SH13A-228

Exploring impulsive solar magnetic energy release with direct hard X-ray imaging spectroscopy

SH13A-228 FOXSI X-RAY IMAGER

FXI Telescope (2x)

The FOXSI X-ray Imager (FXI) uses a proven approach of focusing X-rays onto pixelated detectors, with the Solar Position Sensor and Metrology Camera providing the pointing and alignment knowledge needed to reconstruct the origin in the sky for each X-ray photon. The X-ray Flux Sensor (XFS) provides complementary X-ray spectroscopy with the same FOV and boresight as FXI. Also shown are photographs of heritage for key subsystems.

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NASA Goddard Space Flight Center, Space Sciences Lab, Univ. of California at Berkeley, Univ. of Applied Sciences NW Switzerland, Univ. of Minnesota, 5 Southwest Research Institute, 6 New Jersey Institute of Technology, 7 Univ. of Maryland, 8 Space Research Centre of the Polish Academy of Sciences, 9 Caltech, 10 NASA Marshall Space Flight Center, 11 Univ. of Glasgow, 12 Institute of Space and Astronautical Science (ISAS)/JAXA, 13 University of Colorado/NSO, 14 Montana State University, 15 Univ. of Genoa, 16 Leibniz Institute for Astrophysics Potsdam, 17 Observatoire de Paris, 18 Univ. of Graz, 19 Air Force Research Lab, 20 LASP 2

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Providing a revolutionary new view on explosive solar magnetic energy release.

• Answers fundamental questions about how the Sun accelerates particles to high energies • Differentiates between different models of coronal heating in hot active regions. • Characterizes potentially Earth-directed energetic electrons at the Sun.

5 arcsec

dynamic range than previous instruments. • FOXSI is high heritage with all required components at ≥TRL6, and tested on multiple sounding rockets and balloons.

Sun

-X

Metering Assembly (MA)

DB Sunward

Tip/tilt adjustment mechanism (1 of 2) Grazing-incidence mirror optics

FXI Detector Assemblies FXI Electronics (incl. IDPU, DIBs, and HVPS)

XFS Electronics

Solar Position Sensor (SPS)

Radiator Panel for FXI Detectors XFS FOV Composite Truss Structure

XFS Instrument Energy Range (ERA) Effective Area (EA) Largest Flare Observable Energy Resolution (ERE) Field of View (FOV)

Detector Bench (DB) Star trackers (2 of 4) Boom canister MA release mechanism (1 of 3)

FXI FOVs

DB Anti-Sunward

Metrology LEDs (3 of 6)

Attenuator Wheel Composite Alignment Bench Thermal blanketing on both benches is not shown.

XFS Detectors

Sun -750.0

(Left) The co-boresighted FXI and XFS FOVs (9 × 9 arcmin) are large enough to cover entire active regions, flares, and even large solar eruptive events. The spacecraft pointing control capability can keep targets within the 6-arcmin diameter circle of FXI’s 50% vignetting at 40 keV, which is centered in the FOV. Predicted boom motions are negligible on the scales shown here.

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(Right): (A) FXI has greater on-axis effective area compared to RHESSI over the required energy range (5 to 50 keV). (B) FXI has ~20 x better HXR sensitivity (3σ) for a background-dominated source compared to RHESSI (5-minute integration, energy bin width ΔE = E, and an active-region-sized region of interest 2 arcmin in diameter). Ghost rays from any active regions outside of the FOC would affect the sensitivity only below ~8 keV. The FXI sensitivity limit when integrating over the entire FOV is ~5 times worse, illustrating an advantage of using direct imaging.

