al
Fig. 4.3 Spectra of 3 He, 4 He, O and Fe are shown in the (a) 9 September 1998 and the (b) 21 March 1999 events (Mason et al

Abundances for 34 Z 82

Power-Law Enhancements in A/Q: Source-Plasma

It is also possible to determine the most suitable temperature and a power law fit for individual impulsive SEP events. Thus, impulsive SEP events outside solar active regions are rare and very small (but see also Sect.4.8).

Fig. 4.9. Values of Q vs. T below Fe are from Arnaud and Rothen fl ug (1985), Fe is from Arnaud and Raymond (1992) and elements in the high-Z region from Post et al
Fig. 4.9. Values of Q vs. T below Fe are from Arnaud and Rothen fl ug (1985), Fe is from Arnaud and Raymond (1992) and elements in the high-Z region from Post et al

Associations: CMEs, Flares, and Jets

Particle-in-cell simulations show Fermi acceleration of ions reflected back and forth from the tips of the collapsing islands of reconnection (Drake et al. 2009). Magnetic flux rise is still considered an important triggering mechanism for solar flares (Paraschiv et al. 2020).

Fig. 4.13 Properties of the impulsive-SEP-associated CMEs and fl ares are as follows: fl are longitude (top), CME width and speed, and the CME-SEP delay (Reames et al
Fig. 4.13 Properties of the impulsive-SEP-associated CMEs and fl ares are as follows: fl are longitude (top), CME width and speed, and the CME-SEP delay (Reames et al

Can We Have It Both Ways?

Active-region jets tend to have temperatures of ~3 MK (see Fig. 14 of Raouafiet al.2016) like those we infer from impulsive SEP events (Fig. 4.10). Solar jets near active regions have temperatures around 3 MK while those of coronal holes are closer to 1.5 MK (see Fig. 14 of Raouafi et al. 2016).

Fig. 4.19 Mass histograms of the 16 May 2014 3 He-rich event are shown in the left two panels and some corresponding energy spectra are shown in the right panel (Mason et al
Fig. 4.19 Mass histograms of the 16 May 2014 3 He-rich event are shown in the left two panels and some corresponding energy spectra are shown in the right panel (Mason et al

Nuclear Reactions: Gamma-Ray Lines and Neutrons

Nuclear reactions in the corona also produce 2H, 3H, positrons, π-mesons and isotopes of Li, Be and B as deduced from the γ-ray line spectroscopy. Neutrons are also produced in nuclear reactions in solar flares and 50–300 MeV neutrons have been observed directly in space (Chupp et al. 1982; Chupp 1984).

Open Questions

Mason, G.M., Klecker, B.: A possible mechanism for heavy ion enrichment in 3He-rich solar powered particle events. Gradual Solar Energetic Particle Events (SEPs) are "large proton events" and are usually much more "gradual" in their decay than in their onset.

Fig. 5.1 Proton intensities vs. time from the NOAA/GOES satellite are shown for the large gradual SEP event of 4 November 2001 at solar longitude W19 (compare Fig
Fig. 5.1 Proton intensities vs. time from the NOAA/GOES satellite are shown for the large gradual SEP event of 4 November 2001 at solar longitude W19 (compare Fig

Parallel Transport

  • Diffusive Transport
  • Wave Growth
  • Particle Transport
  • Initial Abundance Ratios
  • The Streaming Limit
  • Electron Transport

The growth rate of the σ polarization mode of Alfvén waves (see Ng et al. 2003; Stix 1992; Melrose 1980) produced by protons is clearest and simplest in the wave frame, where it is given by. 5.6) represents focusing of the particles in the diverging magnetic field, while the fourth term represents pitch-angle scattering with the diffusion coefficient Dμμ.

Fig. 5.2 Particle intensities and abundance ratios are shown for small (left) and large (center) gradual SEP events (Reames et al
Fig. 5.2 Particle intensities and abundance ratios are shown for small (left) and large (center) gradual SEP events (Reames et al

Angular Distributions

Low-energy electrons typically propagate without scattering with a highly anisotropic angular distribution mainly due to solar wind absorption of frequencies of 0.1–1 Hz that would resonate with these electrons. However, small impulsive and gradual events tend to remain undispersed and the angular distributions are rapidly isotropized in more intense gradual events and especially in GLEs (see Reames et al. 2001 ).

Models and Shock Acceleration

The time-dependent self-consistent model of wave-amplified particle transport (Ng et al.2003) was applied to shock acceleration by Ng and Reames (2008) resulting in the modeling of the time evolution of the proton spectrum in the shock shown in Fig. The right panel shows the time evolution of the spatial distribution of 12.3 MeV protons upstream of the shock.

