Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V08/V8_305.TXT

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Date: Sat, 30 Jul 88 19:05:19 PDT
From: Ted Anderson <[e-mail]>
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Subject: SPACE Digest V8 #305

SPACE Digest                                      Volume 8 : Issue 305

Today's Topics:
   Pioneer data reveals nature of the outer heliosphere (Forwarded)
             Re: Ramscoop engine
             Getting opinions to Dukakis
          Subroutine for computing orbital position
----------------------------------------------------------------------

Date: 16 Jul 88 18:41:12 GMT
From: [e-mail]  (Peter E. Yee)
Subject: Pioneer data reveals nature of the outer heliosphere (Forwarded)

Charles Redmond
Headquarters, Washington, D.C.                     July 15, 1988

Peter W. Waller
Ames Research Center, Mountain View, Calif.


RELEASE:  88-100

PIONEER DATA REVEALS NATURE OF THE OUTER HELIOSPHERE


     As NASA's Pioneer 11 and Voyager 2 pass through the outer
reaches of the solar system and NASA's Pioneer 10 speeds far
beyond the planets, these distant spacecraft are measuring
drastic changes in the flow patterns of the solar wind -- a
million-mile-an-hour stream of charged particles which constantly
boil off the Sun.

     NASA scientists have discovered a connection between the
speed changes in the solar wind (near the spacecraft) and
periodic changes in the Sun itself.  The Sun's constant
variations are manifested in shifts of its magnetic field and
movements in the hot gases of its corona.  Streams of faster wind
particles tend to flow from thin areas, called corona holes, in
the corona.  Solar wind changes also are triggered by movements
of a vast electromagnetic structure, called the current sheet,
which bisects the Sun's field.  Particles slow down as this sheet
"flaps" toward them.

     Over the last 3 years, the Sun has been going through a
phase called solar minimum -- a turning point in its 11-year
cycle.  "No one knew what happened during solar minimum in the
farthest reaches of the solar system and beyond until the
Pioneers and Voyager sent back their measurements.  This is the
first solar minimum for which we have been able to see what's
going on in the solar wind out past Pluto," says NASA
astrophysicist John Mihalov.

     The solar wind streams out from the Sun and envelops the
entire solar system in charged particles, mostly electrons and
protons.  No one knows exactly how far this five-particle-per
cubic-centimeter flow of particles extends.  One recent guess is
about 18 billion miles, or four times the distance of Neptune
from the Sun.

     Before 1985, Pioneer 10 and Voyager 2, both positioned near
the equatorial plane, measured periodic gusts in the solar wind
called "high speed streams."  The particles would speed up and
then slow down about once every 27 days.  In June 1985, the wind
stream pattern stopped and the winds slowed down dramatically at
Voyager 2's distance -- two billion miles from the Sun.  There
was no slowing measured at Pioneer 11, about the same distance as
Voyager 2, but 15 degrees higher in latitude.  Pioneer 11
measured the usual pattern of high speed streams.  Eventually,
the winds were flowing only about half as fast at Voyager 2 as
they were at Pioneer 11.

     Three months later, in August, the solar wind slowed and the
high speed streams also stopped at Pioneer 10, which is out twice
the distance of the other two probes and in the equatorial
region.  Mihalov believes this change is connected to the earlier
wind speed decrease at Voyager 2.  The first slower particles,
which were blowing past Voyager 2 in June, would have just
reached Pioneer 10 by August.  Solar winds actually sped up at
the higher altitude position of Pioneer 11.

     The Sun's slower particles, that first reached Voyager and
Pioneer 10, were boiling off in March of 1985.  Mihalov and Aaron
Barnes, Ames' senior scientist, proposed that changes in the Sun
at this time, set off the changes in the far solar wind, which
reached the vicinity of the distant probes months later.

     The changes in the Sun were part of a regular variation that
it undergoes in 11-year cycles, or sunspot cycles.  This cycle
affects the number of sunspots, the configuration of the magnetic
field, and the distribution of the 2-million-degree gas making up
the solar corona.

