seminar in association with the medoc 12 campaign, nov 2003 solar orbiter work of the esa/nasa solar...

Seminar in association with the MEDOC 12 campaign, Nov 2003

Solar Orbiter

Work of the ESA/NASA Solar Orbiter Study Team

Presented byAlan Gabriel, IAS


Unique properties of the Solar Orbiter mission

Explore in situ the uncharted innermost regions of our solar system

Observe by remote sensing the Sun from close-up (45 solar radii)

Orbit the Sun tuned to its rotation and examine the solar surface and the space above from a co-rotating vantage point

Provide images of the Sun’s polar regions from heliographic latitudes in excess of 30°


Orbit

Earth departure

1.5Earth swing-by

Subsequent Venus swing-by’s

First Venus swing-by

Closer to the Sun

Out of the ecliptic


Mission profile

- Spacecraft heliographic latitude


Mission Profile - Perihelion distance


Mission Profile - Relative angular speed


Four main scientific goals

With Solar Orbiter we will, for the first time:A. Determine the properties, dynamics and

interactions of plasma, fields and particles in the near-Sun heliosphere

B. Investigate the links between the solar surface, corona and inner heliosphere

C. Explore, at all latitudes, the energetics, dynamics and fine-scale structure of the Sun’s magnetized atmosphere

D. Probe the solar dynamo by observing the Sun’s high-latitude field, flows and seismic waves


Q: Plasma, field and particles......

What is the character and radial evolution of solar wind structures in the inner heliosphere?

What is the nature of solar wind stream interactions in the inner heliosphere, and how does it depend on latitude?

What is the influence of CMEs on the structure of the inner heliosphere?

What is the nature of particle acceleration and transport in the near-Sun environment?

What is the role of shocks and flares in accelerating particles near the Sun?

How does the solar wind microstate evolve with radial distance?


Kinetics of the solar wind

Plasma microstate

• Temperature anisotropies

• Ion beams

• Plasma instabilities

• Interplanetary heating

Solar Orbiter will make high-resolution ion and electron measurements

Solar wind protons (Helios)


Turbulence near the Sun

Magnetohydrodynamic waves and turbulence

Spectrum of Alfvénic fluctuations

Steepening and dissipation!

Solar Orbiter will show

• how MHD turbulence varies and evolves spatially

• what generates Alfvén waves in the corona

• how the turbulence is dissipated


Tracing of energetic particles

Solar Orbiter will provide novel information on shock, flare and CME related particle acceleration, by virtue of

• proximity to the Sun (particles less influenced by transport effects)

• co-rotating orbit (long-term magnetic linkage)

• imaging of source regions

• timing from tracing radio emissions


Co-rotation observations

Boundaries and interfaces

Solar Orbiter will

• determine relationships between coronal and solar wind structures on all scales

• correlate in-situ particle characteristics with their coronal sources

• identify plasma boundaries and coronal origins


Sun, most powerful accelerator in solar system

Protons up to 10’s GeV Electrons up to 100’s MeV

Flares, powerful explosions Energy release up to 1032 - 1033

erg in 10 -103 s. Flare accelerated 10 -100 keV

electrons and 1 MeV ions contain 10 - 50% of the energy

Hierarchy of flare processes, relevant for coronal heating

Sun as accelerator


Tracing boundaries by minor ions


Q: Linking sun and heliosphere.....

How does the evolution of the solar magnetic field affect the heliosphere at all scales?

What are the sources of the slow solar wind, and what is its temporal and spatial evolution?

What are the sources and the global dynamics of eruptive events and what are their effects on the inner heliosphere?

What are the relevant physical processes that lead to turbulence in the tenuous magnetofluid of the inner heliosphere, and how does this turbulence interact with heliospheric particles?

What is the solar source of the solar wind plasma (including that of CMEs) and energetic particles seen in the interplanetary medium (IPM)?

What regions at the Sun are the sources of the magnetic field lines in the IPM?


Solar wind sources

SOHO: The fast solar wind flows from supergranulation cell boundaries in polar coronal holes

The Solar Orbiter will provide:

• appropriate line-of-sight for detailed analysis of the polar outflows

• passages into different wind regimes and across flow boundaries

• co-rotation, enabling steady magnetic linkage


Linking corona and heliosphere

Global solar corona and solar wind

SOHO

Solar Orbiter will enable us to link specific sources to their in-situ manifestations and to discriminate between spatial and temporal variations, especially through co-rotation observations

Ulysses


Magnetic field modelling

Accompanying modelling efforts for the solar magnetic field will allow us to:

• better identify and track solar magnetic features on all scales

• better establish the magnetic linkage between the corona and inner heliosphere


Q: Sun’s dynamic atmosphere....

How is the polar high-speed wind generated and how does this relate to the polar plume phenomenon?

How does the structure and evolution of polar coronal hole regions project into the inner heliosphere?

