Current Challenges in the Outer Heliosphere - some recent results from SHIELD DSC - Merav Opher (PI) John Richardson (PM) - Laboratory for ...
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Current Challenges in the Outer Heliosphere – some recent results from SHIELD DSC Merav Opher (PI) John Richardson (PM)
Heliosphere: the only known habitable Astrosphere
Sol
G2V Main Sequence Star
24 km/s
Habitable
Mira
BZ Camelopardalis
LL Orionis
IRC+10216 Zeta Ophiuchi
2
Interstellar Probe Webinar
The Heliosphere is an immense shield that
vp, B, Tp
protects the solar system from harsh galactic
Cosmic Ray radiation.
Diffusion This
inradiation
the HSaffects not only life on
Neutrals
Particle Tracker
Earth, but human space exploration as well
(AMPS)
Sρv, Sε
Cosmic Ray measurements at Voyager 1
Galactic cosmic rays
(GCRs) - highly
energetic charged
particles that permeate The heliosphere shields
the ISM >75% of the cosmic rays
from the Milky Way
Harmful to us
– Damaging to satellites
– major obstacle to long
term human spaceflight
Heliosheath 3
75% of GCRs entering
the heliosphere are
Credit: Ed Stone
shielded by the HS
3
SHIELD’s VISION :
The vision of SHIELD (Solar wind with Hydrogen Ion charge Exchange and
Large-Scale Dynamics) is to Understand Our Heliospheric Shield laying the
Groundwork to predict Habitable Solar Like and M-Dwarf Astrospheres and
Cosmic Radiation enabling future Human Exploration to Mars
SHIELD goal is to create a predictive model of the heliosphere and
uses a combination of observations, theory, localized kinetic and MHD
models to achieve this goal.
http://sites.bu.edu/shield-drive/
4
Kinetic Model of
T2, T3 PUIs
Reconnection
T1-T4
AwSOM
Global MHD
Turbulence
T4, T5
T5 AMPS
Transport of
Acceleration of Cosmic Rays
Particles
Phase 1 Phase 2
The Science Team: more are joining as SHIELD activities grow Collaborators:
SHIELD Science Questions • Science Question A: What is the global structure of the heliosphere? • Science Question B: How do Pick-Up Ions evolve from “cradle to grave”? • Science Question C: How does the heliosphere interact with and influence the interstellar medium (ISM)? • Science Question D: How do cosmic rays get filtered by and transported through the heliosphere
coupled with SWMF. The overall evolution of the modeling component of SHIELD towards a
complete self-consistent prediction model is shown in Figure 14. The science questions tackled
by SHIELD are explained below. The overall evolution how we will progress from Phase I to II
to reach closure in each of the science questions is shown in Table 1. Each science question will
have a Director responsible within the center to ensure progress.
Overall Center Structure: SHIELD center has 6 directors, each responsible for one of the
aspects of the center. Within these 6, 4 are responsible for each of the Science Questions of the
Center; one (Toth) is responsible for overseeing the code coupling and one (Wong) for
Overall
overseeing the Broadening Impact Center
efforts. Structure
The schematic of the directors is outlined in the
management structure chart below.
Code Coupling:
Director/PI: M. Opher
Advisory Board G. Toth
(Boston University)
(Univ. of
PM: J. Richardson (MIT)
Michigan)
Interaction of Cosmic Rays
Evolution of PUIs Broadening
Heliosphere with Global Structure Transport and
G. Zank Impacts
LISM of Heliosphere Filtration
(Univ. of Alabama) J. Wong
V. Florinski S. Fuselier J. Giacalone
(Boston
(Univ of (SwRI) (Univ. of
University)
Alabama) Arizona)
Science Question A. What is the global structure of the heliosphere?
A.1 Shape of the Heliosphere
What we know: There is an on-going debate concerning the shape of the heliosphere (is it a
long comet-like shape, bubble shaped, or “croissant”-like). The shape of the heliosphere has been
explored and modeled since the classic works of Davis Jr. (1955), Dessler (1967), Axford et al.
