Spp sweap nes_osa_oct2011

Solar Probe PlusA NASA Mission to Touch the Sun

Solar Probe PlusA NASA Mission to Touch the SunA NASA Mission to Touch the Sun

Kelly KorreckSWEAP Science and Operations Lead

Smithsonian Astrophysical [email protected]

Exploring the Sun Up Close: The Solar Wind Electron, Alphas, and

Protons (SWEAP) Instrument Suite aboard Solar Probe Plus


Outline

Solar Physics background and current unanswered questions Solar Probe Plus Mission What measurements do we need to solve solar mysteries? SWEAP Instruments SWEAP Technology Advancement Summary

SOLAR PHYSICS BACKGROUND AND UNANSWERED QUESTIONS

Why is the Sun yellow?• The surface of the Sun is

hot because energy released through fusion in the solar core radiates and convects up to the surface

• What is the spectrum of light from an object so hot it glows?

• An ideal object without any intrinsic color emits light in a “Blackbody radiation curve” with a peak at one wavelength

• Most of the solar surface is at 6000C

Is there anything above the surface?

THE SOLAR ATMOSPHEREThe Solar Corona

How can you see the solar corona?• The photosphere of the Sun is

too bright to look for signatures of an atmosphere

• We can use solar eclipses, when the Moon blocks the Sun, to search for anything beyond the disk

• Astronomers have used solar eclipses to study the Moon and the Sun for thousands of years

• Earliest recorded observations of eclipses date back to 6000BC

• "Astronomers Studying an Eclipse," a 1571 painting by Antoine Caron, oil on panel

Solar eclipse, as seen from the International Space Station over Turkey, March 2006

Druckmuller, Aniol, Rusin

SOLAR MYSTERIESWhy so big?

The Scale Height Problem• The scale height of an atmosphere is the distance

in altitude you have to travel for the density to drop by a third

• In a simple atmosphere with one temperature and one type of particle, there is a pretty simple relationship for the scale height of:

• Using 6000 degrees C as a temperature and assuming the atmosphere is made of hydrogen then H = 175 km (110 miles)

• Instead, from the eclipses the scale height is clearly like the radius of the Sun, or H = 695,500 km (430,000 miles)

• We have a problem! The solar atmosphere is either:

– 1000+ times hotter than the surface of the Sun– Made up of a new form of matter, 1000 times lighter

than hydrogen

Mass

eTemperaturHeight

New Matter or High Temperature?

• By 1905, scientists thought they had discovered a new form of matter, which they called “Coronium”– A thousand times lighter than hydrogen– Only found in the atmosphere of the Sun– Other evidence (mysterious green lines), and a

precedent…

Evidence for a hot corona• By the 1940s, we realized

that the mysterious green lines were consistent with iron heated to millions of degrees

• The interpretation was that the corona is extremely hot is slowly accepted

• Today we can see this easily from space, by looking at x-rays from the Sun

Modern Images of the Hot Corona

Modern Artificial Eclipses

Going into the Eclipse

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Solar Probe Plus closest

approach

SOLAR PROBE PLUS MISSION Mission to Touch the Sun


The Rationale for Solar Probe Plus is Five Decades Old

Current study in line of studies dating back to “Simpson’s Current study in line of studies dating back to “Simpson’s Committee” of the Space Science Board (National Academy of Committee” of the Space Science Board (National Academy of Sciences, 24 October 1958)Sciences, 24 October 1958)

Why is the solar corona so much hotter than the photosphere? Why is the solar corona so much hotter than the photosphere? And how is the solar wind accelerated?And how is the solar wind accelerated?

The answers to these questions can be obtained only through in-The answers to these questions can be obtained only through in-situ measurements of the solar wind down in the corona.situ measurements of the solar wind down in the corona.