Metrology LEDs (6x) Detector Bench (DB)

E ective area

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Sensitivity limit (3ơ) for 5-minute integration

100.0

A FXI

~30% more HXR e . area

40 RHESSI

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10.0

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40 Energy (keV)

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RHESSI FXI (FOV-integrated)

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Required Energy Range 0 5

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FXI (2’-diameter region) ~20x better sensitivity Required Energy Range 20

40 Energy (keV)

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Requirement 1.0 keV to 15 keV ≥0.01 cm2 X5 0.3 keV at 1.5 keV Same as FXI

COILABLE BOOM Built by Orbital/ATK Goleta the FOXSI Coilable boom, with a wide base, provides a high-heritage and stiff connection between the detectors and optics that exceeds requirements. With a length of 13.3-m the boom has three sides, with the vertices on an 88-cm-diameter circle, with no sock covering the structure. Three graphite longerons provide thermal stability, and precision preloaded joints provide deployment repeatability. OATK-Goleta, the boom provider, has built over 60 flight Coilable booms with 100% deployment success.

• Transmitter Type: S-band

Flare ribbons

Performance 0.8 to 20 keV 0.01 cm2 X10 0.25 keV at 1.5 keV Same as FXI

(Left) FXI’s major instrument components are on three assemblies—the Detector Bench (DB), Metering Assembly (MA), and Optical Bench (OB). The fields of view (FOVs) of FXI and XFS are unobstructed, and the attenuator wheel is positioned between the Sun and the FXI detectors. (Right) All FXI components have high heritage and are provided by proven providers.

FOXSI Sounding Rocket

RHESSI 0

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Y (arcsecs)

Performance 3 to 55 keV 20:1 at 20" 1000:1 at 45" 55 cm2 ~0.3 photon/cm2 0.1 s 8" FWHM over 300" 9 x 9 arcmin 0.8 keV 0.8 keV X10

FXI Heritage

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XFS Detector

XFS Electronics

SOL2012-11-02 17:59 -800 GOES B2.7 200 400 600 800 1000 X (arcsecs)

(Above) Superiority of FXI imaging over RHESSI’s indirect technique is proven by this comparison of a flare observed simultaneously in 2012 by RHESSI and using FOXSI optics on a sounding rocket flight.

FXI Components Name

Provider

Parameter

Repeatability

Transverse o set Tip/tilt o set Twist o set

±0.1 mm ±2 arcmin ±8 arcmin

Orbital Stability ±0.1 mm ±3 arcsec ±10 arcsec

Optical-Axis Stability ±1.5 arcsec ±3 arcsec ±0.15 arcsec

The boom deployment repeatability and orbital stability have been modeled for FOXSI’s orbit and exceed requirements. The corresponding orbital stability of the optical axis is measured in flight by a Metrology System to remove the impact on the angular resolution.

D FXI (deconvolved)

C FXI

Y (arcsecs)

Requirements ≤5 to ≥ 50 keV ≥10:1 at 20" ≥100:1 at 45" ≥40 cm2 1 photon/cm2 ≤0.25 s ≤10" FWHM over 300" ≥5 x 5 arcmin ≤1.2 keV 2 keV X5

XFS Instrument Performance

Boom (deployed)

FXI Resolution 8 arcsec (FWHM)

-100

FOXSI On Axis RHESSI NuSTAR -50 0 50 x (arcsec)

• Orbit: LEO, Circular • Altitude: 590 km • Inclination: 28.5° • Pegasus XL Launch Vehicle • Ground Stations: Near Earth Network (White Sands,

FXI can image faint coronal sources, even in the presence of bright footpoints, that cannot be imaged by RHESSI. (A) The input sources for simulations, from bottom to top, are the footpoints, the flare loop, two above-the-looptop sources bracketing a reconnection region, and an extended CME-associated source. The sizes and intensities of the coronal sources (89% Margin • R/F Link: NEN>1.31 dB, SN>0.11 dB above requirements

350 300 250

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Projection

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S-Band Transceiver

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SPP Proposal Date

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Launch 10/2021

RF Switch

Fuse Assembly

MTBs (3x)

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Dual CSS (2x) on solar array

ST (3x)

F10.7 Flux Prediction

Phase E SEO (2 years) (2 years)

2005

2010

2015

Year

DKIST 2020

Number of Flares

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Hyperboloid

Photon uence (photons cm-2)