(1963), and Parker (1961). The work of Baranov et al. (1993), which ignored the solar magnetic
Science Question A:
What is the global structure of the heliosphere?
9
Models predict a much thicker heliosheath than
observations
Models predict 60-70AU while thickness was 28AU at V1 and 35AU at V2
Time Dependent effects cannot reconcile these measurements
(Izmodenov et al. 2005; 2008)
ISM
Indicating that some
physics is missing in the models
300 AU
300 AU
23 July 2021 10How Porous is the Heliopause?
Voyager 1 Voyager 2
The Properties of the Heliopause are not understood
The23 crossing
July 2021 of the Heliopause were drastically different at Voyager 1 and 2. 11Formation of a Confined HS plasma by the Solar B in Both Models
BU Model
Moscow Model
Kornbleuth et al. 2021
Fig. 2.— Comparison of BU (top) and Moscow (bottom) solutions of the heliosphere in
the meridional plane Included are color contours and lines of proton density [cm 3 ] (left),
magnetic field intensity [nT] (middle) and neutral H density [cm 3 ] (right).The white lines– 33 –
Draping of the interstellar magnetic field
Kornbleuth et al. 2021
SHIELD/BU
Moscow
Fig. 4.— Draping of interstellar magnetic field lines around the heliopause for the BU model 13
(top) and Moscow model (bottom). Left: port-side view of the heliosphere. Middle/Right:
view from outside of the heliosphere along the direction of ISM flow. Green lines reflect
interstellar magnetic field lines that have not undergone magnetic reconnection. Red lines
reflect interstellar magnetic that have undergone magnetic reconnection with solar magneticReconnection in the flanks predicts no field rotation at the HP
At V1 and V2The Astrophysical Journal Letters, 839:L12 (6pp), 2017 April 10
the neutrals captures the main features of the kinetic model
(Izmodenov et al. 2009).
Opher et al.
The inner boundary of our domain is a sphere at 30 au, and
the outer boundary is at x=±1500 au, y=±1500 au, z=
±1500 au. Parameters of the solar wind at the inner boundary at
Reconnection
30 au are: vSW 417 km s 1, nSW 8.74 10 3 cm 3, TSW
1.087 10 5 K (OMNI solar data; http://omniweb.gsfc.nasa.
Re-Arrange the
gov/). The Mach number of the solar wind is 7.5 and is therefore Interstellar Magnetic Field
super-fast-magnetosonic. Therefore, all the flow parameters can be
specified at this boundary. The magnetic field is given by the ahead of the Heliopause to
Parker spiral magnetic field (Parker 1958).
We assume that the magnetic axis is aligned with the solar be solar like
rotation axis. The solar wind flow at the inner boundary is
assumed to be spherically symmetric. The coordinate system is
such that the z-axis is parallel to the solar rotation axis, the
x-axis is 5◦ above the direction of interstellar flow, and y
completes the right-handed coordinate system.
We use a monopole configuration for the solar magnetic
field. This description while capturing the topology of the field
line does not capture its change of polarity with solar cycle or
across the heliospheric current sheet. This choice, however,
minimizes artificial reconnection effects, especially in the
heliospheric current sheet. Such a procedure was used by other
Issue is how the field
groups (e.g., Izmodenov & Alexashov 2015; Zirnstein et al.
