1. Radial Dependence of Solar Energetic Particle Intensities
D.Lario, A. Aran*, R.B. Decker, G.C. Ho
The Johns Hopkins University. Applied Physics Laboratory, Laurel MD
*Dpt. Astronomia i Meteorologia, Universitat de Barcelona
Fifth Solar Orbiter Workshop
Brugge, België
September 10-14, 2012

2. WHY?
Determine the energetic particle environment that missions such as Solar Orbiter and Solar Probe Plus (at heliocentric distances R<1 AU) will have to survive.
Determine the maximum intensities that particle instruments on board these spacecraft may detect.
Understand the processes of particle acceleration and transport close to the Sun.

3. HOW?
OBSERVATIONALLY:
Combining data from Helios and MESSENGER with near-1 AU spacecraft observations
[Lario et al., 2006, 2012].
MODELLING:
Using simulations of energetic particle injection and transport in the interplanetary medium with observers located at different radial distances
[Hamilton, 1988; Ruzmaikin et al., 2005; Lario et al., 2007; Dayeh et al., 2010; Aran et al., 2005, 2011; Verkhoglyadova et al., 2012].

4. HISTORY

5. MODELS (1): Hamilton (1988)

6. MODELS (1): Hamilton (1988)
If V=0, the equation is a pure diffusion equation, and jmax ~r-3

7. MODELS (1): Hamilton (1988)
Application of the model (with V≠0) to Pioneer 10/11 and Voyager 1/2 observations beyond 1 AU yield radial dependences for peak intensities as~r
(Hamilton et al., 1990)
Injection: delta function (Hamilton, 1977) convolved with a Reid-Axford profile (Beeck et al., 1987)

8. MODELS (2): Lario et al. (2007)
(from Aran et al. 2011, SEPEM Project)

9. MODELS (2): Lario et al. (2007)

10. MODELS (2): Lario et al. (2007)

11. MODELS (3): Injection from shocks
Ruzmaikin et al. (2005) (inner boundary at 0.1 AU)
Kozarev et al. (2010) Dayeh et al. (2010) (from 1 AU outwards)
Verkhoglyadova et al.(2012) (inner boundary at 0.1 AU, 1D)
Aran et al. (2005, 2011, 2012, details given in the next talk) +
W00
W60
(from Aran et al. 2011, SEPEM Project)
(from Aran, 2007, PhD Thesis)

12. OBSERVATIONAL STUDIES
PROBLEMS:
Need to isolate radial from longitudinal dependences
Single events at 1 AU may appear as multiple events at r<1 AU.
OBSERVATIONS (1): Lario et al. (2006)
Combination of Helios 1/2 with IMP-8 observations
Helios-1
Helios-2
IMP-8

13. OBSERVATIONS (1): Lario et al. (2006)
Events with good nominal connection (<20°) between spacecraft

14. OBSERVATIONS (1): Lario et al. (2006)
Events with good nominal connection (<20°) between spacecraft

15. OBSERVATIONS (2): Lario et al. (2012)
Combination of MESSENGER and near-1AU (STEREOs, ACE) data

16. OBSERVATIONS (2): Lario et al. (2012)
Events with good nominal connection (<20°) between spacecraft

17. OBSERVATIONS (2): Lario et al. (2012)
Events with good nominal connection (<20°) between spacecraft

18. OBSERVATIONS (2): Lario et al. (2012)
Events with good nominal connection (<20°) between spacecraft
R-5.29

19. EFFECTS OF INTERVENING STRUCTURES
Lario et al. (2008, AIP Conf. Proc.)

20. EFFECTS OF INTERVENING STRUCTURES
Lario et al. (2008, AIP Conf. Proc.)
R-1.45 nominal conditions
R-2.61 intervening structure

21. CONCLUSIONS
Both modeling and observational studies are used to determine the radial dependences of SEP peak intensities.
For impulsive injections close to the Sun, radial dependences beyond 1 AU are usually steeper than at <1 AU, because focusing effect dominates at <1 AU, whereas diffusion dominates at >1 AU.
For impulsive injections close to the Sun, radial dependences of peak intensities are steeper when scattering processes dominate the SEP transport than when the transport is under scatter-free conditions.
For continuous injection from a traveling shock, magnetic connection and shock efficiency in particle injection determines the radial dependence of peak intensities (see next talk).
In order to determine radial dependences, longitude effects need to be isolated.
Intervening structures modify (and strengthen) the radial dependences obtained from models.

22. MESSENGER
EPS

23. LASCO 06:48 UT LASCO 22:05 UT ~1400 km/s ~2425 km/s STEREO-A
SECCHI Obs.
LASCO
06:48 UT
~1400 km/s
LASCO
22:05 UT
~2425 km/s

24. MESSENGER Orbit Orbit insertion: 18 March 2011.
Elliptical, near-polar orbit.
Inclination: 82.5°.
Initial periapsis alt.: 200 km.
Apoapsis alt.: 15,300 km.
Orbit period: 12 h.
Orbit local-time precession: 0.2 h/day.