Lyrids or V1 Comet Tail -- Viz's perspective 

4/21/03 6:14:15 AM Pacific Daylight Time

Discussion on the Hot Sheets Solar Board about what is in the 7:42 SOHO image of 4-20:
Image showed up on the Solar Board and Viz has a different perspective on what these might be. I've pasted some of the thread for your perusal. Notably:
"Calculations on solar wind dispersal of the debris field
show that we could get the first Earth-evident meteor 'tracer'
event on the morning of April 24th. Could be significant
bolide activity from late on the 23rd to sunrise on the 24th."
Personally, I've never heard of the Lyrids, tho that doesn't mean squat. Lots of things I've never heard or even dreamed of going on these days!!!

Date: April 21, 2003 at 03:09:42
From: Viz,
Subject: Raining Debris?

If the artifacts noted in the image are each individual pieces
of debris, which I am inclined to believe they are, then this
is really interesting.

Were the 'debris' artifacts stationary in space, SOHO would
be whipping through them at about 66,000 mph. In the
average 20 second exposure for C3, this would make the
relative velocity about 18.3 mi/sec, or about 366 miles for
the duration of the exposure.

There is a good deal of consistency to the general motion
of the field, with the estimable proximity to camera showing
up in the lengths of the artifact strokes and being further
predicated upon the predominant stroke direction and
variations in their length and brightness. This was a
relatively small field of debris, perhaps no more than a few
thousand miles across, with SOHO actually moving
through the edge of the field, or very close to it. The longest
streak moving with the general 'flow' of the group nearest
the camera centre measures about 6.5 cm in length. Other
similarly oriented objects, which are still easily visible,
measure only about 1 cm in length. And since more of
these shorter artifacts are positioned to camera-right
versus camera-left, it would be reasonable to assume that
they are moving roughly toward camera from the right. This
is also supported by the distortion in the viewed objects, as
if they are emerging from some distant point in space, to
our right. This would also mean that the relative velocity of
their passage is higher than SOHO's actual movement if
they were still. Their true Rel.Vel. according to SOHO is
probably more like 100,000 mph, meaning that SOHO
would have passed through this "solar-motivated comet
streamer" in somewhat less than a minute. As we move
through more of these in the weeks to come, I would expect
a more acute angle of incidence to develop -- similar to that
of the more anomalous streaks in this image. The density
per square mile of small objects will also likely increase
and decrease as we move through these 'bands', but the
tendency would we be more to increased traffic during the
days leading up to May 7, 2003, with a lessening of activity
generally after that point. The actual observed period of
heaviest activity (in perceived hindsight) could come
anywhere between May 1st and 14th.

Date: April 21, 2003 at 01:57:22
From: Viz,
Subject: New IR scope grounded 'til after V1 debris

The key factors here are that V1 was such an active comet
and that it attained perihelion inside our own orbit -- in fact,
within the orbit of Venus AND Mercury.

Debris shed by the comet will naturally be blown directly
away from the centre of the sun, with variations built in for
initial trajectory and velocity of the comet (and its particulate
trail), as well as for subsequent solar wind events which
may affect this loose field.

The degree of degradation of V1's surface during its
passage was very high, owing to its close approach to the
solar disc. This gave us a relatively large debris field to
begin with. As you know, a comet will quickly begin to lose
its tail as it moves away from the sun; meaning that the
shunted debris becomes rather quickly unfettered from its
former host. If the sun were to "shut off" for a few minutes
just as the object reached perihelion (usually its most
active stage, give or take a few degrees of trajectory), the
comet's tail would show a distinct separation between the
segment of tail created prior to the shutoff and the newly
emergent tail segment after reintroduction of the solar
stimulus. You'll see this effect whenever there is an
opportunity for cooling to take place.

V1 took a pretty considerable solar discharge just prior to
heading into the final stretch pre-perihelion, during which it
is logical to presume that additional activity probably took
place both on the surface of the comet and at its reactive
centre of mass. This could cause additional fissures to
appear on the surface and the possible loss of additional
rubble from these cracks and surrounding areas, both
below and above the comet's surface.