What is the nature of coronal hole boundaries, how do they evolve and how do they project into the inner heliosphere?

What is the nature of fundamental processes in the Sun’s atmosphere, including wave activity from source to the corona, the physics of transient events and flux emergence, over all latitudes?


Resolving fundamental scales

Due to proximity, Solar Orbiter will resolve scales such as the photon mean free path, barometric scale height and flux tube diameters in the photosphere (~100 km)

SOHO/EIT TRACE Solar Orbiter

1850 km pixels 350 km pixels 35 km pixels


Plasma dynamics in loops

TRACE 350 km pixel imaging

Solar Orbiter will provide:

- plasma diagnostics, Doppler shifts and broadenings, and images,

- both an order of magnitude better resolution (35 km and 75 km) than currently available


Q: Sun’s polar magnetic field...

How does the high-latitude field of the Sun evolve on a range of scales?

What are the properties of the Sun's surface and sub-surface meridional flow and differential rotation at high latitude, and how do these vary with time and position?

Is there a second cell in the meridional flow near the poles?

What are the properties of emerging flux at high latitudes? Is the sub-surface polar “jet-stream” real or not? What are the signatures of the solar dynamo action near

the bottom of the convective envelope?


Polar convection and dynamo

Solar Orbiter will allow us to study the:

• magnetic structure and evolution of the polar regions

• detailed flow patterns in the polar regions

• development of sub-surface magnetic structures using local-area helioseismology at high latitudes


Out of ecliptic study of the corona

Solar Orbiter will allow studies of:

• longitudinal spreads, structure and directions of CMEs, streamers etc…

• the entire equatorial corona

• current sheets at all latitudes

• the global distribution of CMEs and their 3-D structure


Exploratory measurements

First in-situ detection of neutral (hydrogen) atoms from the Sun

First measurement of near-Sun dust (e.g., from sun-grazing comets)

First detection of low-energy solar neutrons from flares


Q: Dust, neutrals and neutrons....

What are the sources and properties of dust in the inner heliosphere. Do Sun-grazing comets contribute to the dust?

What is the role played by the near-Sun dust for the interplanetary pick-up ions?

What are the fluxes and spectra of low-energy solar neutrons? Can one probe remotely nuclear reactions and ion acceleration

on the Sun? Is there a neutral solar wind, and what are its properties? How does the solar corona look like when being imaged by

energetic neutral atoms? How does the solar luminosity vary, and does it change

globally (depend on latitude)?


Science Definition Team (SDT)

Chair: E. Marsch. The SDT is currently: reviewing the scientific goals of the mission as

presently understood refining these goals where needed prioritising them in order to achieve a well-balanced,

and highly focused scientific mission defining the sets of measurements needed (baseline

and minimum) to achieve the mission’s scientific goals, taking into account the output of the Payload Working Group

Output: Science Requirements Document to be completed by SDT in November 2003


Baseline mission (SDT)

Instrument Mass

kg

Power

W

Rate

kbpsPlasma Package (SWA) 15.5 11 14

Fields Package (MAG +RPW + CRS) 11 13 5.8

Particles Package (incl. Neutrons,gammas & dust)

15 15 4.5

Visible Light Imager & Magnetograph (VIM)

30 25 20

EU Imager (3 telescopes incl. FSI) 30 25 20

EU Spectrometer 25 25 17

Spectrometer/Telescope Imaging X-rays (STIX)

4 4 0.2

Coronagraph (COR) 10 10 7

Total 140.5 128 88.5


Summary

The exciting mission concept for Solar Orbiter has led to intensive studies demonstrating technical feasibility of this challenging mission and a strong scientific and multinational desire to realise it in a timely manner.

Solar Orbiter offers unique scientific opportunities for: Exploration of unknown territory near the Sun Investigation of the solar poles Observations of the Sun at unprecedented high

resolution Understanding the links between Sun and heliosphere

Given such a strong scientific case, we believe that Solar Orbiter is an indispensable part of ESA’s future science programme.


Comparison with other missions

The multi-national solar/heliospheric strategy We have SOHO (ESA/NASA) – the World‘s flagship solar

observatory We had Helios and have Ulysses (ESA), together

providing solar wind data to 0.3 AU in the ecliptic, and over all latitudes beyond 1 AU – neither with remote sensing

We had Yohkoh (ISAS) and have TRACE (NASA) providing solar X-ray and UV imaging

What next?


Comparison with other missions

In the Solar Orbiter time-frame (launch 2011/12): SOHO, TRACE, Ulysses missions will be over STEREO, Solar-B missions likely to be complete Solar Dynamics Observatory (SDO) may be operational

However, Solar Orbiter will open a new research chapter, because:

The orbit is unique exploration and potential revelations

No solar imaging mission has yet ‘encountered’ the Sun or climbed out of the ecliptic unprecedented views

seminar in association with the medoc 12 campaign, nov 2003 solar orbiter work of the esa/nasa solar...

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