The Solar Wind and Heliosphere

(with a space weather emphasis!)

V J Pizzo (NOAA/SEC)

Key role of solar wind of the solar wind in Space Weather

Sun is source of disturbances launched at Earth, but …

structure at Sun is poorly observedstructure evolves during propagation to Eartheffect on geospace depends upon prior state of

magnetosphere

State of science: terrestrial weather prediction analog

observationally, like 1890 (telegraph alert) numerically (models) like 2000?

Another key point:

Over 4π sphere (or even 1 sterad spread of major IP disturbance), TINY element actually strikes Earth

Solar wind fronts can be structured on these scales

Main components of solar input to SW

global ambient solar winderupted magnetic flux distributionoutward pressure due to hot coronaextended heating for fast windrotational interactions

transients

solar energetic particles and cosmic rays

energetic photon emission

Basics of solar wind expansion

Parker model (hydrodynamic, spherically sym, thermally driven)

Two insights: behave as fluidpressure gradient out to stellar background

Confirmed by Mariner 2 s/c in 1962

How measured

in situ: detectors (0.3 to >80 AU) protons, electrons, ions

(neutrals, neutrons, dust)

remote: coronagraphXUVIPS – radio wavesurface field extrapolation

What you should know about Observations

In situcalibration and intercalibration problemsat point within enormous 4π volumepart that intercepts Earth

Remote sensingline of sight integrationfog3D overlapforward modeling

What you should know about Observations

[LOS Fig]

C3 May 13 event

Global ambient

Why study:

recurrent activitymost of SWpath for CMEspath for SEPs and CRs“killer” electrons

Non-uniform outflow distribution

Fast from holes (fig -- xray phenomenon)

uniform, hot, low density

Slow from over streamer belt

ragged, cold, high density

Varies over solar cycle (min/max corona plot)

IMF formed by drawing rooted open field into IP space(Parker spiral)

Helios, Ulysses confirmation

Rotational interaction (streams)

Coronal Holes

Non-uniform outflow distribution

Rotational interaction (streams)

Kinematics versus Dynamics

Modeling

solar surface synoptic maps ground-based, MDI

MHS or MHD assumption for low corona

Big difference: NOT!

what does this tell us?

topology is the key

Boundary Conditions

Some Coronal Issues

“rigid” coronal vs photospheric differential rotation

Solar rotation – field line dragging – IP consequences

Some Coronal Issues

Random walk of fieldlines

Some Coronal Issues

Open field and Interchange reconnection

Some Coronal Issues

open flux

Transients

Fundamentally a magnetic phenomenon

General interaction – gopal

Specific interaction – O & Pshock much biggerinteraction strongly a function of bkgd

Cme/cme interaction

Particles (SEPs)

flare vs coronal shock origin controversy

CMEs in a Structured Ambient

Transients

Associations game – relating events at Sun with subsequent events at Earth

cant see what you really need towhat are they? – coronal field, 3D mass distr

too often judged on only what you can see

flare/cme myth

Signatures (incl helioseismology)

SOHO EIT coronal wave event

SOHO LASCO Halo Event

acan-hb4d4tq.gif

Transients

Magnetic Clouds

Transients

Stereo –multi-perspective viewing will allow for first time accurate determination of CME location, size, direction (3D structure?)

Heliospheric imaging

IPS – radio wave: front tracking

Heliospheric Imager (case 1)

3-D IPS TOMOGRAPHY• Assume static structures in frame corotating with Sun, use

rotation to provide multiple views

• Several different realizations (e.g., Jackson and Hick, Kojima et al.) incorporate density and velocity info

Cosmic Rays and Space Weather

SEPs are hazard to astronauts outside LEO, but…

High-Z Gev particle flux main CR concern

Source is galaxy (also some from termination shock)

Spectrum, spatial and temporal variation well established by Voyager, Pioneer

Biological effects? Historical experience

Shielding?

Philosophy of Modeling

Purposeoperational prediction (forecast tool)basic research

(understanding – gedanken experiment)

Internet downsideavailability (Zeus)

Most profitable approach:

Use model to address specific questions

Concentrate on physical understanding rather than modeling technique or methodology (unless that is your specific goal!)

the criterion for “good modeling” –

you should learn something about underlying physical system!

but be careful – it is the visuals or the essence?

12 May 1997 1 May 1998

21 April 2002 24 August 2002