From SSL: “MAVEN Instruments Study the Solar Wind at Mars”

SSL UC Berkeley

Space Science Lab, UC Berkeley

February 20, 2016
Christopher Scholz

The ‪MAVEN‬ spacecraft is equipped with several instruments devoted to measuring the solar wind and how solar energetic particles and extreme ultraviolet irradiance interact with Mars’ upper atmosphere.

Solar Wind Electron Analyzer (SWEA)-The Solar Wind Electron Analyzer (SWEA) is a part of the Particles and Fields (P&F) Package and will measure the solar wind and ionospheric electrons.

Goals:

Deduce magneto-plasma topology in and above the Martian ionosphere based on electron spectra and pitch angle distributions
Measure atmospheric electron impact ionization effects

Observations:

Measure energy and angle distributions of electrons in the Mars environment
Determine magnetic topology from pitch angle distributions
Measure solar wind, sheath and primary ionospheric photoelectron spectrum
Determine electron impact ionization rates
Measure auroral electron populations
Evaluate plasma environment

Technical details and heritage:

Hemispherical Electrostatic Analyzer with deflectors
Electrons with energies from 5 eV to 4.6 keV
FOV 360o x 120o (Azimuth x Elevation)
Angular resolution 22.5o in azimuth x 20o in elevation
Energy fluxes 103 to 109 eV/cm2-s-ster-eV
Energy resolution: ΔE/E = 17%, FWHM (capability for 9% below 50 eV)
Time resolution: 2 sec
Mounted at end of 1.5-meter boom
Heritage from STEREO SWEA

Solar Wind Ion Analyzer (SWIA)-The Solar Wind Ion Analyzer (SWIA) is a part of the Particles and Fields (P&F) Package and measures the solar wind and magnetosheath proton flow around Mars and constrains the nature of solar wind interactions with the upper atmosphere.

Goals:

Determine the ionization rates of neutrals from charge exchange, as an input to atmospheric loss processes
Determine the pickup acceleration of newly formed ions by the v x B electric field
Measure the flow of solar wind energy through the Martian magnetosphere
Measure the structure and variability of the Martian magnetosphere
Measure basic space plasma phenomena, including reconnection, flux ropes, plasmoids, bulk plasma escape, auroral processes, and boundary instabilities, throughout the Martian system

Observations:

Measure the properties of solar wind and magnetosheath ions, including density, temperature, and velocity, in order to determine the energy input to the upper atmosphere, the charge exchange rate, and the bulk plasma flow from solar wind speeds (~350 to ~1000 km/s) down to stagnating magnetosheath speeds (tens of km/s)

Technical details and heritage:

Coarse 3d covers 360°x90° with 22.5° resolution and energies 5 eV/q – 25 keV/q
Fine 3d covers solar wind beam w/ 4.5° resolution and 10% energy windows
Intrinsic time resolution of 4 s
Mechanical attenuator provides variable dynamic range to cover from tenuous magnetosphere up to extreme solar wind fluxes [5×104 to 7×1011 eV/(cm2 s sr eV)]
Heritage from Wind, FAST, and THEMIS

Suprathermal and Thermal Ion Composition (STATIC)-The Suprathermal and Thermal Ion Composition (STATIC) instrument is part of the Particles and Fields (P&F) Package and measures thermal ions to moderate energy escaping ions.

Goals:

Measure the source ion populations near periapsis, the heated ionospheric ions at intermediate altitudes that achieve escape velocity, and the pickup acceleration of these ions in the magnetosheath and solar wind
Allow direct measurements of the Martian sheath plasma, separating shocked solar wind and planetary ions that populate the sheath and plasma sheet

Observations:

Escaping ions and processes
Composition of thermal to energetic ions; energy distributions and pitch angle variations
Ionospheric Ions 0.1-10 eV
Tail Superthermal ions (5-100eV)
Pick-up Ions (100-20,000 eV)
Key ions H+, O+, O2+, CO2+

Technical details and heritage:

Toroidal Electrostatic Analyzer with Time of Flight section
Mass Range 1-70 AMU, ΔM/M > 4
Energy range ~0.1 eV to 30 keV, ΔE/E~15%
FOV 360o X 90o
Angular Resolution 22.5o x 6o
Energy Flux < 104 to 109 eV/cm2-s-sr-eV (to 1012 w/attenuators for low energy beam)
Can be oriented to measure either upwelling/downwelling or horizontal flows
Heritage from Cluster CODIF

Solar Energetic Particle (SEP)-The Solar Energetic Particle (SEP) instrument is part of the Particles and Fields (P&F) Package and determines the impact of SEPs on the upper atmosphere.