Shock Acceleration In Situ

The shock and background spectra are shown on the right with the spectral slopes indicated (Reames2012#AAS). Particle intensity peaks at shock transit time in almost all events in the Reames (2012) study.

Averaging SEP Abundances

This is the issue of cosmic ray mediated shocks discussed by Terasawa et al. 2006) for two additional interplanetary shocks.

Source-Plasma Temperatures

C/He, for intervals during the gradual SEP events, in both panels, with Tas symbols in the lower panel and power of A/Qas symbols in the upper. The region of abundances showing active-region temperatures T 2 MK is immediately distinguishable, clustering in the upper left of the lower panel of Fig.5.15.

Fig. 5.11 A/Q is plotted as a function of the theoretical equilibrium temperature for the elements named along each curve
Fig. 5.11 A/Q is plotted as a function of the theoretical equilibrium temperature for the elements named along each curve

Spatial Distributions and the Reservoir

Reservoirs, Loops, and Long-Duration γ Rays

Non-thermal Variations: Impulsive vs. Gradual SEPs

More significantly, the spread in the distribution of gradual events is much smaller than that of impulsive events in Fig. The distribution in the impulsive events must originate from non-thermal abundance variations in the local plasma of jets where the magnetic reconnection occurs.

The Abundance of He and the FIP Effect

However, if we really expect to reduce the spread of the distributions as seen in the gradual events, we need to average over several small jets that produce impulsive SEP events rather than just one; no events will reduce the spread by a factor of√n. We need only a small increase in the number of jets producing impulsive SEP events that are too small to resolve as separate events, yet sufficient to contribute to the seed population in the pool of impulsive suprathermal ions above a solar active region that can be sampled later and averaged by a shock wave.

Fig. 5.20 Best fi ts to enhancement vs. A/Q assuming the source He/O ¼ 57 at times during three gradual SEP events (Reames 2017b)
Fig. 5.20 Best fi ts to enhancement vs. A/Q assuming the source He/O ¼ 57 at times during three gradual SEP events (Reames 2017b)

Open Questions

Ng, C.K., Reames, D.V., Tylka, A.J.: The effect of proton-enhanced waves on the compositional evolution of solar energetic particles in gradual events. Sandroos, A., Vainio, R.: Simulation results for the spectral variability of heavy ions in large step solar-powered particle events.

High-Energy Spectra

Most GLEs have spectral stiffness indices between 5 and 7. The parameters of these double power-law fits to GLE stiffness spectra are tabulated by Raukunen et al. 2018), who, based on these results, also discusses the interdependence of fit parameters and fluence models. They find enhanced acceleration of GV protons in high Mach number shock regions and highlight the importance of velocity differences between the upscattering and downscattering centers.

Fig. 6.2 Integral rigidity spectra are shown for two large GLEs. Cutoff rigidities for individual neutron-monitor stations (listed) are used; the spectra are corrected for neutron production vs
Fig. 6.2 Integral rigidity spectra are shown for two large GLEs. Cutoff rigidities for individual neutron-monitor stations (listed) are used; the spectra are corrected for neutron production vs

The Streaming Limit

The black dashed lines in Fig. 6.4 are power laws below the streaming limit that decay as ~0.4 power of intensity. The rate of increase of proton intensity can also be a factor in the establishment of flux limit equilibrium, as shown in Figure 6.6.

Fig. 6.3 The upper panel shows the proton fl uence above 1 GV (430 MeV) vs. time for each GLE.
Fig. 6.3 The upper panel shows the proton fl uence above 1 GV (430 MeV) vs. time for each GLE.

Radial Dependence

Most events have slower evolution and do not exceed the limit. 2009) pointed out that trapping can also allow intensities to exceed the current limit. Shortly after arriving at a given radius, intensities rise to the current limit at that radius.

Fig. 6.6 The left panel shows that intensities in the event of January 20, 2005 brie fl y exceed the expected streaming limits from Fig
Fig. 6.6 The left panel shows that intensities in the event of January 20, 2005 brie fl y exceed the expected streaming limits from Fig

Radiation Hazards and an SEP Storm Shelter

However, the probability of the occurrence of a large gradual SEP event during a short passage of the spacecraft's perihelion may be small. On planets or moons, it may be possible to build effective shelters from local materials.

