Reflecting on MAGIC reflections

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Reflecting on MAGIC reflections

• MAGIC Cherenkov telescope looking for gamma
  searchin for GRBs, Extended AirShowers and more

BUT...
What about the cloudy nights?
MAGIC can still keep operative and search for
reflections.
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These reflections are published
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What can be done

• MAGIC should spot lights reflected by the sea
  under certain seeing conditions.
• MAGIC is able to point the mountain side and
  probably see the diffused light by inclined
  airshowers hitting the ground.
• MAGIC could watch the opportune huge screen made
  by the clouds laying below 2,2 km of altitude.
• MAGIC, in cooperation with the second eye, can
  efficently follow any GRB or known active source
  pointing it in the sky and at the same time
  looking in the opposite direction if an overcast
  sky is present.

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Morfology of a Sea reflection

• Yeah, but... which shape we should expect to have
  a reflection from an inclined shower on the
  water?

Surelly, on an ideal flat sea it would come as a
circle projected on a plane, so wed spot a
bright ellipse whose area grows when we look
farer.
The calculation is trivial for a flat earth while
it is not even in the sphere approximation.
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Reflectivity increase with angle
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Morfology of a Sea reflection

• A common downward vertical airshower will project
  on the water surface an ellipse because its
  secondaries at low altitude (dense atmosphere)
  are randomized in a disk. The resultant Cherenkov
  lights will shine on a Moliére disk of about a
  hundred meter size.

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Morfology of a Sea reflection
For inclined airshowers (qgt70), the lower air
density allow the geomagnetic field to split the
shower into 2 twin charged beams. Electromagnetic
component is spread more than the energetic
collimated muons that keep themselves on the main
shower axis though they still show some
splitting.
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AUGER event showing the splitting
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(No Transcript)
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Diffused Vs Beamed

• Diffused and beamed reflection have different
  signatures on the telescope.
• Vertical showers light circles on the sea that
  are diffused and appears on the telescope as
  lines of pixels.
• Inclined ones are beamed and appears as vertical
  column of pixels.

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Geometry

• MAGIC is located at about 2,2 km of altitude an
  observer such high sees the horizon at about

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Ellipse area Vs Zenith Angle
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Reflections from the mountain
Naturally, if we have iced ground or snow the
albedo is boosted and we have more possibilities.

• A second way MAGIC can work in the dead time of a
  cluody night is by looking for reflection from
  the mountain.

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Reflections from the clouds

• Another possibility is to look the huge screen
  offered by the eventual clouds below the
  telescope.

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Skimming tau in Rock
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Reflections from the clouds

• Finally, another possibility is to look up toward
  overcast sky, searching for Cherenkov reflections
  from rare up-going tau airshower. Fluxes are
  surelly low but they can be boosted if we look in
  opposite direction of a known active source while
  it is setting at horizon.

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Thanx Very Much!