Istituto di Astrofisica Spaziale e Fisica CosmicaIstituto di Fisica dello Spazio Interplanetario...

Istituto di Astrofisica Spaziale e Fisica CosmicaIstituto di Fisica dello Spazio Interplanetario

Roma, 15-16 dicembre 2003Relatore: B. Bavassano - IFSI

SunSunandand

Solar WindSolar Wind



"Laboratorio" Attività Prospettive



Our Star

Our Star



SOHO images in EUV (1.5 ·106 K) showing the ‘birth’ of the solar wind‘birth’ of the solar wind inside a polar coronal hole. The doppler blue-shift indicates an out-flow speed of approximately 8 km/h. artistic view

Our attention is turned to the study of the Sun's atmosphere and heliosphere because these uniquely accessible domains of space are excellent laboratories for studying in detail fundamental processes common to astrophysics, solar and plasma physics



The solar activity The solar activity cyclecycle

The magnetic The magnetic flux at the solar flux at the solar surface varies surface varies quasi-periodicallyquasi-periodicallyin the 11-year in the 11-year solar cycle.solar cycle.The structure of The structure of the corona has the corona has a a dramatic dramatic change through change through the activity the activity cycle. cycle.

This holds for This holds for the solar wind the solar wind too.too.

Magnetic fluxMagnetic fluxX-raysX-rays

MinimumMinimum

MaximumMaximumMaximumMaximum



The solar wind pervades the whole interplanetary space (heliosphere).The characteristics of this plasma, like density, temperature, ion composition etc, strongly depend on speed.

(McComas et al., 2003)

Solar Wind vs. Solar Activity



SOLE VENTO SOLARE

THEMIS HELIOS

SOHO ULYSSES

TRACE WIND

ACE



Principali Collaborazioni Nazionali

• Osservatori Arcetri Capodimonte Catania Torino

• Università Roma – Tor Vergata L’Aquila Calabria



Principali Collaborazioni Internazionali

• MPI – Lindau

• Univ. Bern

• Univ. Kiel

• CESR (Toulouse)

• SWRI (Texas)

• NASA – GSFC

• NASA – JPL



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ASI Ag.CNR Totale

kЄ



THEMIS

Campo di velocità verticale a diverse quote in fotosfera

Trasferimento di massa ed energia nei bassi strati dell’atmosfera solare

Generazione del vento solare



Plasma theories study physical phenomena at different levels:

MicroscopicMicroscopic

Time evolution of positionand velocity for all particles

KineticKinetic

Evolution of f(v) in space and time

FluidFluid

Conservation of mass,momentum and energy

In the fluid approximation the equivalent of the Navier-Stokes eq. can be written in a compact way (seminal paper by Dobrowolny et al., 1980):

z28

1z)z(

z 22

Bp

t

non-linear term linear dissipative term

Elsässerz+

outward=v+vA

z-inward =v- vA

z=0

solar wind plasma When non-linear terms dominate, energy is transferred from large to small scales along a turbulent cascade.

8m,v 10

termedissipativ

termlinearnonR



k-1

k-3

k-5/3

fc

integral scales

inertial range(nonlinear energy transfer)

dissipation scales

Turbulence• contributes to solar wind heating and acceleration• accelerates particles to high energies

• affects cosmic ray propagation (Bruno, et al., 1985)



One of the major topics regards the physical processes governing the radial evolution of zradial evolution of z++ and z and z--. This is extremely important to discover the mechanisms acting on turbulent development of interplanetary fluctuations.

(Bavassano, et al., 2000)

Our observations supported by numerical MHD simulation by our colleagues of Univ. Calabria (Malara et al., 2001) strongly indicate for the first time that parametric decay mechanism is the best candidate to explain the radial behaviour of interplanetary MHD turbulence.



