Ulysses: Cosmic rays in 4 Dimensions

Bernd Heber on behalf of the KET team

Rome, 12.05.2009

Mathematisch-Naturwissenschaftliche Fakultät

Ulysses: Cosmic rays in 4 Dimensions

Outline


• The Sun and the Heliosphere • The Ulysses mission• Energetic Particles (in the heliosphere)• Importance of the polar regions (Ulysses results)• Summary and Outlook

The Sun and the Heliosphere



• The Atmosphere of the Sun extends into interstellar space

• Forming the heliosphere

• Termination shock (90 AU)

• Heliopause (180 AU)• Bow shock (350 AU)

What is Ulysses?


Ulysses is ...• A collaborative project between ESA and NASA

• The only space-probe in a solar-polar orbit

• A mission to explore the heliosphere as an integrated system and conduct investigations of the Sun, the local interstellar medium, and the universe

History ...• A mission that eventually became Ulysses was

proposed as early as 1959 (2 years after Sputnik!)

• The project started officially in 1977, with a launch foreseen in 1983

• After many delays, Ulysses was finally launched on 6 October 1990, from the space shuttle Discovery

Exploration of the polar regions by Ulysses



McComas et al., GRL, 2002

Photons: direct connection

g

Propagation

e+e-

Charged particles: Reflection in galactic magnetic fields

Modulation in the heliosphere

Space probes in the heliosphere


• 1 AU: IMP, ACE, Sampex, SOHO, STEREO, neutron monitors, and PAMELA

• Ulysses: (1.3<r< 5AU 80,2 < θ < 80,2)

• Voyager 1 (r >100 AU)

• Voyager 2 (r>80 AU

Observations of galactic cosmic rays in the heliosphere:Solar modulation at neutron monitor energies


• Variations with the 11-year solar magnetic cycle

• The amplitude depend on particle rigidity

Observations of galactic cosmic rays in the heliosphere:Charge sign dependence


• Shape and amplitude depend on particle charge sign

• Solar modulation cycle is the 22-year Hale cycle

Observations of galactic cosmic rays in the heliosphere


Latitudinal Gradient

Radial Gradient

Exploration of the polar regions by Ulysses


Kiel Electron Telescope on board Ulysses


Relativistic Electrons: ~10 Minutes

50 MeV Protons: 30-80 Minutes

Kiel Electron Telescope on board Ulysses


Relativistic Electrons: ~10 Minutes

50 MeV Protons: 30-80 Minutes

Ulysses COSPIN/KET observations

Three fast latitde scans:

1.1994/1995: Solar minimum; A>0-magnetic epoch2.2000/2001: Solar maximum3.2007/2008: : Solar minimum; A<0-magnetic epoch

The heliosphere and the heliospheric magnetic field


• Expectation in the 1970’s for galactic cosmic ray intensities over the poles of the Sun

Cosmic ray distribution at solar minimum (A > 0)


The LIS ca

n not be m

easured over t

he poles

of the Sun

Expectation before Ulysses:Ulysses will measure the LIS over the poles of the Sun

Electron gradients at solar minimum (A > 0)


Electrons s

how no latitudinal g

radient

The heliosphere and the heliospheric magnetic field


• Drift pattern in the Parker like heliospheric magnetic field

Ulysses COSPIN/KET observations

Three fast latitde scans:

1.1994/1995: Solar minimum; A>0-magnetic epoch2.2000/2001: Solar maximum3.2007/2008: : Solar minimum; A<0-magnetic epoch

Electron gradients during the A<0-magnetic epoch


The fourth dimension: The solar cycle


Variations with the 22-year solar magnetic cycle



Tilt [degree]

Consequences for the recent solar minimum


The galactic c

osmic r

ay intensit

y should

increase by m

ore than 20% w

hen the tilt a

ngle

drops below 10o

Summary


• The galactic cosmic ray intensity is altered by solar modulation

• Latitudinal gradients of protons and electrons in the inner heliosphere are smaller than expected and even vanishing for the A>0-solar magnetic epoch.

• The opposite is true for the A<0-solar magnetic epoch.• Current solar minimum remarkable because tilt and

sunspot number out of phase• Simultaneous electron and proton measurements

allow to predict the real solar minimum flux.


The galactic c

osmic r

ay dist

ribution sh

ows a

North-South Asym

metry1. No gradient →

ratio = 12. Latitudinal

gradient → ratio depend on latitude (He)

3. GCR-distribution expected to be symmetric around the heliospheric equator

Documents

Ulysses: Cosmic rays in 4 Dimensions