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The Spacecraft SPC

SPAN-A

FIELDS

WISPR

SPAN-B

ISIS


SPP Instrument Suites Electromagnetic Fields (FIELDS)

Investigation PI. S. Bale, University of California Space

Sciences Laboratory, Berkeley, CA Integrated Science Investigation of

the Sun Energetic Particle Instruments (ISIS-EPI), PI. D. McComas, South West Research

Institution, San Antonio, TX Solar Wind Electrons Alphas and

Protons (SWEAP) Investigation PI. J. Kasper, Smithsonian Astrophysical

Observatory, Cambridge, MA Wide field Imager for Solar Probe

(WISPR) PI. R. Howard Naval Research Laboratory,

Washington, DC

Heliospheric Origins with Solar Probe Plus - Observatory Scientist (HeliOSPP) PI. M. Velli, Jet Propulsion Laboratory,

Pasadena, CA

SPP Participation 31 institutions participate

in SPP science teams 23 in the US, 8 foreign 17 educational, 5 non-profit, 8

government labs 106 science team

members 69 PIs and Co-Is 37 additional scientists Next generation graduate

students and post-docs


Final Orbit Near-Sun Trajectory

MEASUREMENTS NEEDED


Magnetic measurements that hints at the heating of the solar corona and acceleration of the solar wind

Bruno & Carbone 2006

FIELDS Measurements


ISIS Energetic Particle Suite

Energetic Particle are produced in flaring active regions on the Sun as well as in shocks between the Sun and Earth.

These particles are hazardous to our space assets.

The acceleration mechanisms of these high energy particles are of interest throughout astronomy and physics.

ISIS

EPI-Lo EPI-Hi


Wide field Imager for Solar Probe Imaging

The Solar Wind Structures and Fluctuations Directly. CME and Shock Propagation and Evolution and Their

Connection to the Site of Production of SEPs. Provides the Links Between the

Solar Wind Structure and SPP in-situ Instruments Solar Orbiter and Solar Probe Plus Missions

Characteristic Value

Image Type White Light Broadband

Aperture and Focal Length 3.78 cm diameter, 1.78 cm focal length

Spatial Resolution 6.25 arc min

Maximum Cadence – Full Frame <2 min

Sensor APS – new design

Format 2K x 2K, 10 µ square


Overview of STEREO’s Heliospheric Imager

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WISPR Observations

• Images over an encounter used to determine large scale structure, inverted to produce electron density profile

• High time resolution images used to study variable structures near the spacecraft: shocks, streams, reconnection exhausts, turbulence

Polar Wind

SWEAP INSTRUMENT SUITEElectrons, Alphas and Protons


The Role of SWEAP SWEAP makes detailed measurements of the electrons,

alpha-particles (fully ionized helium), and protons (fully ionized hydrogen) that make up 99% of the solar corona and solar wind

SWEAP observations map out the number of particles moving at different velocities. These maps are then used to determine, e.g.: Velocities, densities, temperatures, anisotropies Electron temperature, anisotropy, heat flux Interactions between particles and electromagnetic waves


Overview – SWEAP Suite SWEAP Consists of Two

Instruments (SPC & SPAN) and an Electronics Module (SWEM)

SPC – Solar Probe Cup Sun-viewing Faraday Cup

SPAN – Solar Probe Analyzers SPAN-A, ion and electron

electrostatic analyzers (ESAs) on ram-side of spacecraft bus

SPAN-B, electron ESA on anti-ram size of spacecraft bus

SWEM – SWEAP Electronics Module (not shown) Single electrical interface to

SPP, distributes power, commands instruments, formats and buffers data products, interfaces with FIELDS

SPAN-B

SPC

Ram

Dire

ctio

nSPAN-A


Overview – SWEAP Science (1/4)Objective 1: Trace the flow of energy that heats and accelerates the solar corona and solar wind.

How is magnetic energy converted into heating ions and electrons?

How does thermal and kinetic energy of plasma change with distance?

NASA/SDO/AIA

Reconnection?Wave/Turbulence?

Hinode/XRT


Overview – SWEAP Science (2/4)

SPP

Hinode/SOT

G-band bright points

SUMER/SOHO

Helios &

Ulysses

UVCS/SOHO

Undamped (WKB) wavesDamped (non-WKB)waves

SPP


Overview – SWEAP Science (3/4)Objective 2: Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind.

What is the fraction of closed magnetic field lines? How do solar wind sources evolve with time? How does coronal structure evolve into the solar wind?


Overview – SWEAP Science (4/4) Objective 3: Explore

mechanisms that accelerate and transport energetic particles. What are the roles of

shocks, reconnection, waves, and turbulence in the acceleration of energetic particles?

What are the source populations and physical conditions necessary for energetic particle acceleration?NASA/SDO/AIA

Flare and corona mass ejection

WHAT SWEAP MEASUREMENTS DO WE NEED TO SOLVE SOLAR MYSTERIES?