2016). We chose the solar field polarity that corresponds to will drape from the HP
solar cycle 24, with the azimuthal angle λ (between the radial
and T directions in heliospheric coordinates) 270◦ in the north to the pristine
Opher et al. 2017
and south. The interstellar magnetic field has a T component of
270◦ as detected by Voyager 1. Such a configuration minimizes
reconnection at the nose (Figure 1(a)). direction and value
Two family lines:
Here, we show results from two different simulations with
different orientations for the BISM. Model A has the BISM in the
Red: connected to reconnection site in the
hydrogen deflection plane ( 34 . 7 and 57 . 9 in ecliptic latitude
and longitude, respectively) consistent with the measurements
flanks
of deflection of He atoms with respect to the H atoms
(Lallement et al. 2005, 2010). Model B is the one used in works
Green: rotation towards the BISM
that constrain the orientation of BISM based on the circularity of 14
the IBEX ribbon and the ribbon location (Zirnstein et al. 2016;
Figure 1. Pattern of convection and transport of the interstellar magnetic field
34 . 62 and 47 . 3 in ecliptic latitude and longitude, respec- lines around the heliosphere. The left column show a series of cartoons, while
tively). The specific orientation of BISM for the present Letter is the right-hand column shows magnetic field lines taken from the 3D MHD
not important since the solar wind conditions are idealized so simulation that exemplify each cartoon. The solar magnetic field is shown in
the exact shape of the heliosphere is not important. The main red, while the interstellar magnetic field is shown in black. The heliopause is
shown in the 3D MHD simulation by an iso-surface of temperature
point of this Letter depends on the fact that the interstellar field T 2.683 10 5 K in green and in gray in the cartoon (left column). The
is highly inclined to the east–west direction, which is true for yellow circle indicates the reconnection site. The MHD model used here is
both cases. model A.
Model A has v ISM 26.4 km s 1, nISM 0.06 cm 3, and
TISM 6519 K . Model B has v ISM 25.4 km s 1, nISM 3. Reconnection and Transport and Convection of the
0.0925 cm 3, and T 7500 K . The magnitude of B is0.055 550 BU - Voyager 1
SHIELD - Voyager 1
500 Moscow
Moscow -- Voyager
Voyager 1
0.05
BU - Voyager
SHIELD 1
- Voyager 1 BU - Voyager
SHIELD 2
- Voyager 2
0.045 Moscow
Moscow -- Voyager
Voyager 11 450 Moscow -- Voyager
Moscow Voyager 2
2
BU - Voyager
SHIELD 2
- Voyager 2 10
6
Moscow
Moscow -- Voyager
Voyager 2 400
0.04
350
0.035
np [cm-3]
300
U [km/s]
Tp [K]
0.03
250
0.025
200
0.02
150 BU - Voyager 1
5
SHIELD - Voyager 1
0.015 10 Moscow
Moscow -- Voyager
Voyager 11
100
BU - Voyager
SHIELD 2
- Voyager 2
0.01 50 Moscow
Moscow -- Voyager
Voyager 2
0.005 0
0 -50
60 80 100 120 140 60 80 100 120 140 60 80 100 120 140
Distance from Sun [AU] Distance from Sun [AU] Distance from Sun [AU]
BU - Voyager
SHIELD 1
- Voyager 1 BU - Voyager
SHIELD 1
- Voyager 1 BU - Voyager
SHIELD 1
- Voyager 1
Moscow
Moscow -- Voyager
Voyager 11 Moscow
Moscow -- Voyager
Voyager 1
1 Moscow
Moscow -- Voyager
Voyager 11
550 120 60
BU - Voyager
SHIELD 2
- Voyager 2 BU - Voyager
SHIELD 2
- Voyager 2 BU - Voyager
SHIELD 2
- Voyager 2
500 Moscow - Voyager 2
Moscow 100 Moscow
Moscow -- Voyager
Voyager 2 Moscow
Moscow - Voyager 2
450 80 40
400
60
350
40
20
