The Sources of Solar Hazardsin Interplanetary Space

Leonard Strachan & Jun Lin(Harvard – Smithsonian Center for Astrophysics)

Paper [72.05] “Contributions from Ultraviolet Spectroscopy to the Prediction of High-energy Proton Hazards from CME

Shocks”

– J. Lin, J. C. Raymond, S. R. Cranmer, and J. L. Kohl

AAS 204th Meeting May 31, 2004 Denver, Colorado

The Sources of Solar Hazards in Space

Introduction and Overview

NASA has announced its new vision of human interplanetary space exploration

To accomplish this goal, astronauts will need to contend with solar particle radiation that may be hazardous to themselves and their equipment

In order to warn astronauts of impending risks, we need to understand HOW and WHERE these particles are produced

The Sources of Solar Hazards in Space

Anatomy of the Flare/CME System:

Flare/CME initiation Rising CME bubble Current sheet between

the flare and CME

We believe there are two regions where the particle radiation is produced:

1. Electrified “Current Sheet” 2. Shock wave in front of the

Coronal Mass Ejection

CME

Sun

CME

The Sources of Solar Hazards in Space

Lin & Forbes model predicts a hot current sheet where energetic particles are produced

As predicted, UVCS observes a 6 million degree Celsius current sheet thus validating the model

The Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft

The Sources of Solar Hazards in Space

Theories predict shock- heated gas and energetic particle production near the CME front

Tsurutani, et al. (2003)

As predicted, UVCS measured a 30 million degree Celsius gas behind the CME shock, indicating the production of energetic particles

Hot gas

The Sources of Solar Hazards in Space

UVCS observations determine the physical properties at the sites where energetic particles are produced.

shock temperatures shock speed

precise location of source regions

shock strength magnetic field strength

UVCS provides quantitative information on:

The Sources of Solar Hazards in Space

Role of the current sheet: Converts magnetic energy to heating and kinetic energy

Plasma is heated to 6-10 Million degrees Celsius

Charged particles are accelerated by an electric field across the current sheet

Accelerated particles escape when they reach open magnetic field lines

The Sources of Solar Hazards in Space

A first step: Ongoing ultraviolet observations along with advanced theoretical models provide an improved understanding of the

• onset of solar energetic particle events• and their severity.

A future monitoring and predictive system will benefit from the present work which aims to understand the physical conditions at sites where solar energetic particles are produced.

In Summary …