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Paraboloid

E ective area (cm2)

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20 nested monolithic full Wolter-I shells (only 4 shells depicted, with cuts for clarity)

HXR detector

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25” on-axis HPD: 2.3x better than NuSTAR (64”)

Grazing-incidence mirror optic

X-rays from the Sun

SODA Index

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Normalized Amplitude

2,3

y (arcsec)

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30 Measured PSF from FOXSI Sounding Rocket 20

Steven Christe , A. Shih , S. Krucker , L. Glesener , P. Saint-Hilaire , A. Caspi , M. Abdallaoui , J. Allred , M. Battaglia , B. Chen , J. Drake , B. Dennis , G. Fleishman , D. Gary6, S. Gburek8, K. Goetz4, B. Grefenstette9, M. Gubarev10, I. Hannah11, G. Holman1, H. Hudson2, A. Inglis1, J. Ireland1, S. Ishikawa12, N. Jeffrey11, J. Klimchuk1, E. Kontar11, A. Kowalski13, D. Longcope14, A. Massone15, S. Musset4, M. Piana15, B. Ramsey10, D. Ryan1, R. Schwartz1, M. Stęślicki8, M. Swisdak7, P. Turin2, A. Veronig16, N. Vilmer17, A. Warmuth18, C. Wilson-Hodge10, S. White19, T. Woods20 1

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X-ray Flux Sensor (XFS)

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Now is the time for FOXSI! FOXSI’s launch date is perfectly timed to cover the rising phase of the next solar cycle to observe many large solar eruptions as well as quiescent active regions to achieve its science objectives. The next solar cycle, predicted by the Solar Dynamo Amplitude (SODA) model is expected to produce over 1200 flares including 90 M-class flares, and 7 X-class flares during phase-E. Coordinated observations with Solar Probe Plus (SPP) as well as Solar Orbiter (perihelions shown as grey bars) and DKIST will increase science return. An extended mission which covers the solar maximum would provide more than 200% more large events (160 M-class, 13 X-class flares) and would observe during SPP’s closest approach (black bar).

CONCLUSIONS FOXSI will address the following fundament science goals and objectives How particles are accelerated at the Sun? Where are electrons accelerated and on what time scales? What fraction of electrons is accelerated out of the ambient medium? Where do escaping flare-accelerated electrons originate? How do solar plasmas get heated to high temperatures? What is the energy input of accelerated electrons into the chromosphere and corona? How do hot coornal flare plasmas originate and evolve? How much do flare-like processes heat the corona above active regions? How does magnetic energy release on the Sun lead to flares and eruptions? How does coronal energy release drive the evolution of flares, jets, and CMEs? How do energy release processes scale from the smallest bursts to the largest flares?

FOXSI provides a revolutionary new view on explosive magnetic energy release on the Sun and answers fundamental questions about particle acceleration in magnetized plasmas that occurs at the Sun but also throughout the Universe. It will differentiate between coronal heating models in active regions and characterize potentially Earth-directed energetic electrons at the Sun. FOXSI does this as the first platform to focus X-rays from the largest solar flares to small heating events in the quiet Sun. It provides 20x more sensitivity and 20x faster imaging along with 10 to 100 times better imaging dynamic range than previous instruments. FOXSI does this all using high heritage instrumentation that has been tested on multiple sounding rocket and balloon flights. This opportunity is perfectly aligned with the solar cycle to observe both large solar eruptions and quiescent active regions. For more information see: SH13A-2282 Focusing Solar Hard X-rays: Expected Results from a FOXSI Spacecraft (Now) SH13A-2280 Quiet-sun and non-flaring active region measurements from the FOXSI-2 sounding rocket (Now) SH11D-05 Analysis of Microflares from the Second Sounding Rocket Flight of the Focusing Optics X-ray Solar Imager (FOXSI-2) SH11D-06 Hard X-ray Detectability of Small-Scale Coronal Heating Events