VR [km/s]
VN [km/s]
VT [km/s]
300
20
250
0
200 0
-20
150
-40
100
-60 -20
50
0 -80
-50 -100 -40
60 80 100 120 140 60 80 100 120 140 60 80 100 120 140
Distance from Sun [AU] Distance from Sun [AU] Distance from Sun [AU]
BU - Voyager
SHIELD 1
- Voyager 1 BU - Voyager
SHIELD 1
- Voyager 1 BU - Voyager
SHIELD 1
- Voyager 1
Moscow
Moscow -- Voyager
Voyager 11 Moscow
Moscow -- Voyager
Voyager 11 Moscow
Moscow -- Voyager
Voyager 11
0.25 0.1 0.8
BU - Voyager
SHIELD 2
- Voyager 2 BU - Voyager
SHIELD 2
- Voyager 2 BU - Voyager
SHIELD 2
- Voyager 2
Moscow -- Voyager
Moscow Voyager 2 Moscow - Voyager 2
Moscow Moscow Voyager 22
Moscow - Voyager
0.2
0.05 0.6
0.15
0 0.4
0.1
-0.05 0.2
0.05
BR [nT]
BN [nT]
BT [nT]
0 -0.1 0
-0.05
-0.15 -0.2
-0.1
-0.2 -0.4
-0.15
-0.25 -0.6
-0.2
-0.25 -0.3 -0.8
Kornbleuth et al. 2021
60 80 100 120 140 60 80 100 120 140 60 80 100 120 140
Distance from Sun [AU] Distance from Sun [AU] Distance from Sun [AU]
15
Fig. 10.— 1D cuts along the Voyager 1 (solid) and Voyager 2 (dashed) trajectory for the
BU (black) and Moscow (red) models. First row (from left to right): plasma density, plasma
speed, and plasma temperature. Second row (from left to right): the radial, normal, and(II) Quasi steady-state conditions apply, and adiabatic cooling is negligible. (III) The
radial component of the solar wind speed, Vr(r), decreases with r as observed by LECP
Science Question B:
[10] and approaches zero at the heliopause. (IV) There is a turbulent component to the
radial speed, δur(r), whose amplitude increases with r beyond rC (where rC is about 10
How do Pick-Up Ions evolve from “cradle to grave”?
AU away from the heliopause), becoming comparable to the solar wind speed. Only
by invoking (IV) can we explain the IBEX-LO ~0.16 keV EHA differential intensity.
FIGURE 1. Differential intensity
10 4 of protons in the heliosheath at
Energetic Protons 110 AU measured with LECP on
PUIs are particles with energy
Differential Intensity 1/(cm -sr-s-keV)
Hydrogen Atoms at 110 AU
103 Voy-ager-1 [2,4] and energetic
> ~0.5 keV (hotter than the
neutral hydrogen atoms in the V-1
direc-tion observed recently with
102
(c) thermal component of the
IBEX [1] (corrected for extinction New INCA ENAs
2
Voyager [15]) and C a s s i n i [2], and
101
(a) (b) LECP solar wind)
measured from 1996-2006 by
SoHO [8] ±45° from the nose LO ENA flux IBEX 1/(cm
100 IBEX
near direction. The Cassini Heliosphere
spectrum
heliopause Pickup
Low shown is taken from [4]. Four
Protons
10-1 High (d) model EHA spectra are computed HI ENA flux IBEX 1/(cm
(see text) from four HS proton
10-2
(c)
Voyager is “blind” to PUIs until
populations: (a) HS solar wind, (b)
+
HS pickup H (c) heliosphere
10-3
Cassini INCA 110 AU
28keV
+
pickup H , and (d) Heliosheath
–1.5 power law
Pickup
tail protons. The sum of all four
j_ENA Fig1
SoHO HSTOF Protons
-4 model spectra (bold curve)
10 Solar Wind
0.1 1 10 100 1000 matches theProtons
– 5 tail entire re-cently
Protons
observed EHA spectrum well
Energy (keV)
23 July 2021 within the primarily system-atic 16
errors of the measurements.
METHODOLOGY
New INCA-IBEX ENAs V1 direction 5:14:34 PM 7/13/10
The energetic hydrogen atoms (EHAs) measured by IBEX-LO, IBEX-HI, Cassini
INCA and SoHO HSTOF shown in Fig. 1 are created from energetic protons in theThe Downwind Solar Wind: Model Comparison with
Pioneer 10 Observations, by M. Nakanotini, G.P. Zank, L.
