PHOEBUS: A Proposal PHOEBUS: A Proposal for Solar Physics on LISA for Solar Physics on LISA

(1)

PHOEBUS: A Proposal* PHOEBUS: A Proposal* for Solar Physics on LISA for Solar Physics on LISA

Workshop on Ionising Particle Measurements in Space

ESTEC, 1

^st

February 2005

Catia Grimani ¹ & Helios Vocca ²

(1) Urbino University and INFN Florence (2) University and INFN Perugia

* PHysics * PHysics Of Of Events BUrsted by Events BUrsted by the the Sun Sun

(2)

Helios Vocca - Workshop on Ionising Particle Measurements in Space - ESTEC - 1 February 2005

CME propagation CME propagation

The high fluence active Sun period is of 7 years, from 2 years before the solar

maximum year to 4 years after.

The propagation time (between event and appearance of protons at the spacecraft) is a strong function of the longitude of the solar event.

The time of the onset corresponds to the time at which the shock intercepts the magnetic field lines to the spacecraft

Reames, D. V., 2002, Space Radiation (Japan), 3, 69

The spiral interplanetary magnetic field

generates an asymmetry in the intensity-time profiles of SEP. In particular, events

originating in the western hemisphere of the Sun are more likely to produce SEPs able to reach the Earth with respect to those in the eastern hemisphere.

Protons can arrive from magnetically well- connected sites in tens of minutes.

For particles in the GeV range, the most

effective longitude is close to 60°W.

(3)

LISA spacecraft characteristics LISA spacecraft characteristics

• Distance from the Sun 0.9933 ÷ 1.0133 AU

• Latitude off the ecliptic 0.7 ^o ÷ 1.0 ^o

• Longitude difference with respect to Earth

19 ^o ÷ 21 ^o

(4)

Spacecraft

Test mass x

Displacement sensor

Thrusters

High gain force feedback

Drag-free: keeping the spacecraft

with the proof-mass

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

(13)

(14)

Ac bias

Test mass injection

electrode Ac amplifier

PSD

The drag-free key elements: the displacement

sensor

(15)

Ac bias

Test mass injection

electrode Ac amplifier

PSD

The drag-free key elements: the displacement

sensor

(16)

x

y z

θ

φ

η θ & y

η & x φ & z

The drag-free key elements: the displacement sensor

Ac bias

Test mass injection

electrode Ac amplifier

PSD

(17)

x

The reality

Stray forces Parasitic

coupling

(18)

{{{}{ Force on spacecraftSC2T/Mpn2fbSensor noiseParasitic stiffnessForce on Test-MassDragfreegainRelative diplacementTM wrt nois/

eSC FfxmMa ⁻ +ω+ω= 144424443

The residual test-mass acceleration noise

Main disturbances to free-fall

and design guidelines

(19)

Simulations for the LISA noise budget Simulations for the LISA noise budget

• Simulations have been performed to

calculate the noise induced by the galactic and solar cosmic rays

– GEANT4 (ICL group)

– FLUKA (Fi-Ub & Pg groups)

• The two simulations obtained similar results even if the FLUKA simulation has been

performed using a preliminary scheme for

satellite geometry.

(20)

Proton fluxes

(21)

Proton results:

10720 10700

Solar Flare peak flux

110 15

GCR at solar maximum

206 173

Gradual Event 1

2120 2090

Gradual Event 2

3480 3460

Gradual Event 3

4395 4385

Gradual Event 4

150 42

GCR at solar minimum

4575

Effective charge rate (e/s)

4570 Gradual Event 5

Charge rate

(e

⁺

/s)

Source

(22)

LISA acceleration noise spectral density LISA acceleration noise spectral density

Required acceleration noise limit for random charge:

9.4·10 ^-16 (m s ^-2 Hz ^-1/2 ) [total: 3·10 ^-15 ]

(10 ^-4 ÷ 10 ^-1 Hz)

€

S

^{1/ 2}

( ω ) = 0.8 ×10

⁻¹⁵

m s

²

Hz

4mm gap



  

  V

_dc

10mV



  

  λ

_eff

300s

⁻¹



  

 

1/ 2

0.1mHz f



  

 

(23)

LISA acceleration noise spectral density LISA acceleration noise spectral density

10720 4575 4395 3480 2120 206 150 110

Effective charge rate (e/s)