A Mission to Mars

GCR radiation is not reduced by shielding; it is actually increased by the production of secondary nuclear reaction products, including highly penetrating neutrals (Carnell et al.2016). The problem actually comes when there is a continuous human presence outside the Earth's magnetosphere; then it's not a matter of if, but when.

The Upper Atmosphere of Earth

For the timing of a manned mission to Mars, one can go during solar maximum when SEP events are more likely but GCR intensity is reduced, or during solar minimum when SEPs are reduced but GCRs are at a maximum (see Fig. 1.8 ). It is assumed that the risk of SEP can be somewhat reduced by a safe shelter with protection of 20-40 g cm2, combined with an adequate warning system.

SEPs and Exoplanets

Tylka, A.J., Boberg, P.R., McGuire, R.E., Ng, C.K., Reames, D.V.: ​​Temporal evolution in the spectra of gradual solar particle events. ed.). Verkhoglyadova, O.P., Li, G., Ao, X., Zank, G.P.: Radial dependence of peak proton and iron ion fluxes in solar particle events: application of the PATH code.

Single-Element Detectors

At relativistic energies, dE/dx reaches a broad minimum at ∼2.5 GeV amu1 and then rises slightly from density effects not included here. Unfortunately, these low-priority hitchhikers may even be turned off in transit to the mission destination to save resources, further reducing their finite value.

Δ E Versus E Telescopes

  • An Example: LEMT
  • Isotope Resolution: SIS
  • Angular Distributions
  • Onboard Processing

Figure 7.5 shows the resolution of Ne isotopes by the Solar Isotope Spectrometer (SIS) on the Advanced Composition Explorer (ACE) in two different SEP events. Onboard microprocessors can now handle up to ~10,000 s1 particles, correct the geometry, and identify particle types and energies by looking up 6464 elemental log-log tables (one for 3He-4He, one for 6Z26) that would overlap the regions of Fig. 7.3, for example.

Fig. 7.4 High-Z response of LEMT is shown where resolution (i.e. track width) is comparable with that at Fe, but track locations are well calibrated using beams of Fe, Ag, and Au before launch.
Fig. 7.4 High-Z response of LEMT is shown where resolution (i.e. track width) is comparable with that at Fe, but track locations are well calibrated using beams of Fe, Ag, and Au before launch.

Time-of-Flight Versus E

Buffering is also possible, so that rates can be sampled over longer or shorter periods, multiple samples vs. The resolution using this technique can be greatly improved by adding an additional time plane, using electrostatic mirrors to reflect electrons, and using microchannel plates with position-sensing anodes.

NOAA/GOES

Plots of GOES particle and X-ray data are also shown correlated with CME height-time plots, as shown in the example in Fig.7.8. Note the steep height-time plots (i.e., fast CMEs) in the middle panel near the start of the two large gradual SEP events in the top panel.

Fig. 7.8 CME height-time plots (center) are shown together with GOES X-ray (below) and particle (above) data in the SOHO/LASCO CME catalog (see Gopalswamy et al
Fig. 7.8 CME height-time plots (center) are shown together with GOES X-ray (below) and particle (above) data in the SOHO/LASCO CME catalog (see Gopalswamy et al

High-Energy Measurements

Other data in the catalog include movies of CME evolution and EUVflares along with radio data from Wind/WAVES. While these instruments must deal with geomagnetic field limitations, as neutron monitors do, they can directly measure spectra and abundances and represent a major improvement in the accuracy of measurements at high energies.

Problems and Errors

Mason, G.M., Gold, R.E., Krimigis, S.M., Mazur, J.E., et al.: Ultra-low-energy isotope spectrometer (ULEIS) for the ACE spacecraft. Here, we study the energetic particles themselves as samples of the solar corona, which is their origin, distinguishing the corona from the photosphere and the SEP from the solar wind.

Element Abundances in the Sun

The Solar Wind

A more complete scheme for distinguishing the different regions of the solar wind has been developed with Table 8.1 Photospheric, SEP, CIR and SSW reference abundances. eV]. However, the variations of H and He in the SEP do not appear to be related to those in the solar wind.

Corotating Interaction Regions: Accelerated Solar Wind

The 4He, C and O spectra show similar shapes for all elements in the events in the lower panel of Figure 8.3 and for the normalized Fe and 4He spectra for most of the events in the upper panel. These energetic CIR ions give us another measure of the FIP effect in the solar corona, probably similar to the combined solar wind.

