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Observations of Charge Sign Dependence in Solar Modulation

Kiruna 2006 LEE

(Low Energy Electrons)

August 17, 2005

• John Clem and Paul Evenson• GSFC Collaborators: Louis

Barbier and John Krizmanic• NASA Award NNG05WC08G• NSF Award ATM-0218900

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LEE Scientific Objectives

• Keep the standard candle of electron observations burning

• Continue serving as the 1 AU baseline for Ulysses

• Search for the origin of the turn up in the low energy electron spectrum

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For Decades the Cosmic Ray Electron “Standard Candle” Has Been LEE

• Time profile of helium and electron observations at a rigidity of 1.2 GV

Magnetic Polarity

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LEE Data Were Used to Correct and Validate the Response of the Kiel Electron Telescope (KET) on Ulysses

Correlation of 1.2 GeV and 2.5GeV Electron Fluxes observed at Earth by LEE and ICE with uncorrected Ulysses 1.2 GeV and 2.5GeV electron channel. Solid lines are linear least squares fits to the data. The relative normalization of the LEE and ICE data sets was also adjusted to minimize the chi square of the linear fits.

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Radial Gradient (1 To 5 AU ) of Cosmic Ray Electrons at 1.2 and 2.5 GV

• Prior studies: McDonald et al 1997, Fujii and McDonald 1997, Heber et. al. 2002

• Our analysis uses LEE, ICE, and Ulysses data. – Squares: Gradients

of positive charged particles.

– Circles: Gradients of negative charged particles.

– Red: 1.2 GV– Green: 1.7 GV– Black 2.5 GV

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Electron Latitude Gradient

• Fractional deviation between the observed LEE fluxes and KET fluxes of 1.2GV electrons as a function of helio-latitude of the Ulysses spacecraft.

• Latitude gradient appears after the solar polarity reversal

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Electron/Helium Flux Ratio (At 1.2 GV) as a Function of Current Sheet Tilt Angle

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Investigation Of The Electron Spectrum At Low Energy

• High altitude is critical to the search for the origin of the mysterious turn up in the low energy electron spectrum (NSF Award)

20 MeV

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In August of 2002 LEE flew on a 60mcf balloon reaching float at 161kft (0.9 mbar).

The high altitude provided a low background environment allowing measurements of primary electrons with energies as low as 20MeV.

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The LEE Payload

• LEE detects electrons with– Plastic scintillators T1, T3

and G (anticoincidence)– Gas Cherenkov detector

T2. • It measures the electron

energy with – Cesium iodide (T4)

calorimeter – Lead glass (T5)

calorimeter• Scintillator T6 assists in

particle identification and energy determination by counting the number of particles that escape the calorimeter.

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LEE Flight Requirements

• Float Altitude – Minimum:140 kft

(2.1mb)– Desired:145 kft

(1.7mb) • Float Duration

– Minimum: 10 hrs – Desired : 75 hrs

• Flight Profile– Remain north of

0.5 GV geomagnetic cutoff

– Altitude excursions are helpful

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LEE Power: Heaters Off: 20wattsHeaters On: 90watts

Initially we intended to purchase a flight ready Charge Controller from PSL. However 80-hrs of 32V-battery weigh roughly the same as a solar power system, therefore LEE does not solar power to achieve desired goals.

LEE Telemetry:Downlink: TDRSS high rate, LOSUplink: TDRSS, LOS, 2 Discrete Lines (Power Control)Need data storage on SIP Reliable Fast Internet Service to OCC (Palestine)

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LEE Work Space

• 20 x 20 ft work space • ½ ton overhead lift• 5 x 115V power outlets (50

amp) • 60hz converters for running

motors• Phone line• Reliable internet service to

OCC (Palestine)

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Lynn Lake Hangar

Final check before button up Compatibility check with NSBF equipment

Assembly, calibration and integration

Flight Ready !!!

LEE Work Area Can Be Shared with AESOP as in Canadian Campaigns

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LEE Payload Status

• As with AESOP we expect modifications of LEE to be completed in the fall.

• We expect to be in Palestine early January and ready for compatibility hanging early February

• Typically we require 3-4 days of preparation time in Lynn Lake before declaring flight-ready