4.8 ·10

^-15

Solar Flare peak flux

0.48 ·10

^-15

GCR at solar maximum

0.66 ·10

^-15

Gradual Event 1

2.1 ·10

^-15

Gradual Event 2

2.7 ·10

^-15

Gradual Event 3

3.1·10

^-15

Gradual Event 4

0.57 ·10

^-15

GCR at solar minimum

3.1 ·10

^-15

Gradual Event 5

Acceleration noise spectral density

@ 0.1mHz

(m s

^-2

Hz

^-1/2

)

Source

(24)

LISA sensitivity

(25)

SEPs

SEPs on LISA on LISA

• The shock nose of a typical gradual event

takes about two days to reach Earth or LISA, might take a few hours to propagate

between Earth and Lisa, and the order of one hour to pass through the three LISA detectors

• Gradual event can cause series of signals of

frequency below a few units 10 ^-4 Hz

(26)

The study of Coronal Mass Ejection (CME) dynamics is mandatory for:

• Solar physics modelization

• Space Weather forecasting

(27)

Particle counters devoted to test-mass charging monitoring can be used to map the transit of very energetic solar particle (SEP) fluxes correlated to CMEs through the experiment spacecraft.

LISA OFFERS A BIG CHANCE!!!!

(28)

THE PARTICLE COUNTERS ON BOARD LISA

will allow to monitor the flux of particles with energies larger than 100 MeV.

This energy cut-off has been set on the basis of the minimum energy of primary and solar cosmic rays able to penetrate the matter that surrounds the test- masses. Consequently, only galactic cosmic rays and the transit of CMEs will be detected on LISA, being the maximum energy of impulsive solar flare

accelerated particles 50 MeV.

(29)

SKETCH OF SILICON DETECTORS ON SKETCH OF SILICON DETECTORS ON

LISA PF LISA PF

1.4 cm

1.05 cm

2 cm

2 layers of silicon detectors Dimensions: 1.05 x 1.4 cm ² Thickness: 300 µ

Lobo, 2004

(30)

We have calculated the fluence of strong SEP events (fluence larger than 10 ⁶ protons/cm ² with particle

energies larger than 30 MeV) expected for each year of the LISA mission. Nymmik RA has developed a model of SEP fluence distribution versus time.

•We have determined the number of SEP events during the LISA mission (10 years) on the basis of the

minimum and maximum number of expected solar spots.

•We have determined the number of solar events in individual intervals of fluence for each year

of the LISA mission

(31)

NUMBER OF EXPECTED SEP EVENTS DURING THE FIRST PART OF THE LISA MISSION

(32)

NUMBER OF EXPECTED SEP EVENTS DURING THE LAST PART OF THE LISA MISSION

(33)

Example of flare with a fluence close to 10 ⁶ (May 7th 1978)

Dot-dashed lines: SEP fluxes observed at different times.

The shift in normalization has been done in order not to superpose lines

Flux 5 is the peak flux Dotted lines: peak fluxes of different fluence events according to Nymmik, 1999 Continuous and dashed lines:

primary cosmic-ray proton

spectra at solar minimum and

maximum respectively

(34)

Dot-dashed lines: SEP fluxes observed at different times.

The shift in normalization has been done in order not to superpose lines

Dotted lines: peak fluxes of different fluence events according to Nymmik, 1999 Continuous and dashed lines:

primary cosmic-ray proton spectra at solar minimum and maximum respectively

Example of flare with a fluence close to 10 ⁷ (February 16th 1984)

2 3

4

1

(35)

Thick lines: SEP fluxes observed at different times.

Dotted lines: peak fluxes of different fluence events according to Nymmik, 1999 Continuous and dashed lines:

primary cosmic-ray spectra at solar minimum and maximum respectively

Example of flare with a fluence close to 10 ⁹ (29 September 1989)

2

1 3

(36)

Expected count

Expected count rate on rate on both silicon layers both silicon layers

0 50 100 150 200 250 300 350

GPm GPM F1 F2 F3

Flux1 Flux2 Flux3 Flux4 Flux5

Counting rate

GPm:galactic protons at solar minimum GPM:galactic protons at solar maximum F1: Flare 7 May 1978

F2: Flare 16 February 1984

F3: Flare 29 September 1989

(37)

