1. SWCX and Properties of the Local Hot Bubble from DXL Mission
W. Liu, M. Galeazzi, M. Chiao, M.R. Collier, T. Cravens, D. Koutroumpa, K.D. Kuntz, R. Lallement, S.T. Lepri, D. McCammon, K. Morgan, F.S. Porter, K. Prasai, S.L. Snowden, N.E. Thomas, Y. Uprety, E. Ursino, B.M. Walsh

2. OUTLINE the Local Hot Bubble and Solar Wind Charge eXchange
DXL Mission and Results from DXL Fight 1
Properties of the Local Hot Bubble
Summary

3. Diffuse X-ray Background3

4. Diffuse X-ray Background
Rosat All Sky Survey (RASS) R12 Band = ¼ keV 4

5. Diffuse X-ray Background
~40 AU
~100 pc
~2-5 kpc
~z<1 NH NH
Local hot Bubble
Unresolved
point sources
Galactic Halo
WHIM 5

6. Solar Wind Charge Exchange
IRAS 100 mm
X-rays due to charge transfer of solar wind ions (Cravens 1997)

7. Solar Wind Charge Exchange (SWCX)
IRAS 100 mm
Heliospheric SWCX: Interaction of Solar Wind with the interplanetary neutrals

8. Solar Wind Charge Exchange/Local Hot Bubble
RASS R12 Band = ¼ keV
How much of the diffuse emission is then due to SWCX?
Estimates
25%-50% of the emission from SWCX
All of the soft emission from SWCX (No Local Hot Bubble?)

9. SWCX Characterization
Spectral signature
Temporal signature
Spatial signature
EBIT data
(Courtesy of Greg Brown)
F I R 9

10. SWCX Characterization
Spectral signature
Temporal signature
Spatial signature
11-year modulation due to solar cycle +
Time variation due to solar wind activity 10

11. SWCX Characterization
Spectral signature
Temporal signature
Spatial signature
Sun’s velocity 11

12. Diffuse X-rays from the Local Galaxy (DXL)
Sounding rocket mission with 2 large area proportional counters for the study of SWCX and the LHB
Grasp at ¾ keV ~ 150 times bigger than XMM
Launched from White Sands Missile Range on December 12, 2012
Geometric measurement of the local Diffuse X-ray emission to separate SWCX from LHB

13. DXL Mission He Focusing Cone (HFC) High helium density region
Higher SWCX flux
Compare to ROSAT data
Separate from LHB emission

14. Data reduction and analysis
DXL should measure an excess emission due to SWCX from the He focusing cone
Slow scan region

15. Data reduction and analysis
Solid Lines
Red: Helium, DXL
Blue: Helium, ROSAT
Dotted Lines
Red: Hydrogen, DXL
Blue: Hydrogen, ROSAT

16. Data reduction and analysis
D12 Band (ROSAT R12, ¼ keV)
Cone enhancement

17. Local Hot Bubble the major contributor to ¼ keV emission
Results
D12 Band (ROSAT R12, ¼ keV)
Galactic plane: 38%±4% (±3% systematic error)
Averaged over the whole sky: 27%±3% (±5% systematic error)
Local Hot Bubble the major contributor to ¼ keV emission
SWCX less than 40% in the ¼ keV band
(Galeazzi et al., 2014)

18. RASS R12 Local Emission (Snowden et al. 1998)
Local hot bubble/SWCX
RASS R12 Local Emission (Snowden et al. 1998)
IRAS 100 mm
LHB + SWCX

19. Local Emission (R1)
Local Emission (R2)
SWCX (R1)
SWCX (R2)
LHB (R1)
LHB (R2)

20. LHB R2/R1 Ratio
The peak of R2/R1 distribution is shifted from 1.09 to 0.83

21. LHB Temperature
The temperature is peaked at ~0.097 keV with a FWHM of keV.

22. LHB Emission Measure
EM range from ~ x10-3 cm-6 pc

23. LHB Pressure equilibrium
Local Interstellar Cloud PT/k~3,200 cm−3 K
LHB (pre-SWCX) PT/k~18,000 cm−3 K
DXL + New measurements of Local Cavity (Puspitarini et al. 2014):
 LHB PT/k~10,600 cm−3 K
(ne = 4.68+/-0.47 x10-3 cm-3)
Magnetic field outside heliosphere by Voyager 1 (Burlaga & Ness 2014)
Magnetic pressure PT/k~7,000 cm−3 K
 LIC Pressure PT/k~10,000 cm−3 K
Snowden et al. 2014

24. LHB size and shape
3D model of LHB
Galactic Plane
Vertical Plane

25. LHB size and shape
Lallement et al. 2014
Galactic Plane

26. Summary Quantified SWCX contribution LHB predominant in the ¼ keV band
38% SWCX in the ¼ keV band (on plane)
Properties of the LHB
R2/R1 distribution shifted to small values
Temperature peaked at keV
Generate 3-D structure of LHB

27. THANK yOU