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Solar Probe Plus (SPP)

Solar Probe Plus (SPP)

Solar Probe Plus:

Mission to the
Solar Corona

J. C. Kasper

Harvard
-
Smithsonian Center for Astrophysics

S. D. Bale (UCB/SSL), N. Fox (JHU/APL), R. Howard (NRL),
D. McComas (SwRI), A. Szabo (GSFC), M.
Velli

(JPL)

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Solar Probe Plus (SPP)

Outline


Introduction to Solar Probe Plus


Mission objectives and description


Scientific instrument payload


Examples of SPP Science



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Solar Probe Plus (SPP)

Solar Probe Plus Objectives

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(1) Trace the flow of energy
that heats and accelerates
the solar corona and solar
wind


(2) Determine the structure
and dynamics of the plasma
and magnetic fields at the
sources of the solar wind

(3) Explore mechanisms that
accelerate and transport
energetic particles.

Send a spacecraft within 8.5 R
s

of the surface of the Sun, entering the
solar corona, in order to:

Solar Probe Plus (SPP)

Why close to Sun?


Coronal magnetic structure
still channels the flow


Maxima


Waves, turbulence are
strongest


Temperature maximum


Strongest energetic particle
production


Transitions



<1 to

>1


Sub
-
Alfvénic to Super
-
Alfvénic flow (enter the
magnetic field of the Sun)


Collisional


Collisionless
transition




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Solar Probe Plus (SPP)

Key Dates and Current Project Status


Project formally started in FY 2008


JHU/APL selected to design spacecraft and run mission
in 2009


Science investigations selected in Fall 2010


One year Phase A initial design phase


All instruments accommodated on the spacecraft


Mission level 1 requirements written


Preparation for Mission Design Review in October 2011


Instrument delivery 2017


Launch 2018



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Solar Probe Plus (SPP)

Organizational Structure


NASA


Solar Probe Plus is part of
the NASA Living With a Star
line of missions


Adam Szabo (GSFC) is the
Mission Scientist


JHU/APL


Building and operated the
spacecraft and integrates
the instruments


Nicky Fox is the Project
Scientist


SWEAP


PI Justin Kasper (SAO)


Solar wind plasma suite


FIELDS


PI Stuart Bale (UCB/SSL)


Electromagnetic field
instrument suite


WISPR


PI Russ Howard (NRL)


White light imager


ISIS


PI David McComas (SwRI)


Energetic particle
instrument suite


Observatory Scientist


Marco
Velli

(JPL)

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Mission Profile


Launch


July 30,
2018


First Encounter


October, 2018 (0.16
AU or 35 R
s
)


Seven Venus flyby
and gravitational
assists


SEPTEMBER 27, 2018


DECEMBER 21, 2019


JULY 5, 2020


FEBRUARY 15, 2021


OCTOBER 10, 2021


AUGUST 15, 2023


OCTOBER 31, 2024


First encounter at
closest approach


December 19, 2024


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0
0.2
0.4
0.6
0.8
1
1.2
0
300
600
900
1200
1500
1800
2100
2400
2700
Time (days from launch)
Solar Distance (AU)
Radius

Hours

<10 Rs

30

<15 Rs

434

<20 Rs

961

<30
Rs

2149

Solar Probe Plus (SPP)

The Solar Probe Plus Spacecraft

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Magnetometer boom

Retractable solar panel

Sun Limb Sensor

Water
-
filled radiator

Carbon heat shield

Atlas V 551 Launch Vehicle

Solar Probe Plus (SPP)

THE INVESTIGATIONS

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Solar Wind Electrons Alphas and Protons
(SWEAP) Investigation

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SWEAP Electronics Module (SWEM)


interface to
s/c, operates SPC and SPAN, 32GB internal storage

Solar Probe Cup (SPC)


Faraday Cup faces
the Sun, high cadence (up to 128 Hz) bulk
ion and electron measurements

Solar Probe
ANalyzers

(SPAN)


Electrostatic Analyzers behind the
heat shield, detailed measurements
of 3D ion and electron velocity
distribution functions

Themis

SPAN
-
B:
Looks
“behind”,
electrons

SPAN
-
A:
Looks
“ahead”,
ions and
electrons

Solar Probe Plus (SPP)

Reproducing a solar encounter

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Solar Probe Plus (SPP)

SWEAP Observations

Solar Probe Cup (SPC)


Proton Tracking (PT): 1.5D proton
VDF at 8 Hz, solved for
V
p
,
T
p
,
n
p


Full Scan (FS) at 1 Hz, e
-

1.5D VDF
from 50
eV



2 keV at 0.1 Hz,
i
+ 1.5D
VDF from 50
eV



8 keV at 0.1 Hz


Flux
-
Angle (FA): Total flux and flow
angles at 128 Hz



Solar Probe
ANalyzers

(SPAN)