0 500 1000 1500 2000 2500 3000 3500 4000

GPm GPM F1 F2 F3

Flux1 Flux2 Flux3 Flux4 Flux5

Counting rate

GPm:galactic protons at solar minimum GPM:galactic protons at solar maximum F1: Flare 7 May 1978

F2: Flare 16 February 1984 F3: Flare 29 September 1989

Expected count

Expected count rate on one rate on one silicon layer silicon layer

(38)

Conclusions:

• Lisa offers special conditions to study strong CMEs

• Earth detectors measurements, and eventually other space experiments, might be correlated to the LISA particle counters measurements

• Small step (2 degrees) and large step (20 degrees

for Earth-LISA) longitude CME measurements

might give precious hints on solar physics and

space weather

(39)

PHOEBUS*: A Proposal PHOEBUS*: A Proposal for Solar Physics on LISA for Solar Physics on LISA

PHOEBUS*: A Proposal PHOEBUS*: A Proposal for Solar Physics on LISA for Solar Physics on LISA

Workshop on Ionising Particle Measurements in Space

ESTEC, 1

February 2005

Catia Grimani 1 & Helios Vocca 2

(1) Urbino University and INFN Florence (2) University and INFN Perugia

* PHysics * PHysics Of Of Events BUrsted by Events BUrsted by the the Sun Sun

CME propagation CME propagation

The high fluence active Sun period is of 7 years, from 2 years before the solar

maximum year to 4 years after.

The propagation time (between event and appearance of protons at the spacecraft) is a strong function of the longitude of the solar event.

The time of the onset corresponds to the time at which the shock intercepts the magnetic field lines to the spacecraft

The spiral interplanetary magnetic field

generates an asymmetry in the intensity-time profiles of SEP. In particular, events

originating in the western hemisphere of the Sun are more likely to produce SEPs able to reach the Earth with respect to those in the eastern hemisphere.

Protons can arrive from magnetically well- connected sites in tens of minutes.

For particles in the GeV range, the most

effective longitude is close to 60°W.

LISA spacecraft characteristics LISA spacecraft characteristics

• Distance from the Sun 0.9933 ÷ 1.0133 AU

• Latitude off the ecliptic 0.7 o ÷ 1.0 o

• Longitude difference with respect to Earth

19 o ÷ 21 o

Spacecraft

Test mass x

Displacement sensor

Thrusters

High gain force feedback

Drag-free: keeping the spacecraft

with the proof-mass

Ac bias

Test mass injection

electrode Ac amplifier

PSD

The drag-free key elements: the displacement

sensor

Ac bias

Test mass injection

electrode Ac amplifier

PSD

The drag-free key elements: the displacement

sensor

x

y z

θ

φ

η θ & y

η & x φ & z

The drag-free key elements: the displacement sensor

Ac bias

Test mass injection

electrode Ac amplifier

PSD

x

The reality

Stray forces Parasitic

coupling

{{{}{ Force on spacecraftSC2T/Mpn2fbSensor noiseParasitic stiffnessForce on Test-MassDragfreegainRelative diplacementTM wrt nois/

eSC FfxmMa − +ω+ω= 144424443

The residual test-mass acceleration noise

Main disturbances to free-fall

and design guidelines

Simulations for the LISA noise budget Simulations for the LISA noise budget

• Simulations have been performed to

calculate the noise induced by the galactic and solar cosmic rays

– GEANT4 (ICL group)

– FLUKA (Fi-Ub & Pg groups)

• The two simulations obtained similar results even if the FLUKA simulation has been

performed using a preliminary scheme for

satellite geometry.

Proton fluxes

Proton fluxes

Proton results:

Proton results:

10720 10700

Solar Flare peak flux

110 15

GCR at solar maximum

206 173

PHOEBUS: A Proposal PHOEBUS: A Proposal for Solar Physics on LISA for Solar Physics on LISA

PHOEBUS: A Proposal* PHOEBUS: A Proposal* for Solar Physics on LISA for Solar Physics on LISA

Catia Grimani ¹ & Helios Vocca ²

• Latitude off the ecliptic 0.7 ^o ÷ 1.0 ^o

19 ^o ÷ 21 ^o

eSC FfxmMa ⁻ +ω+ω= 144424443

9.4·10 ^-16 (m s ^-2 Hz ^-1/2 ) [total: 3·10 ^-15 ]

(10 ^-4 ÷ 10 ^-1 Hz)