Data Needed


Kinetic Physics We are driven by two main questions and puzzling observations

Why is the solar corona so hot? Plasma in corona 100-1000x hotter than photosphere (apparently

violating 2nd law of thermodynamics) Temperature anisotropies (10-100x hotter in one direction than

another) How is the solar wind accelerated so efficiently?

Too much mass escaping at too high a speed Why are these questions so hard to answer?

Kinetic physics f(time, space, velocity) is needed, but we do not understand it well - 7 dimensions!

We cannot make the needed measurements remotely, we cannot reproduce the environment in a laboratory, and we cannot simulate it on a computer

What can Solar Probe Plus do? Enter the corona and make direct observations Capture the particle distributions and electromagnetic field fluctuations

with high precision and cadence to get to the kinetic physics


Background: Physics of a Classical Gas

It is too difficult to describe the motion of every single particle in a gas or plasma, so we adopt statistical approaches

If there are many collisions, then the distribution of particles with speed follows a Bell Curve

However, in the Solar Wind, there are very few collisions. Leading to Temperature anisotropies and wave propagation and

instabilities

A gas of particles Maxwell-Boltzmann distribution (the Bell Curve)

Rel

ativ

e nu

mbe

r of

par

ticle

sSpeed


SWEAP Measurements SWEAP measures velocity distribution

functions Need to determine velocity (speed and

direction), density, and temperature of the solar wind.

Why not just fly an anemometer and a weather vane?

Because the solar wind is not in equilibrium Relative densities change Species have different velocities Species have different temperatures Temperature can be hard to define

A SWEAP measurement is a map of the number of electrons, alphas, and protons as a function of direction and energy

Speed#

of P

artic

les

density

velocity (speed and direction)

temperature

Hydrogen(protons)

Helium(alphas)


SPC Operating Principle

HV Waveform

AC-Coupled Current

Convert signal to voltage and amplifyMeasure amplitude with digital lock-in amplifier

Move on to next energy window

HV Grid

Four collector plates


SPAN Operating Principle

All three electrostatic analyzers in SPAN begin with top hat hemispherical analyzers Voltage across pair of

deflector plates selects elevation angle

Voltage across pair of curved plates selects energy/charge

Anodes arranged in a ring determine the azimuth angle of each particle

Counters record flux of particles as a function of energy/charge, elevation, and azimuth

Symmetry axis

Deflectors

Curved Plates

SWEAP TECHNOLOGY ADVANCEMENTSSolar Research in the Laboratory


The Faraday Cup on Voyager I & II

Star Trek: The Motion Picture


Faraday CupsMore than 20 Faraday cups built by members of the SWEAP team have flown on a variety of

spacecraft in a wide range of environmentse.g. Wind, Voyager, SOLRAD A-B,

Pioneer 6-7

How do we build this to survive close to the Sun?

How do we know we got it right?


SPC Technology AdvancementMission: Bring Solar Probe Cup to TRL6

Driving Requirement TRL 6=Show instrument operates in the

thermal and particle environment of solar encounters

Key Development Milestones High temperature/high solar intensity

material testing in solar furnace Exposure of SPC thermal test model in

solar furnace Exposure to simulated solar photon and

particle environments

Experimental Practices Use multiple facilities for measurement of

materials properties Use multiple facilities for solar simulator

You can clearly see the furnace from the highway.

The control room we were in where you steer the

mirrors

The laboratory with the vacuum chamberThe focusing parabola

The mirrors

The “iris”: a pair of doors that open and close to adjust the amount of sunlight that hits the

chamber

Solar Furnace

This is the view from the operations center. At the moment the mirrors are all stowed pointing straight forward.

In this example, the center 32 mirrors have just been commanded to move from

standby to projecting the Sun onto the focusing parabola. As the mirrors tilt downward, the Sun shines into the

window of the control center and then to the center of the parabola. The light is

bright but not dangerous because we are not at any kind of focus. This entire

sequence of images took place in less than 60 seconds.


Summary

There are outstanding mysteries about our Sun Why is the corona so hot? Why is the solar wind so fast?

The Solar Probe Plus mission will enter the atmosphere of our Sun in 2018 Using measurements ranging from white light images to proton

distribution functions, we will help answer the outstanding solar mysteries.

Follow our adventure! http://twitter.com/TheSWEAPLife

Spp sweap nes_osa_oct2011

Technology

Transcript of Spp sweap nes_osa_oct2011