Goals:

Determine SEP input into the atmosphere as a function of altitude
Determine SEP heating, ionization, and sputtering of upper atmosphere
Detect the highest energy pickup ions (>30 to 100s of keV)

Observations:

Characterize solar particles in an energy range that affects upper atmosphere and ionospheric processes (~120 – 200 km)
Time resolution adequate to capture major SEP events (<1 hour)

Technical details and heritage:

Two dual double-ended telescopes
Four look directions per species, optimized for parallel and perpendicular Parker Spiral viewing
Protons and heavier ions from ~25 keV to 12 MeV
Electrons from ~25 keV to 1 MeV
Energy fluxes 10 to 106 eV/cm2-sec-ster-eV
Better than 50% energy resolution
Heritage from (nearly identical to) SST on THEMIS

Langmuir Probe and Waves (LPW)Langmuir Probe and Waves (LPW)-The Langmuir Probe and Waves (LPW) instrument is part of the Particles and Fields (P&F) Package and determines ionospheric properties, wave heating of the upper atmosphere, and solar EUV input to the atmosphere.

Goals:

Measure the in situ electron density and electron temperature from the ionospheric peak up to the nominal ionopause location. It will also measure the electric field wave power important for ion heating
Characterize the basic state of the ionosphere—its global structure, variability, and thermal properties
Determine the effects of solar wind generated plasma waves and auroral precipitation on ionosphere heating and relationship to plasma escape
Determine the electron temperatures required for deriving ion recombination rates and ionospheric chemistry
Identify the ionopause and detached, escaping ionosphere clouds

Observations:

Electron temperature and number density throughout upper atmosphere
Electric field wave power at low frequencies important for ion heating
Wave spectra of naturally emitted and actively stimulated Langmuir waves to calibrate density measurements

Technical details and heritage:

Cylindrical sensors on two 7-meter booms
Sensor I-V sweeps (at least ±50 V range)
Low frequency (f: 0.05-10 Hz) E-field power; sensitivity 10-8 (V/m)2/Hz (f0/f)2 where fo=10 Hz and 100% bandwidth
E-Spectra measurements up to 2 MHz
White noise (50 kHz – 2 MHz ) sounding
Thermal Electron density 100 to 106 cm-3
Electron temperatures 500 to 5000oK
Heritage from THEMIS and RBSP

Extreme Ultraviolet (EUV) Monitor-The Extreme Ultraviolet (EUV) monitor is part of the Langmuir Probe and Waves (LPW) instrument and measures solar EUV input and variability, and wave heating of the Martian upper atmosphere.

Goals:

Measure solar emissions from different regions of the Sun in three distinct EUV bands
Three channels will provide a complete EUV spectrum (0.1-190 nm) to serve as a proxy for input to the Flare Irradiance Spectral Model (FISM) model

Observations:

Solar EUV irradiance variability at wavelengths important for ionization, dissociation, and heating of the upper atmosphere (wavelengths shortward of HI Ly-α 121.6 nm)

Technical details and heritage:

Three photometers at key wavelengths representing different temperature solar emissions (0.1-7, 17-22, and 121.6 nm)
Full spectrum (0-200 nm) derived from measurements using Flare Irradiance Spectral Model (FISM)
Heritage from TIMED, SORCE, SDO, and rocket instruments

Magnetometer (MAG)-The Magnetometer (MAG) is a part of the Particles and Fields (P&F) Package and measures interplanetary solar wind and ionospheric magnetic fields.

Goals:

Measure vector magnetic field
Characterize solar wind interaction
Support particles and fields package (ions, electrons, energetic particles & waves)

Observations:

Vector magnetic field in the unperturbed solar wind (B ~ 3 nT), magnetosheath (B ~ 10-50 nT), and crustal magnetospheres (B < 3000 nT), with the ability to spatially resolve crustal magnetic cusps (horizontal length scales of ~100 km)

Technical details and heritage:

Two sensors, outboard of solar array
Magnetic field over a dynamic range of ~60,000 nT; resolution 0.05 nT
32 samples/sec intrinsic sample rate averaged and decimated as necessary
Sensor scale factor accuracy of 0.05%
Heritage from MGS, Voyager, AMPTE, GIOTTO, CLUSTER, Lunar Prospector, MESSENGER , STEREO, Juno, and Van Allen Probes

NASA MAVEN
NASA/Mars MAVEN

These experiments have been specifically designed to determine whether space weather events increase atmospheric escape rates to historically important levels.

In analyzing data from these instruments, MAVEN scientists will take three approaches to derive the history of Mars’ atmosphere:

1. Use ratios of stable isotopes to determine the integrated loss to space
2. Use observed changes in escape in response to changing energetic inputs to directly extrapolate back in time
3. Model escape processes using current conditions and extrapolate models back in time

Taking these approaches enables our team scientists to determine how various space weather events affect the upper atmosphere of Mars today and how they have contributed to its evolution over time. Capturing events of different magnitudes becomes more likely over time and contributes to producing more accurate model extrapolations back in time.

MAVEN data is allowing scientists to:

Investigate atmospheric escape response to regular solar wind variations and to major events (solar flares, coronal mass ejections)
Update an estimate of solar wind evolution
Determine how solar energetic particles contribute to escape, and
Estimate integrated historical loss to space

NASA Goddard

For images, fuller descriptions, publications, see the original SSL article.

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