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Observations of Charge Sign Dependence in Solar Modulation

Kiruna 2011 LEE

Low Energy Electrons

P.I.C.

June 30, 2010

• John Clem and Paul Evenson

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Overview

• I will discuss LEE science and the interface of LEE to the MIP

• John Clem will discuss AESOP science and all other aspects of the campaign

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LEE Scientific Objectives

• Keep the standard candle of electron observations burning

• Provide an intercalibration with PAMELA

• 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

• Voyager is now out far enough to see the outer heliosphere spectrum above background

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 even at solar maximum (particle flux minimum).

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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

• Desired– Altitude 150 kft– Duration 30 hrs

• Minimum– Altitude 100 kft– Duration 48 hrs (with10 hrs above

135kft)• Flight Profile

– Remain north of 0.5 GV geomagnetic cutoff

– Altitude excursions are helpful

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LEE Power (Battery):

Heaters Off: 20wattsHeaters On: 90watts

(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:

COMM1 Connection to MIPDownlink: Iridium, LOSUplink: Iridium, LOS

Two Discrete Lines (Power On/Off)High Rate Umbilical for Final Checkout

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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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LEE Payload Status

Successful flight with MIP in 2009We expect to be in Palestine mid-

January and ready for compatibility hanging early February

Typically we require 7 days of preparation time in Kiruna before declaring flight-ready