Fine Resolution (FR)


3D VDF at maximum
energy and angular
resolution at 0.5 Hz


Alternating Sweep (AS)


Coarse 3D VDF over full
energy range and fine
resolution 3D VDF at 4 Hz


Rapid 2D VDF (RD)


High frequency 2D VDF
using
B

from FIELDS

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SPP Mission Kickoff
-

SWEAP Science Overview

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FIELDS Investigation

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1 vector search
-
coil
magnetometer for
AC vector magnetic
fluctuations

2 flux gate
magnetometers for
“DC” vector magnetic
field

Four electric field
antennas for DC
-
AC
electric fields

Solar Probe Plus (SPP)

FIELDS
Observatons

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E

B

Solar Probe Plus (SPP)

ISIS
-
EPI (Energetic Particle Instruments)

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EPI
-
Lo


Electrons (25
-
500 keV) and ions (0.02
-
7
MeV

protons and 0.02
-
2
MeV
/
nuc

heavier ions).
Resolves all major
species and
3
He and
4
He
in multiple directions

EPI
-
Lo single
wedge
prototype

EPI
-
Hi


Two Low
Energy Telescopes
(LET) and a High
Energy Telescope (HET)
they cover 1 to >100
MeV
/
nuc

for protons
and heavy elements
and 0.5 to 6
MeV

for
electrons

Solar Probe Plus (SPP)

ISIS Observations

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SWEAP

Solar Probe Plus (SPP)

Wide Field Imager for Solar Probe (WISPR)

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WISPR


white light images of Thompson
scattered sunlight

Solar Probe Plus (SPP)

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

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Polar
Wind

Solar Probe Plus (SPP)

Observatory Scientist

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?


As the mission's observatory scientist, Marco is
responsible for serving as a senior scientist on the
science working group. He provides an independent
assessment of scientific performance and acts as a
community advocate for the mission.


Solar Probe Plus (SPP)

SP+ SCIENCE

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Evolution of the energy budget

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Solar Probe Plus (SPP)

Identification of dominant heating mechanisms

10/21/2010

SPP Mission Kickoff
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SWEAP Science Overview

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Solar Probe Plus (SPP)

Collisional/Collisionless transition

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SPP Mission Kickoff
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SWEAP Science Overview

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Solar Probe Plus (SPP)

Role of instabilities in the inner heliosphere

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SPP Mission Kickoff
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SWEAP Science Overview

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Solar Probe Plus (SPP)

Evolution of solar wind solar sources



Interfaces between
streams of wind more
distinct closer to Sun



In situ
measurements of solar
wind state:
temperature, density,
velocity, He/H,
magnetic field strength,
turbulence



Remote imaging of
local structures with
WISPR



Connect to solar
surface and corona
observations, and to
models

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SWEAP Science Overview

Solar Probe Plus (SPP)

Connection between coronal sources, streamer
belt, and heliospheric current sheet



In situ measurements of solar wind state: temperature,
density, velocity, He/H, magnetic field strength, turbulence



Remote imaging of local and global structures with WISPR



Connect to solar observations and models


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(
Antiochos

et al. 2011)

Solar Probe Plus (SPP)

Small coronal structures in the solar wind


Width of streamer belt, flux tubes, discontinuities, reconnection
exhausts, shocks, current sheets, fast/slow transitions, flux
ropes, filaments


Fine
-
scale structures extending from coronal base. Fast 50
-
150
km/s Type
-
II
Spicules

200 km thick and occur at great frequency


Bulk plasma properties, e
-

strahl, and e
-

PAD from SWEAP. Link
to Type III radio bursts seen by FIELDS, energetic particles from
ISIS, density column from WISPR


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SWEAP Science Overview

Solar Probe Plus (SPP)

Variable magnetic connection


Determine the fraction of
the corona magnetically
open to interplanetary
space, change in total open
flux over solar cycle,
variability of connectivity
on short timescales.


Combine SWEAP solar wind
conditions, electron pitch
angle distributions, FIELDS
magnetic field direction,
WISPR images of local
structure

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SWEAP Science Overview

Solar Probe Plus (SPP)

Crossing the Alfvén surface


Where is the Alfvén surface located?


Does the corona really co
-
rotate at this
surface?


How do coronal waves pass through
this transition?


Signatures: Alfvénic Mach number, ratio
of ingoing/outgoing wave power,
rotational speed of plasma

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(
Ofer

Cohen)

(
Velli
)

Solar Probe Plus (SPP)

Energetic particle propagation


Understanding solar
energetic particle (SEP)
acceleration at 1 AU is
difficult


distance from sources


mixing during transport


Helios showed advantages of
near
-
Sun observations of SEP
processes near origin


SP+ will observe 50
-
100 ISEP
and

50 large SEP events
inside 0.25 AU


Enabling detailed studies of


flare and CME
-
shock
acceleration


seed particle identities


the effects of particle transport
in the interplanetary medium.