The fact that (Energy Transfer Rate) is not scale independent brings up another interesting aspect of turbulence:

an intermittent signal alternates strong activity to quiescence

IntermittencyIntermittency

Based on these observations and using modern techniques relying on the properties of wavelets, we have been able to localize for the first time the nature of events causing intermittency in the solar wind.



Local Alfvénic Local Alfvénic fluctuationsfluctuations

local magnetic local magnetic field field

average background field direction

average background field direction

A simple sketch of interplanetary flux tubes resembling a spaghetti-like structure

Some of the intermittent events can be associated with the border (TD) between adjacent flux tubes.

Magnetic Field fluctuations in 3D Magnetic Field fluctuations in 3D

(Bruno et al., 2001, 2003)

Turbulence has a spotty distribution

Studio di Leonardo da Vinciper eliminare le rapide dall’Arno



LIVING WITH A STAR

INTERNATIONALLIVING WITH A STAR



SOLE VENTO SOLARE

THEMIS, ... STEREO (2005)

SOLAR-B (2006) SOLAR ORBITER

SDO (2008) SOLAR PROBE

SOLAR SENTINELS



SDO (Solar Dynamics Observatory)

Solar Sentinels

Solar Probe

STEREO



The futureThe futureour expertise allowed us to participate directly to the proposal* for a new mission to the Sun

A high-resolution mission to the Sun and

inner heliosphere

Solar OrbiterSolar Orbiter

* ESA-SCI(2000)6



Basic questionsBasic questions• Why does the Sun vary and how does the

solar dynamo work?• What are the fundamental processes at work

in the solar atmosphere and heliosphere?• What are the links between the magnetic

field dominated regime near the Sun and the particle dominated regime in the heliosphere?

These questions are basic to astrophysics in generalESA-SCI(2000)6



Novel orbital designNovel orbital design

- closer to the Sun (0.2 AU)

-out of the ecliptic (up to 38°)

- corotation ESA-SCI(2000)6



The inheritance of the Composition The inheritance of the Composition and Ion Spectrometry Instrument and Ion Spectrometry Instrument onboard Clusteronboard Cluster

IFSI (Formisano et al.) contributed to: •Numerical studies •Mechanics •Electronics •on-board software•Data reduction



A long A long experienceexperience in heliospheric in heliospheric plasma instrumentationplasma instrumentation

The beginning of space activity at IFSI dates back to 1964 when ESA started its own space program in the field of satellites with terrestrial orbit

major successes:HEOS 1, HEOS 2 to measure positive ions in the

solar wind and to study the solar wind-magnetosphere

interaction

ISEE 2 to measure the particles energy spectrum of the solar wind, the bow-shock and the magnetosphere

GIOTTO to measure the energy spectrum and ion composition of the gas emitted by comet Halley

CLUSTER 1 e 2 to measure the energy spectrum and ion composition in the magnetosphere and in the solar

wind with 4 satellitesWhen the AO for Solar Orbit will be released by ESA, we will participate to a

proposal for an ion spectrometer with our colleagues of Univ. Bern, Univ. Kiel, CESR(Toulouse), SWRI (Texas).



Our group has the necessary Our group has the necessary know-how to design, know-how to design, numerically simulate and numerically simulate and experimentally validate our experimentally validate our simulation simulation

ions (2 KeV)

electrons (150 eV)

3-D view through a longitudinal section

+30V

-200V

-150V

+150V

(D’Amicis et al., 2002)

(Bruno et al., 2001)

(Di Lellis, Baldetti et al.)

-200V



The scientific and technological returnThe scientific and technological return

IFSI is the reference point in Italy for data analysis and studies related to the interplanetary medium, from large scale structure to MHD turbulence.

IFSI is the only scientific institute in Italy where an electrostatic analyzer for hot and cold space plasma (from few eV up to 50 keV) can be fully designed, numerically simulated and experimentally tested in a vacuum chamber.



FINEFINE

Istituto di Astrofisica Spaziale e Fisica CosmicaIstituto di Fisica dello Spazio Interplanetario...

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