Adhikari, L.-L. Zhao, J. Giacalone, M. Opher, and J.D. Richardson,
ApJLetters, 2020
Left panel: Monthly (blue) and 24 year (orange) average of the ratio μ of solar radiation pressure to solar gravity, right panel:
Hydrogen density distribution and the trajectories of Pioneer 10, Voyager 1 and 2. The H distribution is based on the “hot
model” (Wu & Judge 1979; Thomas 1978).The theoretical model for the downwind solar wind (red line), and Pioneer 10 observations (filled points). Top left: the magnitude of the background azimuthal magnetic field, top right: the bulk flow speed, bottom left: the thermal plasma (solid) and PUI (dashed) number density, and bottom right: the thermal plasma (solid) and PUI (dashed) temperature. Black dashed line is the upwind solar wind obtained from the same model but with uH = 20km/s, θ=0◦, and L=7au.
Comparison of spectra at the nose and flank of the termination
shock, J. Giacalone (Zank, G., Nakanotani, M., Kota, J., Opher,
M., Richardson, J.)
Giacalone et al. 2021
Ø The flux of the shock-accelerated tail
particles (5-40 keV) is very similar in
these two locations
Ø In both cases, the spectrum falls off
rapidly above about 50 keV, which is due
to the small simulation domain and
simulation time.Science Question C: How does the heliosphere interacts with Interstellar Medium? 23 July 2021 20
Magnetic Trapping of GCRs in Outer Heliosheath
Cosmic-ray trapping in outer heliosheath 7
where γ Florinski,
= [1 + (p2! +V.,
p2⊥Chanbari,
)/(mc)2 ]1/2 isK.,
theKleiman,
relativisticJ.factor,
Opher, andM.,
B!∗ Giacalone, Kota,(9)
= B∗ · b̂. Equation Cummings
contains the electric,
curvature, gradient, and polarizations drift motions, while eq. (10) includes the effects of parallel electric field and
focusing. Non-adiabatic effects, such as pitch angle scattering, will be considered in the next section.
Figure 4. One complete orbit of a 1 GeV cosmic-ray proton placed in a magnetic trap with an initial pitch angle of 80◦ (red
line). The trajectory integration time was 3950 days. A single magnetic field line “ending” at the null point is shown in blue.
The surface is the heliopause is light gray in color.
Figure 4 presents a guiding-center path of a 1 GeV proton injected into the trap nearly perpendicular to the magnetic 21
field line. The injection point was 10 AU away from the “centerline” of the trap, defined here as the field line striking
the null point (blue in Figure 4). The trajectory completed one full drift period lasting 8 years; it is not closed
because of the electric drift (this was verified by tracing the same particle with the electric field set to zero, which
produced a fully periodic trajectory). Trajectories started farther away from the centerline take progressively longer
to complete a full cycle; at the 1 GeV energy the shortest time to orbit the centerline is 4–5 years, while farther away
the period increases to several decades. Even the shortest period is comparable or larger than the typical time between
scatterings, so one would not expect the particles at this energy to be contained long enough to complete even a singleSHIELD WEBINAR SERIES
Heather Elliott Margaret Galland Parisa Mostafavi
Stamatios Krimigis Nancy Crooker
Southwest Research Kivelson Nicola Fox Johns Hopkins Applied
Johns Hopkins Applied Boston University
UCLA, NASA Headquarters Physics Laboratory
Institute Physics Laboratory
University of Michigan
Fran Bagenal Charles Kohlhase Suzanne Dodd Mayra Natalia
Emily Lichko Laura Delgadoópez
University of Colorado Jet Propulsion Laboratory, Jet Propulsion Laboratory, Hernández
University of Science Mission
Laboratory of Atmospheric California Institute of California Institute of Science Mission
Arizona Directorate (SMD) of NASA
and Space Physics Technology Technology Directorate (SMD) of NASAYou can also read