Figure 8.2 shows time variations of element abundances during passage of a CIR and during three impulsive SEP events
Figure 8.2 shows time variations of element abundances during passage of a CIR and during three impulsive SEP events

Comparing FIP Patterns of SEPs and the Solar Wind

Theory suggests that SEPs may be more likely to be accelerated by closed field lines while the solar wind should come from open field lines near the base of the corona (Reames2018a; Laming2015; Laming et al.2019). Spectral line measurements of the corona also show suppressed values ​​of S/O (Schmelz et al. 2012) apparently in closed field lines.

Fig. 8.4 Best- fi t power laws (blue) and element abundance enhancements (black) relative to O, divided by
Fig. 8.4 Best- fi t power laws (blue) and element abundance enhancements (black) relative to O, divided by

FIP Theory: The Sources of SEPs and the Solar Wind

Thus, at energies above a few MeV amu1, SEP cannot therefore simply be reaccelerated solar wind; they are an independent sample of coronal material (Reames2018a). This irreconcilable difference in FIP patterns was first noted by Mewaldt et al. 2003) also noted that SEPs were not simply reaccelerated solar wind.

Fig. 8.6 Average abundances of (a) SEPs, (b) CIR ions and (c) slow solar wind (SSW; Bochsler 2009), relative to solar photospheric abundances, (solid blue) are shown as a function of the FIP of each element and compared with theoretical calculations (open
Fig. 8.6 Average abundances of (a) SEPs, (b) CIR ions and (c) slow solar wind (SSW; Bochsler 2009), relative to solar photospheric abundances, (solid blue) are shown as a function of the FIP of each element and compared with theoretical calculations (open

A Full-Sun Map of FIP

The most significant difference between all the observed open and closed field patterns is in C/O as shown in Table 8.2. Actually, the closed field measurements are significantly lower than the recent photospheric values, contrary to any expectations.

A Possible SW-SEP Model

In the upper panel, the CME-driven shock (gray) accelerates the SEP from weakly closed loops and from suprathermal ions and plasma remnants from jets when present (Reames2018b). Therefore, a single CME-driven shock shown in the top panel of Fig. 8.8 can reaccelerate material from impulsive SEPs and jet bursts over the active region and can also accelerate cooler plasma from closed loops on its flanks.

Fig. 8.8 The lower panel shows a possible con fi guration of the solar magnetic fi eld where the fast solar wind fl ows from coronal holes (blue), the slow wind from highly divergent open fi elds (green, yellow) and jets (brown) emerge from active regions (red
Fig. 8.8 The lower panel shows a possible con fi guration of the solar magnetic fi eld where the fast solar wind fl ows from coronal holes (blue), the slow wind from highly divergent open fi elds (green, yellow) and jets (brown) emerge from active regions (red

FIP-Dependent Variations in He

Open Questions

Fisk, L.A., Lee, M.A.: Energetic particle shock acceleration in corotating interaction regions in the solar wind. However, in Chapter 8 we saw that the SEP abundances are not related to those of the solar wind.

Impulsive SEP Events

Event numbers 3 and 4, which indicate the time of event initiation, refer to the list of Reames et al. 2014); the coordinates of the solar source are also given. Event numbers 34 and 35, which indicate the start time of the event, refer to the list of Reames et al. 2014); the coordinates of the solar source are also given.

Figure 9.4b shows that small events tend to fi t while increasingly larger ones do not.
Figure 9.4b shows that small events tend to fi t while increasingly larger ones do not.

Gradual SEP Events

Waves Coupling Proton Velocity with A/Q

Compound Seed Particles

CME Associations of Impulsive and Gradual Events

Four Subtypes of SEP Events

Spatial Distributions

Rigidity-Dependence: Acceleration or Transport?

Correlations Between Spectra and Abundances

Open Questions

Hình ảnh

Figure 1.2 shows an image of the Sun in ultraviolet (UV) light taken by the Atmospheric Imaging Assembly (AIA) on the NASA spacecraft Solar Dynamics Observatory (SDO; https://sdo.gsfc.nasa.gov/)
Fig. 2.2 Variation of the appearance of typical SEP events is shown as viewed from three solar longitudes (see text; after Reames 1999 # Springer; see also Cane et al
Fig. 2.9 The left panel compares the energy dependence of Fe/C for two gradual events that are otherwise similar in their properties (Tylka et al
Fig. 3.7 The left panel shows H and He in the large GLE of September 29, 1989 (Lovell et al.
+7

Tài liệu tham khảo

Tài liệu liên quan

Do đó, với tư cách là những người làm công tác giảng dạy lý luận chính trị trong các trường đại học, cao đẳng, nhóm tác giả nghĩ rằng, việc quán triệt những điểm