Once essentially free of the comet's gravitational pull, these
relatively small pieces of dispensed debris will seek to
align themselves to their new master; the sun and its local
environment. That's just gravitational inertia. The inertia of
the micro-objects' initial momentum, provided by V1,
quickly begins to lose sway with this debris. The lighter
particles (much of it no coarser than dust) will be swept
away easily by the solar winds, while higher mass objects
within that field will be less easily influenced. But, in the
end, they will be influenced. No one says "no" to something
as big as the sun -- especially in such close proximity.

In that the movement of V1 was essentially Southbound
during this portion of its transit, any debris being toted
behind would be inclined to follow it, but for the continuous
solar winds which would buffet it. This gives the heaveir
particulate matter (comprising less than an estimated 5%
of the debris total) an impetus to travel downward and away
from the sun.

By now, much of the lighter debris from V1 would have
moved beyond our orbit, shuttled along by the solar winds.
However, larger chunks of this 'cloud' will retreat at varying
speeds from the bracing wind. As time passes, they will
surrender more and more of their initial (V1) momentum to
the constant solar breeze.

Just prior to the passage of V1 through its perihelion point,
it passed through our ecliptic plane -- which was just
shortly after the CME intersection and just after the comet's
most active behaviour of the session.

The passage was swift and relatively violent by normal
comet standards. The tail of V1 was so large that it was
onerous for the sun to blow it straight back away from itself,
as is the custom with smaller and more distant comets.
We've always been taught that a comet's tail always points
AWAY from the sun, but this passage was truly exceptional.
The delay period between solar action and effect was of an
extremely long duration, especially considering the close
distance by which the sun and comet were separated.
There was a massive amount of debris -- which makes the
5% of heavier debris a more pertinent percent.

We are just beginning to enter the portion of space which
will be 'inhabited' by the larger remnants of V1, still fleeing
the solar winds, and retaining some southward inertia lent
them by the comet's orbit. The effects will be more
apparent in the northern hemisphere, due to the orientation
of the earth's axis and the predominant leading edge of our
own orbit, but some activity south of the equator can also
be expected.

You can track out the general debris trail using the V1
orbital solution JAVA applet from neo.jpl, along with a
history of the solar winds from about February 16th until
now. You'll have to make some velocity assumptions for
winds impacting that region due to solar eruptions facing
that side (debris centre) throughout this intervening time.

We shuffle through cometary debris fields every year, but
this one is very fresh. It could become a yearly event, but
we'll have to wait and see. Right now, I'm more concerned
about this run through the mill than I am about future
(probably more routine) encounters.

Date: April 20, 2003 at 14:56:51
From: Viz,
Subject: New IR scope grounded 'til after V1 debris

URL: <>

Launch of Space Infrared Telescope
Facility Delayed

20 April 2003

Observatory will be stuck on the ground
for a few more months.

The space agency delayed the April 27
launch of the Space Infrared Telescope
Facility on a Delta 2 Heavy rocket until no
earlier than mid-August from Pad 17B at
Cape Canaveral Air Force Station.

A problem with a solid fueled booster on
the rocket caused the delay. There wasn't
enough time to replace the booster and
get another rocket assembled on that
same pad in time to launch the last of the
twin Mars Exploration Rovers on June 25.

SRB my @ss

Date: April 21, 2003 at 04:06:00
From: Viz,
Subject: New IR scope grounded 'til after V1 debris

Hi Sherwood,

Calculations on solar wind dispersal of the debris field
show that we could get the first Earth-evident meteor 'tracer'
event on the morning of April 24th. Could be significant
bolide activity from late on the 23rd to sunrise on the 24th.

If it happens, it will be a small show in comparison to what
we will probably see in the ensuing weeks. This is just one
strand of a fairly broad field, but one of the earliest
intersections I can project at this time.

Date: April 21, 2003 at 04:51:21
From: Viz,
Subject: New IR scope grounded 'til after V1 debris

One more thing...

The heaviest period could come as late as May 23-25, but
I'm betting (though not literally) on a max somewhere
between May 3rd and May 19th.