     The coronal holes are located around the Sun's North and
South poles.  When the Sun approaches the part of its most active
phase, called solar maximum, these coronal holes creep toward the
equator by extending "tongues" 10 or 20 degrees in longitude.  In
the last 3 years, the Sun has been near the opposite condition,
called solar minimum, when the holes retreat back toward the
direction of the poles.

     The wind blows out fastest from these lower density holes.
Barnes explains that holes form in areas where strong winds have
blown the coronal particles away.  As the holes retreat toward
the poles, the high-speed streams migrate along with them.

     The Sun's magnetic field also influences the solar wind.
The Sun's field, like the Earth's, has basically a North and
South magnetic pole, but the Sun's more complex magnetic field
deviates from this dipolar structure during parts of the solar
cycle, becoming most complicated during solar maximum, when the
two magnetic poles swap places.

     In the Earth's simpler magnetic field, field lines (the
lines following the direction of force the Earth would exert on a
magnetic object) wrap around the planet, connecting the North and
South magnetic poles.  In the Sun's field, the solar wind
stretches the Sun's field lines near the equator far out into
space.  One region, corresponding loosely with one hemisphere,
has more field lines pointing out from the Sun, and is called the
positive sector, while the remaining region, with more field
lines coming in, is called the negative sector.  These sectors
are divided by an equator, so at the Sun's surface, a point 15
degrees North of the equator would be above this equator in some
areas and below it in others.

     Away from the Sun, the positive and negative sectors are
bisected by an imaginary wavy curtain called the current sheet,
which extends from this buckled equator.  (It is called the
current sheet because laws of physics state that there must be an
electric current at the boundary between opposite magnetic fields
and, indeed, there is a net flow of positive charges outward and
negative particles inward in this region.)  During the present
solar cycle, the region above the current sheet is the negative
sector and, below it, the positive sector.

     Back in early 1985, Pioneer 11 -- 15 degrees above the
equatorial plane -- would sometimes be above and beneath the
"current sheet" as the Sun rotated.  Normally, as the Sun
approaches solar minimum and the coronal holes retreat toward the
poles, the current sheet's ridges flatten out.  As the Sun
approached solar minimum in 1985, Pioneer 11 was located above
the current sheet, in the negative sector more of the time.  By
mid-1985, Pioneer 11 was always in the negative sector,
indicating that the current sheet had flattened out beneath it.

     The closer you go to the current sheet, the slower the solar
wind.  As the current sheet "flapped" down toward the equator,
even with Voyager 2 and Pioneer 10, the solar winds slowed in
this region and sped up near the poles.  The equatorial winds
slowed as far as Pioneer 10, showing that the Sun's magnetic
field and the associated current sheet are exerting powerful
control over the solar wind even at great distances.

     "The Sun, its corona and magnetic fields, and the solar wind
are all part of one system," says Barnes.  And even well past
Pluto, the solar winds are apparently still under the control of
the rest of the system.

------------------------------

Date: 15 Jul 88 13:48:59 GMT
From: mcvax!ukc!etive![e-mail]  (B Gray)
Subject: Re: Ramscoop engine

In article <[e-mail]> [e-mail] (Peter da Silva) writes:
>Niven brought this objection up, and handwaved his way out of it by
>havng the "ramjet" fuel a laser. The ship was accelerated by light
>pressure from this super laser. Is this even theoretically possible
>(assuming some magic 100% efficient laser)?

The most recent incarnation of the ramscoop idea I have seen
was in Donald Moffitt's books "The Genesis Quest" and "Second Genesis".

He seems to realise this problem exists and has one of the
physicists in the story explain how it works.

I quote. from page 159 and 160 of "The Genesis Quest"