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(
Wibberenz

and Cane
2006)

Solar Probe Plus (SPP)

Shocks in the inner heliosphere


Acceleration of
particles


Structure of CMEs


Heating of corona?


Observations


Derive local shock
properties using SWEAP
and FIELDS


Large scale shock
structure from WISPR


Energetic particle
production with ISIS

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Solar Probe Plus (SPP)

Suprathermal tails


What mechanisms produce
the widely observed
suprathermal tails and how
do they feed into SEP
acceleration?


Are they produced in the
corona by flares or are they
produced in the heliosphere
by stochastic acceleration?


Investigate by combining


Variation of the suprathermal
tail itself


EPI
-
Lo


Electromagnetic fluctuations


FIELDS


Plasma fluctuations and type of
solar wind


SWEAP


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10
-9
10
-7
10
-5
10
-3
10
-1
10
1
10
3
10
5
10
7
10
9
FW
FW ULEIS
bulk SW
sum
ß=5
ß=6
Halo SW
Tail
10
8
10
9
Phase Space Density (s
3
/km
6
)
H
+
f = f
o
v

-5
Suprathermal Tail
Bul k
Sol ar
Wind
Hal o
Sol ar
Wind
Pi ckup
Protons
Proton Speed (cm/s)
2007.0 – 2008.0
Quiet times
V
sw
< 320 km/s
ACE SWICS and ULEIS
ULEIS
SWICS
Bulk SW Density = 2.1
Pressure (dyne/cm^2) = 21*1.655529E-13 = 3.47661e-12
SW Halo Density = 0.45
Pressure (dyne/cm^2) = 7.791439E-13*4.5 = 3.50615e-12
P/(1.6e-12)(eV/cm^3) = 0.486357*4.5
Tail Density = 1.404805E-05
Pressure (dyne/cm^2) = 4.555991E-14
PI Density= 2.7065E-04 Pressure= 2.0297E-13
INTERSTELLAR PARAMETERS: Uo(km) Temp(k) Ninf(cm^3)
22.00 12000. 0.5500E-01
HELIOSPHERIC: Vsw(km/s) Mu nNU
321.0 0.9000 1.500
Bprod + BRp*(R^p)= 6.000E-07 + 0.000E+00*(R^ 0.60)
Bloss + BRs*(R^s)= 5.000E-07 + 0.000E+00*(R^ 0.60)
SPACECRAFT PARAMETERS: R(au) THETA(deg) SPE(deg)
1.00 5.00 5.00
ANISOTROPY: MeanFreePath Br Bt Bn
0.00
Eo = 214.843 keV = (20*321/438)^2
alpha = 1.1
10
-9
10
-7
10
-5
10
-3
10
-1
10
1
10
3
10
5
10
7
10
9
10
8
10
9
1_U3HE_HPI98.ALL;1 7:21:08 PM 11/9/08
98 corrected M21H1d| w0.94-1.10| M/Q1.00-1.00|
ßp=ßl =6.1e-7; µ=.9
Hal o SW
(1/1.59)
Tai l
Phase Space Density (s
3
/km
6
)
Proton Speed (cm/s)
H
+
1998
<R> = 5.35 AU
<V
sw
> = 419 km/s
v
He
=418.7
V
thHe
= 19.6
R = 5.3548
SPE= 6.9326
HLat= -9.8616
FW PI H+ 98 all *1.5
Bulk Solar Wind
Halo Solar Wind
Pickup
Hydrogen
-5 Suprathermal Tail
Bul k SW Densi ty = 0.116
Pressure (dyne/cm^2) = 0.116*3.151440E-12 = 3.65567e-13
Hal o SW Densi ty = 0.0167
Pressure (dyne/cm^2) = 0.0167*1.384765E-11 = 2.31256e-13
Eo = 22.769 keV
Tai l Densi ty = 120*3.142546E-07 = 3.77106e-05
Pressure (dyne/cm^2) = 120*7.782642E-16 = 9.33917e-14
PI Densi ty= 3.1285E-04
Pressure= (2/3)*3.3672E-13 = 2.2448e-13

Solar Probe Plus (SPP)

Conclusions


Exciting science


First direct sampling of the atmosphere of a star


General interest to plasma astrophysics


Heating


Acceleration


Shocks


Co
-
rotation


Suggestions for related work


Numerical simulations to guide planning for observations


Solar wind structures on global and kinetic scales


Predictions of wave power


Magnetic reconnection exhausts


Theoretical work and observational techniques


How do you study turbulence when the Taylor hypothesis breaks down?


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