航空航天(中英翻译版)

ISWI: Global Space Weather Science

Some of the first results from the International Space Weather Initiative focus on the ionosphere

–

the region of the atmosphere from 60 to 500 miles (100-800 km) up above the surface of Earth.

Filled with charged particles, the ionosphere changes in response to incoming energy from the sun

or lightning and can disrupt communication signals traveling through it. Credit: NASA/GSFC

In 2009, as a follow up to the International

Heliophysical

Y

ear of 2007, a group of scientists at

NASA

’s

Goddard

Space

Flight

Center

in

Greenbelt,

Md.,

had

an

idea

to

dramatically

increase

heliophysics

observatories

around

the world. Their

plan:

place

science

instruments

all

over

the

globe to fill in gaps of observations of the near-Earth environment and of Earth's atmosphere and

also to encourage heliophysics research and education in developing nations

In conjunction with the United Nations, the group began something called the International Space

Weather Initiative (ISWI) and they began to encourage scientists and engineers all over the world

to help out. Now, five years later, close to 1,000 instruments have been installed in more than 100

UN member states, numerous science papers have been written on the data, new graduate school

programs have been established -- and the project continues to grow. Recently in Feb. 2012, for

example,

says

Hans

Haubold

from

the

United

Nations

Office

for

Outer

Space

Affairs,

an

International

Center

for

Space

Weather

Science

and

Education

was

inaugurated

at

Kyushu

University, Fukuoka, Japan, with support from the United Nations.

each

instrument

is

not

groundbreaking,

says

Joe

Davila,

a

space

scientist

at

Goddard.

by

placing

relatively

inexpensive

instruments

in

the

right

spots,

you

can

get

constant

viewing

of

both

the

sun

and

of

the

ionosphere,

the

boundary

between

space

and

the

regular atmosphere. We always have a view of the sun from somewhere on the globe.

Such global data gathering relies heavily on participation from scientists in other countries. That

translates

to cost sharing

across

borders

for these complimentary

observations.

Davila

says

that

one

of

ISWI's

goals

has

been

to

encourage

growth

in

the

number

of space scientists

around

the

world. In Ethiopia, for example,

Bahir-Dar University taught no space science. Now, the school

has a department that already has seven master's students.

Encouraging this kind of growth and the international relationships they create is a key part of the

UN's

interest

in

the

program.

But

five

years

in,

the

scientific

rewards

are

also

proving

to

be

important,

says

Keith

Groves,

a scientist

at

Boston

College

in

Boston,

Mass.

Groves

began

his

association

with

the

program when

he was working

on

a

global

project

for

the

U.S.

Air

Force

Research Laboratory called SCINDA

that sought to better understand how radio communications

degrade as they travel through active regions in the ionosphere.

some Pacific islands

–

but we had a big gap over Africa,

Africa was where

some of the maximum ionospheric activity occurred. Now, through this program, we have 14 sites

up in Africa.

The set up for each instrument in this experiment is minimal

–

a Global Positioning Systems (GPS)

receiver

the size

of

a

loaf

of

bread

attached

to

a computer.

In some cases,

there

is

also

a

large

antenna

radio

receiver.

This

is

enough

to

track

how communications

signals,

such

as those for

GPS, are affected by ionospheric disturbances.

While

satellites

had

measured

some

of

these

effects

from

above

and

tracked

seasonal

changes,

they had not successfully mapped daily changes in the ionosphere over Africa. These simple set

ups have now provided some of the first observations of the daily cycles in this radio degradation,

also called

the same degradation over South America or over the Pacific. Scientists are working now to better

characterize the differences.

Another ISWI project has put 30 very low frequency radio receivers around the globe to observe a

different

aspect

of

the

ionosphere

–

how

its

lowest

region

changes

in

response

to

outside

input

such as solar flares on the sun, or even the tremendous energy release from lightning. The lower

ionosphere is difficult to study as it is too high for hot air balloon measurements, yet too low for

satellite measurements. Morris Cohen, a space scientist at Stanford University in Palo Alto, Calif.,

oversees the project, known as the A

WESOME project, and he explains that understanding how

the ionosphere reacts to this kind of energy input is equally important to understanding how radio

signals

travel.

Each

of

the

receivers

can

send

and receive

low

frequency signals

from

a

set

of

communications beacons whose signals act like laser beams that travel along the ionosphere.

there

is

a

grid

of

these receivers

and

a

mesh

of

laser

beams,

Cohen.

all

provide a slice of information about what's going on in the ionosphere at any given time.