    "Under certain circumstances, it's possible to increase the
    energy of a photon by a factor of from one to ten bollion.
    And when you do, it takes on the properties of a hadron. It
    acts as though it has mass, like a proton, for instance."
...
    "It's done strictly through electromagnetic interactions
    that we know how to handle. In theory, at least."
...
    "What you do is swat pulsed laser photons with a high energy
    electrin beam and scatter them a hundred and eighty degrees,
    [....] They pick up the energy of the swat."
...
    "Then you focus the back scattered photons - hadronic
    photons now - in the electromagnetic throat of the drive,
    and since they have a temporary non-zero mass, your vehicle
    not only gets a healthy kick, but gets it at the speed of
    light."
...
    "[a] four wave conjugate mirror [....] collect[s] all those
    muscular photons thatr'e scattering in all directions and
    herd them into a tight beam."
...
    "Of course, these aren't real photons [....] They're virtual
    photons. They exist by courtesy of the uncertainty principle."
...
    "The hadronic photon has no right to be. It's supposed to
    hold hands with another photon, so that the momentum and
    energy can be balanced. But it doesn't. It lives it's brief
    and solitary life violating all the superstitions of quantum
    electrodynamics. The universe finds this a very
    unsatisfactory state of affairs. So [it] disappears before
    it can be detected. It materializes into a rho vector meson,
    which immediately decays into two pions [......] By that
    time out mythical photon's given it's mythical kick to the
    vehicle.

Now, anyone who has bothered to read this far is either
rolling around with laughter or thinking "I wonder if it
works".

Given the number of other mistakes Moffitt makes with
elementary physics I think it unlikely that the above
is anything more than handwaving rubbish with buzz words
thrown in. Would any real physicists like to comment.

I have crossposted this article to the sf-lovers newsgroup
with followups directed there. This stuff is getting too far
from reality to be posted in sci.space.
    Bob.

------------------------------

Date: Sun, 17 Jul 88 12:42:11 PST
From: Peter Scott <[e-mail]>
Subject: Getting opinions to Dukakis
X-Vms-Mail-To: EXOS%"[e-mail],[e-mail]"

A friend of mine tells me that Carol Rosin of the Institute for Security
and Cooperation in Outer Space meets regularly with Jesse Jackson and
has agreed to pass on all requests, opinions, etc, received in respect
of directions national space policy should take; and that Jackson has
Dukakis's ear.  This compares favorably with writing letters to Dukakis,
which he is unlikely to see personally (although opinions may be
tallied, I guess).  If you wish to write, the address is: 8 Logan
Circle, Washington, DC 20005, tel.  [phone].

I am neither a member of ISCOS nor any political party and do not
represent them here; I am merely passing along a suggestion that had
some face-value merit for a certain segment of the population.

Peter Scott ([e-mail])

------------------------------

Date: 18 Jul 88 17:03:04 GMT
From: linus![e-mail]  (Robert Munck)
Subject: Subroutine for computing orbital position

-------------------------
I'd like to call on the combined expertise of the net for something I've
been unable to find;  it's entirely on a "hobby" basis, no connection
with anything commercial.

I want a simple, fast subroutine that will compute orbital motions.  The
ideal subroutine would be something like this:

Input parameters:
    position, velocity, mass of a free-falling body (whatever coordinate system
                                                     and units works best)

    array of positions and masses of relatively massive bodies (planets, sun)

    an elapsed time (small, minutes or less)

Output parameters:
    position and velocity of the free-falling body at the end of the
    elapsed time, accuracy at least 1% and .0001% is more than enough.

This can be in any programming language that I'd have a prayer of being
able to figure out -- APL, Ada, FORTRAN, even COBOL.  I want to re-code
it in the tightest machine code I can manage for the 80387 arithmetic
chip (in my Compaq 386) and use it to drive 2-D and 3-D graphic displays
of various things.  I would pre-compute the motions of the massive
bodies and use the subroutine to move one or several small things like
satellites.  My AB in Apple Math is twenty-one years old and rusty, but
I'm very good at squeezing microseconds out of a program.

Request II:  for the second generation program, I'd like to add to the
original a constraint on the motion of the free-falling body, say the
actual position and velocity of it at the end of the period, and get as
output the force or acceleration on the body.  This could be used to
fool around with things like orbiting tethers and Beanstalks.  Request
III is the inverse: add a force or acceleration to the original
subroutine.

Any help anyone can give, from an actual working program to references
to a book or two that might help me, will be appreciated.  Any software
I manage to get working will be freely available.

                         -- Bob Munck, MITRE Corporation
                            [e-mail]
                            ...!linus!munck.uucp
                            617-271-3671.bell

------------------------------

End of SPACE Digest V8 #305
*******************